Btrfs: introduce BTRFS_IOC_SEND for btrfs send/receive

This patch introduces the BTRFS_IOC_SEND ioctl that is
required for send. It allows btrfs-progs to implement
full and incremental sends. Patches for btrfs-progs will
follow.

Signed-off-by: Alexander Block <ablock84@googlemail.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Reviewed-by: Arne Jansen <sensille@gmx.net>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Reviewed-by: Alex Lyakas <alex.bolshoy.btrfs@gmail.com>

5 files changed, 4717 insertions, 1 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 0c4fa2befae7..f740644bb5a5 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -8,7 +8,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
 	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
-	   reada.o backref.o ulist.o
+	   reada.o backref.o ulist.o send.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 99fe2ce7f721..bca6997fdb80 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -54,6 +54,7 @@
 #include "inode-map.h"
 #include "backref.h"
 #include "rcu-string.h"
+#include "send.h"
 
 /* Mask out flags that are inappropriate for the given type of inode. */
 static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
@@ -3571,6 +3572,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_balance_progress(root, argp);
 	case BTRFS_IOC_SET_RECEIVED_SUBVOL:
 		return btrfs_ioctl_set_received_subvol(file, argp);
+	case BTRFS_IOC_SEND:
+		return btrfs_ioctl_send(file, argp);
 	case BTRFS_IOC_GET_DEV_STATS:
 		return btrfs_ioctl_get_dev_stats(root, argp, 0);
 	case BTRFS_IOC_GET_AND_RESET_DEV_STATS:
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 0c505d7ff8ed..27097e8bfa39 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -310,6 +310,15 @@ struct btrfs_ioctl_received_subvol_args {
 	__u64	reserved[16];		/* in */
 };
 
+struct btrfs_ioctl_send_args {
+	__s64 send_fd;			/* in */
+	__u64 clone_sources_count;	/* in */
+	__u64 __user *clone_sources;	/* in */
+	__u64 parent_root;		/* in */
+	__u64 flags;			/* in */
+	__u64 reserved[4];		/* in */
+};
+
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
 				   struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -376,6 +385,7 @@ struct btrfs_ioctl_received_subvol_args {
 					struct btrfs_ioctl_ino_path_args)
 #define BTRFS_IOC_SET_RECEIVED_SUBVOL _IOWR(BTRFS_IOCTL_MAGIC, 37, \
 				struct btrfs_ioctl_received_subvol_args)
+#define BTRFS_IOC_SEND _IOW(BTRFS_IOCTL_MAGIC, 38, struct btrfs_ioctl_send_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_GET_AND_RESET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 53, \
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
new file mode 100644
index 000000000000..5394cb75012a
--- /dev/null
+++ b/fs/btrfs/send.c
@@ -0,0 +1,4570 @@
+/*
+ * Copyright (C) 2012 Alexander Block.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/bsearch.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/sort.h>
+#include <linux/mount.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/radix-tree.h>
+#include <linux/crc32c.h>
+
+#include "send.h"
+#include "backref.h"
+#include "locking.h"
+#include "disk-io.h"
+#include "btrfs_inode.h"
+#include "transaction.h"
+
+static int g_verbose = 0;
+
+#define verbose_printk(...) if (g_verbose) printk(__VA_ARGS__)
+
+/*
+ * A fs_path is a helper to dynamically build path names with unknown size.
+ * It reallocates the internal buffer on demand.
+ * It allows fast adding of path elements on the right side (normal path) and
+ * fast adding to the left side (reversed path). A reversed path can also be
+ * unreversed if needed.
+ */
+struct fs_path {
+	union {
+		struct {
+			char *start;
+			char *end;
+			char *prepared;
+
+			char *buf;
+			int buf_len;
+			int reversed:1;
+			int virtual_mem:1;
+			char inline_buf[];
+		};
+		char pad[PAGE_SIZE];
+	};
+};
+#define FS_PATH_INLINE_SIZE \
+	(sizeof(struct fs_path) - offsetof(struct fs_path, inline_buf))
+
+
+/* reused for each extent */
+struct clone_root {
+	struct btrfs_root *root;
+	u64 ino;
+	u64 offset;
+
+	u64 found_refs;
+};
+
+#define SEND_CTX_MAX_NAME_CACHE_SIZE 128
+#define SEND_CTX_NAME_CACHE_CLEAN_SIZE (SEND_CTX_MAX_NAME_CACHE_SIZE * 2)
+
+struct send_ctx {
+	struct file *send_filp;
+	loff_t send_off;
+	char *send_buf;
+	u32 send_size;
+	u32 send_max_size;
+	u64 total_send_size;
+	u64 cmd_send_size[BTRFS_SEND_C_MAX + 1];
+
+	struct vfsmount *mnt;
+
+	struct btrfs_root *send_root;
+	struct btrfs_root *parent_root;
+	struct clone_root *clone_roots;
+	int clone_roots_cnt;
+
+	/* current state of the compare_tree call */
+	struct btrfs_path *left_path;
+	struct btrfs_path *right_path;
+	struct btrfs_key *cmp_key;
+
+	/*
+	 * infos of the currently processed inode. In case of deleted inodes,
+	 * these are the values from the deleted inode.
+	 */
+	u64 cur_ino;
+	u64 cur_inode_gen;
+	int cur_inode_new;
+	int cur_inode_new_gen;
+	int cur_inode_deleted;
+	int cur_inode_first_ref_orphan;
+	u64 cur_inode_size;
+	u64 cur_inode_mode;
+
+	u64 send_progress;
+
+	struct list_head new_refs;
+	struct list_head deleted_refs;
+
+	struct radix_tree_root name_cache;
+	struct list_head name_cache_list;
+	int name_cache_size;
+
+	struct file *cur_inode_filp;
+	char *read_buf;
+};
+
+struct name_cache_entry {
+	struct list_head list;
+	struct list_head use_list;
+	u64 ino;
+	u64 gen;
+	u64 parent_ino;
+	u64 parent_gen;
+	int ret;
+	int need_later_update;
+	int name_len;
+	char name[];
+};
+
+static void fs_path_reset(struct fs_path *p)
+{
+	if (p->reversed) {
+		p->start = p->buf + p->buf_len - 1;
+		p->end = p->start;
+		*p->start = 0;
+	} else {
+		p->start = p->buf;
+		p->end = p->start;
+		*p->start = 0;
+	}
+}
+
+static struct fs_path *fs_path_alloc(struct send_ctx *sctx)
+{
+	struct fs_path *p;
+
+	p = kmalloc(sizeof(*p), GFP_NOFS);
+	if (!p)
+		return NULL;
+	p->reversed = 0;
+	p->virtual_mem = 0;
+	p->buf = p->inline_buf;
+	p->buf_len = FS_PATH_INLINE_SIZE;
+	fs_path_reset(p);
+	return p;
+}
+
+static struct fs_path *fs_path_alloc_reversed(struct send_ctx *sctx)
+{
+	struct fs_path *p;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return NULL;
+	p->reversed = 1;
+	fs_path_reset(p);
+	return p;
+}
+
+static void fs_path_free(struct send_ctx *sctx, struct fs_path *p)
+{
+	if (!p)
+		return;
+	if (p->buf != p->inline_buf) {
+		if (p->virtual_mem)
+			vfree(p->buf);
+		else
+			kfree(p->buf);
+	}
+	kfree(p);
+}
+
+static int fs_path_len(struct fs_path *p)
+{
+	return p->end - p->start;
+}
+
+static int fs_path_ensure_buf(struct fs_path *p, int len)
+{
+	char *tmp_buf;
+	int path_len;
+	int old_buf_len;
+
+	len++;
+
+	if (p->buf_len >= len)
+		return 0;
+
+	path_len = p->end - p->start;
+	old_buf_len = p->buf_len;
+	len = PAGE_ALIGN(len);
+
+	if (p->buf == p->inline_buf) {
+		tmp_buf = kmalloc(len, GFP_NOFS);
+		if (!tmp_buf) {
+			tmp_buf = vmalloc(len);
+			if (!tmp_buf)
+				return -ENOMEM;
+			p->virtual_mem = 1;
+		}
+		memcpy(tmp_buf, p->buf, p->buf_len);
+		p->buf = tmp_buf;
+		p->buf_len = len;
+	} else {
+		if (p->virtual_mem) {
+			tmp_buf = vmalloc(len);
+			if (!tmp_buf)
+				return -ENOMEM;
+			memcpy(tmp_buf, p->buf, p->buf_len);
+			vfree(p->buf);
+		} else {
+			tmp_buf = krealloc(p->buf, len, GFP_NOFS);
+			if (!tmp_buf) {
+				tmp_buf = vmalloc(len);
+				if (!tmp_buf)
+					return -ENOMEM;
+				memcpy(tmp_buf, p->buf, p->buf_len);
+				kfree(p->buf);
+				p->virtual_mem = 1;
+			}
+		}
+		p->buf = tmp_buf;
+		p->buf_len = len;
+	}
+	if (p->reversed) {
+		tmp_buf = p->buf + old_buf_len - path_len - 1;
+		p->end = p->buf + p->buf_len - 1;
+		p->start = p->end - path_len;
+		memmove(p->start, tmp_buf, path_len + 1);
+	} else {
+		p->start = p->buf;
+		p->end = p->start + path_len;
+	}
+	return 0;
+}
+
+static int fs_path_prepare_for_add(struct fs_path *p, int name_len)
+{
+	int ret;
+	int new_len;
+
+	new_len = p->end - p->start + name_len;
+	if (p->start != p->end)
+		new_len++;
+	ret = fs_path_ensure_buf(p, new_len);
+	if (ret < 0)
+		goto out;
+
+	if (p->reversed) {
+		if (p->start != p->end)
+			*--p->start = '/';
+		p->start -= name_len;
+		p->prepared = p->start;
+	} else {
+		if (p->start != p->end)
+			*p->end++ = '/';
+		p->prepared = p->end;
+		p->end += name_len;
+		*p->end = 0;
+	}
+
+out:
+	return ret;
+}
+
+static int fs_path_add(struct fs_path *p, const char *name, int name_len)
+{
+	int ret;
+
+	ret = fs_path_prepare_for_add(p, name_len);
+	if (ret < 0)
+		goto out;
+	memcpy(p->prepared, name, name_len);
+	p->prepared = NULL;
+
+out:
+	return ret;
+}
+
+static int fs_path_add_path(struct fs_path *p, struct fs_path *p2)
+{
+	int ret;
+
+	ret = fs_path_prepare_for_add(p, p2->end - p2->start);
+	if (ret < 0)
+		goto out;
+	memcpy(p->prepared, p2->start, p2->end - p2->start);
+	p->prepared = NULL;
+
+out:
+	return ret;
+}
+
+static int fs_path_add_from_extent_buffer(struct fs_path *p,
+					  struct extent_buffer *eb,
+					  unsigned long off, int len)
+{
+	int ret;
+
+	ret = fs_path_prepare_for_add(p, len);
+	if (ret < 0)
+		goto out;
+
+	read_extent_buffer(eb, p->prepared, off, len);
+	p->prepared = NULL;
+
+out:
+	return ret;
+}
+
+static void fs_path_remove(struct fs_path *p)
+{
+	BUG_ON(p->reversed);
+	while (p->start != p->end && *p->end != '/')
+		p->end--;
+	*p->end = 0;
+}
+
+static int fs_path_copy(struct fs_path *p, struct fs_path *from)
+{
+	int ret;
+
+	p->reversed = from->reversed;
+	fs_path_reset(p);
+
+	ret = fs_path_add_path(p, from);
+
+	return ret;
+}
+
+
+static void fs_path_unreverse(struct fs_path *p)
+{
+	char *tmp;
+	int len;
+
+	if (!p->reversed)
+		return;
+
+	tmp = p->start;
+	len = p->end - p->start;
+	p->start = p->buf;
+	p->end = p->start + len;
+	memmove(p->start, tmp, len + 1);
+	p->reversed = 0;
+}
+
+static struct btrfs_path *alloc_path_for_send(void)
+{
+	struct btrfs_path *path;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return NULL;
+	path->search_commit_root = 1;
+	path->skip_locking = 1;
+	return path;
+}
+
+static int write_buf(struct send_ctx *sctx, const void *buf, u32 len)
+{
+	int ret;
+	mm_segment_t old_fs;
+	u32 pos = 0;
+
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	while (pos < len) {
+		ret = vfs_write(sctx->send_filp, (char *)buf + pos, len - pos,
+				&sctx->send_off);
+		/* TODO handle that correctly */
+		/*if (ret == -ERESTARTSYS) {
+			continue;
+		}*/
+		if (ret < 0)
+			goto out;
+		if (ret == 0) {
+			ret = -EIO;
+			goto out;
+		}
+		pos += ret;
+	}
+
+	ret = 0;
+
+out:
+	set_fs(old_fs);
+	return ret;
+}
+
+static int tlv_put(struct send_ctx *sctx, u16 attr, const void *data, int len)
+{
+	struct btrfs_tlv_header *hdr;
+	int total_len = sizeof(*hdr) + len;
+	int left = sctx->send_max_size - sctx->send_size;
+
+	if (unlikely(left < total_len))
+		return -EOVERFLOW;
+
+	hdr = (struct btrfs_tlv_header *) (sctx->send_buf + sctx->send_size);
+	hdr->tlv_type = cpu_to_le16(attr);
+	hdr->tlv_len = cpu_to_le16(len);
+	memcpy(hdr + 1, data, len);
+	sctx->send_size += total_len;
+
+	return 0;
+}
+
+#if 0
+static int tlv_put_u8(struct send_ctx *sctx, u16 attr, u8 value)
+{
+	return tlv_put(sctx, attr, &value, sizeof(value));
+}
+
+static int tlv_put_u16(struct send_ctx *sctx, u16 attr, u16 value)
+{
+	__le16 tmp = cpu_to_le16(value);
+	return tlv_put(sctx, attr, &tmp, sizeof(tmp));
+}
+
+static int tlv_put_u32(struct send_ctx *sctx, u16 attr, u32 value)
+{
+	__le32 tmp = cpu_to_le32(value);
+	return tlv_put(sctx, attr, &tmp, sizeof(tmp));
+}
+#endif
+
+static int tlv_put_u64(struct send_ctx *sctx, u16 attr, u64 value)
+{
+	__le64 tmp = cpu_to_le64(value);
+	return tlv_put(sctx, attr, &tmp, sizeof(tmp));
+}
+
+static int tlv_put_string(struct send_ctx *sctx, u16 attr,
+			  const char *str, int len)
+{
+	if (len == -1)
+		len = strlen(str);
+	return tlv_put(sctx, attr, str, len);
+}
+
+static int tlv_put_uuid(struct send_ctx *sctx, u16 attr,
+			const u8 *uuid)
+{
+	return tlv_put(sctx, attr, uuid, BTRFS_UUID_SIZE);
+}
+
+#if 0
+static int tlv_put_timespec(struct send_ctx *sctx, u16 attr,
+			    struct timespec *ts)
+{
+	struct btrfs_timespec bts;
+	bts.sec = cpu_to_le64(ts->tv_sec);
+	bts.nsec = cpu_to_le32(ts->tv_nsec);
+	return tlv_put(sctx, attr, &bts, sizeof(bts));
+}
+#endif
+
+static int tlv_put_btrfs_timespec(struct send_ctx *sctx, u16 attr,
+				  struct extent_buffer *eb,
+				  struct btrfs_timespec *ts)
+{
+	struct btrfs_timespec bts;
+	read_extent_buffer(eb, &bts, (unsigned long)ts, sizeof(bts));
+	return tlv_put(sctx, attr, &bts, sizeof(bts));
+}
+
+
+#define TLV_PUT(sctx, attrtype, attrlen, data) \
+	do { \
+		ret = tlv_put(sctx, attrtype, attrlen, data); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+#define TLV_PUT_INT(sctx, attrtype, bits, value) \
+	do { \
+		ret = tlv_put_u##bits(sctx, attrtype, value); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+#define TLV_PUT_U8(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 8, data)
+#define TLV_PUT_U16(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 16, data)
+#define TLV_PUT_U32(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 32, data)
+#define TLV_PUT_U64(sctx, attrtype, data) TLV_PUT_INT(sctx, attrtype, 64, data)
+#define TLV_PUT_STRING(sctx, attrtype, str, len) \
+	do { \
+		ret = tlv_put_string(sctx, attrtype, str, len); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+#define TLV_PUT_PATH(sctx, attrtype, p) \
+	do { \
+		ret = tlv_put_string(sctx, attrtype, p->start, \
+			p->end - p->start); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while(0)
+#define TLV_PUT_UUID(sctx, attrtype, uuid) \
+	do { \
+		ret = tlv_put_uuid(sctx, attrtype, uuid); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+#define TLV_PUT_TIMESPEC(sctx, attrtype, ts) \
+	do { \
+		ret = tlv_put_timespec(sctx, attrtype, ts); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+#define TLV_PUT_BTRFS_TIMESPEC(sctx, attrtype, eb, ts) \
+	do { \
+		ret = tlv_put_btrfs_timespec(sctx, attrtype, eb, ts); \
+		if (ret < 0) \
+			goto tlv_put_failure; \
+	} while (0)
+
+static int send_header(struct send_ctx *sctx)
+{
+	struct btrfs_stream_header hdr;
+
+	strcpy(hdr.magic, BTRFS_SEND_STREAM_MAGIC);
+	hdr.version = cpu_to_le32(BTRFS_SEND_STREAM_VERSION);
+
+	return write_buf(sctx, &hdr, sizeof(hdr));
+}
+
+/*
+ * For each command/item we want to send to userspace, we call this function.
+ */
+static int begin_cmd(struct send_ctx *sctx, int cmd)
+{
+	struct btrfs_cmd_header *hdr;
+
+	if (!sctx->send_buf) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	BUG_ON(sctx->send_size);
+
+	sctx->send_size += sizeof(*hdr);
+	hdr = (struct btrfs_cmd_header *)sctx->send_buf;
+	hdr->cmd = cpu_to_le16(cmd);
+
+	return 0;
+}
+
+static int send_cmd(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_cmd_header *hdr;
+	u32 crc;
+
+	hdr = (struct btrfs_cmd_header *)sctx->send_buf;
+	hdr->len = cpu_to_le32(sctx->send_size - sizeof(*hdr));
+	hdr->crc = 0;
+
+	crc = crc32c(0, (unsigned char *)sctx->send_buf, sctx->send_size);
+	hdr->crc = cpu_to_le32(crc);
+
+	ret = write_buf(sctx, sctx->send_buf, sctx->send_size);
+
+	sctx->total_send_size += sctx->send_size;
+	sctx->cmd_send_size[le16_to_cpu(hdr->cmd)] += sctx->send_size;
+	sctx->send_size = 0;
+
+	return ret;
+}
+
+/*
+ * Sends a move instruction to user space
+ */
+static int send_rename(struct send_ctx *sctx,
+		     struct fs_path *from, struct fs_path *to)
+{
+	int ret;
+
+verbose_printk("btrfs: send_rename %s -> %s\n", from->start, to->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_RENAME);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, from);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_TO, to);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends a link instruction to user space
+ */
+static int send_link(struct send_ctx *sctx,
+		     struct fs_path *path, struct fs_path *lnk)
+{
+	int ret;
+
+verbose_printk("btrfs: send_link %s -> %s\n", path->start, lnk->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_LINK);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_LINK, lnk);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends an unlink instruction to user space
+ */
+static int send_unlink(struct send_ctx *sctx, struct fs_path *path)
+{
+	int ret;
+
+verbose_printk("btrfs: send_unlink %s\n", path->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_UNLINK);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Sends a rmdir instruction to user space
+ */
+static int send_rmdir(struct send_ctx *sctx, struct fs_path *path)
+{
+	int ret;
+
+verbose_printk("btrfs: send_rmdir %s\n", path->start);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_RMDIR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+/*
+ * Helper function to retrieve some fields from an inode item.
+ */
+static int get_inode_info(struct btrfs_root *root,
+			  u64 ino, u64 *size, u64 *gen,
+			  u64 *mode, u64 *uid, u64 *gid)
+{
+	int ret;
+	struct btrfs_inode_item *ii;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_inode_item);
+	if (size)
+		*size = btrfs_inode_size(path->nodes[0], ii);
+	if (gen)
+		*gen = btrfs_inode_generation(path->nodes[0], ii);
+	if (mode)
+		*mode = btrfs_inode_mode(path->nodes[0], ii);
+	if (uid)
+		*uid = btrfs_inode_uid(path->nodes[0], ii);
+	if (gid)
+		*gid = btrfs_inode_gid(path->nodes[0], ii);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+typedef int (*iterate_inode_ref_t)(int num, u64 dir, int index,
+				   struct fs_path *p,
+				   void *ctx);
+
+/*
+ * Helper function to iterate the entries in ONE btrfs_inode_ref.
+ * The iterate callback may return a non zero value to stop iteration. This can
+ * be a negative value for error codes or 1 to simply stop it.
+ *
+ * path must point to the INODE_REF when called.
+ */
+static int iterate_inode_ref(struct send_ctx *sctx,
+			     struct btrfs_root *root, struct btrfs_path *path,
+			     struct btrfs_key *found_key, int resolve,
+			     iterate_inode_ref_t iterate, void *ctx)
+{
+	struct extent_buffer *eb;
+	struct btrfs_item *item;
+	struct btrfs_inode_ref *iref;
+	struct btrfs_path *tmp_path;
+	struct fs_path *p;
+	u32 cur;
+	u32 len;
+	u32 total;
+	int slot;
+	u32 name_len;
+	char *start;
+	int ret = 0;
+	int num;
+	int index;
+
+	p = fs_path_alloc_reversed(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	tmp_path = alloc_path_for_send();
+	if (!tmp_path) {
+		fs_path_free(sctx, p);
+		return -ENOMEM;
+	}
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	item = btrfs_item_nr(eb, slot);
+	iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
+	cur = 0;
+	len = 0;
+	total = btrfs_item_size(eb, item);
+
+	num = 0;
+	while (cur < total) {
+		fs_path_reset(p);
+
+		name_len = btrfs_inode_ref_name_len(eb, iref);
+		index = btrfs_inode_ref_index(eb, iref);
+		if (resolve) {
+			start = btrfs_iref_to_path(root, tmp_path, iref, eb,
+						found_key->offset, p->buf,
+						p->buf_len);
+			if (IS_ERR(start)) {
+				ret = PTR_ERR(start);
+				goto out;
+			}
+			if (start < p->buf) {
+				/* overflow , try again with larger buffer */
+				ret = fs_path_ensure_buf(p,
+						p->buf_len + p->buf - start);
+				if (ret < 0)
+					goto out;
+				start = btrfs_iref_to_path(root, tmp_path, iref,
+						eb, found_key->offset, p->buf,
+						p->buf_len);
+				if (IS_ERR(start)) {
+					ret = PTR_ERR(start);
+					goto out;
+				}
+				BUG_ON(start < p->buf);
+			}
+			p->start = start;
+		} else {
+			ret = fs_path_add_from_extent_buffer(p, eb,
+					(unsigned long)(iref + 1), name_len);
+			if (ret < 0)
+				goto out;
+		}
+
+
+		len = sizeof(*iref) + name_len;
+		iref = (struct btrfs_inode_ref *)((char *)iref + len);
+		cur += len;
+
+		ret = iterate(num, found_key->offset, index, p, ctx);
+		if (ret)
+			goto out;
+
+		num++;
+	}
+
+out:
+	btrfs_free_path(tmp_path);
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+typedef int (*iterate_dir_item_t)(int num, struct btrfs_key *di_key,
+				  const char *name, int name_len,
+				  const char *data, int data_len,
+				  u8 type, void *ctx);
+
+/*
+ * Helper function to iterate the entries in ONE btrfs_dir_item.
+ * The iterate callback may return a non zero value to stop iteration. This can
+ * be a negative value for error codes or 1 to simply stop it.
+ *
+ * path must point to the dir item when called.
+ */
+static int iterate_dir_item(struct send_ctx *sctx,
+			    struct btrfs_root *root, struct btrfs_path *path,
+			    struct btrfs_key *found_key,
+			    iterate_dir_item_t iterate, void *ctx)
+{
+	int ret = 0;
+	struct extent_buffer *eb;
+	struct btrfs_item *item;
+	struct btrfs_dir_item *di;
+	struct btrfs_path *tmp_path = NULL;
+	struct btrfs_key di_key;
+	char *buf = NULL;
+	char *buf2 = NULL;
+	int buf_len;
+	int buf_virtual = 0;
+	u32 name_len;
+	u32 data_len;
+	u32 cur;
+	u32 len;
+	u32 total;
+	int slot;
+	int num;
+	u8 type;
+
+	buf_len = PAGE_SIZE;
+	buf = kmalloc(buf_len, GFP_NOFS);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	tmp_path = alloc_path_for_send();
+	if (!tmp_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	item = btrfs_item_nr(eb, slot);
+	di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
+	cur = 0;
+	len = 0;
+	total = btrfs_item_size(eb, item);
+
+	num = 0;
+	while (cur < total) {
+		name_len = btrfs_dir_name_len(eb, di);
+		data_len = btrfs_dir_data_len(eb, di);
+		type = btrfs_dir_type(eb, di);
+		btrfs_dir_item_key_to_cpu(eb, di, &di_key);
+
+		if (name_len + data_len > buf_len) {
+			buf_len = PAGE_ALIGN(name_len + data_len);
+			if (buf_virtual) {
+				buf2 = vmalloc(buf_len);
+				if (!buf2) {
+					ret = -ENOMEM;
+					goto out;
+				}
+				vfree(buf);
+			} else {
+				buf2 = krealloc(buf, buf_len, GFP_NOFS);
+				if (!buf2) {
+					buf2 = vmalloc(buf_len);
+					if (!buf2) {
+						ret = -ENOMEM;
+						goto out;
+					}
+					kfree(buf);
+					buf_virtual = 1;
+				}
+			}
+
+			buf = buf2;
+			buf2 = NULL;
+		}
+
+		read_extent_buffer(eb, buf, (unsigned long)(di + 1),
+				name_len + data_len);
+
+		len = sizeof(*di) + name_len + data_len;
+		di = (struct btrfs_dir_item *)((char *)di + len);
+		cur += len;
+
+		ret = iterate(num, &di_key, buf, name_len, buf + name_len,
+				data_len, type, ctx);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+
+		num++;
+	}
+
+out:
+	btrfs_free_path(tmp_path);
+	if (buf_virtual)
+		vfree(buf);
+	else
+		kfree(buf);
+	return ret;
+}
+
+static int __copy_first_ref(int num, u64 dir, int index,
+			    struct fs_path *p, void *ctx)
+{
+	int ret;
+	struct fs_path *pt = ctx;
+
+	ret = fs_path_copy(pt, p);
+	if (ret < 0)
+		return ret;
+
+	/* we want the first only */
+	return 1;
+}
+
+/*
+ * Retrieve the first path of an inode. If an inode has more then one
+ * ref/hardlink, this is ignored.
+ */
+static int get_inode_path(struct send_ctx *sctx, struct btrfs_root *root,
+			  u64 ino, struct fs_path *path)
+{
+	int ret;
+	struct btrfs_key key, found_key;
+	struct btrfs_path *p;
+
+	p = alloc_path_for_send();
+	if (!p)
+		return -ENOMEM;
+
+	fs_path_reset(path);
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(root, &key, p, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = 1;
+		goto out;
+	}
+	btrfs_item_key_to_cpu(p->nodes[0], &found_key, p->slots[0]);
+	if (found_key.objectid != ino ||
+		found_key.type != BTRFS_INODE_REF_KEY) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = iterate_inode_ref(sctx, root, p, &found_key, 1,
+			__copy_first_ref, path);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	btrfs_free_path(p);
+	return ret;
+}
+
+struct backref_ctx {
+	struct send_ctx *sctx;
+
+	/* number of total found references */
+	u64 found;
+
+	/*
+	 * used for clones found in send_root. clones found behind cur_objectid
+	 * and cur_offset are not considered as allowed clones.
+	 */
+	u64 cur_objectid;
+	u64 cur_offset;
+
+	/* may be truncated in case it's the last extent in a file */
+	u64 extent_len;
+
+	/* Just to check for bugs in backref resolving */
+	int found_in_send_root;
+};
+
+static int __clone_root_cmp_bsearch(const void *key, const void *elt)
+{
+	u64 root = (u64)key;
+	struct clone_root *cr = (struct clone_root *)elt;
+
+	if (root < cr->root->objectid)
+		return -1;
+	if (root > cr->root->objectid)
+		return 1;
+	return 0;
+}
+
+static int __clone_root_cmp_sort(const void *e1, const void *e2)
+{
+	struct clone_root *cr1 = (struct clone_root *)e1;
+	struct clone_root *cr2 = (struct clone_root *)e2;
+
+	if (cr1->root->objectid < cr2->root->objectid)
+		return -1;
+	if (cr1->root->objectid > cr2->root->objectid)
+		return 1;
+	return 0;
+}
+
+/*
+ * Called for every backref that is found for the current extent.
+ */
+static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
+{
+	struct backref_ctx *bctx = ctx_;
+	struct clone_root *found;
+	int ret;
+	u64 i_size;
+
+	/* First check if the root is in the list of accepted clone sources */
+	found = bsearch((void *)root, bctx->sctx->clone_roots,
+			bctx->sctx->clone_roots_cnt,
+			sizeof(struct clone_root),
+			__clone_root_cmp_bsearch);
+	if (!found)
+		return 0;
+
+	if (found->root == bctx->sctx->send_root &&
+	    ino == bctx->cur_objectid &&
+	    offset == bctx->cur_offset) {
+		bctx->found_in_send_root = 1;
+	}
+
+	/*
+	 * There are inodes that have extents that lie behind it's i_size. Don't
+	 * accept clones from these extents.
+	 */
+	ret = get_inode_info(found->root, ino, &i_size, NULL, NULL, NULL, NULL);
+	if (ret < 0)
+		return ret;
+
+	if (offset + bctx->extent_len > i_size)
+		return 0;
+
+	/*
+	 * Make sure we don't consider clones from send_root that are
+	 * behind the current inode/offset.
+	 */
+	if (found->root == bctx->sctx->send_root) {
+		/*
+		 * TODO for the moment we don't accept clones from the inode
+		 * that is currently send. We may change this when
+		 * BTRFS_IOC_CLONE_RANGE supports cloning from and to the same
+		 * file.
+		 */
+		if (ino >= bctx->cur_objectid)
+			return 0;
+		/*if (ino > ctx->cur_objectid)
+			return 0;
+		if (offset + ctx->extent_len > ctx->cur_offset)
+			return 0;*/
+
+		bctx->found++;
+		found->found_refs++;
+		found->ino = ino;
+		found->offset = offset;
+		return 0;
+	}
+
+	bctx->found++;
+	found->found_refs++;
+	if (ino < found->ino) {
+		found->ino = ino;
+		found->offset = offset;
+	} else if (found->ino == ino) {
+		/*
+		 * same extent found more then once in the same file.
+		 */
+		if (found->offset > offset + bctx->extent_len)
+			found->offset = offset;
+	}
+
+	return 0;
+}
+
+/*
+ * path must point to the extent item when called.
+ */
+static int find_extent_clone(struct send_ctx *sctx,
+			     struct btrfs_path *path,
+			     u64 ino, u64 data_offset,
+			     u64 ino_size,
+			     struct clone_root **found)
+{
+	int ret;
+	int extent_type;
+	u64 logical;
+	u64 num_bytes;
+	u64 extent_item_pos;
+	struct btrfs_file_extent_item *fi;
+	struct extent_buffer *eb = path->nodes[0];
+	struct backref_ctx backref_ctx;
+	struct clone_root *cur_clone_root;
+	struct btrfs_key found_key;
+	struct btrfs_path *tmp_path;
+	u32 i;
+
+	tmp_path = alloc_path_for_send();
+	if (!tmp_path)
+		return -ENOMEM;
+
+	if (data_offset >= ino_size) {
+		/*
+		 * There may be extents that lie behind the file's size.
+		 * I at least had this in combination with snapshotting while
+		 * writing large files.
+		 */
+		ret = 0;
+		goto out;
+	}
+
+	fi = btrfs_item_ptr(eb, path->slots[0],
+			struct btrfs_file_extent_item);
+	extent_type = btrfs_file_extent_type(eb, fi);
+	if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	num_bytes = btrfs_file_extent_num_bytes(eb, fi);
+	logical = btrfs_file_extent_disk_bytenr(eb, fi);
+	if (logical == 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+	logical += btrfs_file_extent_offset(eb, fi);
+
+	ret = extent_from_logical(sctx->send_root->fs_info,
+			logical, tmp_path, &found_key);
+	btrfs_release_path(tmp_path);
+
+	if (ret < 0)
+		goto out;
+	if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+		ret = -EIO;
+		goto out;
+	}
+
+	/*
+	 * Setup the clone roots.
+	 */
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		cur_clone_root = sctx->clone_roots + i;
+		cur_clone_root->ino = (u64)-1;
+		cur_clone_root->offset = 0;
+		cur_clone_root->found_refs = 0;
+	}
+
+	backref_ctx.sctx = sctx;
+	backref_ctx.found = 0;
+	backref_ctx.cur_objectid = ino;
+	backref_ctx.cur_offset = data_offset;
+	backref_ctx.found_in_send_root = 0;
+	backref_ctx.extent_len = num_bytes;
+
+	/*
+	 * The last extent of a file may be too large due to page alignment.
+	 * We need to adjust extent_len in this case so that the checks in
+	 * __iterate_backrefs work.
+	 */
+	if (data_offset + num_bytes >= ino_size)
+		backref_ctx.extent_len = ino_size - data_offset;
+
+	/*
+	 * Now collect all backrefs.
+	 */
+	extent_item_pos = logical - found_key.objectid;
+	ret = iterate_extent_inodes(sctx->send_root->fs_info,
+					found_key.objectid, extent_item_pos, 1,
+					__iterate_backrefs, &backref_ctx);
+	if (ret < 0)
+		goto out;
+
+	if (!backref_ctx.found_in_send_root) {
+		/* found a bug in backref code? */
+		ret = -EIO;
+		printk(KERN_ERR "btrfs: ERROR did not find backref in "
+				"send_root. inode=%llu, offset=%llu, "
+				"logical=%llu\n",
+				ino, data_offset, logical);
+		goto out;
+	}
+
+verbose_printk(KERN_DEBUG "btrfs: find_extent_clone: data_offset=%llu, "
+		"ino=%llu, "
+		"num_bytes=%llu, logical=%llu\n",
+		data_offset, ino, num_bytes, logical);
+
+	if (!backref_ctx.found)
+		verbose_printk("btrfs:    no clones found\n");
+
+	cur_clone_root = NULL;
+	for (i = 0; i < sctx->clone_roots_cnt; i++) {
+		if (sctx->clone_roots[i].found_refs) {
+			if (!cur_clone_root)
+				cur_clone_root = sctx->clone_roots + i;
+			else if (sctx->clone_roots[i].root == sctx->send_root)
+				/* prefer clones from send_root over others */
+				cur_clone_root = sctx->clone_roots + i;
+			break;
+		}
+
+	}
+
+	if (cur_clone_root) {
+		*found = cur_clone_root;
+		ret = 0;
+	} else {
+		ret = -ENOENT;
+	}
+
+out:
+	btrfs_free_path(tmp_path);
+	return ret;
+}
+
+static int read_symlink(struct send_ctx *sctx,
+			struct btrfs_root *root,
+			u64 ino,
+			struct fs_path *dest)
+{
+	int ret;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_file_extent_item *ei;
+	u8 type;
+	u8 compression;
+	unsigned long off;
+	int len;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = ino;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	BUG_ON(ret);
+
+	ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_file_extent_item);
+	type = btrfs_file_extent_type(path->nodes[0], ei);
+	compression = btrfs_file_extent_compression(path->nodes[0], ei);
+	BUG_ON(type != BTRFS_FILE_EXTENT_INLINE);
+	BUG_ON(compression);
+
+	off = btrfs_file_extent_inline_start(ei);
+	len = btrfs_file_extent_inline_len(path->nodes[0], ei);
+
+	ret = fs_path_add_from_extent_buffer(dest, path->nodes[0], off, len);
+	if (ret < 0)
+		goto out;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Helper function to generate a file name that is unique in the root of
+ * send_root and parent_root. This is used to generate names for orphan inodes.
+ */
+static int gen_unique_name(struct send_ctx *sctx,
+			   u64 ino, u64 gen,
+			   struct fs_path *dest)
+{
+	int ret = 0;
+	struct btrfs_path *path;
+	struct btrfs_dir_item *di;
+	char tmp[64];
+	int len;
+	u64 idx = 0;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	while (1) {
+		len = snprintf(tmp, sizeof(tmp) - 1, "o%llu-%llu-%llu",
+				ino, gen, idx);
+		if (len >= sizeof(tmp)) {
+			/* should really not happen */
+			ret = -EOVERFLOW;
+			goto out;
+		}
+
+		di = btrfs_lookup_dir_item(NULL, sctx->send_root,
+				path, BTRFS_FIRST_FREE_OBJECTID,
+				tmp, strlen(tmp), 0);
+		btrfs_release_path(path);
+		if (IS_ERR(di)) {
+			ret = PTR_ERR(di);
+			goto out;
+		}
+		if (di) {
+			/* not unique, try again */
+			idx++;
+			continue;
+		}
+
+		if (!sctx->parent_root) {
+			/* unique */
+			ret = 0;
+			break;
+		}
+
+		di = btrfs_lookup_dir_item(NULL, sctx->parent_root,
+				path, BTRFS_FIRST_FREE_OBJECTID,
+				tmp, strlen(tmp), 0);
+		btrfs_release_path(path);
+		if (IS_ERR(di)) {
+			ret = PTR_ERR(di);
+			goto out;
+		}
+		if (di) {
+			/* not unique, try again */
+			idx++;
+			continue;
+		}
+		/* unique */
+		break;
+	}
+
+	ret = fs_path_add(dest, tmp, strlen(tmp));
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+enum inode_state {
+	inode_state_no_change,
+	inode_state_will_create,
+	inode_state_did_create,
+	inode_state_will_delete,
+	inode_state_did_delete,
+};
+
+static int get_cur_inode_state(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret;
+	int left_ret;
+	int right_ret;
+	u64 left_gen;
+	u64 right_gen;
+
+	ret = get_inode_info(sctx->send_root, ino, NULL, &left_gen, NULL, NULL,
+			NULL);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	left_ret = ret;
+
+	if (!sctx->parent_root) {
+		right_ret = -ENOENT;
+	} else {
+		ret = get_inode_info(sctx->parent_root, ino, NULL, &right_gen,
+				NULL, NULL, NULL);
+		if (ret < 0 && ret != -ENOENT)
+			goto out;
+		right_ret = ret;
+	}
+
+	if (!left_ret && !right_ret) {
+		if (left_gen == gen && right_gen == gen)
+			ret = inode_state_no_change;
+		else if (left_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_create;
+			else
+				ret = inode_state_will_create;
+		} else if (right_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_delete;
+			else
+				ret = inode_state_will_delete;
+		} else  {
+			ret = -ENOENT;
+		}
+	} else if (!left_ret) {
+		if (left_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_create;
+			else
+				ret = inode_state_will_create;
+		} else {
+			ret = -ENOENT;
+		}
+	} else if (!right_ret) {
+		if (right_gen == gen) {
+			if (ino < sctx->send_progress)
+				ret = inode_state_did_delete;
+			else
+				ret = inode_state_will_delete;
+		} else {
+			ret = -ENOENT;
+		}
+	} else {
+		ret = -ENOENT;
+	}
+
+out:
+	return ret;
+}
+
+static int is_inode_existent(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret;
+
+	ret = get_cur_inode_state(sctx, ino, gen);
+	if (ret < 0)
+		goto out;
+
+	if (ret == inode_state_no_change ||
+	    ret == inode_state_did_create ||
+	    ret == inode_state_will_delete)
+		ret = 1;
+	else
+		ret = 0;
+
+out:
+	return ret;
+}
+
+/*
+ * Helper function to lookup a dir item in a dir.
+ */
+static int lookup_dir_item_inode(struct btrfs_root *root,
+				 u64 dir, const char *name, int name_len,
+				 u64 *found_inode,
+				 u8 *found_type)
+{
+	int ret = 0;
+	struct btrfs_dir_item *di;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	di = btrfs_lookup_dir_item(NULL, root, path,
+			dir, name, name_len, 0);
+	if (!di) {
+		ret = -ENOENT;
+		goto out;
+	}
+	if (IS_ERR(di)) {
+		ret = PTR_ERR(di);
+		goto out;
+	}
+	btrfs_dir_item_key_to_cpu(path->nodes[0], di, &key);
+	*found_inode = key.objectid;
+	*found_type = btrfs_dir_type(path->nodes[0], di);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int get_first_ref(struct send_ctx *sctx,
+			 struct btrfs_root *root, u64 ino,
+			 u64 *dir, u64 *dir_gen, struct fs_path *name)
+{
+	int ret;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_path *path;
+	struct btrfs_inode_ref *iref;
+	int len;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (!ret)
+		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+				path->slots[0]);
+	if (ret || found_key.objectid != key.objectid ||
+	    found_key.type != key.type) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	iref = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_inode_ref);
+	len = btrfs_inode_ref_name_len(path->nodes[0], iref);
+	ret = fs_path_add_from_extent_buffer(name, path->nodes[0],
+			(unsigned long)(iref + 1), len);
+	if (ret < 0)
+		goto out;
+	btrfs_release_path(path);
+
+	ret = get_inode_info(root, found_key.offset, NULL, dir_gen, NULL, NULL,
+			NULL);
+	if (ret < 0)
+		goto out;
+
+	*dir = found_key.offset;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int is_first_ref(struct send_ctx *sctx,
+			struct btrfs_root *root,
+			u64 ino, u64 dir,
+			const char *name, int name_len)
+{
+	int ret;
+	struct fs_path *tmp_name;
+	u64 tmp_dir;
+	u64 tmp_dir_gen;
+
+	tmp_name = fs_path_alloc(sctx);
+	if (!tmp_name)
+		return -ENOMEM;
+
+	ret = get_first_ref(sctx, root, ino, &tmp_dir, &tmp_dir_gen, tmp_name);
+	if (ret < 0)
+		goto out;
+
+	if (name_len != fs_path_len(tmp_name)) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = memcmp(tmp_name->start, name, name_len);
+	if (ret)
+		ret = 0;
+	else
+		ret = 1;
+
+out:
+	fs_path_free(sctx, tmp_name);
+	return ret;
+}
+
+static int will_overwrite_ref(struct send_ctx *sctx, u64 dir, u64 dir_gen,
+			      const char *name, int name_len,
+			      u64 *who_ino, u64 *who_gen)
+{
+	int ret = 0;
+	u64 other_inode = 0;
+	u8 other_type = 0;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	ret = is_inode_existent(sctx, dir, dir_gen);
+	if (ret <= 0)
+		goto out;
+
+	ret = lookup_dir_item_inode(sctx->parent_root, dir, name, name_len,
+			&other_inode, &other_type);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	if (ret) {
+		ret = 0;
+		goto out;
+	}
+
+	if (other_inode > sctx->send_progress) {
+		ret = get_inode_info(sctx->parent_root, other_inode, NULL,
+				who_gen, NULL, NULL, NULL);
+		if (ret < 0)
+			goto out;
+
+		ret = 1;
+		*who_ino = other_inode;
+	} else {
+		ret = 0;
+	}
+
+out:
+	return ret;
+}
+
+static int did_overwrite_ref(struct send_ctx *sctx,
+			    u64 dir, u64 dir_gen,
+			    u64 ino, u64 ino_gen,
+			    const char *name, int name_len)
+{
+	int ret = 0;
+	u64 gen;
+	u64 ow_inode;
+	u8 other_type;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	ret = is_inode_existent(sctx, dir, dir_gen);
+	if (ret <= 0)
+		goto out;
+
+	/* check if the ref was overwritten by another ref */
+	ret = lookup_dir_item_inode(sctx->send_root, dir, name, name_len,
+			&ow_inode, &other_type);
+	if (ret < 0 && ret != -ENOENT)
+		goto out;
+	if (ret) {
+		/* was never and will never be overwritten */
+		ret = 0;
+		goto out;
+	}
+
+	ret = get_inode_info(sctx->send_root, ow_inode, NULL, &gen, NULL, NULL,
+			NULL);
+	if (ret < 0)
+		goto out;
+
+	if (ow_inode == ino && gen == ino_gen) {
+		ret = 0;
+		goto out;
+	}
+
+	/* we know that it is or will be overwritten. check this now */
+	if (ow_inode < sctx->send_progress)
+		ret = 1;
+	else
+		ret = 0;
+
+out:
+	return ret;
+}
+
+static int did_overwrite_first_ref(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret = 0;
+	struct fs_path *name = NULL;
+	u64 dir;
+	u64 dir_gen;
+
+	if (!sctx->parent_root)
+		goto out;
+
+	name = fs_path_alloc(sctx);
+	if (!name)
+		return -ENOMEM;
+
+	ret = get_first_ref(sctx, sctx->parent_root, ino, &dir, &dir_gen, name);
+	if (ret < 0)
+		goto out;
+
+	ret = did_overwrite_ref(sctx, dir, dir_gen, ino, gen,
+			name->start, fs_path_len(name));
+	if (ret < 0)
+		goto out;
+
+out:
+	fs_path_free(sctx, name);
+	return ret;
+}
+
+static int name_cache_insert(struct send_ctx *sctx,
+			     struct name_cache_entry *nce)
+{
+	int ret = 0;
+	struct name_cache_entry **ncea;
+
+	ncea = radix_tree_lookup(&sctx->name_cache, nce->ino);
+	if (ncea) {
+		if (!ncea[0])
+			ncea[0] = nce;
+		else if (!ncea[1])
+			ncea[1] = nce;
+		else
+			BUG();
+	} else {
+		ncea = kmalloc(sizeof(void *) * 2, GFP_NOFS);
+		if (!ncea)
+			return -ENOMEM;
+
+		ncea[0] = nce;
+		ncea[1] = NULL;
+		ret = radix_tree_insert(&sctx->name_cache, nce->ino, ncea);
+		if (ret < 0)
+			return ret;
+	}
+	list_add_tail(&nce->list, &sctx->name_cache_list);
+	sctx->name_cache_size++;
+
+	return ret;
+}
+
+static void name_cache_delete(struct send_ctx *sctx,
+			      struct name_cache_entry *nce)
+{
+	struct name_cache_entry **ncea;
+
+	ncea = radix_tree_lookup(&sctx->name_cache, nce->ino);
+	BUG_ON(!ncea);
+
+	if (ncea[0] == nce)
+		ncea[0] = NULL;
+	else if (ncea[1] == nce)
+		ncea[1] = NULL;
+	else
+		BUG();
+
+	if (!ncea[0] && !ncea[1]) {
+		radix_tree_delete(&sctx->name_cache, nce->ino);
+		kfree(ncea);
+	}
+
+	list_del(&nce->list);
+
+	sctx->name_cache_size--;
+}
+
+static struct name_cache_entry *name_cache_search(struct send_ctx *sctx,
+						    u64 ino, u64 gen)
+{
+	struct name_cache_entry **ncea;
+
+	ncea = radix_tree_lookup(&sctx->name_cache, ino);
+	if (!ncea)
+		return NULL;
+
+	if (ncea[0] && ncea[0]->gen == gen)
+		return ncea[0];
+	else if (ncea[1] && ncea[1]->gen == gen)
+		return ncea[1];
+	return NULL;
+}
+
+static void name_cache_used(struct send_ctx *sctx, struct name_cache_entry *nce)
+{
+	list_del(&nce->list);
+	list_add_tail(&nce->list, &sctx->name_cache_list);
+}
+
+static void name_cache_clean_unused(struct send_ctx *sctx)
+{
+	struct name_cache_entry *nce;
+
+	if (sctx->name_cache_size < SEND_CTX_NAME_CACHE_CLEAN_SIZE)
+		return;
+
+	while (sctx->name_cache_size > SEND_CTX_MAX_NAME_CACHE_SIZE) {
+		nce = list_entry(sctx->name_cache_list.next,
+				struct name_cache_entry, list);
+		name_cache_delete(sctx, nce);
+		kfree(nce);
+	}
+}
+
+static void name_cache_free(struct send_ctx *sctx)
+{
+	struct name_cache_entry *nce;
+	struct name_cache_entry *tmp;
+
+	list_for_each_entry_safe(nce, tmp, &sctx->name_cache_list, list) {
+		name_cache_delete(sctx, nce);
+	}
+}
+
+static int __get_cur_name_and_parent(struct send_ctx *sctx,
+				     u64 ino, u64 gen,
+				     u64 *parent_ino,
+				     u64 *parent_gen,
+				     struct fs_path *dest)
+{
+	int ret;
+	int nce_ret;
+	struct btrfs_path *path = NULL;
+	struct name_cache_entry *nce = NULL;
+
+	nce = name_cache_search(sctx, ino, gen);
+	if (nce) {
+		if (ino < sctx->send_progress && nce->need_later_update) {
+			name_cache_delete(sctx, nce);
+			kfree(nce);
+			nce = NULL;
+		} else {
+			name_cache_used(sctx, nce);
+			*parent_ino = nce->parent_ino;
+			*parent_gen = nce->parent_gen;
+			ret = fs_path_add(dest, nce->name, nce->name_len);
+			if (ret < 0)
+				goto out;
+			ret = nce->ret;
+			goto out;
+		}
+	}
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	ret = is_inode_existent(sctx, ino, gen);
+	if (ret < 0)
+		goto out;
+
+	if (!ret) {
+		ret = gen_unique_name(sctx, ino, gen, dest);
+		if (ret < 0)
+			goto out;
+		ret = 1;
+		goto out_cache;
+	}
+
+	if (ino < sctx->send_progress)
+		ret = get_first_ref(sctx, sctx->send_root, ino,
+				parent_ino, parent_gen, dest);
+	else
+		ret = get_first_ref(sctx, sctx->parent_root, ino,
+				parent_ino, parent_gen, dest);
+	if (ret < 0)
+		goto out;
+
+	ret = did_overwrite_ref(sctx, *parent_ino, *parent_gen, ino, gen,
+			dest->start, dest->end - dest->start);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		fs_path_reset(dest);
+		ret = gen_unique_name(sctx, ino, gen, dest);
+		if (ret < 0)
+			goto out;
+		ret = 1;
+	}
+
+out_cache:
+	nce = kmalloc(sizeof(*nce) + fs_path_len(dest) + 1, GFP_NOFS);
+	if (!nce) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	nce->ino = ino;
+	nce->gen = gen;
+	nce->parent_ino = *parent_ino;
+	nce->parent_gen = *parent_gen;
+	nce->name_len = fs_path_len(dest);
+	nce->ret = ret;
+	strcpy(nce->name, dest->start);
+	memset(&nce->use_list, 0, sizeof(nce->use_list));
+
+	if (ino < sctx->send_progress)
+		nce->need_later_update = 0;
+	else
+		nce->need_later_update = 1;
+
+	nce_ret = name_cache_insert(sctx, nce);
+	if (nce_ret < 0)
+		ret = nce_ret;
+	name_cache_clean_unused(sctx);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Magic happens here. This function returns the first ref to an inode as it
+ * would look like while receiving the stream at this point in time.
+ * We walk the path up to the root. For every inode in between, we check if it
+ * was already processed/sent. If yes, we continue with the parent as found
+ * in send_root. If not, we continue with the parent as found in parent_root.
+ * If we encounter an inode that was deleted at this point in time, we use the
+ * inodes "orphan" name instead of the real name and stop. Same with new inodes
+ * that were not created yet and overwritten inodes/refs.
+ *
+ * When do we have have orphan inodes:
+ * 1. When an inode is freshly created and thus no valid refs are available yet
+ * 2. When a directory lost all it's refs (deleted) but still has dir items
+ *    inside which were not processed yet (pending for move/delete). If anyone
+ *    tried to get the path to the dir items, it would get a path inside that
+ *    orphan directory.
+ * 3. When an inode is moved around or gets new links, it may overwrite the ref
+ *    of an unprocessed inode. If in that case the first ref would be
+ *    overwritten, the overwritten inode gets "orphanized". Later when we
+ *    process this overwritten inode, it is restored at a new place by moving
+ *    the orphan inode.
+ *
+ * sctx->send_progress tells this function at which point in time receiving
+ * would be.
+ */
+static int get_cur_path(struct send_ctx *sctx, u64 ino, u64 gen,
+			struct fs_path *dest)
+{
+	int ret = 0;
+	struct fs_path *name = NULL;
+	u64 parent_inode = 0;
+	u64 parent_gen = 0;
+	int stop = 0;
+
+	name = fs_path_alloc(sctx);
+	if (!name) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	dest->reversed = 1;
+	fs_path_reset(dest);
+
+	while (!stop && ino != BTRFS_FIRST_FREE_OBJECTID) {
+		fs_path_reset(name);
+
+		ret = __get_cur_name_and_parent(sctx, ino, gen,
+				&parent_inode, &parent_gen, name);
+		if (ret < 0)
+			goto out;
+		if (ret)
+			stop = 1;
+
+		ret = fs_path_add_path(dest, name);
+		if (ret < 0)
+			goto out;
+
+		ino = parent_inode;
+		gen = parent_gen;
+	}
+
+out:
+	fs_path_free(sctx, name);
+	if (!ret)
+		fs_path_unreverse(dest);
+	return ret;
+}
+
+/*
+ * Called for regular files when sending extents data. Opens a struct file
+ * to read from the file.
+ */
+static int open_cur_inode_file(struct send_ctx *sctx)
+{
+	int ret = 0;
+	struct btrfs_key key;
+	struct vfsmount *mnt;
+	struct inode *inode;
+	struct dentry *dentry;
+	struct file *filp;
+	int new = 0;
+
+	if (sctx->cur_inode_filp)
+		goto out;
+
+	key.objectid = sctx->cur_ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+
+	inode = btrfs_iget(sctx->send_root->fs_info->sb, &key, sctx->send_root,
+			&new);
+	if (IS_ERR(inode)) {
+		ret = PTR_ERR(inode);
+		goto out;
+	}
+
+	dentry = d_obtain_alias(inode);
+	inode = NULL;
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		goto out;
+	}
+
+	mnt = mntget(sctx->mnt);
+	filp = dentry_open(dentry, mnt, O_RDONLY | O_LARGEFILE, current_cred());
+	dentry = NULL;
+	mnt = NULL;
+	if (IS_ERR(filp)) {
+		ret = PTR_ERR(filp);
+		goto out;
+	}
+	sctx->cur_inode_filp = filp;
+
+out:
+	/*
+	 * no xxxput required here as every vfs op
+	 * does it by itself on failure
+	 */
+	return ret;
+}
+
+/*
+ * Closes the struct file that was created in open_cur_inode_file
+ */
+static int close_cur_inode_file(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	if (!sctx->cur_inode_filp)
+		goto out;
+
+	ret = filp_close(sctx->cur_inode_filp, NULL);
+	sctx->cur_inode_filp = NULL;
+
+out:
+	return ret;
+}
+
+/*
+ * Sends a BTRFS_SEND_C_SUBVOL command/item to userspace
+ */
+static int send_subvol_begin(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *send_root = sctx->send_root;
+	struct btrfs_root *parent_root = sctx->parent_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_root_ref *ref;
+	struct extent_buffer *leaf;
+	char *name = NULL;
+	int namelen;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	name = kmalloc(BTRFS_PATH_NAME_MAX, GFP_NOFS);
+	if (!name) {
+		btrfs_free_path(path);
+		return -ENOMEM;
+	}
+
+	key.objectid = send_root->objectid;
+	key.type = BTRFS_ROOT_BACKREF_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot_for_read(send_root->fs_info->tree_root,
+				&key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+	if (key.type != BTRFS_ROOT_BACKREF_KEY ||
+	    key.objectid != send_root->objectid) {
+		ret = -ENOENT;
+		goto out;
+	}
+	ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
+	namelen = btrfs_root_ref_name_len(leaf, ref);
+	read_extent_buffer(leaf, name, (unsigned long)(ref + 1), namelen);
+	btrfs_release_path(path);
+
+	if (ret < 0)
+		goto out;
+
+	if (parent_root) {
+		ret = begin_cmd(sctx, BTRFS_SEND_C_SNAPSHOT);
+		if (ret < 0)
+			goto out;
+	} else {
+		ret = begin_cmd(sctx, BTRFS_SEND_C_SUBVOL);
+		if (ret < 0)
+			goto out;
+	}
+
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_PATH, name, namelen);
+	TLV_PUT_UUID(sctx, BTRFS_SEND_A_UUID,
+			sctx->send_root->root_item.uuid);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CTRANSID,
+			sctx->send_root->root_item.ctransid);
+	if (parent_root) {
+		TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+				sctx->parent_root->root_item.uuid);
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_CTRANSID,
+				sctx->parent_root->root_item.ctransid);
+	}
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	btrfs_free_path(path);
+	kfree(name);
+	return ret;
+}
+
+static int send_truncate(struct send_ctx *sctx, u64 ino, u64 gen, u64 size)
+{
+	int ret = 0;
+	struct fs_path *p;
+
+verbose_printk("btrfs: send_truncate %llu size=%llu\n", ino, size);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_TRUNCATE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_SIZE, size);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int send_chmod(struct send_ctx *sctx, u64 ino, u64 gen, u64 mode)
+{
+	int ret = 0;
+	struct fs_path *p;
+
+verbose_printk("btrfs: send_chmod %llu mode=%llu\n", ino, mode);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CHMOD);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_MODE, mode & 07777);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int send_chown(struct send_ctx *sctx, u64 ino, u64 gen, u64 uid, u64 gid)
+{
+	int ret = 0;
+	struct fs_path *p;
+
+verbose_printk("btrfs: send_chown %llu uid=%llu, gid=%llu\n", ino, uid, gid);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CHOWN);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_UID, uid);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_GID, gid);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int send_utimes(struct send_ctx *sctx, u64 ino, u64 gen)
+{
+	int ret = 0;
+	struct fs_path *p = NULL;
+	struct btrfs_inode_item *ii;
+	struct btrfs_path *path = NULL;
+	struct extent_buffer *eb;
+	struct btrfs_key key;
+	int slot;
+
+verbose_printk("btrfs: send_utimes %llu\n", ino);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	path = alloc_path_for_send();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = ino;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_search_slot(NULL, sctx->send_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	ii = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_UTIMES);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, ino, gen, p);
+	if (ret < 0)
+		goto out;
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_ATIME, eb,
+			btrfs_inode_atime(ii));
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_MTIME, eb,
+			btrfs_inode_mtime(ii));
+	TLV_PUT_BTRFS_TIMESPEC(sctx, BTRFS_SEND_A_CTIME, eb,
+			btrfs_inode_ctime(ii));
+	/* TODO otime? */
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Sends a BTRFS_SEND_C_MKXXX or SYMLINK command to user space. We don't have
+ * a valid path yet because we did not process the refs yet. So, the inode
+ * is created as orphan.
+ */
+static int send_create_inode(struct send_ctx *sctx, struct btrfs_path *path,
+			     struct btrfs_key *key)
+{
+	int ret = 0;
+	struct extent_buffer *eb = path->nodes[0];
+	struct btrfs_inode_item *ii;
+	struct fs_path *p;
+	int slot = path->slots[0];
+	int cmd;
+	u64 mode;
+
+verbose_printk("btrfs: send_create_inode %llu\n", sctx->cur_ino);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ii = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
+	mode = btrfs_inode_mode(eb, ii);
+
+	if (S_ISREG(mode))
+		cmd = BTRFS_SEND_C_MKFILE;
+	else if (S_ISDIR(mode))
+		cmd = BTRFS_SEND_C_MKDIR;
+	else if (S_ISLNK(mode))
+		cmd = BTRFS_SEND_C_SYMLINK;
+	else if (S_ISCHR(mode) || S_ISBLK(mode))
+		cmd = BTRFS_SEND_C_MKNOD;
+	else if (S_ISFIFO(mode))
+		cmd = BTRFS_SEND_C_MKFIFO;
+	else if (S_ISSOCK(mode))
+		cmd = BTRFS_SEND_C_MKSOCK;
+	else {
+		printk(KERN_WARNING "btrfs: unexpected inode type %o",
+				(int)(mode & S_IFMT));
+		ret = -ENOTSUPP;
+		goto out;
+	}
+
+	ret = begin_cmd(sctx, cmd);
+	if (ret < 0)
+		goto out;
+
+	ret = gen_unique_name(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_INO, sctx->cur_ino);
+
+	if (S_ISLNK(mode)) {
+		fs_path_reset(p);
+		ret = read_symlink(sctx, sctx->send_root, sctx->cur_ino, p);
+		if (ret < 0)
+			goto out;
+		TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH_LINK, p);
+	} else if (S_ISCHR(mode) || S_ISBLK(mode) ||
+		   S_ISFIFO(mode) || S_ISSOCK(mode)) {
+		TLV_PUT_U64(sctx, BTRFS_SEND_A_RDEV, btrfs_inode_rdev(eb, ii));
+	}
+
+	ret = send_cmd(sctx);
+	if (ret < 0)
+		goto out;
+
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+struct recorded_ref {
+	struct list_head list;
+	char *dir_path;
+	char *name;
+	struct fs_path *full_path;
+	u64 dir;
+	u64 dir_gen;
+	int dir_path_len;
+	int name_len;
+};
+
+/*
+ * We need to process new refs before deleted refs, but compare_tree gives us
+ * everything mixed. So we first record all refs and later process them.
+ * This function is a helper to record one ref.
+ */
+static int record_ref(struct list_head *head, u64 dir,
+		      u64 dir_gen, struct fs_path *path)
+{
+	struct recorded_ref *ref;
+	char *tmp;
+
+	ref = kmalloc(sizeof(*ref), GFP_NOFS);
+	if (!ref)
+		return -ENOMEM;
+
+	ref->dir = dir;
+	ref->dir_gen = dir_gen;
+	ref->full_path = path;
+
+	tmp = strrchr(ref->full_path->start, '/');
+	if (!tmp) {
+		ref->name_len = ref->full_path->end - ref->full_path->start;
+		ref->name = ref->full_path->start;
+		ref->dir_path_len = 0;
+		ref->dir_path = ref->full_path->start;
+	} else {
+		tmp++;
+		ref->name_len = ref->full_path->end - tmp;
+		ref->name = tmp;
+		ref->dir_path = ref->full_path->start;
+		ref->dir_path_len = ref->full_path->end -
+				ref->full_path->start - 1 - ref->name_len;
+	}
+
+	list_add_tail(&ref->list, head);
+	return 0;
+}
+
+static void __free_recorded_refs(struct send_ctx *sctx, struct list_head *head)
+{
+	struct recorded_ref *cur;
+	struct recorded_ref *tmp;
+
+	list_for_each_entry_safe(cur, tmp, head, list) {
+		fs_path_free(sctx, cur->full_path);
+		kfree(cur);
+	}
+	INIT_LIST_HEAD(head);
+}
+
+static void free_recorded_refs(struct send_ctx *sctx)
+{
+	__free_recorded_refs(sctx, &sctx->new_refs);
+	__free_recorded_refs(sctx, &sctx->deleted_refs);
+}
+
+/*
+ * Renames/moves a file/dir to it's orphan name. Used when the first
+ * ref of an unprocessed inode gets overwritten and for all non empty
+ * directories.
+ */
+static int orphanize_inode(struct send_ctx *sctx, u64 ino, u64 gen,
+			  struct fs_path *path)
+{
+	int ret;
+	struct fs_path *orphan;
+
+	orphan = fs_path_alloc(sctx);
+	if (!orphan)
+		return -ENOMEM;
+
+	ret = gen_unique_name(sctx, ino, gen, orphan);
+	if (ret < 0)
+		goto out;
+
+	ret = send_rename(sctx, path, orphan);
+
+out:
+	fs_path_free(sctx, orphan);
+	return ret;
+}
+
+/*
+ * Returns 1 if a directory can be removed at this point in time.
+ * We check this by iterating all dir items and checking if the inode behind
+ * the dir item was already processed.
+ */
+static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 send_progress)
+{
+	int ret = 0;
+	struct btrfs_root *root = sctx->parent_root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_key loc;
+	struct btrfs_dir_item *di;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = dir;
+	key.type = BTRFS_DIR_INDEX_KEY;
+	key.offset = 0;
+
+	while (1) {
+		ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+		if (ret < 0)
+			goto out;
+		if (!ret) {
+			btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+					path->slots[0]);
+		}
+		if (ret || found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			break;
+		}
+
+		di = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				struct btrfs_dir_item);
+		btrfs_dir_item_key_to_cpu(path->nodes[0], di, &loc);
+
+		if (loc.objectid > send_progress) {
+			ret = 0;
+			goto out;
+		}
+
+		btrfs_release_path(path);
+		key.offset = found_key.offset + 1;
+	}
+
+	ret = 1;
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+struct finish_unordered_dir_ctx {
+	struct send_ctx *sctx;
+	struct fs_path *cur_path;
+	struct fs_path *dir_path;
+	u64 dir_ino;
+	int need_delete;
+	int delete_pass;
+};
+
+int __finish_unordered_dir(int num, struct btrfs_key *di_key,
+			   const char *name, int name_len,
+			   const char *data, int data_len,
+			   u8 type, void *ctx)
+{
+	int ret = 0;
+	struct finish_unordered_dir_ctx *fctx = ctx;
+	struct send_ctx *sctx = fctx->sctx;
+	u64 di_gen;
+	u64 di_mode;
+	int is_orphan = 0;
+
+	if (di_key->objectid >= fctx->dir_ino)
+		goto out;
+
+	fs_path_reset(fctx->cur_path);
+
+	ret = get_inode_info(sctx->send_root, di_key->objectid,
+			NULL, &di_gen, &di_mode, NULL, NULL);
+	if (ret < 0)
+		goto out;
+
+	ret = is_first_ref(sctx, sctx->send_root, di_key->objectid,
+			fctx->dir_ino, name, name_len);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		is_orphan = 1;
+		ret = gen_unique_name(sctx, di_key->objectid, di_gen,
+				fctx->cur_path);
+	} else {
+		ret = get_cur_path(sctx, di_key->objectid, di_gen,
+				fctx->cur_path);
+	}
+	if (ret < 0)
+		goto out;
+
+	ret = fs_path_add(fctx->dir_path, name, name_len);
+	if (ret < 0)
+		goto out;
+
+	if (!fctx->delete_pass) {
+		if (S_ISDIR(di_mode)) {
+			ret = send_rename(sctx, fctx->cur_path,
+					fctx->dir_path);
+		} else {
+			ret = send_link(sctx, fctx->dir_path,
+					fctx->cur_path);
+			if (is_orphan)
+				fctx->need_delete = 1;
+		}
+	} else if (!S_ISDIR(di_mode)) {
+		ret = send_unlink(sctx, fctx->cur_path);
+	} else {
+		ret = 0;
+	}
+
+	fs_path_remove(fctx->dir_path);
+
+out:
+	return ret;
+}
+
+/*
+ * Go through all dir items and see if we find refs which could not be created
+ * in the past because the dir did not exist at that time.
+ */
+static int finish_outoforder_dir(struct send_ctx *sctx, u64 dir, u64 dir_gen)
+{
+	int ret = 0;
+	struct btrfs_path *path = NULL;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	struct finish_unordered_dir_ctx fctx;
+	int slot;
+
+	path = alloc_path_for_send();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	memset(&fctx, 0, sizeof(fctx));
+	fctx.sctx = sctx;
+	fctx.cur_path = fs_path_alloc(sctx);
+	fctx.dir_path = fs_path_alloc(sctx);
+	if (!fctx.cur_path || !fctx.dir_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	fctx.dir_ino = dir;
+
+	ret = get_cur_path(sctx, dir, dir_gen, fctx.dir_path);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * We do two passes. The first links in the new refs and the second
+	 * deletes orphans if required. Deletion of orphans is not required for
+	 * directory inodes, as we always have only one ref and use rename
+	 * instead of link for those.
+	 */
+
+again:
+	key.objectid = dir;
+	key.type = BTRFS_DIR_ITEM_KEY;
+	key.offset = 0;
+	while (1) {
+		ret = btrfs_search_slot_for_read(sctx->send_root, &key, path,
+				1, 0);
+		if (ret < 0)
+			goto out;
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			btrfs_release_path(path);
+			break;
+		}
+
+		ret = iterate_dir_item(sctx, sctx->send_root, path,
+				&found_key, __finish_unordered_dir,
+				&fctx);
+		if (ret < 0)
+			goto out;
+
+		key.offset = found_key.offset + 1;
+		btrfs_release_path(path);
+	}
+
+	if (!fctx.delete_pass && fctx.need_delete) {
+		fctx.delete_pass = 1;
+		goto again;
+	}
+
+out:
+	btrfs_free_path(path);
+	fs_path_free(sctx, fctx.cur_path);
+	fs_path_free(sctx, fctx.dir_path);
+	return ret;
+}
+
+/*
+ * This does all the move/link/unlink/rmdir magic.
+ */
+static int process_recorded_refs(struct send_ctx *sctx)
+{
+	int ret = 0;
+	struct recorded_ref *cur;
+	struct ulist *check_dirs = NULL;
+	struct ulist_iterator uit;
+	struct ulist_node *un;
+	struct fs_path *valid_path = NULL;
+	u64 ow_inode;
+	u64 ow_gen;
+	int did_overwrite = 0;
+	int is_orphan = 0;
+
+verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
+
+	valid_path = fs_path_alloc(sctx);
+	if (!valid_path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	check_dirs = ulist_alloc(GFP_NOFS);
+	if (!check_dirs) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * First, check if the first ref of the current inode was overwritten
+	 * before. If yes, we know that the current inode was already orphanized
+	 * and thus use the orphan name. If not, we can use get_cur_path to
+	 * get the path of the first ref as it would like while receiving at
+	 * this point in time.
+	 * New inodes are always orphan at the beginning, so force to use the
+	 * orphan name in this case.
+	 * The first ref is stored in valid_path and will be updated if it
+	 * gets moved around.
+	 */
+	if (!sctx->cur_inode_new) {
+		ret = did_overwrite_first_ref(sctx, sctx->cur_ino,
+				sctx->cur_inode_gen);
+		if (ret < 0)
+			goto out;
+		if (ret)
+			did_overwrite = 1;
+	}
+	if (sctx->cur_inode_new || did_overwrite) {
+		ret = gen_unique_name(sctx, sctx->cur_ino,
+				sctx->cur_inode_gen, valid_path);
+		if (ret < 0)
+			goto out;
+		is_orphan = 1;
+	} else {
+		ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				valid_path);
+		if (ret < 0)
+			goto out;
+	}
+
+	list_for_each_entry(cur, &sctx->new_refs, list) {
+		/*
+		 * Check if this new ref would overwrite the first ref of
+		 * another unprocessed inode. If yes, orphanize the
+		 * overwritten inode. If we find an overwritten ref that is
+		 * not the first ref, simply unlink it.
+		 */
+		ret = will_overwrite_ref(sctx, cur->dir, cur->dir_gen,
+				cur->name, cur->name_len,
+				&ow_inode, &ow_gen);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = is_first_ref(sctx, sctx->parent_root,
+					ow_inode, cur->dir, cur->name,
+					cur->name_len);
+			if (ret < 0)
+				goto out;
+			if (ret) {
+				ret = orphanize_inode(sctx, ow_inode, ow_gen,
+						cur->full_path);
+				if (ret < 0)
+					goto out;
+			} else {
+				ret = send_unlink(sctx, cur->full_path);
+				if (ret < 0)
+					goto out;
+			}
+		}
+
+		/*
+		 * link/move the ref to the new place. If we have an orphan
+		 * inode, move it and update valid_path. If not, link or move
+		 * it depending on the inode mode.
+		 */
+		if (is_orphan && !sctx->cur_inode_first_ref_orphan) {
+			ret = send_rename(sctx, valid_path, cur->full_path);
+			if (ret < 0)
+				goto out;
+			is_orphan = 0;
+			ret = fs_path_copy(valid_path, cur->full_path);
+			if (ret < 0)
+				goto out;
+		} else {
+			if (S_ISDIR(sctx->cur_inode_mode)) {
+				/*
+				 * Dirs can't be linked, so move it. For moved
+				 * dirs, we always have one new and one deleted
+				 * ref. The deleted ref is ignored later.
+				 */
+				ret = send_rename(sctx, valid_path,
+						cur->full_path);
+				if (ret < 0)
+					goto out;
+				ret = fs_path_copy(valid_path, cur->full_path);
+				if (ret < 0)
+					goto out;
+			} else {
+				ret = send_link(sctx, cur->full_path,
+						valid_path);
+				if (ret < 0)
+					goto out;
+			}
+		}
+		ret = ulist_add(check_dirs, cur->dir, cur->dir_gen,
+				GFP_NOFS);
+		if (ret < 0)
+			goto out;
+	}
+
+	if (S_ISDIR(sctx->cur_inode_mode) && sctx->cur_inode_deleted) {
+		/*
+		 * Check if we can already rmdir the directory. If not,
+		 * orphanize it. For every dir item inside that gets deleted
+		 * later, we do this check again and rmdir it then if possible.
+		 * See the use of check_dirs for more details.
+		 */
+		ret = can_rmdir(sctx, sctx->cur_ino, sctx->cur_ino);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = send_rmdir(sctx, valid_path);
+			if (ret < 0)
+				goto out;
+		} else if (!is_orphan) {
+			ret = orphanize_inode(sctx, sctx->cur_ino,
+					sctx->cur_inode_gen, valid_path);
+			if (ret < 0)
+				goto out;
+			is_orphan = 1;
+		}
+
+		list_for_each_entry(cur, &sctx->deleted_refs, list) {
+			ret = ulist_add(check_dirs, cur->dir, cur->dir_gen,
+					GFP_NOFS);
+			if (ret < 0)
+				goto out;
+		}
+	} else if (!S_ISDIR(sctx->cur_inode_mode)) {
+		/*
+		 * We have a non dir inode. Go through all deleted refs and
+		 * unlink them if they were not already overwritten by other
+		 * inodes.
+		 */
+		list_for_each_entry(cur, &sctx->deleted_refs, list) {
+			ret = did_overwrite_ref(sctx, cur->dir, cur->dir_gen,
+					sctx->cur_ino, sctx->cur_inode_gen,
+					cur->name, cur->name_len);
+			if (ret < 0)
+				goto out;
+			if (!ret) {
+				/*
+				 * In case the inode was moved to a directory
+				 * that was not created yet (see
+				 * __record_new_ref), we can not unlink the ref
+				 * as it will be needed later when the parent
+				 * directory is created, so that we can move in
+				 * the inode to the new dir.
+				 */
+				if (!is_orphan &&
+				    sctx->cur_inode_first_ref_orphan) {
+					ret = orphanize_inode(sctx,
+							sctx->cur_ino,
+							sctx->cur_inode_gen,
+							cur->full_path);
+					if (ret < 0)
+						goto out;
+					ret = gen_unique_name(sctx,
+							sctx->cur_ino,
+							sctx->cur_inode_gen,
+							valid_path);
+					if (ret < 0)
+						goto out;
+					is_orphan = 1;
+
+				} else {
+					ret = send_unlink(sctx, cur->full_path);
+					if (ret < 0)
+						goto out;
+				}
+			}
+			ret = ulist_add(check_dirs, cur->dir, cur->dir_gen,
+					GFP_NOFS);
+			if (ret < 0)
+				goto out;
+		}
+
+		/*
+		 * If the inode is still orphan, unlink the orphan. This may
+		 * happen when a previous inode did overwrite the first ref
+		 * of this inode and no new refs were added for the current
+		 * inode.
+		 * We can however not delete the orphan in case the inode relies
+		 * in a directory that was not created yet (see
+		 * __record_new_ref)
+		 */
+		if (is_orphan && !sctx->cur_inode_first_ref_orphan) {
+			ret = send_unlink(sctx, valid_path);
+			if (ret < 0)
+				goto out;
+		}
+	}
+
+	/*
+	 * We did collect all parent dirs where cur_inode was once located. We
+	 * now go through all these dirs and check if they are pending for
+	 * deletion and if it's finally possible to perform the rmdir now.
+	 * We also update the inode stats of the parent dirs here.
+	 */
+	ULIST_ITER_INIT(&uit);
+	while ((un = ulist_next(check_dirs, &uit))) {
+		if (un->val > sctx->cur_ino)
+			continue;
+
+		ret = get_cur_inode_state(sctx, un->val, un->aux);
+		if (ret < 0)
+			goto out;
+
+		if (ret == inode_state_did_create ||
+		    ret == inode_state_no_change) {
+			/* TODO delayed utimes */
+			ret = send_utimes(sctx, un->val, un->aux);
+			if (ret < 0)
+				goto out;
+		} else if (ret == inode_state_did_delete) {
+			ret = can_rmdir(sctx, un->val, sctx->cur_ino);
+			if (ret < 0)
+				goto out;
+			if (ret) {
+				ret = get_cur_path(sctx, un->val, un->aux,
+						valid_path);
+				if (ret < 0)
+					goto out;
+				ret = send_rmdir(sctx, valid_path);
+				if (ret < 0)
+					goto out;
+			}
+		}
+	}
+
+	/*
+	 * Current inode is now at it's new position, so we must increase
+	 * send_progress
+	 */
+	sctx->send_progress = sctx->cur_ino + 1;
+
+	/*
+	 * We may have a directory here that has pending refs which could not
+	 * be created before (because the dir did not exist before, see
+	 * __record_new_ref). finish_outoforder_dir will link/move the pending
+	 * refs.
+	 */
+	if (S_ISDIR(sctx->cur_inode_mode) && sctx->cur_inode_new) {
+		ret = finish_outoforder_dir(sctx, sctx->cur_ino,
+				sctx->cur_inode_gen);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = 0;
+
+out:
+	free_recorded_refs(sctx);
+	ulist_free(check_dirs);
+	fs_path_free(sctx, valid_path);
+	return ret;
+}
+
+static int __record_new_ref(int num, u64 dir, int index,
+			    struct fs_path *name,
+			    void *ctx)
+{
+	int ret = 0;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+	u64 gen;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = get_inode_info(sctx->send_root, dir, NULL, &gen, NULL, NULL,
+			NULL);
+	if (ret < 0)
+		goto out;
+
+	/*
+	 * The parent may be non-existent at this point in time. This happens
+	 * if the ino of the parent dir is higher then the current ino. In this
+	 * case, we can not process this ref until the parent dir is finally
+	 * created. If we reach the parent dir later, process_recorded_refs
+	 * will go through all dir items and process the refs that could not be
+	 * processed before. In case this is the first ref, we set
+	 * cur_inode_first_ref_orphan to 1 to inform process_recorded_refs to
+	 * keep an orphan of the inode so that it later can be used for
+	 * link/move
+	 */
+	ret = is_inode_existent(sctx, dir, gen);
+	if (ret < 0)
+		goto out;
+	if (!ret) {
+		ret = is_first_ref(sctx, sctx->send_root, sctx->cur_ino, dir,
+				name->start, fs_path_len(name));
+		if (ret < 0)
+			goto out;
+		if (ret)
+			sctx->cur_inode_first_ref_orphan = 1;
+		ret = 0;
+		goto out;
+	}
+
+	ret = get_cur_path(sctx, dir, gen, p);
+	if (ret < 0)
+		goto out;
+	ret = fs_path_add_path(p, name);
+	if (ret < 0)
+		goto out;
+
+	ret = record_ref(&sctx->new_refs, dir, gen, p);
+
+out:
+	if (ret)
+		fs_path_free(sctx, p);
+	return ret;
+}
+
+static int __record_deleted_ref(int num, u64 dir, int index,
+				struct fs_path *name,
+				void *ctx)
+{
+	int ret = 0;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+	u64 gen;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = get_inode_info(sctx->parent_root, dir, NULL, &gen, NULL, NULL,
+			NULL);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, dir, gen, p);
+	if (ret < 0)
+		goto out;
+	ret = fs_path_add_path(p, name);
+	if (ret < 0)
+		goto out;
+
+	ret = record_ref(&sctx->deleted_refs, dir, gen, p);
+
+out:
+	if (ret)
+		fs_path_free(sctx, p);
+	return ret;
+}
+
+static int record_new_ref(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = iterate_inode_ref(sctx, sctx->send_root, sctx->left_path,
+			sctx->cmp_key, 0, __record_new_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+static int record_deleted_ref(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = iterate_inode_ref(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, 0, __record_deleted_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+struct find_ref_ctx {
+	u64 dir;
+	struct fs_path *name;
+	int found_idx;
+};
+
+static int __find_iref(int num, u64 dir, int index,
+		       struct fs_path *name,
+		       void *ctx_)
+{
+	struct find_ref_ctx *ctx = ctx_;
+
+	if (dir == ctx->dir && fs_path_len(name) == fs_path_len(ctx->name) &&
+	    strncmp(name->start, ctx->name->start, fs_path_len(name)) == 0) {
+		ctx->found_idx = num;
+		return 1;
+	}
+	return 0;
+}
+
+static int find_iref(struct send_ctx *sctx,
+		     struct btrfs_root *root,
+		     struct btrfs_path *path,
+		     struct btrfs_key *key,
+		     u64 dir, struct fs_path *name)
+{
+	int ret;
+	struct find_ref_ctx ctx;
+
+	ctx.dir = dir;
+	ctx.name = name;
+	ctx.found_idx = -1;
+
+	ret = iterate_inode_ref(sctx, root, path, key, 0, __find_iref, &ctx);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.found_idx == -1)
+		return -ENOENT;
+
+	return ctx.found_idx;
+}
+
+static int __record_changed_new_ref(int num, u64 dir, int index,
+				    struct fs_path *name,
+				    void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = find_iref(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, dir, name);
+	if (ret == -ENOENT)
+		ret = __record_new_ref(num, dir, index, name, sctx);
+	else if (ret > 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int __record_changed_deleted_ref(int num, u64 dir, int index,
+					struct fs_path *name,
+					void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = find_iref(sctx, sctx->send_root, sctx->left_path, sctx->cmp_key,
+			dir, name);
+	if (ret == -ENOENT)
+		ret = __record_deleted_ref(num, dir, index, name, sctx);
+	else if (ret > 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int record_changed_ref(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_inode_ref(sctx, sctx->send_root, sctx->left_path,
+			sctx->cmp_key, 0, __record_changed_new_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = iterate_inode_ref(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, 0, __record_changed_deleted_ref, sctx);
+	if (ret < 0)
+		goto out;
+	ret = 0;
+
+out:
+	return ret;
+}
+
+/*
+ * Record and process all refs at once. Needed when an inode changes the
+ * generation number, which means that it was deleted and recreated.
+ */
+static int process_all_refs(struct send_ctx *sctx,
+			    enum btrfs_compare_tree_result cmd)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+	iterate_inode_ref_t cb;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	if (cmd == BTRFS_COMPARE_TREE_NEW) {
+		root = sctx->send_root;
+		cb = __record_new_ref;
+	} else if (cmd == BTRFS_COMPARE_TREE_DELETED) {
+		root = sctx->parent_root;
+		cb = __record_deleted_ref;
+	} else {
+		BUG();
+	}
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_INODE_REF_KEY;
+	key.offset = 0;
+	while (1) {
+		ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+		if (ret < 0) {
+			btrfs_release_path(path);
+			goto out;
+		}
+		if (ret) {
+			btrfs_release_path(path);
+			break;
+		}
+
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			btrfs_release_path(path);
+			break;
+		}
+
+		ret = iterate_inode_ref(sctx, sctx->parent_root, path,
+				&found_key, 0, cb, sctx);
+		btrfs_release_path(path);
+		if (ret < 0)
+			goto out;
+
+		key.offset = found_key.offset + 1;
+	}
+
+	ret = process_recorded_refs(sctx);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int send_set_xattr(struct send_ctx *sctx,
+			  struct fs_path *path,
+			  const char *name, int name_len,
+			  const char *data, int data_len)
+{
+	int ret = 0;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_SET_XATTR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_XATTR_NAME, name, name_len);
+	TLV_PUT(sctx, BTRFS_SEND_A_XATTR_DATA, data, data_len);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+static int send_remove_xattr(struct send_ctx *sctx,
+			  struct fs_path *path,
+			  const char *name, int name_len)
+{
+	int ret = 0;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_REMOVE_XATTR);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, path);
+	TLV_PUT_STRING(sctx, BTRFS_SEND_A_XATTR_NAME, name, name_len);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	return ret;
+}
+
+static int __process_new_xattr(int num, struct btrfs_key *di_key,
+			       const char *name, int name_len,
+			       const char *data, int data_len,
+			       u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+	posix_acl_xattr_header dummy_acl;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	/*
+	 * This hack is needed because empty acl's are stored as zero byte
+	 * data in xattrs. Problem with that is, that receiving these zero byte
+	 * acl's will fail later. To fix this, we send a dummy acl list that
+	 * only contains the version number and no entries.
+	 */
+	if (!strncmp(name, XATTR_NAME_POSIX_ACL_ACCESS, name_len) ||
+	    !strncmp(name, XATTR_NAME_POSIX_ACL_DEFAULT, name_len)) {
+		if (data_len == 0) {
+			dummy_acl.a_version =
+					cpu_to_le32(POSIX_ACL_XATTR_VERSION);
+			data = (char *)&dummy_acl;
+			data_len = sizeof(dummy_acl);
+		}
+	}
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	ret = send_set_xattr(sctx, p, name, name_len, data, data_len);
+
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int __process_deleted_xattr(int num, struct btrfs_key *di_key,
+				   const char *name, int name_len,
+				   const char *data, int data_len,
+				   u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	struct fs_path *p;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	ret = send_remove_xattr(sctx, p, name, name_len);
+
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int process_new_xattr(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_dir_item(sctx, sctx->send_root, sctx->left_path,
+			sctx->cmp_key, __process_new_xattr, sctx);
+
+	return ret;
+}
+
+static int process_deleted_xattr(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = iterate_dir_item(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, __process_deleted_xattr, sctx);
+
+	return ret;
+}
+
+struct find_xattr_ctx {
+	const char *name;
+	int name_len;
+	int found_idx;
+	char *found_data;
+	int found_data_len;
+};
+
+static int __find_xattr(int num, struct btrfs_key *di_key,
+			const char *name, int name_len,
+			const char *data, int data_len,
+			u8 type, void *vctx)
+{
+	struct find_xattr_ctx *ctx = vctx;
+
+	if (name_len == ctx->name_len &&
+	    strncmp(name, ctx->name, name_len) == 0) {
+		ctx->found_idx = num;
+		ctx->found_data_len = data_len;
+		ctx->found_data = kmalloc(data_len, GFP_NOFS);
+		if (!ctx->found_data)
+			return -ENOMEM;
+		memcpy(ctx->found_data, data, data_len);
+		return 1;
+	}
+	return 0;
+}
+
+static int find_xattr(struct send_ctx *sctx,
+		      struct btrfs_root *root,
+		      struct btrfs_path *path,
+		      struct btrfs_key *key,
+		      const char *name, int name_len,
+		      char **data, int *data_len)
+{
+	int ret;
+	struct find_xattr_ctx ctx;
+
+	ctx.name = name;
+	ctx.name_len = name_len;
+	ctx.found_idx = -1;
+	ctx.found_data = NULL;
+	ctx.found_data_len = 0;
+
+	ret = iterate_dir_item(sctx, root, path, key, __find_xattr, &ctx);
+	if (ret < 0)
+		return ret;
+
+	if (ctx.found_idx == -1)
+		return -ENOENT;
+	if (data) {
+		*data = ctx.found_data;
+		*data_len = ctx.found_data_len;
+	} else {
+		kfree(ctx.found_data);
+	}
+	return ctx.found_idx;
+}
+
+
+static int __process_changed_new_xattr(int num, struct btrfs_key *di_key,
+				       const char *name, int name_len,
+				       const char *data, int data_len,
+				       u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+	char *found_data = NULL;
+	int found_data_len  = 0;
+	struct fs_path *p = NULL;
+
+	ret = find_xattr(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, name, name_len, &found_data,
+			&found_data_len);
+	if (ret == -ENOENT) {
+		ret = __process_new_xattr(num, di_key, name, name_len, data,
+				data_len, type, ctx);
+	} else if (ret >= 0) {
+		if (data_len != found_data_len ||
+		    memcmp(data, found_data, data_len)) {
+			ret = __process_new_xattr(num, di_key, name, name_len,
+					data, data_len, type, ctx);
+		} else {
+			ret = 0;
+		}
+	}
+
+	kfree(found_data);
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int __process_changed_deleted_xattr(int num, struct btrfs_key *di_key,
+					   const char *name, int name_len,
+					   const char *data, int data_len,
+					   u8 type, void *ctx)
+{
+	int ret;
+	struct send_ctx *sctx = ctx;
+
+	ret = find_xattr(sctx, sctx->send_root, sctx->left_path, sctx->cmp_key,
+			name, name_len, NULL, NULL);
+	if (ret == -ENOENT)
+		ret = __process_deleted_xattr(num, di_key, name, name_len, data,
+				data_len, type, ctx);
+	else if (ret >= 0)
+		ret = 0;
+
+	return ret;
+}
+
+static int process_changed_xattr(struct send_ctx *sctx)
+{
+	int ret = 0;
+
+	ret = iterate_dir_item(sctx, sctx->send_root, sctx->left_path,
+			sctx->cmp_key, __process_changed_new_xattr, sctx);
+	if (ret < 0)
+		goto out;
+	ret = iterate_dir_item(sctx, sctx->parent_root, sctx->right_path,
+			sctx->cmp_key, __process_changed_deleted_xattr, sctx);
+
+out:
+	return ret;
+}
+
+static int process_all_new_xattrs(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	root = sctx->send_root;
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_XATTR_ITEM_KEY;
+	key.offset = 0;
+	while (1) {
+		ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			ret = 0;
+			goto out;
+		}
+
+		ret = iterate_dir_item(sctx, root, path, &found_key,
+				__process_new_xattr, sctx);
+		if (ret < 0)
+			goto out;
+
+		btrfs_release_path(path);
+		key.offset = found_key.offset + 1;
+	}
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Read some bytes from the current inode/file and send a write command to
+ * user space.
+ */
+static int send_write(struct send_ctx *sctx, u64 offset, u32 len)
+{
+	int ret = 0;
+	struct fs_path *p;
+	loff_t pos = offset;
+	int readed;
+	mm_segment_t old_fs;
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	/*
+	 * vfs normally only accepts user space buffers for security reasons.
+	 * we only read from the file and also only provide the read_buf buffer
+	 * to vfs. As this buffer does not come from a user space call, it's
+	 * ok to temporary allow kernel space buffers.
+	 */
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+
+verbose_printk("btrfs: send_write offset=%llu, len=%d\n", offset, len);
+
+	ret = open_cur_inode_file(sctx);
+	if (ret < 0)
+		goto out;
+
+	ret = vfs_read(sctx->cur_inode_filp, sctx->read_buf, len, &pos);
+	if (ret < 0)
+		goto out;
+	readed = ret;
+	if (!readed)
+		goto out;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_WRITE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+	TLV_PUT(sctx, BTRFS_SEND_A_DATA, sctx->read_buf, readed);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	set_fs(old_fs);
+	if (ret < 0)
+		return ret;
+	return readed;
+}
+
+/*
+ * Send a clone command to user space.
+ */
+static int send_clone(struct send_ctx *sctx,
+		      u64 offset, u32 len,
+		      struct clone_root *clone_root)
+{
+	int ret = 0;
+	struct btrfs_root *clone_root2 = clone_root->root;
+	struct fs_path *p;
+	u64 gen;
+
+verbose_printk("btrfs: send_clone offset=%llu, len=%d, clone_root=%llu, "
+	       "clone_inode=%llu, clone_offset=%llu\n", offset, len,
+		clone_root->root->objectid, clone_root->ino,
+		clone_root->offset);
+
+	p = fs_path_alloc(sctx);
+	if (!p)
+		return -ENOMEM;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_CLONE);
+	if (ret < 0)
+		goto out;
+
+	ret = get_cur_path(sctx, sctx->cur_ino, sctx->cur_inode_gen, p);
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_FILE_OFFSET, offset);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_LEN, len);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_PATH, p);
+
+	if (clone_root2 == sctx->send_root) {
+		ret = get_inode_info(sctx->send_root, clone_root->ino, NULL,
+				&gen, NULL, NULL, NULL);
+		if (ret < 0)
+			goto out;
+		ret = get_cur_path(sctx, clone_root->ino, gen, p);
+	} else {
+		ret = get_inode_path(sctx, clone_root2, clone_root->ino, p);
+	}
+	if (ret < 0)
+		goto out;
+
+	TLV_PUT_UUID(sctx, BTRFS_SEND_A_CLONE_UUID,
+			clone_root2->root_item.uuid);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_CTRANSID,
+			clone_root2->root_item.ctransid);
+	TLV_PUT_PATH(sctx, BTRFS_SEND_A_CLONE_PATH, p);
+	TLV_PUT_U64(sctx, BTRFS_SEND_A_CLONE_OFFSET,
+			clone_root->offset);
+
+	ret = send_cmd(sctx);
+
+tlv_put_failure:
+out:
+	fs_path_free(sctx, p);
+	return ret;
+}
+
+static int send_write_or_clone(struct send_ctx *sctx,
+			       struct btrfs_path *path,
+			       struct btrfs_key *key,
+			       struct clone_root *clone_root)
+{
+	int ret = 0;
+	struct btrfs_file_extent_item *ei;
+	u64 offset = key->offset;
+	u64 pos = 0;
+	u64 len;
+	u32 l;
+	u8 type;
+
+	ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+			struct btrfs_file_extent_item);
+	type = btrfs_file_extent_type(path->nodes[0], ei);
+	if (type == BTRFS_FILE_EXTENT_INLINE)
+		len = btrfs_file_extent_inline_len(path->nodes[0], ei);
+	else
+		len = btrfs_file_extent_num_bytes(path->nodes[0], ei);
+
+	if (offset + len > sctx->cur_inode_size)
+		len = sctx->cur_inode_size - offset;
+	if (len == 0) {
+		ret = 0;
+		goto out;
+	}
+
+	if (!clone_root) {
+		while (pos < len) {
+			l = len - pos;
+			if (l > BTRFS_SEND_READ_SIZE)
+				l = BTRFS_SEND_READ_SIZE;
+			ret = send_write(sctx, pos + offset, l);
+			if (ret < 0)
+				goto out;
+			if (!ret)
+				break;
+			pos += ret;
+		}
+		ret = 0;
+	} else {
+		ret = send_clone(sctx, offset, len, clone_root);
+	}
+
+out:
+	return ret;
+}
+
+static int is_extent_unchanged(struct send_ctx *sctx,
+			       struct btrfs_path *left_path,
+			       struct btrfs_key *ekey)
+{
+	int ret = 0;
+	struct btrfs_key key;
+	struct btrfs_path *path = NULL;
+	struct extent_buffer *eb;
+	int slot;
+	struct btrfs_key found_key;
+	struct btrfs_file_extent_item *ei;
+	u64 left_disknr;
+	u64 right_disknr;
+	u64 left_offset;
+	u64 right_offset;
+	u64 left_offset_fixed;
+	u64 left_len;
+	u64 right_len;
+	u8 left_type;
+	u8 right_type;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	eb = left_path->nodes[0];
+	slot = left_path->slots[0];
+
+	ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+	left_type = btrfs_file_extent_type(eb, ei);
+	left_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+	left_len = btrfs_file_extent_num_bytes(eb, ei);
+	left_offset = btrfs_file_extent_offset(eb, ei);
+
+	if (left_type != BTRFS_FILE_EXTENT_REG) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * Following comments will refer to these graphics. L is the left
+	 * extents which we are checking at the moment. 1-8 are the right
+	 * extents that we iterate.
+	 *
+	 *       |-----L-----|
+	 * |-1-|-2a-|-3-|-4-|-5-|-6-|
+	 *
+	 *       |-----L-----|
+	 * |--1--|-2b-|...(same as above)
+	 *
+	 * Alternative situation. Happens on files where extents got split.
+	 *       |-----L-----|
+	 * |-----------7-----------|-6-|
+	 *
+	 * Alternative situation. Happens on files which got larger.
+	 *       |-----L-----|
+	 * |-8-|
+	 * Nothing follows after 8.
+	 */
+
+	key.objectid = ekey->objectid;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = ekey->offset;
+	ret = btrfs_search_slot_for_read(sctx->parent_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * Handle special case where the right side has no extents at all.
+	 */
+	eb = path->nodes[0];
+	slot = path->slots[0];
+	btrfs_item_key_to_cpu(eb, &found_key, slot);
+	if (found_key.objectid != key.objectid ||
+	    found_key.type != key.type) {
+		ret = 0;
+		goto out;
+	}
+
+	/*
+	 * We're now on 2a, 2b or 7.
+	 */
+	key = found_key;
+	while (key.offset < ekey->offset + left_len) {
+		ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+		right_type = btrfs_file_extent_type(eb, ei);
+		right_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+		right_len = btrfs_file_extent_num_bytes(eb, ei);
+		right_offset = btrfs_file_extent_offset(eb, ei);
+
+		if (right_type != BTRFS_FILE_EXTENT_REG) {
+			ret = 0;
+			goto out;
+		}
+
+		/*
+		 * Are we at extent 8? If yes, we know the extent is changed.
+		 * This may only happen on the first iteration.
+		 */
+		if (found_key.offset + right_len < ekey->offset) {
+			ret = 0;
+			goto out;
+		}
+
+		left_offset_fixed = left_offset;
+		if (key.offset < ekey->offset) {
+			/* Fix the right offset for 2a and 7. */
+			right_offset += ekey->offset - key.offset;
+		} else {
+			/* Fix the left offset for all behind 2a and 2b */
+			left_offset_fixed += key.offset - ekey->offset;
+		}
+
+		/*
+		 * Check if we have the same extent.
+		 */
+		if (left_disknr + left_offset_fixed !=
+				right_disknr + right_offset) {
+			ret = 0;
+			goto out;
+		}
+
+		/*
+		 * Go to the next extent.
+		 */
+		ret = btrfs_next_item(sctx->parent_root, path);
+		if (ret < 0)
+			goto out;
+		if (!ret) {
+			eb = path->nodes[0];
+			slot = path->slots[0];
+			btrfs_item_key_to_cpu(eb, &found_key, slot);
+		}
+		if (ret || found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			key.offset += right_len;
+			break;
+		} else {
+			if (found_key.offset != key.offset + right_len) {
+				/* Should really not happen */
+				ret = -EIO;
+				goto out;
+			}
+		}
+		key = found_key;
+	}
+
+	/*
+	 * We're now behind the left extent (treat as unchanged) or at the end
+	 * of the right side (treat as changed).
+	 */
+	if (key.offset >= ekey->offset + left_len)
+		ret = 1;
+	else
+		ret = 0;
+
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int process_extent(struct send_ctx *sctx,
+			  struct btrfs_path *path,
+			  struct btrfs_key *key)
+{
+	int ret = 0;
+	struct clone_root *found_clone = NULL;
+
+	if (S_ISLNK(sctx->cur_inode_mode))
+		return 0;
+
+	if (sctx->parent_root && !sctx->cur_inode_new) {
+		ret = is_extent_unchanged(sctx, path, key);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+	}
+
+	ret = find_extent_clone(sctx, path, key->objectid, key->offset,
+			sctx->cur_inode_size, &found_clone);
+	if (ret != -ENOENT && ret < 0)
+		goto out;
+
+	ret = send_write_or_clone(sctx, path, key, found_clone);
+
+out:
+	return ret;
+}
+
+static int process_all_extents(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct extent_buffer *eb;
+	int slot;
+
+	root = sctx->send_root;
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = sctx->cmp_key->objectid;
+	key.type = BTRFS_EXTENT_DATA_KEY;
+	key.offset = 0;
+	while (1) {
+		ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret = 0;
+			goto out;
+		}
+
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		if (found_key.objectid != key.objectid ||
+		    found_key.type != key.type) {
+			ret = 0;
+			goto out;
+		}
+
+		ret = process_extent(sctx, path, &found_key);
+		if (ret < 0)
+			goto out;
+
+		btrfs_release_path(path);
+		key.offset = found_key.offset + 1;
+	}
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int process_recorded_refs_if_needed(struct send_ctx *sctx, int at_end)
+{
+	int ret = 0;
+
+	if (sctx->cur_ino == 0)
+		goto out;
+	if (!at_end && sctx->cur_ino == sctx->cmp_key->objectid &&
+	    sctx->cmp_key->type <= BTRFS_INODE_REF_KEY)
+		goto out;
+	if (list_empty(&sctx->new_refs) && list_empty(&sctx->deleted_refs))
+		goto out;
+
+	ret = process_recorded_refs(sctx);
+
+out:
+	return ret;
+}
+
+static int finish_inode_if_needed(struct send_ctx *sctx, int at_end)
+{
+	int ret = 0;
+	u64 left_mode;
+	u64 left_uid;
+	u64 left_gid;
+	u64 right_mode;
+	u64 right_uid;
+	u64 right_gid;
+	int need_chmod = 0;
+	int need_chown = 0;
+
+	ret = process_recorded_refs_if_needed(sctx, at_end);
+	if (ret < 0)
+		goto out;
+
+	if (sctx->cur_ino == 0 || sctx->cur_inode_deleted)
+		goto out;
+	if (!at_end && sctx->cmp_key->objectid == sctx->cur_ino)
+		goto out;
+
+	ret = get_inode_info(sctx->send_root, sctx->cur_ino, NULL, NULL,
+			&left_mode, &left_uid, &left_gid);
+	if (ret < 0)
+		goto out;
+
+	if (!S_ISLNK(sctx->cur_inode_mode)) {
+		if (!sctx->parent_root || sctx->cur_inode_new) {
+			need_chmod = 1;
+			need_chown = 1;
+		} else {
+			ret = get_inode_info(sctx->parent_root, sctx->cur_ino,
+					NULL, NULL, &right_mode, &right_uid,
+					&right_gid);
+			if (ret < 0)
+				goto out;
+
+			if (left_uid != right_uid || left_gid != right_gid)
+				need_chown = 1;
+			if (left_mode != right_mode)
+				need_chmod = 1;
+		}
+	}
+
+	if (S_ISREG(sctx->cur_inode_mode)) {
+		ret = send_truncate(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				sctx->cur_inode_size);
+		if (ret < 0)
+			goto out;
+	}
+
+	if (need_chown) {
+		ret = send_chown(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				left_uid, left_gid);
+		if (ret < 0)
+			goto out;
+	}
+	if (need_chmod) {
+		ret = send_chmod(sctx, sctx->cur_ino, sctx->cur_inode_gen,
+				left_mode);
+		if (ret < 0)
+			goto out;
+	}
+
+	/*
+	 * Need to send that every time, no matter if it actually changed
+	 * between the two trees as we have done changes to the inode before.
+	 */
+	ret = send_utimes(sctx, sctx->cur_ino, sctx->cur_inode_gen);
+	if (ret < 0)
+		goto out;
+
+out:
+	return ret;
+}
+
+static int changed_inode(struct send_ctx *sctx,
+			 enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+	struct btrfs_key *key = sctx->cmp_key;
+	struct btrfs_inode_item *left_ii = NULL;
+	struct btrfs_inode_item *right_ii = NULL;
+	u64 left_gen = 0;
+	u64 right_gen = 0;
+
+	ret = close_cur_inode_file(sctx);
+	if (ret < 0)
+		goto out;
+
+	sctx->cur_ino = key->objectid;
+	sctx->cur_inode_new_gen = 0;
+	sctx->cur_inode_first_ref_orphan = 0;
+	sctx->send_progress = sctx->cur_ino;
+
+	if (result == BTRFS_COMPARE_TREE_NEW ||
+	    result == BTRFS_COMPARE_TREE_CHANGED) {
+		left_ii = btrfs_item_ptr(sctx->left_path->nodes[0],
+				sctx->left_path->slots[0],
+				struct btrfs_inode_item);
+		left_gen = btrfs_inode_generation(sctx->left_path->nodes[0],
+				left_ii);
+	} else {
+		right_ii = btrfs_item_ptr(sctx->right_path->nodes[0],
+				sctx->right_path->slots[0],
+				struct btrfs_inode_item);
+		right_gen = btrfs_inode_generation(sctx->right_path->nodes[0],
+				right_ii);
+	}
+	if (result == BTRFS_COMPARE_TREE_CHANGED) {
+		right_ii = btrfs_item_ptr(sctx->right_path->nodes[0],
+				sctx->right_path->slots[0],
+				struct btrfs_inode_item);
+
+		right_gen = btrfs_inode_generation(sctx->right_path->nodes[0],
+				right_ii);
+		if (left_gen != right_gen)
+			sctx->cur_inode_new_gen = 1;
+	}
+
+	if (result == BTRFS_COMPARE_TREE_NEW) {
+		sctx->cur_inode_gen = left_gen;
+		sctx->cur_inode_new = 1;
+		sctx->cur_inode_deleted = 0;
+		sctx->cur_inode_size = btrfs_inode_size(
+				sctx->left_path->nodes[0], left_ii);
+		sctx->cur_inode_mode = btrfs_inode_mode(
+				sctx->left_path->nodes[0], left_ii);
+		if (sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID)
+			ret = send_create_inode(sctx, sctx->left_path,
+					sctx->cmp_key);
+	} else if (result == BTRFS_COMPARE_TREE_DELETED) {
+		sctx->cur_inode_gen = right_gen;
+		sctx->cur_inode_new = 0;
+		sctx->cur_inode_deleted = 1;
+		sctx->cur_inode_size = btrfs_inode_size(
+				sctx->right_path->nodes[0], right_ii);
+		sctx->cur_inode_mode = btrfs_inode_mode(
+				sctx->right_path->nodes[0], right_ii);
+	} else if (result == BTRFS_COMPARE_TREE_CHANGED) {
+		if (sctx->cur_inode_new_gen) {
+			sctx->cur_inode_gen = right_gen;
+			sctx->cur_inode_new = 0;
+			sctx->cur_inode_deleted = 1;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->right_path->nodes[0], right_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->right_path->nodes[0], right_ii);
+			ret = process_all_refs(sctx,
+					BTRFS_COMPARE_TREE_DELETED);
+			if (ret < 0)
+				goto out;
+
+			sctx->cur_inode_gen = left_gen;
+			sctx->cur_inode_new = 1;
+			sctx->cur_inode_deleted = 0;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->left_path->nodes[0], left_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->left_path->nodes[0], left_ii);
+			ret = send_create_inode(sctx, sctx->left_path,
+					sctx->cmp_key);
+			if (ret < 0)
+				goto out;
+
+			ret = process_all_refs(sctx, BTRFS_COMPARE_TREE_NEW);
+			if (ret < 0)
+				goto out;
+			ret = process_all_extents(sctx);
+			if (ret < 0)
+				goto out;
+			ret = process_all_new_xattrs(sctx);
+			if (ret < 0)
+				goto out;
+		} else {
+			sctx->cur_inode_gen = left_gen;
+			sctx->cur_inode_new = 0;
+			sctx->cur_inode_new_gen = 0;
+			sctx->cur_inode_deleted = 0;
+			sctx->cur_inode_size = btrfs_inode_size(
+					sctx->left_path->nodes[0], left_ii);
+			sctx->cur_inode_mode = btrfs_inode_mode(
+					sctx->left_path->nodes[0], left_ii);
+		}
+	}
+
+out:
+	return ret;
+}
+
+static int changed_ref(struct send_ctx *sctx,
+		       enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	BUG_ON(sctx->cur_ino != sctx->cmp_key->objectid);
+
+	if (!sctx->cur_inode_new_gen &&
+	    sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID) {
+		if (result == BTRFS_COMPARE_TREE_NEW)
+			ret = record_new_ref(sctx);
+		else if (result == BTRFS_COMPARE_TREE_DELETED)
+			ret = record_deleted_ref(sctx);
+		else if (result == BTRFS_COMPARE_TREE_CHANGED)
+			ret = record_changed_ref(sctx);
+	}
+
+	return ret;
+}
+
+static int changed_xattr(struct send_ctx *sctx,
+			 enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	BUG_ON(sctx->cur_ino != sctx->cmp_key->objectid);
+
+	if (!sctx->cur_inode_new_gen && !sctx->cur_inode_deleted) {
+		if (result == BTRFS_COMPARE_TREE_NEW)
+			ret = process_new_xattr(sctx);
+		else if (result == BTRFS_COMPARE_TREE_DELETED)
+			ret = process_deleted_xattr(sctx);
+		else if (result == BTRFS_COMPARE_TREE_CHANGED)
+			ret = process_changed_xattr(sctx);
+	}
+
+	return ret;
+}
+
+static int changed_extent(struct send_ctx *sctx,
+			  enum btrfs_compare_tree_result result)
+{
+	int ret = 0;
+
+	BUG_ON(sctx->cur_ino != sctx->cmp_key->objectid);
+
+	if (!sctx->cur_inode_new_gen && !sctx->cur_inode_deleted) {
+		if (result != BTRFS_COMPARE_TREE_DELETED)
+			ret = process_extent(sctx, sctx->left_path,
+					sctx->cmp_key);
+	}
+
+	return ret;
+}
+
+
+static int changed_cb(struct btrfs_root *left_root,
+		      struct btrfs_root *right_root,
+		      struct btrfs_path *left_path,
+		      struct btrfs_path *right_path,
+		      struct btrfs_key *key,
+		      enum btrfs_compare_tree_result result,
+		      void *ctx)
+{
+	int ret = 0;
+	struct send_ctx *sctx = ctx;
+
+	sctx->left_path = left_path;
+	sctx->right_path = right_path;
+	sctx->cmp_key = key;
+
+	ret = finish_inode_if_needed(sctx, 0);
+	if (ret < 0)
+		goto out;
+
+	if (key->type == BTRFS_INODE_ITEM_KEY)
+		ret = changed_inode(sctx, result);
+	else if (key->type == BTRFS_INODE_REF_KEY)
+		ret = changed_ref(sctx, result);
+	else if (key->type == BTRFS_XATTR_ITEM_KEY)
+		ret = changed_xattr(sctx, result);
+	else if (key->type == BTRFS_EXTENT_DATA_KEY)
+		ret = changed_extent(sctx, result);
+
+out:
+	return ret;
+}
+
+static int full_send_tree(struct send_ctx *sctx)
+{
+	int ret;
+	struct btrfs_trans_handle *trans = NULL;
+	struct btrfs_root *send_root = sctx->send_root;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_path *path;
+	struct extent_buffer *eb;
+	int slot;
+	u64 start_ctransid;
+	u64 ctransid;
+
+	path = alloc_path_for_send();
+	if (!path)
+		return -ENOMEM;
+
+	spin_lock(&send_root->root_times_lock);
+	start_ctransid = btrfs_root_ctransid(&send_root->root_item);
+	spin_unlock(&send_root->root_times_lock);
+
+	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
+	key.type = BTRFS_INODE_ITEM_KEY;
+	key.offset = 0;
+
+join_trans:
+	/*
+	 * We need to make sure the transaction does not get committed
+	 * while we do anything on commit roots. Join a transaction to prevent
+	 * this.
+	 */
+	trans = btrfs_join_transaction(send_root);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		trans = NULL;
+		goto out;
+	}
+
+	/*
+	 * Make sure the tree has not changed
+	 */
+	spin_lock(&send_root->root_times_lock);
+	ctransid = btrfs_root_ctransid(&send_root->root_item);
+	spin_unlock(&send_root->root_times_lock);
+
+	if (ctransid != start_ctransid) {
+		WARN(1, KERN_WARNING "btrfs: the root that you're trying to "
+				     "send was modified in between. This is "
+				     "probably a bug.\n");
+		ret = -EIO;
+		goto out;
+	}
+
+	ret = btrfs_search_slot_for_read(send_root, &key, path, 1, 0);
+	if (ret < 0)
+		goto out;
+	if (ret)
+		goto out_finish;
+
+	while (1) {
+		/*
+		 * When someone want to commit while we iterate, end the
+		 * joined transaction and rejoin.
+		 */
+		if (btrfs_should_end_transaction(trans, send_root)) {
+			ret = btrfs_end_transaction(trans, send_root);
+			trans = NULL;
+			if (ret < 0)
+				goto out;
+			btrfs_release_path(path);
+			goto join_trans;
+		}
+
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+
+		ret = changed_cb(send_root, NULL, path, NULL,
+				&found_key, BTRFS_COMPARE_TREE_NEW, sctx);
+		if (ret < 0)
+			goto out;
+
+		key.objectid = found_key.objectid;
+		key.type = found_key.type;
+		key.offset = found_key.offset + 1;
+
+		ret = btrfs_next_item(send_root, path);
+		if (ret < 0)
+			goto out;
+		if (ret) {
+			ret  = 0;
+			break;
+		}
+	}
+
+out_finish:
+	ret = finish_inode_if_needed(sctx, 1);
+
+out:
+	btrfs_free_path(path);
+	if (trans) {
+		if (!ret)
+			ret = btrfs_end_transaction(trans, send_root);
+		else
+			btrfs_end_transaction(trans, send_root);
+	}
+	return ret;
+}
+
+static int send_subvol(struct send_ctx *sctx)
+{
+	int ret;
+
+	ret = send_header(sctx);
+	if (ret < 0)
+		goto out;
+
+	ret = send_subvol_begin(sctx);
+	if (ret < 0)
+		goto out;
+
+	if (sctx->parent_root) {
+		ret = btrfs_compare_trees(sctx->send_root, sctx->parent_root,
+				changed_cb, sctx);
+		if (ret < 0)
+			goto out;
+		ret = finish_inode_if_needed(sctx, 1);
+		if (ret < 0)
+			goto out;
+	} else {
+		ret = full_send_tree(sctx);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	if (!ret)
+		ret = close_cur_inode_file(sctx);
+	else
+		close_cur_inode_file(sctx);
+
+	free_recorded_refs(sctx);
+	return ret;
+}
+
+long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
+{
+	int ret = 0;
+	struct btrfs_root *send_root;
+	struct btrfs_root *clone_root;
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_ioctl_send_args *arg = NULL;
+	struct btrfs_key key;
+	struct file *filp = NULL;
+	struct send_ctx *sctx = NULL;
+	u32 i;
+	u64 *clone_sources_tmp = NULL;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	send_root = BTRFS_I(fdentry(mnt_file)->d_inode)->root;
+	fs_info = send_root->fs_info;
+
+	arg = memdup_user(arg_, sizeof(*arg));
+	if (IS_ERR(arg)) {
+		ret = PTR_ERR(arg);
+		arg = NULL;
+		goto out;
+	}
+
+	if (!access_ok(VERIFY_READ, arg->clone_sources,
+			sizeof(*arg->clone_sources *
+			arg->clone_sources_count))) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	sctx = kzalloc(sizeof(struct send_ctx), GFP_NOFS);
+	if (!sctx) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	INIT_LIST_HEAD(&sctx->new_refs);
+	INIT_LIST_HEAD(&sctx->deleted_refs);
+	INIT_RADIX_TREE(&sctx->name_cache, GFP_NOFS);
+	INIT_LIST_HEAD(&sctx->name_cache_list);
+
+	sctx->send_filp = fget(arg->send_fd);
+	if (IS_ERR(sctx->send_filp)) {
+		ret = PTR_ERR(sctx->send_filp);
+		goto out;
+	}
+
+	sctx->mnt = mnt_file->f_path.mnt;
+
+	sctx->send_root = send_root;
+	sctx->clone_roots_cnt = arg->clone_sources_count;
+
+	sctx->send_max_size = BTRFS_SEND_BUF_SIZE;
+	sctx->send_buf = vmalloc(sctx->send_max_size);
+	if (!sctx->send_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	sctx->read_buf = vmalloc(BTRFS_SEND_READ_SIZE);
+	if (!sctx->read_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	sctx->clone_roots = vzalloc(sizeof(struct clone_root) *
+			(arg->clone_sources_count + 1));
+	if (!sctx->clone_roots) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (arg->clone_sources_count) {
+		clone_sources_tmp = vmalloc(arg->clone_sources_count *
+				sizeof(*arg->clone_sources));
+		if (!clone_sources_tmp) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		ret = copy_from_user(clone_sources_tmp, arg->clone_sources,
+				arg->clone_sources_count *
+				sizeof(*arg->clone_sources));
+		if (ret) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		for (i = 0; i < arg->clone_sources_count; i++) {
+			key.objectid = clone_sources_tmp[i];
+			key.type = BTRFS_ROOT_ITEM_KEY;
+			key.offset = (u64)-1;
+			clone_root = btrfs_read_fs_root_no_name(fs_info, &key);
+			if (!clone_root) {
+				ret = -EINVAL;
+				goto out;
+			}
+			if (IS_ERR(clone_root)) {
+				ret = PTR_ERR(clone_root);
+				goto out;
+			}
+			sctx->clone_roots[i].root = clone_root;
+		}
+		vfree(clone_sources_tmp);
+		clone_sources_tmp = NULL;
+	}
+
+	if (arg->parent_root) {
+		key.objectid = arg->parent_root;
+		key.type = BTRFS_ROOT_ITEM_KEY;
+		key.offset = (u64)-1;
+		sctx->parent_root = btrfs_read_fs_root_no_name(fs_info, &key);
+		if (!sctx->parent_root) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	/*
+	 * Clones from send_root are allowed, but only if the clone source
+	 * is behind the current send position. This is checked while searching
+	 * for possible clone sources.
+	 */
+	sctx->clone_roots[sctx->clone_roots_cnt++].root = sctx->send_root;
+
+	/* We do a bsearch later */
+	sort(sctx->clone_roots, sctx->clone_roots_cnt,
+			sizeof(*sctx->clone_roots), __clone_root_cmp_sort,
+			NULL);
+
+	ret = send_subvol(sctx);
+	if (ret < 0)
+		goto out;
+
+	ret = begin_cmd(sctx, BTRFS_SEND_C_END);
+	if (ret < 0)
+		goto out;
+	ret = send_cmd(sctx);
+	if (ret < 0)
+		goto out;
+
+out:
+	if (filp)
+		fput(filp);
+	kfree(arg);
+	vfree(clone_sources_tmp);
+
+	if (sctx) {
+		if (sctx->send_filp)
+			fput(sctx->send_filp);
+
+		vfree(sctx->clone_roots);
+		vfree(sctx->send_buf);
+		vfree(sctx->read_buf);
+
+		name_cache_free(sctx);
+
+		kfree(sctx);
+	}
+
+	return ret;
+}
diff --git a/fs/btrfs/send.h b/fs/btrfs/send.h
new file mode 100644
index 000000000000..9934e948e57f
--- /dev/null
+++ b/fs/btrfs/send.h
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2012 Alexander Block.  All rights reserved.
+ * Copyright (C) 2012 STRATO.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include "ctree.h"
+
+#define BTRFS_SEND_STREAM_MAGIC "btrfs-stream"
+#define BTRFS_SEND_STREAM_VERSION 1
+
+#define BTRFS_SEND_BUF_SIZE (1024 * 64)
+#define BTRFS_SEND_READ_SIZE (1024 * 48)
+
+enum btrfs_tlv_type {
+	BTRFS_TLV_U8,
+	BTRFS_TLV_U16,
+	BTRFS_TLV_U32,
+	BTRFS_TLV_U64,
+	BTRFS_TLV_BINARY,
+	BTRFS_TLV_STRING,
+	BTRFS_TLV_UUID,
+	BTRFS_TLV_TIMESPEC,
+};
+
+struct btrfs_stream_header {
+	char magic[sizeof(BTRFS_SEND_STREAM_MAGIC)];
+	__le32 version;
+} __attribute__ ((__packed__));
+
+struct btrfs_cmd_header {
+	/* len excluding the header */
+	__le32 len;
+	__le16 cmd;
+	/* crc including the header with zero crc field */
+	__le32 crc;
+} __attribute__ ((__packed__));
+
+struct btrfs_tlv_header {
+	__le16 tlv_type;
+	/* len excluding the header */
+	__le16 tlv_len;
+} __attribute__ ((__packed__));
+
+/* commands */
+enum btrfs_send_cmd {
+	BTRFS_SEND_C_UNSPEC,
+
+	BTRFS_SEND_C_SUBVOL,
+	BTRFS_SEND_C_SNAPSHOT,
+
+	BTRFS_SEND_C_MKFILE,
+	BTRFS_SEND_C_MKDIR,
+	BTRFS_SEND_C_MKNOD,
+	BTRFS_SEND_C_MKFIFO,
+	BTRFS_SEND_C_MKSOCK,
+	BTRFS_SEND_C_SYMLINK,
+
+	BTRFS_SEND_C_RENAME,
+	BTRFS_SEND_C_LINK,
+	BTRFS_SEND_C_UNLINK,
+	BTRFS_SEND_C_RMDIR,
+
+	BTRFS_SEND_C_SET_XATTR,
+	BTRFS_SEND_C_REMOVE_XATTR,
+
+	BTRFS_SEND_C_WRITE,
+	BTRFS_SEND_C_CLONE,
+
+	BTRFS_SEND_C_TRUNCATE,
+	BTRFS_SEND_C_CHMOD,
+	BTRFS_SEND_C_CHOWN,
+	BTRFS_SEND_C_UTIMES,
+
+	BTRFS_SEND_C_END,
+	__BTRFS_SEND_C_MAX,
+};
+#define BTRFS_SEND_C_MAX (__BTRFS_SEND_C_MAX - 1)
+
+/* attributes in send stream */
+enum {
+	BTRFS_SEND_A_UNSPEC,
+
+	BTRFS_SEND_A_UUID,
+	BTRFS_SEND_A_CTRANSID,
+
+	BTRFS_SEND_A_INO,
+	BTRFS_SEND_A_SIZE,
+	BTRFS_SEND_A_MODE,
+	BTRFS_SEND_A_UID,
+	BTRFS_SEND_A_GID,
+	BTRFS_SEND_A_RDEV,
+	BTRFS_SEND_A_CTIME,
+	BTRFS_SEND_A_MTIME,
+	BTRFS_SEND_A_ATIME,
+	BTRFS_SEND_A_OTIME,
+
+	BTRFS_SEND_A_XATTR_NAME,
+	BTRFS_SEND_A_XATTR_DATA,
+
+	BTRFS_SEND_A_PATH,
+	BTRFS_SEND_A_PATH_TO,
+	BTRFS_SEND_A_PATH_LINK,
+
+	BTRFS_SEND_A_FILE_OFFSET,
+	BTRFS_SEND_A_DATA,
+
+	BTRFS_SEND_A_CLONE_UUID,
+	BTRFS_SEND_A_CLONE_CTRANSID,
+	BTRFS_SEND_A_CLONE_PATH,
+	BTRFS_SEND_A_CLONE_OFFSET,
+	BTRFS_SEND_A_CLONE_LEN,
+
+	__BTRFS_SEND_A_MAX,
+};
+#define BTRFS_SEND_A_MAX (__BTRFS_SEND_A_MAX - 1)
+
+#ifdef __KERNEL__
+long btrfs_ioctl_send(struct file *mnt_file, void __user *arg);
+#endif