ocfs2: teach ocfs2_file_aio_write() about sparse files

Unfortunately, ocfs2 can no longer make use of generic_file_aio_write_nlock()
because allocating writes will require zeroing of pages adjacent to the I/O
for cluster sizes greater than page size.

Implement a custom file write here, which can order page locks for zeroing.
This also has the advantage that cluster locks can easily be ordered outside
of the page locks.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

7 files changed, 1076 insertions, 57 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f3b0cc5cba1a..5ffb3702b5e9 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -24,6 +24,7 @@
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <asm/byteorder.h>
+#include <linux/swap.h>
 
 #define MLOG_MASK_PREFIX ML_FILE_IO
 #include <cluster/masklog.h>
@@ -37,6 +38,7 @@
 #include "file.h"
 #include "inode.h"
 #include "journal.h"
+#include "suballoc.h"
 #include "super.h"
 #include "symlink.h"
 
@@ -645,23 +647,27 @@ static ssize_t ocfs2_direct_IO(int rw,
 
 	mlog_entry_void();
 
-	/*
-	 * We get PR data locks even for O_DIRECT.  This allows
-	 * concurrent O_DIRECT I/O but doesn't let O_DIRECT with
-	 * extending and buffered zeroing writes race.  If they did
-	 * race then the buffered zeroing could be written back after
-	 * the O_DIRECT I/O.  It's one thing to tell people not to mix
-	 * buffered and O_DIRECT writes, but expecting them to
-	 * understand that file extension is also an implicit buffered
-	 * write is too much.  By getting the PR we force writeback of
-	 * the buffered zeroing before proceeding.
-	 */
-	ret = ocfs2_data_lock(inode, 0);
-	if (ret < 0) {
-		mlog_errno(ret);
-		goto out;
+	if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+		/*
+		 * We get PR data locks even for O_DIRECT.  This
+		 * allows concurrent O_DIRECT I/O but doesn't let
+		 * O_DIRECT with extending and buffered zeroing writes
+		 * race.  If they did race then the buffered zeroing
+		 * could be written back after the O_DIRECT I/O.  It's
+		 * one thing to tell people not to mix buffered and
+		 * O_DIRECT writes, but expecting them to understand
+		 * that file extension is also an implicit buffered
+		 * write is too much.  By getting the PR we force
+		 * writeback of the buffered zeroing before
+		 * proceeding.
+		 */
+		ret = ocfs2_data_lock(inode, 0);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+		ocfs2_data_unlock(inode, 0);
 	}
-	ocfs2_data_unlock(inode, 0);
 
 	ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
 					    inode->i_sb->s_bdev, iov, offset,
@@ -673,6 +679,647 @@ out:
 	return ret;
 }
 
+static void ocfs2_figure_cluster_boundaries(struct ocfs2_super *osb,
+					    u32 cpos,
+					    unsigned int *start,
+					    unsigned int *end)
+{
+	unsigned int cluster_start = 0, cluster_end = PAGE_CACHE_SIZE;
+
+	if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits)) {
+		unsigned int cpp;
+
+		cpp = 1 << (PAGE_CACHE_SHIFT - osb->s_clustersize_bits);
+
+		cluster_start = cpos % cpp;
+		cluster_start = cluster_start << osb->s_clustersize_bits;
+
+		cluster_end = cluster_start + osb->s_clustersize;
+	}
+
+	BUG_ON(cluster_start > PAGE_SIZE);
+	BUG_ON(cluster_end > PAGE_SIZE);
+
+	if (start)
+		*start = cluster_start;
+	if (end)
+		*end = cluster_end;
+}
+
+/*
+ * 'from' and 'to' are the region in the page to avoid zeroing.
+ *
+ * If pagesize > clustersize, this function will avoid zeroing outside
+ * of the cluster boundary.
+ *
+ * from == to == 0 is code for "zero the entire cluster region"
+ */
+static void ocfs2_clear_page_regions(struct page *page,
+				     struct ocfs2_super *osb, u32 cpos,
+				     unsigned from, unsigned to)
+{
+	void *kaddr;
+	unsigned int cluster_start, cluster_end;
+
+	ocfs2_figure_cluster_boundaries(osb, cpos, &cluster_start, &cluster_end);
+
+	kaddr = kmap_atomic(page, KM_USER0);
+
+	if (from || to) {
+		if (from > cluster_start)
+			memset(kaddr + cluster_start, 0, from - cluster_start);
+		if (to < cluster_end)
+			memset(kaddr + to, 0, cluster_end - to);
+	} else {
+		memset(kaddr + cluster_start, 0, cluster_end - cluster_start);
+	}
+
+	kunmap_atomic(kaddr, KM_USER0);
+}
+
+/*
+ * Some of this taken from block_prepare_write(). We already have our
+ * mapping by now though, and the entire write will be allocating or
+ * it won't, so not much need to use BH_New.
+ *
+ * This will also skip zeroing, which is handled externally.
+ */
+static int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
+				 struct inode *inode, unsigned int from,
+				 unsigned int to, int new)
+{
+	int ret = 0;
+	struct buffer_head *head, *bh, *wait[2], **wait_bh = wait;
+	unsigned int block_end, block_start;
+	unsigned int bsize = 1 << inode->i_blkbits;
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, bsize, 0);
+
+	head = page_buffers(page);
+	for (bh = head, block_start = 0; bh != head || !block_start;
+	     bh = bh->b_this_page, block_start += bsize) {
+		block_end = block_start + bsize;
+
+		/*
+		 * Ignore blocks outside of our i/o range -
+		 * they may belong to unallocated clusters.
+		 */
+		if (block_start >= to ||
+		    (block_start + bsize) <= from) {
+			if (PageUptodate(page))
+				set_buffer_uptodate(bh);
+			continue;
+		}
+
+		/*
+		 * For an allocating write with cluster size >= page
+		 * size, we always write the entire page.
+		 */
+
+		if (buffer_new(bh))
+			clear_buffer_new(bh);
+
+		if (!buffer_mapped(bh)) {
+			map_bh(bh, inode->i_sb, *p_blkno);
+			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
+		}
+
+		if (PageUptodate(page)) {
+			if (!buffer_uptodate(bh))
+				set_buffer_uptodate(bh);
+		} else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
+		     (block_start < from || block_end > to)) {
+			ll_rw_block(READ, 1, &bh);
+			*wait_bh++=bh;
+		}
+
+		*p_blkno = *p_blkno + 1;
+	}
+
+	/*
+	 * If we issued read requests - let them complete.
+	 */
+	while(wait_bh > wait) {
+		wait_on_buffer(*--wait_bh);
+		if (!buffer_uptodate(*wait_bh))
+			ret = -EIO;
+	}
+
+	if (ret == 0 || !new)
+		return ret;
+
+	/*
+	 * If we get -EIO above, zero out any newly allocated blocks
+	 * to avoid exposing stale data.
+	 */
+	bh = head;
+	block_start = 0;
+	do {
+		void *kaddr;
+
+		block_end = block_start + bsize;
+		if (block_end <= from)
+			goto next_bh;
+		if (block_start >= to)
+			break;
+
+		kaddr = kmap_atomic(page, KM_USER0);
+		memset(kaddr+block_start, 0, bh->b_size);
+		flush_dcache_page(page);
+		kunmap_atomic(kaddr, KM_USER0);
+		set_buffer_uptodate(bh);
+		mark_buffer_dirty(bh);
+
+next_bh:
+		block_start = block_end;
+		bh = bh->b_this_page;
+	} while (bh != head);
+
+	return ret;
+}
+
+/*
+ * This will copy user data from the iovec in the buffered write
+ * context.
+ */
+int ocfs2_map_and_write_user_data(struct inode *inode,
+				  struct ocfs2_write_ctxt *wc, u64 *p_blkno,
+				  unsigned int *ret_from, unsigned int *ret_to)
+{
+	int ret;
+	unsigned int to, from, cluster_start, cluster_end;
+	unsigned long bytes, src_from;
+	char *dst;
+	struct ocfs2_buffered_write_priv *bp = wc->w_private;
+	const struct iovec *cur_iov = bp->b_cur_iov;
+	char __user *buf;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+	ocfs2_figure_cluster_boundaries(osb, wc->w_cpos, &cluster_start,
+					&cluster_end);
+
+	buf = cur_iov->iov_base + bp->b_cur_off;
+	src_from = (unsigned long)buf & ~PAGE_CACHE_MASK;
+
+	from = wc->w_pos & (PAGE_CACHE_SIZE - 1);
+
+	/*
+	 * This is a lot of comparisons, but it reads quite
+	 * easily, which is important here.
+	 */
+	/* Stay within the src page */
+	bytes = PAGE_SIZE - src_from;
+	/* Stay within the vector */
+	bytes = min(bytes,
+		    (unsigned long)(cur_iov->iov_len - bp->b_cur_off));
+	/* Stay within count */
+	bytes = min(bytes, (unsigned long)wc->w_count);
+	/*
+	 * For clustersize > page size, just stay within
+	 * target page, otherwise we have to calculate pos
+	 * within the cluster and obey the rightmost
+	 * boundary.
+	 */
+	if (wc->w_large_pages) {
+		/*
+		 * For cluster size < page size, we have to
+		 * calculate pos within the cluster and obey
+		 * the rightmost boundary.
+		 */
+		bytes = min(bytes, (unsigned long)(osb->s_clustersize
+				   - (wc->w_pos & (osb->s_clustersize - 1))));
+	} else {
+		/*
+		 * cluster size > page size is the most common
+		 * case - we just stay within the target page
+		 * boundary.
+		 */
+		bytes = min(bytes, PAGE_CACHE_SIZE - from);
+	}
+
+	to = from + bytes;
+
+	if (wc->w_this_page_new)
+		ret = ocfs2_map_page_blocks(wc->w_this_page, p_blkno, inode,
+					    cluster_start, cluster_end, 1);
+	else
+		ret = ocfs2_map_page_blocks(wc->w_this_page, p_blkno, inode,
+					    from, to, 0);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	BUG_ON(from > PAGE_CACHE_SIZE);
+	BUG_ON(to > PAGE_CACHE_SIZE);
+	BUG_ON(from > osb->s_clustersize);
+	BUG_ON(to > osb->s_clustersize);
+
+	dst = kmap(wc->w_this_page);
+	memcpy(dst + from, bp->b_src_buf + src_from, bytes);
+	kunmap(wc->w_this_page);
+
+	/*
+	 * XXX: This is slow, but simple. The caller of
+	 * ocfs2_buffered_write_cluster() is responsible for
+	 * passing through the iovecs, so it's difficult to
+	 * predict what our next step is in here after our
+	 * initial write. A future version should be pushing
+	 * that iovec manipulation further down.
+	 *
+	 * By setting this, we indicate that a copy from user
+	 * data was done, and subsequent calls for this
+	 * cluster will skip copying more data.
+	 */
+	wc->w_finished_copy = 1;
+
+	*ret_from = from;
+	*ret_to = to;
+out:
+
+	return bytes ? (unsigned int)bytes : ret;
+}
+
+/*
+ * Map, fill and write a page to disk.
+ *
+ * The work of copying data is done via callback.  Newly allocated
+ * pages which don't take user data will be zero'd (set 'new' to
+ * indicate an allocating write)
+ *
+ * Returns a negative error code or the number of bytes copied into
+ * the page.
+ */
+int ocfs2_write_data_page(struct inode *inode, handle_t *handle,
+			  u64 *p_blkno, struct page *page,
+			  struct ocfs2_write_ctxt *wc, int new)
+{
+	int ret, copied = 0;
+	unsigned int from = 0, to = 0;
+	unsigned int cluster_start, cluster_end;
+	unsigned int zero_from = 0, zero_to = 0;
+
+	ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), wc->w_cpos,
+					&cluster_start, &cluster_end);
+
+	if ((wc->w_pos >> PAGE_CACHE_SHIFT) == page->index
+	    && !wc->w_finished_copy) {
+
+		wc->w_this_page = page;
+		wc->w_this_page_new = new;
+		ret = wc->w_write_data_page(inode, wc, p_blkno, &from, &to);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		copied = ret;
+
+		zero_from = from;
+		zero_to = to;
+		if (new) {
+			from = cluster_start;
+			to = cluster_end;
+		}
+	} else {
+		/*
+		 * If we haven't allocated the new page yet, we
+		 * shouldn't be writing it out without copying user
+		 * data. This is likely a math error from the caller.
+		 */
+		BUG_ON(!new);
+
+		from = cluster_start;
+		to = cluster_end;
+
+		ret = ocfs2_map_page_blocks(page, p_blkno, inode,
+					    cluster_start, cluster_end, 1);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+	}
+
+	/*
+	 * Parts of newly allocated pages need to be zero'd.
+	 *
+	 * Above, we have also rewritten 'to' and 'from' - as far as
+	 * the rest of the function is concerned, the entire cluster
+	 * range inside of a page needs to be written.
+	 *
+	 * We can skip this if the page is up to date - it's already
+	 * been zero'd from being read in as a hole.
+	 */
+	if (new && !PageUptodate(page))
+		ocfs2_clear_page_regions(page, OCFS2_SB(inode->i_sb),
+					 wc->w_cpos, zero_from, zero_to);
+
+	flush_dcache_page(page);
+
+	if (ocfs2_should_order_data(inode)) {
+		ret = walk_page_buffers(handle,
+					page_buffers(page),
+					from, to, NULL,
+					ocfs2_journal_dirty_data);
+		if (ret < 0)
+			mlog_errno(ret);
+	}
+
+	/*
+	 * We don't use generic_commit_write() because we need to
+	 * handle our own i_size update.
+	 */
+	ret = block_commit_write(page, from, to);
+	if (ret)
+		mlog_errno(ret);
+out:
+
+	return copied ? copied : ret;
+}
+
+/*
+ * Do the actual write of some data into an inode. Optionally allocate
+ * in order to fulfill the write.
+ *
+ * cpos is the logical cluster offset within the file to write at
+ *
+ * 'phys' is the physical mapping of that offset. a 'phys' value of
+ * zero indicates that allocation is required. In this case, data_ac
+ * and meta_ac should be valid (meta_ac can be null if metadata
+ * allocation isn't required).
+ */
+static ssize_t ocfs2_write(struct file *file, u32 phys, handle_t *handle,
+			   struct buffer_head *di_bh,
+			   struct ocfs2_alloc_context *data_ac,
+			   struct ocfs2_alloc_context *meta_ac,
+			   struct ocfs2_write_ctxt *wc)
+{
+	int ret, i, numpages = 1, new;
+	unsigned int copied = 0;
+	u32 tmp_pos;
+	u64 v_blkno, p_blkno;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	unsigned int cbits = OCFS2_SB(inode->i_sb)->s_clustersize_bits;
+	unsigned long index, start;
+	struct page **cpages;
+
+	new = phys == 0 ? 1 : 0;
+
+	/*
+	 * Figure out how many pages we'll be manipulating here. For
+	 * non-allocating write, or any writes where cluster size is
+	 * less than page size, we only need one page. Otherwise,
+	 * allocating writes of cluster size larger than page size
+	 * need cluster size pages.
+	 */
+	if (new && !wc->w_large_pages)
+		numpages = (1 << cbits) / PAGE_SIZE;
+
+	cpages = kzalloc(sizeof(*cpages) * numpages, GFP_NOFS);
+	if (!cpages) {
+		ret = -ENOMEM;
+		mlog_errno(ret);
+		return ret;
+	}
+
+	/*
+	 * Fill our page array first. That way we've grabbed enough so
+	 * that we can zero and flush if we error after adding the
+	 * extent.
+	 */
+	if (new) {
+		start = ocfs2_align_clusters_to_page_index(inode->i_sb,
+							   wc->w_cpos);
+		v_blkno = ocfs2_clusters_to_blocks(inode->i_sb, wc->w_cpos);
+	} else {
+		start = wc->w_pos >> PAGE_CACHE_SHIFT;
+		v_blkno = wc->w_pos >> inode->i_sb->s_blocksize_bits;
+	}
+
+	for(i = 0; i < numpages; i++) {
+		index = start + i;
+
+		cpages[i] = grab_cache_page(mapping, index);
+		if (!cpages[i]) {
+			ret = -ENOMEM;
+			mlog_errno(ret);
+			goto out;
+		}
+	}
+
+	if (new) {
+		/*
+		 * This is safe to call with the page locks - it won't take
+		 * any additional semaphores or cluster locks.
+		 */
+		tmp_pos = wc->w_cpos;
+		ret = ocfs2_do_extend_allocation(OCFS2_SB(inode->i_sb), inode,
+						 &tmp_pos, 1, di_bh, handle,
+						 data_ac, meta_ac, NULL);
+		/*
+		 * This shouldn't happen because we must have already
+		 * calculated the correct meta data allocation required. The
+		 * internal tree allocation code should know how to increase
+		 * transaction credits itself.
+		 *
+		 * If need be, we could handle -EAGAIN for a
+		 * RESTART_TRANS here.
+		 */
+		mlog_bug_on_msg(ret == -EAGAIN,
+				"Inode %llu: EAGAIN return during allocation.\n",
+				(unsigned long long)OCFS2_I(inode)->ip_blkno);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+	}
+
+	ret = ocfs2_extent_map_get_blocks(inode, v_blkno, &p_blkno, NULL);
+	if (ret < 0) {
+
+		/*
+		 * XXX: Should we go readonly here?
+		 */
+
+		mlog_errno(ret);
+		goto out;
+	}
+
+	BUG_ON(p_blkno == 0);
+
+	for(i = 0; i < numpages; i++) {
+		ret = ocfs2_write_data_page(inode, handle, &p_blkno, cpages[i],
+					    wc, new);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		copied += ret;
+	}
+
+out:
+	for(i = 0; i < numpages; i++) {
+		unlock_page(cpages[i]);
+		mark_page_accessed(cpages[i]);
+		page_cache_release(cpages[i]);
+	}
+	kfree(cpages);
+
+	return copied ? copied : ret;
+}
+
+static void ocfs2_write_ctxt_init(struct ocfs2_write_ctxt *wc,
+				  struct ocfs2_super *osb, loff_t pos,
+				  size_t count, ocfs2_page_writer *cb,
+				  void *cb_priv)
+{
+	wc->w_count = count;
+	wc->w_pos = pos;
+	wc->w_cpos = wc->w_pos >> osb->s_clustersize_bits;
+	wc->w_finished_copy = 0;
+
+	if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits))
+		wc->w_large_pages = 1;
+	else
+		wc->w_large_pages = 0;
+
+	wc->w_write_data_page = cb;
+	wc->w_private = cb_priv;
+}
+
+/*
+ * Write a cluster to an inode. The cluster may not be allocated yet,
+ * in which case it will be. This only exists for buffered writes -
+ * O_DIRECT takes a more "traditional" path through the kernel.
+ *
+ * The caller is responsible for incrementing pos, written counts, etc
+ *
+ * For file systems that don't support sparse files, pre-allocation
+ * and page zeroing up until cpos should be done prior to this
+ * function call.
+ *
+ * Callers should be holding i_sem, and the rw cluster lock.
+ *
+ * Returns the number of user bytes written, or less than zero for
+ * error.
+ */
+ssize_t ocfs2_buffered_write_cluster(struct file *file, loff_t pos,
+				     size_t count, ocfs2_page_writer *actor,
+				     void *priv)
+{
+	int ret, credits = OCFS2_INODE_UPDATE_CREDITS;
+	ssize_t written = 0;
+	u32 phys;
+	struct inode *inode = file->f_mapping->host;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	struct buffer_head *di_bh = NULL;
+	struct ocfs2_dinode *di;
+	struct ocfs2_alloc_context *data_ac = NULL;
+	struct ocfs2_alloc_context *meta_ac = NULL;
+	handle_t *handle;
+	struct ocfs2_write_ctxt wc;
+
+	ocfs2_write_ctxt_init(&wc, osb, pos, count, actor, priv);
+
+	ret = ocfs2_meta_lock(inode, &di_bh, 1);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+	di = (struct ocfs2_dinode *)di_bh->b_data;
+
+	/*
+	 * Take alloc sem here to prevent concurrent lookups. That way
+	 * the mapping, zeroing and tree manipulation within
+	 * ocfs2_write() will be safe against ->readpage(). This
+	 * should also serve to lock out allocation from a shared
+	 * writeable region.
+	 */
+	down_write(&OCFS2_I(inode)->ip_alloc_sem);
+
+	ret = ocfs2_get_clusters(inode, wc.w_cpos, &phys, NULL);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_meta;
+	}
+
+	/* phys == 0 means that allocation is required. */
+	if (phys == 0) {
+		ret = ocfs2_lock_allocators(inode, di, 1, &data_ac, &meta_ac);
+		if (ret) {
+			mlog_errno(ret);
+			goto out_meta;
+		}
+
+		credits = ocfs2_calc_extend_credits(inode->i_sb, di, 1);
+	}
+
+	ret = ocfs2_data_lock(inode, 1);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_meta;
+	}
+
+	handle = ocfs2_start_trans(osb, credits);
+	if (IS_ERR(handle)) {
+		ret = PTR_ERR(handle);
+		mlog_errno(ret);
+		goto out_data;
+	}
+
+	written = ocfs2_write(file, phys, handle, di_bh, data_ac,
+			      meta_ac, &wc);
+	if (written < 0) {
+		ret = written;
+		mlog_errno(ret);
+		goto out_commit;
+	}
+
+	ret = ocfs2_journal_access(handle, inode, di_bh,
+				   OCFS2_JOURNAL_ACCESS_WRITE);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_commit;
+	}
+
+	pos += written;
+	if (pos > inode->i_size) {
+		i_size_write(inode, pos);
+		mark_inode_dirty(inode);
+	}
+	inode->i_blocks = ocfs2_align_bytes_to_sectors((u64)(i_size_read(inode)));
+	di->i_size = cpu_to_le64((u64)i_size_read(inode));
+	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
+	di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
+
+	ret = ocfs2_journal_dirty(handle, di_bh);
+	if (ret)
+		mlog_errno(ret);
+
+out_commit:
+	ocfs2_commit_trans(osb, handle);
+
+out_data:
+	ocfs2_data_unlock(inode, 1);
+
+out_meta:
+	up_write(&OCFS2_I(inode)->ip_alloc_sem);
+	ocfs2_meta_unlock(inode, 1);
+
+out:
+	brelse(di_bh);
+	if (data_ac)
+		ocfs2_free_alloc_context(data_ac);
+	if (meta_ac)
+		ocfs2_free_alloc_context(meta_ac);
+
+	return written ? written : ret;
+}
+
 const struct address_space_operations ocfs2_aops = {
 	.readpage	= ocfs2_readpage,
 	.writepage	= ocfs2_writepage,
diff --git a/fs/ocfs2/aops.h b/fs/ocfs2/aops.h
index f446a15eab88..eeb2c42483e8 100644
--- a/fs/ocfs2/aops.h
+++ b/fs/ocfs2/aops.h
@@ -30,6 +30,44 @@ handle_t *ocfs2_start_walk_page_trans(struct inode *inode,
 							 unsigned from,
 							 unsigned to);
 
+struct ocfs2_write_ctxt;
+typedef int (ocfs2_page_writer)(struct inode *, struct ocfs2_write_ctxt *,
+				u64 *, unsigned int *, unsigned int *);
+
+ssize_t ocfs2_buffered_write_cluster(struct file *file, loff_t pos,
+				     size_t count, ocfs2_page_writer *actor,
+				     void *priv);
+
+struct ocfs2_write_ctxt {
+	size_t				w_count;
+	loff_t				w_pos;
+	u32				w_cpos;
+	unsigned int			w_finished_copy;
+
+	/* This is true if page_size > cluster_size */
+	unsigned int			w_large_pages;
+
+	/* Filler callback and private data */
+	ocfs2_page_writer		*w_write_data_page;
+	void				*w_private;
+
+	/* Only valid for the filler callback */
+	struct page			*w_this_page;
+	unsigned int			w_this_page_new;
+};
+
+struct ocfs2_buffered_write_priv {
+	char				*b_src_buf;
+	const struct iovec		*b_cur_iov; /* Current iovec */
+	size_t				b_cur_off; /* Offset in the
+						    * current iovec */
+};
+int ocfs2_map_and_write_user_data(struct inode *inode,
+				  struct ocfs2_write_ctxt *wc,
+				  u64 *p_blkno,
+				  unsigned int *ret_from,
+				  unsigned int *ret_to);
+
 /* all ocfs2_dio_end_io()'s fault */
 #define ocfs2_iocb_is_rw_locked(iocb) \
 	test_bit(0, (unsigned long *)&iocb->private)
diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 3b4322fd369a..937c2722b753 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -67,8 +67,8 @@ static int ocfs2_search_extent_list(struct ocfs2_extent_list *el,
 	return ret;
 }
 
-static int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
-			      u32 *p_cluster, u32 *num_clusters)
+int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
+		       u32 *p_cluster, u32 *num_clusters)
 {
 	int ret, i;
 	struct buffer_head *di_bh = NULL;
diff --git a/fs/ocfs2/extent_map.h b/fs/ocfs2/extent_map.h
index 036e23251448..625d0ee5e04a 100644
--- a/fs/ocfs2/extent_map.h
+++ b/fs/ocfs2/extent_map.h
@@ -25,6 +25,8 @@
 #ifndef _EXTENT_MAP_H
 #define _EXTENT_MAP_H
 
+int ocfs2_get_clusters(struct inode *inode, u32 v_cluster, u32 *p_cluster,
+		       u32 *num_clusters);
 int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
 				int *ret_count);
 
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 3bcf3629265e..667e5a869bf5 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -33,6 +33,7 @@
 #include <linux/sched.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/mount.h>
+#include <linux/writeback.h>
 
 #define MLOG_MASK_PREFIX ML_INODE
 #include <cluster/masklog.h>
@@ -485,13 +486,13 @@ leave:
  * accessed, and lock them, reserving the appropriate number of bits.
  *
  * Called from ocfs2_extend_allocation() for file systems which don't
- * support holes, and from ocfs2_prepare_write() for file systems
- * which understand sparse inodes.
+ * support holes, and from ocfs2_write() for file systems which
+ * understand sparse inodes.
  */
-static int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
-				 u32 clusters_to_add,
-				 struct ocfs2_alloc_context **data_ac,
-				 struct ocfs2_alloc_context **meta_ac)
+int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
+			  u32 clusters_to_add,
+			  struct ocfs2_alloc_context **data_ac,
+			  struct ocfs2_alloc_context **meta_ac)
 {
 	int ret, num_free_extents;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
@@ -518,7 +519,7 @@ static int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
 	 * a cluster lock (because we ran out of room for another
 	 * extent) will violate ordering rules.
 	 *
-	 * Most of the time we'll only be seeing this 1 page at a time
+	 * Most of the time we'll only be seeing this 1 cluster at a time
 	 * anyway.
 	 */
 	if (!num_free_extents ||
@@ -596,13 +597,6 @@ static int ocfs2_extend_allocation(struct inode *inode,
 restart_all:
 	BUG_ON(le32_to_cpu(fe->i_clusters) != OCFS2_I(inode)->ip_clusters);
 
-	status = ocfs2_lock_allocators(inode, fe, clusters_to_add, &data_ac,
-				       &meta_ac);
-	if (status) {
-		mlog_errno(status);
-		goto leave;
-	}
-
 	/* blocks peope in read/write from reading our allocation
 	 * until we're done changing it. We depend on i_mutex to block
 	 * other extend/truncate calls while we're here. Ordering wrt
@@ -610,6 +604,13 @@ restart_all:
 	down_write(&OCFS2_I(inode)->ip_alloc_sem);
 	drop_alloc_sem = 1;
 
+	status = ocfs2_lock_allocators(inode, fe, clusters_to_add, &data_ac,
+				       &meta_ac);
+	if (status) {
+		mlog_errno(status);
+		goto leave;
+	}
+
 	credits = ocfs2_calc_extend_credits(osb->sb, fe, clusters_to_add);
 	handle = ocfs2_start_trans(osb, credits);
 	if (IS_ERR(handle)) {
@@ -1088,10 +1089,49 @@ out:
 	return ret;
 }
 
+/*
+ * Will look for holes and unwritten extents in the range starting at
+ * pos for count bytes (inclusive).
+ */
+static int ocfs2_check_range_for_holes(struct inode *inode, loff_t pos,
+				       size_t count)
+{
+	int ret = 0;
+	unsigned int extent_flags;
+	u32 cpos, clusters, extent_len, phys_cpos;
+	struct super_block *sb = inode->i_sb;
+
+	cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
+	clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
+
+	while (clusters) {
+		ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
+					 &extent_flags);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		if (phys_cpos == 0 || (extent_flags & OCFS2_EXT_UNWRITTEN)) {
+			ret = 1;
+			break;
+		}
+
+		if (extent_len > clusters)
+			extent_len = clusters;
+
+		clusters -= extent_len;
+		cpos += extent_len;
+	}
+out:
+	return ret;
+}
+
 static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
 					 loff_t *ppos,
 					 size_t count,
-					 int appending)
+					 int appending,
+					 int *direct_io)
 {
 	int ret = 0, meta_level = appending;
 	struct inode *inode = dentry->d_inode;
@@ -1143,12 +1183,47 @@ static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
 			saved_pos = *ppos;
 		}
 
+		if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
+			loff_t end = saved_pos + count;
+
+			/*
+			 * Skip the O_DIRECT checks if we don't need
+			 * them.
+			 */
+			if (!direct_io || !(*direct_io))
+				break;
+
+			/*
+			 * Allowing concurrent direct writes means
+			 * i_size changes wouldn't be synchronized, so
+			 * one node could wind up truncating another
+			 * nodes writes.
+			 */
+			if (end > i_size_read(inode)) {
+				*direct_io = 0;
+				break;
+			}
+
+			/*
+			 * We don't fill holes during direct io, so
+			 * check for them here. If any are found, the
+			 * caller will have to retake some cluster
+			 * locks and initiate the io as buffered.
+			 */
+			ret = ocfs2_check_range_for_holes(inode, saved_pos,
+							  count);
+			if (ret == 1) {
+				*direct_io = 0;
+				ret = 0;
+			} else if (ret < 0)
+				mlog_errno(ret);
+			break;
+		}
+
 		/*
 		 * The rest of this loop is concerned with legacy file
 		 * systems which don't support sparse files.
 		 */
-		if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
-			break;
 
 		newsize = count + saved_pos;
 
@@ -1202,55 +1277,264 @@ out:
 	return ret;
 }
 
+static inline void
+ocfs2_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
+{
+	const struct iovec *iov = *iovp;
+	size_t base = *basep;
+
+	do {
+		int copy = min(bytes, iov->iov_len - base);
+
+		bytes -= copy;
+		base += copy;
+		if (iov->iov_len == base) {
+			iov++;
+			base = 0;
+		}
+	} while (bytes);
+	*iovp = iov;
+	*basep = base;
+}
+
+static struct page * ocfs2_get_write_source(struct ocfs2_buffered_write_priv *bp,
+					    const struct iovec *cur_iov,
+					    size_t iov_offset)
+{
+	int ret;
+	char *buf;
+	struct page *src_page = NULL;
+
+	buf = cur_iov->iov_base + iov_offset;
+
+	if (!segment_eq(get_fs(), KERNEL_DS)) {
+		/*
+		 * Pull in the user page. We want to do this outside
+		 * of the meta data locks in order to preserve locking
+		 * order in case of page fault.
+		 */
+		ret = get_user_pages(current, current->mm,
+				     (unsigned long)buf & PAGE_CACHE_MASK, 1,
+				     0, 0, &src_page, NULL);
+		if (ret == 1)
+			bp->b_src_buf = kmap(src_page);
+		else
+			src_page = ERR_PTR(-EFAULT);
+	} else {
+		bp->b_src_buf = buf;
+	}
+
+	return src_page;
+}
+
+static void ocfs2_put_write_source(struct ocfs2_buffered_write_priv *bp,
+				   struct page *page)
+{
+	if (page) {
+		kunmap(page);
+		page_cache_release(page);
+	}
+}
+
+static ssize_t ocfs2_file_buffered_write(struct file *file, loff_t *ppos,
+					 const struct iovec *iov,
+					 unsigned long nr_segs,
+					 size_t count,
+					 ssize_t o_direct_written)
+{
+	int ret = 0;
+	ssize_t copied, total = 0;
+	size_t iov_offset = 0;
+	const struct iovec *cur_iov = iov;
+	struct ocfs2_buffered_write_priv bp;
+	struct page *page;
+
+	/*
+	 * handle partial DIO write.  Adjust cur_iov if needed.
+	 */
+	ocfs2_set_next_iovec(&cur_iov, &iov_offset, o_direct_written);
+
+	do {
+		bp.b_cur_off = iov_offset;
+		bp.b_cur_iov = cur_iov;
+
+		page = ocfs2_get_write_source(&bp, cur_iov, iov_offset);
+		if (IS_ERR(page)) {
+			ret = PTR_ERR(page);
+			goto out;
+		}
+
+		copied = ocfs2_buffered_write_cluster(file, *ppos, count,
+						      ocfs2_map_and_write_user_data,
+						      &bp);
+
+		ocfs2_put_write_source(&bp, page);
+
+		if (copied < 0) {
+			mlog_errno(copied);
+			ret = copied;
+			goto out;
+		}
+
+		total += copied;
+		*ppos = *ppos + copied;
+		count -= copied;
+
+		ocfs2_set_next_iovec(&cur_iov, &iov_offset, copied);
+	} while(count);
+
+out:
+	return total ? total : ret;
+}
+
+static int ocfs2_check_iovec(const struct iovec *iov, size_t *counted,
+			     unsigned long *nr_segs)
+{
+	size_t ocount;		/* original count */
+	unsigned long seg;
+
+	ocount = 0;
+	for (seg = 0; seg < *nr_segs; seg++) {
+		const struct iovec *iv = &iov[seg];
+
+		/*
+		 * If any segment has a negative length, or the cumulative
+		 * length ever wraps negative then return -EINVAL.
+		 */
+		ocount += iv->iov_len;
+		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
+			return -EINVAL;
+		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
+			continue;
+		if (seg == 0)
+			return -EFAULT;
+		*nr_segs = seg;
+		ocount -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+
+	*counted = ocount;
+	return 0;
+}
+
 static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
 				    const struct iovec *iov,
 				    unsigned long nr_segs,
 				    loff_t pos)
 {
-	int ret, rw_level, have_alloc_sem = 0;
-	struct file *filp = iocb->ki_filp;
-	struct inode *inode = filp->f_path.dentry->d_inode;
-	int appending = filp->f_flags & O_APPEND ? 1 : 0;
-
-	mlog_entry("(0x%p, %u, '%.*s')\n", filp,
+	int ret, direct_io, appending, rw_level, have_alloc_sem  = 0;
+	int can_do_direct, sync = 0;
+	ssize_t written = 0;
+	size_t ocount;		/* original count */
+	size_t count;		/* after file limit checks */
+	loff_t *ppos = &iocb->ki_pos;
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file->f_path.dentry->d_inode;
+
+	mlog_entry("(0x%p, %u, '%.*s')\n", file,
 		   (unsigned int)nr_segs,
-		   filp->f_path.dentry->d_name.len,
-		   filp->f_path.dentry->d_name.name);
+		   file->f_path.dentry->d_name.len,
+		   file->f_path.dentry->d_name.name);
 
-	/* happy write of zero bytes */
 	if (iocb->ki_left == 0)
 		return 0;
 
+	ret = ocfs2_check_iovec(iov, &ocount, &nr_segs);
+	if (ret)
+		return ret;
+
+	count = ocount;
+
+	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+
+	appending = file->f_flags & O_APPEND ? 1 : 0;
+	direct_io = file->f_flags & O_DIRECT ? 1 : 0;
+
 	mutex_lock(&inode->i_mutex);
+
+relock:
 	/* to match setattr's i_mutex -> i_alloc_sem -> rw_lock ordering */
-	if (filp->f_flags & O_DIRECT) {
-		have_alloc_sem = 1;
+	if (direct_io) {
 		down_read(&inode->i_alloc_sem);
+		have_alloc_sem = 1;
 	}
 
 	/* concurrent O_DIRECT writes are allowed */
-	rw_level = (filp->f_flags & O_DIRECT) ? 0 : 1;
+	rw_level = !direct_io;
 	ret = ocfs2_rw_lock(inode, rw_level);
 	if (ret < 0) {
-		rw_level = -1;
 		mlog_errno(ret);
-		goto out;
+		goto out_sems;
 	}
 
-	ret = ocfs2_prepare_inode_for_write(filp->f_path.dentry, &iocb->ki_pos,
-					    iocb->ki_left, appending);
+	can_do_direct = direct_io;
+	ret = ocfs2_prepare_inode_for_write(file->f_path.dentry, ppos,
+					    iocb->ki_left, appending,
+					    &can_do_direct);
 	if (ret < 0) {
 		mlog_errno(ret);
 		goto out;
 	}
 
+	/*
+	 * We can't complete the direct I/O as requested, fall back to
+	 * buffered I/O.
+	 */
+	if (direct_io && !can_do_direct) {
+		ocfs2_rw_unlock(inode, rw_level);
+		up_read(&inode->i_alloc_sem);
+
+		have_alloc_sem = 0;
+		rw_level = -1;
+
+		direct_io = 0;
+		sync = 1;
+		goto relock;
+	}
+
+	if (!sync && ((file->f_flags & O_SYNC) || IS_SYNC(inode)))
+		sync = 1;
+
+	/*
+	 * XXX: Is it ok to execute these checks a second time?
+	 */
+	ret = generic_write_checks(file, ppos, &count, S_ISBLK(inode->i_mode));
+	if (ret)
+		goto out;
+
+	/*
+	 * Set pos so that sync_page_range_nolock() below understands
+	 * where to start from. We might've moved it around via the
+	 * calls above. The range we want to actually sync starts from
+	 * *ppos here.
+	 *
+	 */
+	pos = *ppos;
+
 	/* communicate with ocfs2_dio_end_io */
 	ocfs2_iocb_set_rw_locked(iocb);
 
-	ret = generic_file_aio_write_nolock(iocb, iov, nr_segs, iocb->ki_pos);
+	if (direct_io) {
+		written = generic_file_direct_write(iocb, iov, &nr_segs, *ppos,
+						    ppos, count, ocount);
+		if (written < 0) {
+			ret = written;
+			goto out_dio;
+		}
+	} else {
+		written = ocfs2_file_buffered_write(file, ppos, iov, nr_segs,
+						    count, written);
+		if (written < 0) {
+			ret = written;
+			if (ret != -EFAULT || ret != -ENOSPC)
+				mlog_errno(ret);
+			goto out;
+		}
+	}
 
+out_dio:
 	/* buffered aio wouldn't have proper lock coverage today */
-	BUG_ON(ret == -EIOCBQUEUED && !(filp->f_flags & O_DIRECT));
+	BUG_ON(ret == -EIOCBQUEUED && !(file->f_flags & O_DIRECT));
 
 	/* 
 	 * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
@@ -1268,14 +1552,25 @@ static ssize_t ocfs2_file_aio_write(struct kiocb *iocb,
 	}
 
 out:
+	if (rw_level != -1)
+		ocfs2_rw_unlock(inode, rw_level);
+
+out_sems:
 	if (have_alloc_sem)
 		up_read(&inode->i_alloc_sem);
-	if (rw_level != -1) 
-		ocfs2_rw_unlock(inode, rw_level);
+
+	if (written > 0 && sync) {
+		ssize_t err;
+
+		err = sync_page_range_nolock(inode, file->f_mapping, pos, count);
+		if (err < 0)
+			written = err;
+	}
+
 	mutex_unlock(&inode->i_mutex);
 
 	mlog_exit(ret);
-	return ret;
+	return written ? written : ret;
 }
 
 static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
@@ -1300,7 +1595,8 @@ static ssize_t ocfs2_file_splice_write(struct pipe_inode_info *pipe,
 		goto out;
 	}
 
-	ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0);
+	ret = ocfs2_prepare_inode_for_write(out->f_path.dentry, ppos, len, 0,
+					    NULL);
 	if (ret < 0) {
 		mlog_errno(ret);
 		goto out_unlock;
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index e2f6551604d0..2c4460fced52 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -46,6 +46,10 @@ int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
 			       struct ocfs2_alloc_context *data_ac,
 			       struct ocfs2_alloc_context *meta_ac,
 			       enum ocfs2_alloc_restarted *reason);
+int ocfs2_lock_allocators(struct inode *inode, struct ocfs2_dinode *di,
+			  u32 clusters_to_add,
+			  struct ocfs2_alloc_context **data_ac,
+			  struct ocfs2_alloc_context **meta_ac);
 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
 int ocfs2_getattr(struct vfsmount *mnt, struct dentry *dentry,
 		  struct kstat *stat);
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index faeb53f2eecf..2699f7cac21a 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -463,6 +463,38 @@ static inline unsigned long ocfs2_align_bytes_to_sectors(u64 bytes)
 	return (unsigned long)((bytes + 511) >> 9);
 }
 
+static inline unsigned int ocfs2_page_index_to_clusters(struct super_block *sb,
+							unsigned long pg_index)
+{
+	u32 clusters = pg_index;
+	unsigned int cbits = OCFS2_SB(sb)->s_clustersize_bits;
+
+	if (unlikely(PAGE_CACHE_SHIFT > cbits))
+		clusters = pg_index << (PAGE_CACHE_SHIFT - cbits);
+	else if (PAGE_CACHE_SHIFT < cbits)
+		clusters = pg_index >> (cbits - PAGE_CACHE_SHIFT);
+
+	return clusters;
+}
+
+/*
+ * Find the 1st page index which covers the given clusters.
+ */
+static inline unsigned long ocfs2_align_clusters_to_page_index(struct super_block *sb,
+							u32 clusters)
+{
+	unsigned int cbits = OCFS2_SB(sb)->s_clustersize_bits;
+	unsigned long index = clusters;
+
+	if (PAGE_CACHE_SHIFT > cbits) {
+		index = clusters >> (PAGE_CACHE_SHIFT - cbits);
+	} else if (PAGE_CACHE_SHIFT < cbits) {
+		index = clusters << (cbits - PAGE_CACHE_SHIFT);
+	}
+
+	return index;
+}
+
 #define ocfs2_set_bit ext2_set_bit
 #define ocfs2_clear_bit ext2_clear_bit
 #define ocfs2_test_bit ext2_test_bit