Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1431 insertions, 0 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
new file mode 100644
index 000000000000..6f7a4af3bc46
--- /dev/null
+++ b/fs/nfs/write.c
@@ -0,0 +1,1431 @@
+/*
+ * linux/fs/nfs/write.c
+ *
+ * Writing file data over NFS.
+ *
+ * We do it like this: When a (user) process wishes to write data to an
+ * NFS file, a write request is allocated that contains the RPC task data
+ * plus some info on the page to be written, and added to the inode's
+ * write chain. If the process writes past the end of the page, an async
+ * RPC call to write the page is scheduled immediately; otherwise, the call
+ * is delayed for a few seconds.
+ *
+ * Just like readahead, no async I/O is performed if wsize < PAGE_SIZE.
+ *
+ * Write requests are kept on the inode's writeback list. Each entry in
+ * that list references the page (portion) to be written. When the
+ * cache timeout has expired, the RPC task is woken up, and tries to
+ * lock the page. As soon as it manages to do so, the request is moved
+ * from the writeback list to the writelock list.
+ *
+ * Note: we must make sure never to confuse the inode passed in the
+ * write_page request with the one in page->inode. As far as I understand
+ * it, these are different when doing a swap-out.
+ *
+ * To understand everything that goes on here and in the NFS read code,
+ * one should be aware that a page is locked in exactly one of the following
+ * cases:
+ *
+ *  -	A write request is in progress.
+ *  -	A user process is in generic_file_write/nfs_update_page
+ *  -	A user process is in generic_file_read
+ *
+ * Also note that because of the way pages are invalidated in
+ * nfs_revalidate_inode, the following assertions hold:
+ *
+ *  -	If a page is dirty, there will be no read requests (a page will
+ *	not be re-read unless invalidated by nfs_revalidate_inode).
+ *  -	If the page is not uptodate, there will be no pending write
+ *	requests, and no process will be in nfs_update_page.
+ *
+ * FIXME: Interaction with the vmscan routines is not optimal yet.
+ * Either vmscan must be made nfs-savvy, or we need a different page
+ * reclaim concept that supports something like FS-independent
+ * buffer_heads with a b_ops-> field.
+ *
+ * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/config.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/mpage.h>
+#include <linux/writeback.h>
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/nfs_fs.h>
+#include <linux/nfs_mount.h>
+#include <linux/nfs_page.h>
+#include <asm/uaccess.h>
+#include <linux/smp_lock.h>
+
+#include "delegation.h"
+
+#define NFSDBG_FACILITY		NFSDBG_PAGECACHE
+
+#define MIN_POOL_WRITE		(32)
+#define MIN_POOL_COMMIT		(4)
+
+/*
+ * Local function declarations
+ */
+static struct nfs_page * nfs_update_request(struct nfs_open_context*,
+					    struct inode *,
+					    struct page *,
+					    unsigned int, unsigned int);
+static void nfs_writeback_done_partial(struct nfs_write_data *, int);
+static void nfs_writeback_done_full(struct nfs_write_data *, int);
+static int nfs_wait_on_write_congestion(struct address_space *, int);
+static int nfs_wait_on_requests(struct inode *, unsigned long, unsigned int);
+static int nfs_flush_inode(struct inode *inode, unsigned long idx_start,
+			   unsigned int npages, int how);
+
+static kmem_cache_t *nfs_wdata_cachep;
+mempool_t *nfs_wdata_mempool;
+static mempool_t *nfs_commit_mempool;
+
+static DECLARE_WAIT_QUEUE_HEAD(nfs_write_congestion);
+
+static inline struct nfs_write_data *nfs_commit_alloc(void)
+{
+	struct nfs_write_data *p = mempool_alloc(nfs_commit_mempool, SLAB_NOFS);
+	if (p) {
+		memset(p, 0, sizeof(*p));
+		INIT_LIST_HEAD(&p->pages);
+	}
+	return p;
+}
+
+static inline void nfs_commit_free(struct nfs_write_data *p)
+{
+	mempool_free(p, nfs_commit_mempool);
+}
+
+static void nfs_writedata_release(struct rpc_task *task)
+{
+	struct nfs_write_data	*wdata = (struct nfs_write_data *)task->tk_calldata;
+	nfs_writedata_free(wdata);
+}
+
+/* Adjust the file length if we're writing beyond the end */
+static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
+{
+	struct inode *inode = page->mapping->host;
+	loff_t end, i_size = i_size_read(inode);
+	unsigned long end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
+
+	if (i_size > 0 && page->index < end_index)
+		return;
+	end = ((loff_t)page->index << PAGE_CACHE_SHIFT) + ((loff_t)offset+count);
+	if (i_size >= end)
+		return;
+	i_size_write(inode, end);
+}
+
+/* We can set the PG_uptodate flag if we see that a write request
+ * covers the full page.
+ */
+static void nfs_mark_uptodate(struct page *page, unsigned int base, unsigned int count)
+{
+	loff_t end_offs;
+
+	if (PageUptodate(page))
+		return;
+	if (base != 0)
+		return;
+	if (count == PAGE_CACHE_SIZE) {
+		SetPageUptodate(page);
+		return;
+	}
+
+	end_offs = i_size_read(page->mapping->host) - 1;
+	if (end_offs < 0)
+		return;
+	/* Is this the last page? */
+	if (page->index != (unsigned long)(end_offs >> PAGE_CACHE_SHIFT))
+		return;
+	/* This is the last page: set PG_uptodate if we cover the entire
+	 * extent of the data, then zero the rest of the page.
+	 */
+	if (count == (unsigned int)(end_offs & (PAGE_CACHE_SIZE - 1)) + 1) {
+		memclear_highpage_flush(page, count, PAGE_CACHE_SIZE - count);
+		SetPageUptodate(page);
+	}
+}
+
+/*
+ * Write a page synchronously.
+ * Offset is the data offset within the page.
+ */
+static int nfs_writepage_sync(struct nfs_open_context *ctx, struct inode *inode,
+		struct page *page, unsigned int offset, unsigned int count,
+		int how)
+{
+	unsigned int	wsize = NFS_SERVER(inode)->wsize;
+	int		result, written = 0;
+	struct nfs_write_data *wdata;
+
+	wdata = nfs_writedata_alloc();
+	if (!wdata)
+		return -ENOMEM;
+
+	wdata->flags = how;
+	wdata->cred = ctx->cred;
+	wdata->inode = inode;
+	wdata->args.fh = NFS_FH(inode);
+	wdata->args.context = ctx;
+	wdata->args.pages = &page;
+	wdata->args.stable = NFS_FILE_SYNC;
+	wdata->args.pgbase = offset;
+	wdata->args.count = wsize;
+	wdata->res.fattr = &wdata->fattr;
+	wdata->res.verf = &wdata->verf;
+
+	dprintk("NFS:      nfs_writepage_sync(%s/%Ld %d@%Ld)\n",
+		inode->i_sb->s_id,
+		(long long)NFS_FILEID(inode),
+		count, (long long)(page_offset(page) + offset));
+
+	nfs_begin_data_update(inode);
+	do {
+		if (count < wsize)
+			wdata->args.count = count;
+		wdata->args.offset = page_offset(page) + wdata->args.pgbase;
+
+		result = NFS_PROTO(inode)->write(wdata);
+
+		if (result < 0) {
+			/* Must mark the page invalid after I/O error */
+			ClearPageUptodate(page);
+			goto io_error;
+		}
+		if (result < wdata->args.count)
+			printk(KERN_WARNING "NFS: short write, count=%u, result=%d\n",
+					wdata->args.count, result);
+
+		wdata->args.offset += result;
+	        wdata->args.pgbase += result;
+		written += result;
+		count -= result;
+	} while (count);
+	/* Update file length */
+	nfs_grow_file(page, offset, written);
+	/* Set the PG_uptodate flag? */
+	nfs_mark_uptodate(page, offset, written);
+
+	if (PageError(page))
+		ClearPageError(page);
+
+io_error:
+	nfs_end_data_update_defer(inode);
+	nfs_writedata_free(wdata);
+	return written ? written : result;
+}
+
+static int nfs_writepage_async(struct nfs_open_context *ctx,
+		struct inode *inode, struct page *page,
+		unsigned int offset, unsigned int count)
+{
+	struct nfs_page	*req;
+	int		status;
+
+	req = nfs_update_request(ctx, inode, page, offset, count);
+	status = (IS_ERR(req)) ? PTR_ERR(req) : 0;
+	if (status < 0)
+		goto out;
+	/* Update file length */
+	nfs_grow_file(page, offset, count);
+	/* Set the PG_uptodate flag? */
+	nfs_mark_uptodate(page, offset, count);
+	nfs_unlock_request(req);
+ out:
+	return status;
+}
+
+static int wb_priority(struct writeback_control *wbc)
+{
+	if (wbc->for_reclaim)
+		return FLUSH_HIGHPRI;
+	if (wbc->for_kupdate)
+		return FLUSH_LOWPRI;
+	return 0;
+}
+
+/*
+ * Write an mmapped page to the server.
+ */
+int nfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct nfs_open_context *ctx;
+	struct inode *inode = page->mapping->host;
+	unsigned long end_index;
+	unsigned offset = PAGE_CACHE_SIZE;
+	loff_t i_size = i_size_read(inode);
+	int inode_referenced = 0;
+	int priority = wb_priority(wbc);
+	int err;
+
+	/*
+	 * Note: We need to ensure that we have a reference to the inode
+	 *       if we are to do asynchronous writes. If not, waiting
+	 *       in nfs_wait_on_request() may deadlock with clear_inode().
+	 *
+	 *       If igrab() fails here, then it is in any case safe to
+	 *       call nfs_wb_page(), since there will be no pending writes.
+	 */
+	if (igrab(inode) != 0)
+		inode_referenced = 1;
+	end_index = i_size >> PAGE_CACHE_SHIFT;
+
+	/* Ensure we've flushed out any previous writes */
+	nfs_wb_page_priority(inode, page, priority);
+
+	/* easy case */
+	if (page->index < end_index)
+		goto do_it;
+	/* things got complicated... */
+	offset = i_size & (PAGE_CACHE_SIZE-1);
+
+	/* OK, are we completely out? */
+	err = 0; /* potential race with truncate - ignore */
+	if (page->index >= end_index+1 || !offset)
+		goto out;
+do_it:
+	ctx = nfs_find_open_context(inode, FMODE_WRITE);
+	if (ctx == NULL) {
+		err = -EBADF;
+		goto out;
+	}
+	lock_kernel();
+	if (!IS_SYNC(inode) && inode_referenced) {
+		err = nfs_writepage_async(ctx, inode, page, 0, offset);
+		if (err >= 0) {
+			err = 0;
+			if (wbc->for_reclaim)
+				nfs_flush_inode(inode, 0, 0, FLUSH_STABLE);
+		}
+	} else {
+		err = nfs_writepage_sync(ctx, inode, page, 0,
+						offset, priority);
+		if (err >= 0) {
+			if (err != offset)
+				redirty_page_for_writepage(wbc, page);
+			err = 0;
+		}
+	}
+	unlock_kernel();
+	put_nfs_open_context(ctx);
+out:
+	unlock_page(page);
+	if (inode_referenced)
+		iput(inode);
+	return err; 
+}
+
+/*
+ * Note: causes nfs_update_request() to block on the assumption
+ * 	 that the writeback is generated due to memory pressure.
+ */
+int nfs_writepages(struct address_space *mapping, struct writeback_control *wbc)
+{
+	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	struct inode *inode = mapping->host;
+	int err;
+
+	err = generic_writepages(mapping, wbc);
+	if (err)
+		return err;
+	while (test_and_set_bit(BDI_write_congested, &bdi->state) != 0) {
+		if (wbc->nonblocking)
+			return 0;
+		nfs_wait_on_write_congestion(mapping, 0);
+	}
+	err = nfs_flush_inode(inode, 0, 0, wb_priority(wbc));
+	if (err < 0)
+		goto out;
+	wbc->nr_to_write -= err;
+	if (!wbc->nonblocking && wbc->sync_mode == WB_SYNC_ALL) {
+		err = nfs_wait_on_requests(inode, 0, 0);
+		if (err < 0)
+			goto out;
+	}
+	err = nfs_commit_inode(inode, 0, 0, wb_priority(wbc));
+	if (err > 0) {
+		wbc->nr_to_write -= err;
+		err = 0;
+	}
+out:
+	clear_bit(BDI_write_congested, &bdi->state);
+	wake_up_all(&nfs_write_congestion);
+	return err;
+}
+
+/*
+ * Insert a write request into an inode
+ */
+static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	int error;
+
+	error = radix_tree_insert(&nfsi->nfs_page_tree, req->wb_index, req);
+	BUG_ON(error == -EEXIST);
+	if (error)
+		return error;
+	if (!nfsi->npages) {
+		igrab(inode);
+		nfs_begin_data_update(inode);
+		if (nfs_have_delegation(inode, FMODE_WRITE))
+			nfsi->change_attr++;
+	}
+	nfsi->npages++;
+	atomic_inc(&req->wb_count);
+	return 0;
+}
+
+/*
+ * Insert a write request into an inode
+ */
+static void nfs_inode_remove_request(struct nfs_page *req)
+{
+	struct inode *inode = req->wb_context->dentry->d_inode;
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	BUG_ON (!NFS_WBACK_BUSY(req));
+
+	spin_lock(&nfsi->req_lock);
+	radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
+	nfsi->npages--;
+	if (!nfsi->npages) {
+		spin_unlock(&nfsi->req_lock);
+		nfs_end_data_update_defer(inode);
+		iput(inode);
+	} else
+		spin_unlock(&nfsi->req_lock);
+	nfs_clear_request(req);
+	nfs_release_request(req);
+}
+
+/*
+ * Find a request
+ */
+static inline struct nfs_page *
+_nfs_find_request(struct inode *inode, unsigned long index)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_page *req;
+
+	req = (struct nfs_page*)radix_tree_lookup(&nfsi->nfs_page_tree, index);
+	if (req)
+		atomic_inc(&req->wb_count);
+	return req;
+}
+
+static struct nfs_page *
+nfs_find_request(struct inode *inode, unsigned long index)
+{
+	struct nfs_page		*req;
+	struct nfs_inode	*nfsi = NFS_I(inode);
+
+	spin_lock(&nfsi->req_lock);
+	req = _nfs_find_request(inode, index);
+	spin_unlock(&nfsi->req_lock);
+	return req;
+}
+
+/*
+ * Add a request to the inode's dirty list.
+ */
+static void
+nfs_mark_request_dirty(struct nfs_page *req)
+{
+	struct inode *inode = req->wb_context->dentry->d_inode;
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	spin_lock(&nfsi->req_lock);
+	nfs_list_add_request(req, &nfsi->dirty);
+	nfsi->ndirty++;
+	spin_unlock(&nfsi->req_lock);
+	inc_page_state(nr_dirty);
+	mark_inode_dirty(inode);
+}
+
+/*
+ * Check if a request is dirty
+ */
+static inline int
+nfs_dirty_request(struct nfs_page *req)
+{
+	struct nfs_inode *nfsi = NFS_I(req->wb_context->dentry->d_inode);
+	return !list_empty(&req->wb_list) && req->wb_list_head == &nfsi->dirty;
+}
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+/*
+ * Add a request to the inode's commit list.
+ */
+static void
+nfs_mark_request_commit(struct nfs_page *req)
+{
+	struct inode *inode = req->wb_context->dentry->d_inode;
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	spin_lock(&nfsi->req_lock);
+	nfs_list_add_request(req, &nfsi->commit);
+	nfsi->ncommit++;
+	spin_unlock(&nfsi->req_lock);
+	inc_page_state(nr_unstable);
+	mark_inode_dirty(inode);
+}
+#endif
+
+/*
+ * Wait for a request to complete.
+ *
+ * Interruptible by signals only if mounted with intr flag.
+ */
+static int
+nfs_wait_on_requests(struct inode *inode, unsigned long idx_start, unsigned int npages)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_page *req;
+	unsigned long		idx_end, next;
+	unsigned int		res = 0;
+	int			error;
+
+	if (npages == 0)
+		idx_end = ~0;
+	else
+		idx_end = idx_start + npages - 1;
+
+	spin_lock(&nfsi->req_lock);
+	next = idx_start;
+	while (radix_tree_gang_lookup(&nfsi->nfs_page_tree, (void **)&req, next, 1)) {
+		if (req->wb_index > idx_end)
+			break;
+
+		next = req->wb_index + 1;
+		if (!NFS_WBACK_BUSY(req))
+			continue;
+
+		atomic_inc(&req->wb_count);
+		spin_unlock(&nfsi->req_lock);
+		error = nfs_wait_on_request(req);
+		nfs_release_request(req);
+		if (error < 0)
+			return error;
+		spin_lock(&nfsi->req_lock);
+		res++;
+	}
+	spin_unlock(&nfsi->req_lock);
+	return res;
+}
+
+/*
+ * nfs_scan_dirty - Scan an inode for dirty requests
+ * @inode: NFS inode to scan
+ * @dst: destination list
+ * @idx_start: lower bound of page->index to scan.
+ * @npages: idx_start + npages sets the upper bound to scan.
+ *
+ * Moves requests from the inode's dirty page list.
+ * The requests are *not* checked to ensure that they form a contiguous set.
+ */
+static int
+nfs_scan_dirty(struct inode *inode, struct list_head *dst, unsigned long idx_start, unsigned int npages)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	int	res;
+	res = nfs_scan_list(&nfsi->dirty, dst, idx_start, npages);
+	nfsi->ndirty -= res;
+	sub_page_state(nr_dirty,res);
+	if ((nfsi->ndirty == 0) != list_empty(&nfsi->dirty))
+		printk(KERN_ERR "NFS: desynchronized value of nfs_i.ndirty.\n");
+	return res;
+}
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+/*
+ * nfs_scan_commit - Scan an inode for commit requests
+ * @inode: NFS inode to scan
+ * @dst: destination list
+ * @idx_start: lower bound of page->index to scan.
+ * @npages: idx_start + npages sets the upper bound to scan.
+ *
+ * Moves requests from the inode's 'commit' request list.
+ * The requests are *not* checked to ensure that they form a contiguous set.
+ */
+static int
+nfs_scan_commit(struct inode *inode, struct list_head *dst, unsigned long idx_start, unsigned int npages)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	int	res;
+	res = nfs_scan_list(&nfsi->commit, dst, idx_start, npages);
+	nfsi->ncommit -= res;
+	if ((nfsi->ncommit == 0) != list_empty(&nfsi->commit))
+		printk(KERN_ERR "NFS: desynchronized value of nfs_i.ncommit.\n");
+	return res;
+}
+#endif
+
+static int nfs_wait_on_write_congestion(struct address_space *mapping, int intr)
+{
+	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	DEFINE_WAIT(wait);
+	int ret = 0;
+
+	might_sleep();
+
+	if (!bdi_write_congested(bdi))
+		return 0;
+	if (intr) {
+		struct rpc_clnt *clnt = NFS_CLIENT(mapping->host);
+		sigset_t oldset;
+
+		rpc_clnt_sigmask(clnt, &oldset);
+		prepare_to_wait(&nfs_write_congestion, &wait, TASK_INTERRUPTIBLE);
+		if (bdi_write_congested(bdi)) {
+			if (signalled())
+				ret = -ERESTARTSYS;
+			else
+				schedule();
+		}
+		rpc_clnt_sigunmask(clnt, &oldset);
+	} else {
+		prepare_to_wait(&nfs_write_congestion, &wait, TASK_UNINTERRUPTIBLE);
+		if (bdi_write_congested(bdi))
+			schedule();
+	}
+	finish_wait(&nfs_write_congestion, &wait);
+	return ret;
+}
+
+
+/*
+ * Try to update any existing write request, or create one if there is none.
+ * In order to match, the request's credentials must match those of
+ * the calling process.
+ *
+ * Note: Should always be called with the Page Lock held!
+ */
+static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx,
+		struct inode *inode, struct page *page,
+		unsigned int offset, unsigned int bytes)
+{
+	struct nfs_server *server = NFS_SERVER(inode);
+	struct nfs_inode *nfsi = NFS_I(inode);
+	struct nfs_page		*req, *new = NULL;
+	unsigned long		rqend, end;
+
+	end = offset + bytes;
+
+	if (nfs_wait_on_write_congestion(page->mapping, server->flags & NFS_MOUNT_INTR))
+		return ERR_PTR(-ERESTARTSYS);
+	for (;;) {
+		/* Loop over all inode entries and see if we find
+		 * A request for the page we wish to update
+		 */
+		spin_lock(&nfsi->req_lock);
+		req = _nfs_find_request(inode, page->index);
+		if (req) {
+			if (!nfs_lock_request_dontget(req)) {
+				int error;
+				spin_unlock(&nfsi->req_lock);
+				error = nfs_wait_on_request(req);
+				nfs_release_request(req);
+				if (error < 0)
+					return ERR_PTR(error);
+				continue;
+			}
+			spin_unlock(&nfsi->req_lock);
+			if (new)
+				nfs_release_request(new);
+			break;
+		}
+
+		if (new) {
+			int error;
+			nfs_lock_request_dontget(new);
+			error = nfs_inode_add_request(inode, new);
+			if (error) {
+				spin_unlock(&nfsi->req_lock);
+				nfs_unlock_request(new);
+				return ERR_PTR(error);
+			}
+			spin_unlock(&nfsi->req_lock);
+			nfs_mark_request_dirty(new);
+			return new;
+		}
+		spin_unlock(&nfsi->req_lock);
+
+		new = nfs_create_request(ctx, inode, page, offset, bytes);
+		if (IS_ERR(new))
+			return new;
+	}
+
+	/* We have a request for our page.
+	 * If the creds don't match, or the
+	 * page addresses don't match,
+	 * tell the caller to wait on the conflicting
+	 * request.
+	 */
+	rqend = req->wb_offset + req->wb_bytes;
+	if (req->wb_context != ctx
+	    || req->wb_page != page
+	    || !nfs_dirty_request(req)
+	    || offset > rqend || end < req->wb_offset) {
+		nfs_unlock_request(req);
+		return ERR_PTR(-EBUSY);
+	}
+
+	/* Okay, the request matches. Update the region */
+	if (offset < req->wb_offset) {
+		req->wb_offset = offset;
+		req->wb_pgbase = offset;
+		req->wb_bytes = rqend - req->wb_offset;
+	}
+
+	if (end > rqend)
+		req->wb_bytes = end - req->wb_offset;
+
+	return req;
+}
+
+int nfs_flush_incompatible(struct file *file, struct page *page)
+{
+	struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
+	struct inode	*inode = page->mapping->host;
+	struct nfs_page	*req;
+	int		status = 0;
+	/*
+	 * Look for a request corresponding to this page. If there
+	 * is one, and it belongs to another file, we flush it out
+	 * before we try to copy anything into the page. Do this
+	 * due to the lack of an ACCESS-type call in NFSv2.
+	 * Also do the same if we find a request from an existing
+	 * dropped page.
+	 */
+	req = nfs_find_request(inode, page->index);
+	if (req) {
+		if (req->wb_page != page || ctx != req->wb_context)
+			status = nfs_wb_page(inode, page);
+		nfs_release_request(req);
+	}
+	return (status < 0) ? status : 0;
+}
+
+/*
+ * Update and possibly write a cached page of an NFS file.
+ *
+ * XXX: Keep an eye on generic_file_read to make sure it doesn't do bad
+ * things with a page scheduled for an RPC call (e.g. invalidate it).
+ */
+int nfs_updatepage(struct file *file, struct page *page,
+		unsigned int offset, unsigned int count)
+{
+	struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
+	struct dentry	*dentry = file->f_dentry;
+	struct inode	*inode = page->mapping->host;
+	struct nfs_page	*req;
+	int		status = 0;
+
+	dprintk("NFS:      nfs_updatepage(%s/%s %d@%Ld)\n",
+		dentry->d_parent->d_name.name, dentry->d_name.name,
+		count, (long long)(page_offset(page) +offset));
+
+	if (IS_SYNC(inode)) {
+		status = nfs_writepage_sync(ctx, inode, page, offset, count, 0);
+		if (status > 0) {
+			if (offset == 0 && status == PAGE_CACHE_SIZE)
+				SetPageUptodate(page);
+			return 0;
+		}
+		return status;
+	}
+
+	/* If we're not using byte range locks, and we know the page
+	 * is entirely in cache, it may be more efficient to avoid
+	 * fragmenting write requests.
+	 */
+	if (PageUptodate(page) && inode->i_flock == NULL) {
+		loff_t end_offs = i_size_read(inode) - 1;
+		unsigned long end_index = end_offs >> PAGE_CACHE_SHIFT;
+
+		count += offset;
+		offset = 0;
+		if (unlikely(end_offs < 0)) {
+			/* Do nothing */
+		} else if (page->index == end_index) {
+			unsigned int pglen;
+			pglen = (unsigned int)(end_offs & (PAGE_CACHE_SIZE-1)) + 1;
+			if (count < pglen)
+				count = pglen;
+		} else if (page->index < end_index)
+			count = PAGE_CACHE_SIZE;
+	}
+
+	/*
+	 * Try to find an NFS request corresponding to this page
+	 * and update it.
+	 * If the existing request cannot be updated, we must flush
+	 * it out now.
+	 */
+	do {
+		req = nfs_update_request(ctx, inode, page, offset, count);
+		status = (IS_ERR(req)) ? PTR_ERR(req) : 0;
+		if (status != -EBUSY)
+			break;
+		/* Request could not be updated. Flush it out and try again */
+		status = nfs_wb_page(inode, page);
+	} while (status >= 0);
+	if (status < 0)
+		goto done;
+
+	status = 0;
+
+	/* Update file length */
+	nfs_grow_file(page, offset, count);
+	/* Set the PG_uptodate flag? */
+	nfs_mark_uptodate(page, req->wb_pgbase, req->wb_bytes);
+	nfs_unlock_request(req);
+done:
+        dprintk("NFS:      nfs_updatepage returns %d (isize %Ld)\n",
+			status, (long long)i_size_read(inode));
+	if (status < 0)
+		ClearPageUptodate(page);
+	return status;
+}
+
+static void nfs_writepage_release(struct nfs_page *req)
+{
+	end_page_writeback(req->wb_page);
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+	if (!PageError(req->wb_page)) {
+		if (NFS_NEED_RESCHED(req)) {
+			nfs_mark_request_dirty(req);
+			goto out;
+		} else if (NFS_NEED_COMMIT(req)) {
+			nfs_mark_request_commit(req);
+			goto out;
+		}
+	}
+	nfs_inode_remove_request(req);
+
+out:
+	nfs_clear_commit(req);
+	nfs_clear_reschedule(req);
+#else
+	nfs_inode_remove_request(req);
+#endif
+	nfs_unlock_request(req);
+}
+
+static inline int flush_task_priority(int how)
+{
+	switch (how & (FLUSH_HIGHPRI|FLUSH_LOWPRI)) {
+		case FLUSH_HIGHPRI:
+			return RPC_PRIORITY_HIGH;
+		case FLUSH_LOWPRI:
+			return RPC_PRIORITY_LOW;
+	}
+	return RPC_PRIORITY_NORMAL;
+}
+
+/*
+ * Set up the argument/result storage required for the RPC call.
+ */
+static void nfs_write_rpcsetup(struct nfs_page *req,
+		struct nfs_write_data *data,
+		unsigned int count, unsigned int offset,
+		int how)
+{
+	struct rpc_task		*task = &data->task;
+	struct inode		*inode;
+
+	/* Set up the RPC argument and reply structs
+	 * NB: take care not to mess about with data->commit et al. */
+
+	data->req = req;
+	data->inode = inode = req->wb_context->dentry->d_inode;
+	data->cred = req->wb_context->cred;
+
+	data->args.fh     = NFS_FH(inode);
+	data->args.offset = req_offset(req) + offset;
+	data->args.pgbase = req->wb_pgbase + offset;
+	data->args.pages  = data->pagevec;
+	data->args.count  = count;
+	data->args.context = req->wb_context;
+
+	data->res.fattr   = &data->fattr;
+	data->res.count   = count;
+	data->res.verf    = &data->verf;
+
+	NFS_PROTO(inode)->write_setup(data, how);
+
+	data->task.tk_priority = flush_task_priority(how);
+	data->task.tk_cookie = (unsigned long)inode;
+	data->task.tk_calldata = data;
+	/* Release requests */
+	data->task.tk_release = nfs_writedata_release;
+
+	dprintk("NFS: %4d initiated write call (req %s/%Ld, %u bytes @ offset %Lu)\n",
+		task->tk_pid,
+		inode->i_sb->s_id,
+		(long long)NFS_FILEID(inode),
+		count,
+		(unsigned long long)data->args.offset);
+}
+
+static void nfs_execute_write(struct nfs_write_data *data)
+{
+	struct rpc_clnt *clnt = NFS_CLIENT(data->inode);
+	sigset_t oldset;
+
+	rpc_clnt_sigmask(clnt, &oldset);
+	lock_kernel();
+	rpc_execute(&data->task);
+	unlock_kernel();
+	rpc_clnt_sigunmask(clnt, &oldset);
+}
+
+/*
+ * Generate multiple small requests to write out a single
+ * contiguous dirty area on one page.
+ */
+static int nfs_flush_multi(struct list_head *head, struct inode *inode, int how)
+{
+	struct nfs_page *req = nfs_list_entry(head->next);
+	struct page *page = req->wb_page;
+	struct nfs_write_data *data;
+	unsigned int wsize = NFS_SERVER(inode)->wsize;
+	unsigned int nbytes, offset;
+	int requests = 0;
+	LIST_HEAD(list);
+
+	nfs_list_remove_request(req);
+
+	nbytes = req->wb_bytes;
+	for (;;) {
+		data = nfs_writedata_alloc();
+		if (!data)
+			goto out_bad;
+		list_add(&data->pages, &list);
+		requests++;
+		if (nbytes <= wsize)
+			break;
+		nbytes -= wsize;
+	}
+	atomic_set(&req->wb_complete, requests);
+
+	ClearPageError(page);
+	SetPageWriteback(page);
+	offset = 0;
+	nbytes = req->wb_bytes;
+	do {
+		data = list_entry(list.next, struct nfs_write_data, pages);
+		list_del_init(&data->pages);
+
+		data->pagevec[0] = page;
+		data->complete = nfs_writeback_done_partial;
+
+		if (nbytes > wsize) {
+			nfs_write_rpcsetup(req, data, wsize, offset, how);
+			offset += wsize;
+			nbytes -= wsize;
+		} else {
+			nfs_write_rpcsetup(req, data, nbytes, offset, how);
+			nbytes = 0;
+		}
+		nfs_execute_write(data);
+	} while (nbytes != 0);
+
+	return 0;
+
+out_bad:
+	while (!list_empty(&list)) {
+		data = list_entry(list.next, struct nfs_write_data, pages);
+		list_del(&data->pages);
+		nfs_writedata_free(data);
+	}
+	nfs_mark_request_dirty(req);
+	nfs_unlock_request(req);
+	return -ENOMEM;
+}
+
+/*
+ * Create an RPC task for the given write request and kick it.
+ * The page must have been locked by the caller.
+ *
+ * It may happen that the page we're passed is not marked dirty.
+ * This is the case if nfs_updatepage detects a conflicting request
+ * that has been written but not committed.
+ */
+static int nfs_flush_one(struct list_head *head, struct inode *inode, int how)
+{
+	struct nfs_page		*req;
+	struct page		**pages;
+	struct nfs_write_data	*data;
+	unsigned int		count;
+
+	if (NFS_SERVER(inode)->wsize < PAGE_CACHE_SIZE)
+		return nfs_flush_multi(head, inode, how);
+
+	data = nfs_writedata_alloc();
+	if (!data)
+		goto out_bad;
+
+	pages = data->pagevec;
+	count = 0;
+	while (!list_empty(head)) {
+		req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		nfs_list_add_request(req, &data->pages);
+		ClearPageError(req->wb_page);
+		SetPageWriteback(req->wb_page);
+		*pages++ = req->wb_page;
+		count += req->wb_bytes;
+	}
+	req = nfs_list_entry(data->pages.next);
+
+	data->complete = nfs_writeback_done_full;
+	/* Set up the argument struct */
+	nfs_write_rpcsetup(req, data, count, 0, how);
+
+	nfs_execute_write(data);
+	return 0;
+ out_bad:
+	while (!list_empty(head)) {
+		struct nfs_page *req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		nfs_mark_request_dirty(req);
+		nfs_unlock_request(req);
+	}
+	return -ENOMEM;
+}
+
+static int
+nfs_flush_list(struct list_head *head, int wpages, int how)
+{
+	LIST_HEAD(one_request);
+	struct nfs_page		*req;
+	int			error = 0;
+	unsigned int		pages = 0;
+
+	while (!list_empty(head)) {
+		pages += nfs_coalesce_requests(head, &one_request, wpages);
+		req = nfs_list_entry(one_request.next);
+		error = nfs_flush_one(&one_request, req->wb_context->dentry->d_inode, how);
+		if (error < 0)
+			break;
+	}
+	if (error >= 0)
+		return pages;
+
+	while (!list_empty(head)) {
+		req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		nfs_mark_request_dirty(req);
+		nfs_unlock_request(req);
+	}
+	return error;
+}
+
+/*
+ * Handle a write reply that flushed part of a page.
+ */
+static void nfs_writeback_done_partial(struct nfs_write_data *data, int status)
+{
+	struct nfs_page		*req = data->req;
+	struct page		*page = req->wb_page;
+
+	dprintk("NFS: write (%s/%Ld %d@%Ld)",
+		req->wb_context->dentry->d_inode->i_sb->s_id,
+		(long long)NFS_FILEID(req->wb_context->dentry->d_inode),
+		req->wb_bytes,
+		(long long)req_offset(req));
+
+	if (status < 0) {
+		ClearPageUptodate(page);
+		SetPageError(page);
+		req->wb_context->error = status;
+		dprintk(", error = %d\n", status);
+	} else {
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+		if (data->verf.committed < NFS_FILE_SYNC) {
+			if (!NFS_NEED_COMMIT(req)) {
+				nfs_defer_commit(req);
+				memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
+				dprintk(" defer commit\n");
+			} else if (memcmp(&req->wb_verf, &data->verf, sizeof(req->wb_verf))) {
+				nfs_defer_reschedule(req);
+				dprintk(" server reboot detected\n");
+			}
+		} else
+#endif
+			dprintk(" OK\n");
+	}
+
+	if (atomic_dec_and_test(&req->wb_complete))
+		nfs_writepage_release(req);
+}
+
+/*
+ * Handle a write reply that flushes a whole page.
+ *
+ * FIXME: There is an inherent race with invalidate_inode_pages and
+ *	  writebacks since the page->count is kept > 1 for as long
+ *	  as the page has a write request pending.
+ */
+static void nfs_writeback_done_full(struct nfs_write_data *data, int status)
+{
+	struct nfs_page		*req;
+	struct page		*page;
+
+	/* Update attributes as result of writeback. */
+	while (!list_empty(&data->pages)) {
+		req = nfs_list_entry(data->pages.next);
+		nfs_list_remove_request(req);
+		page = req->wb_page;
+
+		dprintk("NFS: write (%s/%Ld %d@%Ld)",
+			req->wb_context->dentry->d_inode->i_sb->s_id,
+			(long long)NFS_FILEID(req->wb_context->dentry->d_inode),
+			req->wb_bytes,
+			(long long)req_offset(req));
+
+		if (status < 0) {
+			ClearPageUptodate(page);
+			SetPageError(page);
+			req->wb_context->error = status;
+			end_page_writeback(page);
+			nfs_inode_remove_request(req);
+			dprintk(", error = %d\n", status);
+			goto next;
+		}
+		end_page_writeback(page);
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+		if (data->args.stable != NFS_UNSTABLE || data->verf.committed == NFS_FILE_SYNC) {
+			nfs_inode_remove_request(req);
+			dprintk(" OK\n");
+			goto next;
+		}
+		memcpy(&req->wb_verf, &data->verf, sizeof(req->wb_verf));
+		nfs_mark_request_commit(req);
+		dprintk(" marked for commit\n");
+#else
+		nfs_inode_remove_request(req);
+#endif
+	next:
+		nfs_unlock_request(req);
+	}
+}
+
+/*
+ * This function is called when the WRITE call is complete.
+ */
+void nfs_writeback_done(struct rpc_task *task)
+{
+	struct nfs_write_data	*data = (struct nfs_write_data *) task->tk_calldata;
+	struct nfs_writeargs	*argp = &data->args;
+	struct nfs_writeres	*resp = &data->res;
+
+	dprintk("NFS: %4d nfs_writeback_done (status %d)\n",
+		task->tk_pid, task->tk_status);
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+	if (resp->verf->committed < argp->stable && task->tk_status >= 0) {
+		/* We tried a write call, but the server did not
+		 * commit data to stable storage even though we
+		 * requested it.
+		 * Note: There is a known bug in Tru64 < 5.0 in which
+		 *	 the server reports NFS_DATA_SYNC, but performs
+		 *	 NFS_FILE_SYNC. We therefore implement this checking
+		 *	 as a dprintk() in order to avoid filling syslog.
+		 */
+		static unsigned long    complain;
+
+		if (time_before(complain, jiffies)) {
+			dprintk("NFS: faulty NFS server %s:"
+				" (committed = %d) != (stable = %d)\n",
+				NFS_SERVER(data->inode)->hostname,
+				resp->verf->committed, argp->stable);
+			complain = jiffies + 300 * HZ;
+		}
+	}
+#endif
+	/* Is this a short write? */
+	if (task->tk_status >= 0 && resp->count < argp->count) {
+		static unsigned long    complain;
+
+		/* Has the server at least made some progress? */
+		if (resp->count != 0) {
+			/* Was this an NFSv2 write or an NFSv3 stable write? */
+			if (resp->verf->committed != NFS_UNSTABLE) {
+				/* Resend from where the server left off */
+				argp->offset += resp->count;
+				argp->pgbase += resp->count;
+				argp->count -= resp->count;
+			} else {
+				/* Resend as a stable write in order to avoid
+				 * headaches in the case of a server crash.
+				 */
+				argp->stable = NFS_FILE_SYNC;
+			}
+			rpc_restart_call(task);
+			return;
+		}
+		if (time_before(complain, jiffies)) {
+			printk(KERN_WARNING
+			       "NFS: Server wrote zero bytes, expected %u.\n",
+					argp->count);
+			complain = jiffies + 300 * HZ;
+		}
+		/* Can't do anything about it except throw an error. */
+		task->tk_status = -EIO;
+	}
+
+	/*
+	 * Process the nfs_page list
+	 */
+	data->complete(data, task->tk_status);
+}
+
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+static void nfs_commit_release(struct rpc_task *task)
+{
+	struct nfs_write_data	*wdata = (struct nfs_write_data *)task->tk_calldata;
+	nfs_commit_free(wdata);
+}
+
+/*
+ * Set up the argument/result storage required for the RPC call.
+ */
+static void nfs_commit_rpcsetup(struct list_head *head,
+		struct nfs_write_data *data, int how)
+{
+	struct rpc_task		*task = &data->task;
+	struct nfs_page		*first, *last;
+	struct inode		*inode;
+	loff_t			start, end, len;
+
+	/* Set up the RPC argument and reply structs
+	 * NB: take care not to mess about with data->commit et al. */
+
+	list_splice_init(head, &data->pages);
+	first = nfs_list_entry(data->pages.next);
+	last = nfs_list_entry(data->pages.prev);
+	inode = first->wb_context->dentry->d_inode;
+
+	/*
+	 * Determine the offset range of requests in the COMMIT call.
+	 * We rely on the fact that data->pages is an ordered list...
+	 */
+	start = req_offset(first);
+	end = req_offset(last) + last->wb_bytes;
+	len = end - start;
+	/* If 'len' is not a 32-bit quantity, pass '0' in the COMMIT call */
+	if (end >= i_size_read(inode) || len < 0 || len > (~((u32)0) >> 1))
+		len = 0;
+
+	data->inode	  = inode;
+	data->cred	  = first->wb_context->cred;
+
+	data->args.fh     = NFS_FH(data->inode);
+	data->args.offset = start;
+	data->args.count  = len;
+	data->res.count   = len;
+	data->res.fattr   = &data->fattr;
+	data->res.verf    = &data->verf;
+	
+	NFS_PROTO(inode)->commit_setup(data, how);
+
+	data->task.tk_priority = flush_task_priority(how);
+	data->task.tk_cookie = (unsigned long)inode;
+	data->task.tk_calldata = data;
+	/* Release requests */
+	data->task.tk_release = nfs_commit_release;
+	
+	dprintk("NFS: %4d initiated commit call\n", task->tk_pid);
+}
+
+/*
+ * Commit dirty pages
+ */
+static int
+nfs_commit_list(struct list_head *head, int how)
+{
+	struct nfs_write_data	*data;
+	struct nfs_page         *req;
+
+	data = nfs_commit_alloc();
+
+	if (!data)
+		goto out_bad;
+
+	/* Set up the argument struct */
+	nfs_commit_rpcsetup(head, data, how);
+
+	nfs_execute_write(data);
+	return 0;
+ out_bad:
+	while (!list_empty(head)) {
+		req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		nfs_mark_request_commit(req);
+		nfs_unlock_request(req);
+	}
+	return -ENOMEM;
+}
+
+/*
+ * COMMIT call returned
+ */
+void
+nfs_commit_done(struct rpc_task *task)
+{
+	struct nfs_write_data	*data = (struct nfs_write_data *)task->tk_calldata;
+	struct nfs_page		*req;
+	int res = 0;
+
+        dprintk("NFS: %4d nfs_commit_done (status %d)\n",
+                                task->tk_pid, task->tk_status);
+
+	while (!list_empty(&data->pages)) {
+		req = nfs_list_entry(data->pages.next);
+		nfs_list_remove_request(req);
+
+		dprintk("NFS: commit (%s/%Ld %d@%Ld)",
+			req->wb_context->dentry->d_inode->i_sb->s_id,
+			(long long)NFS_FILEID(req->wb_context->dentry->d_inode),
+			req->wb_bytes,
+			(long long)req_offset(req));
+		if (task->tk_status < 0) {
+			req->wb_context->error = task->tk_status;
+			nfs_inode_remove_request(req);
+			dprintk(", error = %d\n", task->tk_status);
+			goto next;
+		}
+
+		/* Okay, COMMIT succeeded, apparently. Check the verifier
+		 * returned by the server against all stored verfs. */
+		if (!memcmp(req->wb_verf.verifier, data->verf.verifier, sizeof(data->verf.verifier))) {
+			/* We have a match */
+			nfs_inode_remove_request(req);
+			dprintk(" OK\n");
+			goto next;
+		}
+		/* We have a mismatch. Write the page again */
+		dprintk(" mismatch\n");
+		nfs_mark_request_dirty(req);
+	next:
+		nfs_unlock_request(req);
+		res++;
+	}
+	sub_page_state(nr_unstable,res);
+}
+#endif
+
+static int nfs_flush_inode(struct inode *inode, unsigned long idx_start,
+			   unsigned int npages, int how)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	LIST_HEAD(head);
+	int			res,
+				error = 0;
+
+	spin_lock(&nfsi->req_lock);
+	res = nfs_scan_dirty(inode, &head, idx_start, npages);
+	spin_unlock(&nfsi->req_lock);
+	if (res)
+		error = nfs_flush_list(&head, NFS_SERVER(inode)->wpages, how);
+	if (error < 0)
+		return error;
+	return res;
+}
+
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+int nfs_commit_inode(struct inode *inode, unsigned long idx_start,
+		    unsigned int npages, int how)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+	LIST_HEAD(head);
+	int			res,
+				error = 0;
+
+	spin_lock(&nfsi->req_lock);
+	res = nfs_scan_commit(inode, &head, idx_start, npages);
+	if (res) {
+		res += nfs_scan_commit(inode, &head, 0, 0);
+		spin_unlock(&nfsi->req_lock);
+		error = nfs_commit_list(&head, how);
+	} else
+		spin_unlock(&nfsi->req_lock);
+	if (error < 0)
+		return error;
+	return res;
+}
+#endif
+
+int nfs_sync_inode(struct inode *inode, unsigned long idx_start,
+		  unsigned int npages, int how)
+{
+	int	error,
+		wait;
+
+	wait = how & FLUSH_WAIT;
+	how &= ~FLUSH_WAIT;
+
+	do {
+		error = 0;
+		if (wait)
+			error = nfs_wait_on_requests(inode, idx_start, npages);
+		if (error == 0)
+			error = nfs_flush_inode(inode, idx_start, npages, how);
+#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
+		if (error == 0)
+			error = nfs_commit_inode(inode, idx_start, npages, how);
+#endif
+	} while (error > 0);
+	return error;
+}
+
+int nfs_init_writepagecache(void)
+{
+	nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
+					     sizeof(struct nfs_write_data),
+					     0, SLAB_HWCACHE_ALIGN,
+					     NULL, NULL);
+	if (nfs_wdata_cachep == NULL)
+		return -ENOMEM;
+
+	nfs_wdata_mempool = mempool_create(MIN_POOL_WRITE,
+					   mempool_alloc_slab,
+					   mempool_free_slab,
+					   nfs_wdata_cachep);
+	if (nfs_wdata_mempool == NULL)
+		return -ENOMEM;
+
+	nfs_commit_mempool = mempool_create(MIN_POOL_COMMIT,
+					   mempool_alloc_slab,
+					   mempool_free_slab,
+					   nfs_wdata_cachep);
+	if (nfs_commit_mempool == NULL)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void nfs_destroy_writepagecache(void)
+{
+	mempool_destroy(nfs_commit_mempool);
+	mempool_destroy(nfs_wdata_mempool);
+	if (kmem_cache_destroy(nfs_wdata_cachep))
+		printk(KERN_INFO "nfs_write_data: not all structures were freed\n");
+}
+