nfs: always make sure page is up-to-date before extending a write to cover the entire page (263b4509) · Commits · 戴 / test

We should always make sure the cached page is up-to-date when we're determining whether we can extend a write to cover the full page -- even if we've received a write delegation from the server. Commit added logic to skip this check if we have a write delegation, which can lead to data corruption such as the following scenario if client B receives a write delegation from the NFS server: Client A: # echo 123456789 > /mnt/file Client B: # echo abcdefghi >> /mnt/file # cat /mnt/file 0�D0�abcdefghi Just because we hold a write delegation doesn't mean that we've read in the entire page contents. Cc: <stable@vger.kernel.org> # v3.11+ Signed-off-by:

Scott Mayhew <smayhew@redhat.com> Signed-off-by:

Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/write.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -922,19 +922,20 @@ out:
		* extend the write to cover the entire page in order to avoid fragmentation
		* inefficiencies.
		*
		* If the file is opened for synchronous writes or if we have a write delegation
		* from the server then we can just skip the rest of the checks.
		* If the file is opened for synchronous writes then we can just skip the rest
		* of the checks.
		*/
		static int nfs_can_extend_write(struct file file, struct page page, struct inode *inode)
		{
		if (file->f_flags & O_DSYNC)
		return 0;
		if (!nfs_write_pageuptodate(page, inode))
		return 0;
		if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
		return 1;
		if (nfs_write_pageuptodate(page, inode) && (inode->i_flock == NULL \|\|
		(inode->i_flock->fl_start == 0 &&
		if (inode->i_flock == NULL \|\| (inode->i_flock->fl_start == 0 &&
		inode->i_flock->fl_end == OFFSET_MAX &&
		inode->i_flock->fl_type != F_RDLCK)))
		inode->i_flock->fl_type != F_RDLCK))
		return 1;
		return 0;
		}

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