git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 263b4509ec4d47e0da3e753f85a39ea12d1eff24 Mon Sep 17 00:00:00 2001
   2 From: Scott Mayhew <smayhew@redhat.com>
   3 Date: Fri, 17 Jan 2014 15:12:05 -0500
   4 Subject: nfs: always make sure page is up-to-date before extending a write to cover the entire page
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   8
   9 From: Scott Mayhew <smayhew@redhat.com>
  10
  11 commit 263b4509ec4d47e0da3e753f85a39ea12d1eff24 upstream.
  12
  13 We should always make sure the cached page is up-to-date when we're
  14 determining whether we can extend a write to cover the full page -- even
  15 if we've received a write delegation from the server.
  16
  17 Commit c7559663 added logic to skip this check if we have a write
  18 delegation, which can lead to data corruption such as the following
  19 scenario if client B receives a write delegation from the NFS server:
  20
  21 Client A:
  22     # echo 123456789 > /mnt/file
  23
  24 Client B:
  25     # echo abcdefghi >> /mnt/file
  26     # cat /mnt/file
  27     0�D0�abcdefghi
  28
  29 Just because we hold a write delegation doesn't mean that we've read in
  30 the entire page contents.
  31
  32 Signed-off-by: Scott Mayhew <smayhew@redhat.com>
  33 Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
  34 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  35
  36 ---
  37  fs/nfs/write.c |   11 ++++++-----
  38  1 file changed, 6 insertions(+), 5 deletions(-)
  39
  40 --- a/fs/nfs/write.c
  41 +++ b/fs/nfs/write.c
  42 @@ -922,19 +922,20 @@ out:
  43   * extend the write to cover the entire page in order to avoid fragmentation
  44   * inefficiencies.
  45   *
  46 - * If the file is opened for synchronous writes or if we have a write delegation
  47 - * from the server then we can just skip the rest of the checks.
  48 + * If the file is opened for synchronous writes then we can just skip the rest
  49 + * of the checks.
  50   */
  51  static int nfs_can_extend_write(struct file *file, struct page *page, struct inode *inode)
  52  {
  53         if (file->f_flags & O_DSYNC)
  54                 return 0;
  55 +       if (!nfs_write_pageuptodate(page, inode))
  56 +               return 0;
  57         if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
  58                 return 1;
  59 -       if (nfs_write_pageuptodate(page, inode) && (inode->i_flock == NULL ||
  60 -                       (inode->i_flock->fl_start == 0 &&
  61 +       if (inode->i_flock == NULL || (inode->i_flock->fl_start == 0 &&
  62                         inode->i_flock->fl_end == OFFSET_MAX &&
  63 -                       inode->i_flock->fl_type != F_RDLCK)))
  64 +                       inode->i_flock->fl_type != F_RDLCK))
  65                 return 1;
  66         return 0;
  67  }