src/patches/suse-2.6.27.31/patches.fixes/nfs-handle-ESTALE-on-ACCESS

   1 From: Suresh Jayaraman <sjayaraman@suse.de>
   2 Subject: NFS: Handle -ESTALE error in access()
   3 References: 465955
   4 Patch-mainline: 2.6.29-rc7
   5
   6 Upstream commit a71ee337b31271e701f689d544b6153b75609bc5.
   7
   8 Hi Trond,
   9
  10     I have been looking at a bugreport where trying to open applications on KDE
  11     on a NFS mounted home fails temporarily. There have been multiple reports on
  12     different kernel versions pointing to this common issue:
  13     http://bugzilla.kernel.org/show_bug.cgi?id=12557
  14     https://bugs.launchpad.net/ubuntu/+source/linux/+bug/269954
  15     http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=508866.html
  16
  17     This issue can be reproducible consistently by doing this on a NFS mounted
  18     home (KDE):
  19     1. Open 2 xterm sessions
  20     2. From one of the xterm session, do "ssh -X <remote host>"
  21     3. "stat ~/.Xauthority" on the remote SSH session
  22     4. Close the two xterm sessions
  23     5. On the server do a "stat ~/.Xauthority"
  24     6. Now on the client, try to open xterm
  25     This will fail.
  26
  27     Even if the filehandle had become stale, the NFS client should invalidate
  28     the cache/inode and should repeat LOOKUP. Looking at the packet capture when
  29     the failure occurs shows that there were two subsequent ACCESS() calls with
  30     the same filehandle and both fails with -ESTALE error.
  31
  32     I have tested the fix below. Now the client issue a LOOKUP after the
  33     ACCESS() call fails with -ESTALE. If all this makes sense to you, can you
  34     consider this for inclusion?
  35
  36     If the server returns an -ESTALE error due to stale filehandle in response to
  37     an ACCESS() call, we need to invalidate the cache and inode so that LOOKUP()
  38     can be retried. Without this change, the nfs client retries ACCESS() with the
  39     same filehandle, fails again and could lead to temporary failure of
  40     applications running on nfs mounted home.
  41
  42 Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
  43 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
  44 ---
  45
  46  fs/nfs/dir.c |    8 +++++++-
  47  1 file changed, 7 insertions(+), 1 deletion(-)
  48
  49 --- a/fs/nfs/dir.c
  50 +++ b/fs/nfs/dir.c
  51 @@ -1879,8 +1879,14 @@ static int nfs_do_access(struct inode *i
  52         cache.cred = cred;
  53         cache.jiffies = jiffies;
  54         status = NFS_PROTO(inode)->access(inode, &cache);
  55 -       if (status != 0)
  56 +       if (status != 0) {
  57 +               if (status == -ESTALE) {
  58 +                       nfs_zap_caches(inode);
  59 +                       if (!S_ISDIR(inode->i_mode))
  60 +                               set_bit(NFS_INO_STALE, &NFS_I(inode)->flags);
  61 +               }
  62                 return status;
  63 +       }
  64         nfs_access_add_cache(inode, &cache);
  65  out:
  66         if ((mask & ~cache.mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)