NFS: Fix spurious readdir cookie loop messages

If the directory contents change, then we have to accept that the
file->f_pos value may shrink if we do a 'search-by-cookie'. In that
case, we should turn off the loop detection and let the NFS client
try to recover.

The patch also fixes a second loop detection bug by ensuring
that after turning on the ctx->duped flag, we read at least one new
cookie into ctx->dir_cookie before attempting to match with
ctx->dup_cookie.

Reported-by: Petr Vandrovec <petr@vandrovec.name>
Cc: stable@kernel.org [2.6.39+]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 8b579beb6358..b96fb99072ff 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -99,9 +99,10 @@ struct nfs_open_context {
 
 struct nfs_open_dir_context {
         struct rpc_cred *cred;
+        unsigned long attr_gencount;
         __u64 dir_cookie;
         __u64 dup_cookie;
-        int duped;
+        signed char duped;
 };
 
 /*