ext4: return 32/64-bit dir name hash according to usage type

Traditionally ext2/3/4 has returned a 32-bit hash value from llseek()
to appease NFSv2, which can only handle a 32-bit cookie for seekdir()
and telldir().  However, this causes problems if there are 32-bit hash
collisions, since the NFSv2 server can get stuck resending the same
entries from the directory repeatedly.

Allow ext4 to return a full 64-bit hash (both major and minor) for
telldir to decrease the chance of hash collisions.  This still needs
integration on the NFS side.

Patch-updated-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
(blame me if something is not correct)

Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index ac8f168c8ab4..fa8e4911d354 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -200,8 +200,8 @@ int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
                 return -1;
         }
         hash = hash & ~1;
-        if (hash == (EXT4_HTREE_EOF << 1))
-                hash = (EXT4_HTREE_EOF-1) << 1;
+        if (hash == (EXT4_HTREE_EOF_32BIT << 1))
+                hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
         hinfo->hash = hash;
         hinfo->minor_hash = minor_hash;
         return 0;