vfs: Add open by file handle support

[AV: duplicate of open() guts removed; file_open_root() used instead]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfe55731b6d..b05acb79613 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -374,6 +374,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
         /*
          * Try to get any dentry for the given file handle from the filesystem.
          */
+        if (!nop || !nop->fh_to_dentry)
+                return ERR_PTR(-ESTALE);
         result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
         if (!result)
                 result = ERR_PTR(-ESTALE);