NFS: Fix a race in sillyrename

lookup() and sillyrename() can race one another because the sillyrename()
completion cannot take the parent directory's inode->i_mutex since the
latter may be held by whoever is calling dput().

We therefore have little option but to add extra locking to ensure that
nfs_lookup() and nfs_atomic_open() do not race with the sillyrename
completion.
If somebody has looked up the sillyrenamed file in the meantime, we just
transfer the sillydelete information to the new dentry.

Please refer to the bug-report at
	http://bugzilla.linux-nfs.org/show_bug.cgi?id=150

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index cb99fd90a9ac..2cb3b8b71ee7 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1372,6 +1372,7 @@ out_close:
 struct dentry *
 nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 {
+        struct dentry *parent;
         struct path path = {
                 .mnt = nd->mnt,
                 .dentry = dentry,
@@ -1394,6 +1395,9 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
         cred = rpcauth_lookupcred(NFS_CLIENT(dir)->cl_auth, 0);
         if (IS_ERR(cred))
                 return (struct dentry *)cred;
+        parent = dentry->d_parent;
+        /* Protect against concurrent sillydeletes */
+        nfs_block_sillyrename(parent);
         state = nfs4_do_open(dir, &path, nd->intent.open.flags, &attr, cred);
         put_rpccred(cred);
         if (IS_ERR(state)) {
@@ -1401,12 +1405,14 @@ nfs4_atomic_open(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
                         d_add(dentry, NULL);
                         nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
                 }
+                nfs_unblock_sillyrename(parent);
                 return (struct dentry *)state;
         }
         res = d_add_unique(dentry, igrab(state->inode));
         if (res != NULL)
                 path.dentry = res;
         nfs_set_verifier(path.dentry, nfs_save_change_attribute(dir));
+        nfs_unblock_sillyrename(parent);
         nfs4_intent_set_file(nd, &path, state);
         return res;
 }