From: Trond Myklebust Date: Tue, 5 Sep 2006 12:27:44 -0400 NFS: nfs_lookup - don't hash dentry when optimising away the lookup If the open intents tell us that a given lookup is going to result in a, exclusive create, we currently optimize away the lookup call itself. The reason is that the lookup would not be atomic with the create RPC call, so why do it in the first place? A problem occurs, however, if the VFS aborts the exclusive create operation after the lookup, but before the call to create the file/directory: in this case we will end up with a hashed negative dentry in the dcache that has never been looked up. Fix this by only actually hashing the dentry once the create operation has been successfully completed. Signed-off-by: Trond Myklebust --- fs/nfs/dir.c | 14 +++++++++++--- 1 files changed, 11 insertions(+), 3 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 51328ae..3419c2d 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -904,9 +904,15 @@ static struct dentry *nfs_lookup(struct lock_kernel(); - /* If we're doing an exclusive create, optimize away the lookup */ - if (nfs_is_exclusive_create(dir, nd)) - goto no_entry; + /* + * If we're doing an exclusive create, optimize away the lookup + * but don't hash the dentry. + */ + if (nfs_is_exclusive_create(dir, nd)) { + d_instantiate(dentry, NULL); + res = NULL; + goto out_unlock; + } error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr); if (error == -ENOENT) @@ -1161,6 +1167,8 @@ int nfs_instantiate(struct dentry *dentr if (IS_ERR(inode)) return error; d_instantiate(dentry, inode); + if (d_unhashed(dentry)) + d_rehash(dentry); return 0; }