nfs: when attempting to open a directory, fall back on normal lookup (try #5)

commit d953126 changed how nfs_atomic_lookup handles an -EISDIR return
from an OPEN call. Prior to that patch, that caused the client to fall
back to doing a normal lookup. When that patch went in, the code began
returning that error to userspace. The d_revalidate codepath however
never had the corresponding change, so it was still possible to end up
with a NULL ctx->state pointer after that.

That patch caused a regression. When we attempt to open a directory that
does not have a cached dentry, that open now errors out with EISDIR. If
you attempt the same open with a cached dentry, it will succeed.

Fix this by reverting the change in nfs_atomic_lookup and allowing
attempts to open directories to fall back to a normal lookup

Also, add a NFSv4-specific f_ops->open routine that just returns
-ENOTDIR. This should never be called if things are working properly,
but if it ever is, then the dprintk may help in debugging.

To facilitate this, a new file_operations field is also added to the
nfs_rpc_ops struct.

Cc: stable@kernel.org
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 0a1f8312b4dc..6d93e0754b5e 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -886,3 +886,35 @@ static int nfs_setlease(struct file *file, long arg, struct file_lock **fl)
                         file->f_path.dentry->d_name.name, arg);
         return -EINVAL;
 }
+
+#ifdef CONFIG_NFS_V4
+static int
+nfs4_file_open(struct inode *inode, struct file *filp)
+{
+        /*
+         * NFSv4 opens are handled in d_lookup and d_revalidate. If we get to
+         * this point, then something is very wrong
+         */
+        dprintk("NFS: %s called! inode=%p filp=%p\n", __func__, inode, filp);
+        return -ENOTDIR;
+}
+
+const struct file_operations nfs4_file_operations = {
+        .llseek         = nfs_file_llseek,
+        .read           = do_sync_read,
+        .write          = do_sync_write,
+        .aio_read       = nfs_file_read,
+        .aio_write      = nfs_file_write,
+        .mmap           = nfs_file_mmap,
+        .open           = nfs4_file_open,
+        .flush          = nfs_file_flush,
+        .release        = nfs_file_release,
+        .fsync          = nfs_file_fsync,
+        .lock           = nfs_lock,
+        .flock          = nfs_flock,
+        .splice_read    = nfs_file_splice_read,
+        .splice_write   = nfs_file_splice_write,
+        .check_flags    = nfs_check_flags,
+        .setlease       = nfs_setlease,
+};
+#endif /* CONFIG_NFS_V4 */