vfs:glusterfs_fuse: treat ENOATTR as ENOENT

The original implementation of the virtual xattr get_real_filename
in gluster was misusing the ENOENT errno as the authoritative anwer
that the file/dir that we were asking the real filename for does not
exist. But since the getxattr call is done on the parent directory,
this is a violation of the getxattr API which uses ENOENT for the
case that the file/dir that the getxattr call is done against does
not exist.

Now after a recent regression for fuse-mount re-exports due to
gluster mapping ENOENT to ESTALE in the fuse-bridge, the gluster
implementation is changed to more correctly return ENOATTR if the
requested file does not exist.

This patch changes the glusterfs_fuse vfs module to treat ENOATTR as
ENOENT to be fully functional again with latest gluster.

- Without this patch, samba against a new gluster will work correctly,
  but the get_real_filename optimization for a non-existing entry
  is lost.

- With this patch, Samba will not work correctly any more against
  very old gluster servers: Those (correctly) returned ENOATTR
  always, which Samba originally interpreted as EOPNOTSUPP, triggering
  the expensive directory scan. With this patch, ENOATTR is
  interpreted as ENOENT, the authoritative answer that the requested
  entry does not exist, which is wrong unless it really does not exist.

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Fri Jun 28 12:52:03 UTC 2019 on sn-devel-184

diff --git a/source3/modules/vfs_glusterfs_fuse.c b/source3/modules/vfs_glusterfs_fuse.c
index d92f5e2b08bc1014ecfc3d8a8e5706052f483bb6..51515aa0df4cbfe55f17b7240c5164c8ac2c580e 100644 (file)
--- a/source3/modules/vfs_glusterfs_fuse.c
+++ b/source3/modules/vfs_glusterfs_fuse.c
@@ -45,7 +45,7 @@ static int vfs_gluster_fuse_get_real_filename(struct vfs_handle_struct *handle,
        ret = getxattr(path, key_buf, val_buf, GLUSTER_NAME_MAX + 1);
        if (ret == -1) {
                if (errno == ENOATTR) {
-                       errno = EOPNOTSUPP;
+                       errno = ENOENT;
                }
                return -1;
        }