Re: [PATCH 02/11] fanotify: Split fsid check from other fid mode checks

FAN_ERROR will require fsid, but not necessarily require the filesystem
to expose a file handle.  Split those checks into different functions, so
they can be used separately when setting up an event.

Signed-off-by: Gabriel Krisman Bertazi <redacted>

Changes since v1:
  (Amir)
  - Rename fanotify_check_path_fsid -> fanotify_test_fsid
  - Use dentry directly instead of path
---
 fs/notify/fanotify/fanotify_user.c | 43 ++++++++++++++++++------------
 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 3ccdee3c9f1e..9cc6c8808ed5 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c

@@ -1178,15 +1178,31 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 }

 /* Check if filesystem can encode a unique fid */
-static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
+static int fanotify_test_fid(struct dentry *dentry)
+{
+       /*
+        * We need to make sure that the file system supports at least
+        * encoding a file handle so user can use name_to_handle_at() to
+        * compare fid returned with event to the file handle of watched
+        * objects. However, name_to_handle_at() requires that the
+        * filesystem also supports decoding file handles.
+        */
+       if (!dentry->d_sb->s_export_op ||
+           !dentry->d_sb->s_export_op->fh_to_dentry)
+               return -EOPNOTSUPP;
+
+       return 0;
+}
+