fanotify: Split fsid check from other fid mode checks

FAN_FS_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.

While there, update a comment about tmpfs having 0 fsid, which is no
longer true.

Link: https://lore.kernel.org/r/20211025192746.66445-7-krisman@collabora.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 6895ec310b5dd0e3d86589969fefc2203cd1e640..adeae6d65e351148679af5d0eeae170c0f6fca11 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1300,16 +1300,15 @@ out_destroy_group:
        return fd;
 }
 
-/* Check if filesystem can encode a unique fid */
-static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
+static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
 {
        __kernel_fsid_t root_fsid;
        int err;
 
        /*
-        * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
+        * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
         */
-       err = vfs_get_fsid(path->dentry, fsid);
+       err = vfs_get_fsid(dentry, fsid);
        if (err)
                return err;
 
@@ -1317,10 +1316,10 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
                return -ENODEV;
 
        /*
-        * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
+        * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
         * which uses a different fsid than sb root.
         */
-       err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
+       err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
        if (err)
                return err;
 
@@ -1328,6 +1327,12 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
            root_fsid.val[1] != fsid->val[1])
                return -EXDEV;
 
+       return 0;
+}
+
+/* Check if filesystem can encode a unique fid */
+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
@@ -1335,8 +1340,8 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
         * objects. However, name_to_handle_at() requires that the
         * filesystem also supports decoding file handles.
         */
-       if (!path->dentry->d_sb->s_export_op ||
-           !path->dentry->d_sb->s_export_op->fh_to_dentry)
+       if (!dentry->d_sb->s_export_op ||
+           !dentry->d_sb->s_export_op->fh_to_dentry)
                return -EOPNOTSUPP;
 
        return 0;
@@ -1487,7 +1492,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
        }
 
        if (fid_mode) {
-               ret = fanotify_test_fid(&path, &__fsid);
+               ret = fanotify_test_fsid(path.dentry, &__fsid);
+               if (ret)
+                       goto path_put_and_out;
+
+               ret = fanotify_test_fid(path.dentry);
                if (ret)
                        goto path_put_and_out;