On Fri, Aug 18, 2023 at 04:00:50PM +0200, Christian Brauner wrote: > +/** > + * super_lock - wait for superblock to become ready and lock it > + * @sb: superblock to wait for > + * @excl: whether exclusive access is required > + * > + * If the superblock has neither passed through vfs_get_tree() or > + * generic_shutdown_super() yet wait for it to happen. Either superblock > + * creation will succeed and SB_BORN is set by vfs_get_tree() or we're > + * woken and we'll see SB_DYING. > + * > + * The caller must have acquired a temporary reference on @sb->s_count. > + * > + * Return: This returns true if SB_BORN was set, false if SB_DYING was > + * set. The function acquires s_umount and returns with it held. I think this needs slightly stronger language to warn callers that *even if it returns false*, it returns with the lock held! I find this surprising. Usually returning failure means that the lock isn't held, but looking at the callers shows that it wouldn't simplify them to release the lock before returning failure. Here's my suggestion: /** * super_lock - Wait for superblock to become ready and lock it. * @sb: Superblock to wait for. * @excl: Whether exclusive access is required. * * If the superblock has neither passed through vfs_get_tree() or * generic_shutdown_super() yet wait for it to happen. Either superblock * creation will succeed and SB_BORN is set by vfs_get_tree() or we're * woken and we'll see SB_DYING. * * Context: May sleep. The caller must have incremented @sb->s_count. * Return: s_umount is always acquired. Returns true if the superblock * is active, false if the superblock is dying. */
