Merge tag 'fuse-update-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse updates from Miklos Szeredi:

 - Add mechanism for cleaning out unused, stale dentries; controlled via
   a module option (Luis Henriques)

 - Fix various bugs

 - Cleanups

* tag 'fuse-update-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: Uninitialized variable in fuse_epoch_work()
  fuse: fix io-uring list corruption for terminated non-committed requests
  fuse: signal that a fuse inode should exhibit local fs behaviors
  fuse: Always flush the page cache before FOPEN_DIRECT_IO write
  fuse: Invalidate the page cache after FOPEN_DIRECT_IO write
  fuse: rename 'namelen' to 'namesize'
  fuse: use strscpy instead of strcpy
  fuse: refactor fuse_conn_put() to remove negative logic.
  fuse: new work queue to invalidate dentries from old epochs
  fuse: new work queue to periodically invalidate expired dentries
  dcache: export shrink_dentry_list() and add new helper d_dispose_if_unused()
  fuse: add WARN_ON and comment for RCU revalidate
  fuse: Fix whitespace for fuse_uring_args_to_ring() comment
  fuse: missing copy_finish in fuse-over-io-uring argument copies
  fuse: fix readahead reclaim deadlock

fs/overlayfs/super.c

@@ -128,9 +128,17 @@ static int ovl_dentry_revalidate_common(struct dentry *dentry,
 	unsigned int i;
 	int ret = 1;
 
-	/* Careful in RCU mode */
-	if (!inode)
+	if (!inode) {
+		/*
+		 * Lookup of negative dentries will call ovl_dentry_init_flags()
+		 * with NULL upperdentry and NULL oe, resulting in the
+		 * DCACHE_OP*_REVALIDATE flags being cleared.  Hence the only
+		 * way to get a negative inode is due to a race with dentry
+		 * destruction.
+		 */
+		WARN_ON(!(flags & LOOKUP_RCU));
 		return -ECHILD;
+	}
 
 	oe = OVL_I_E(inode);
 	lowerstack = ovl_lowerstack(oe);