Btrfs: fix stale entries in readdir

Josef Bacik · kdave · commit e4fd493c0541 · 2018-01-24T20:27:48.000+01:00
In fixing the readdir+pagefault deadlock I accidentally introduced a stale entry regression in readdir. If we get close to full for the temporary buffer, and then skip a few delayed deletions, and then try to add another entry that won't fit, we will emit the entries we found and retry. Unfortunately we delete entries from our del_list as we find them, assuming we won't need them. However our pos will be with whatever our last entry was, which could be before the delayed deletions we skipped, so the next search will add the deleted entries back into our readdir buffer. So instead don't delete entries we find in our del_list so we can make sure we always find our delayed deletions. This is a slight perf hit for readdir with lots of pending deletions, but hopefully this isn't a common occurrence. If it is we can revist this and optimize it. cc: stable@vger.kernel.org Fixes: 23b5ec7 ("btrfs: fix readdir deadlock with pagefault") Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
@@ -1633,28 +1633,18 @@ void btrfs_readdir_put_delayed_items(struct inode *inode,
 int btrfs_should_delete_dir_index(struct list_head *del_list,
 				  u64 index)
 {
-	struct btrfs_delayed_item *curr, *next;
-	int ret;
-
-	if (list_empty(del_list))
-		return 0;
+	struct btrfs_delayed_item *curr;
+	int ret = 0;
 
-	list_for_each_entry_safe(curr, next, del_list, readdir_list) {
+	list_for_each_entry(curr, del_list, readdir_list) {
 		if (curr->key.offset > index)
 			break;
-
-		list_del(&curr->readdir_list);
-		ret = (curr->key.offset == index);
-
-		if (refcount_dec_and_test(&curr->refs))
-			kfree(curr);
-
-		if (ret)
-			return 1;
-		else
-			continue;
+		if (curr->key.offset == index) {
+			ret = 1;
+			break;
+		}
 	}
-	return 0;
+	return ret;
 }
 
 /*
