Commit ff44c6e3 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
Browse files

Btrfs: do not hold the write_lock on the extent tree while logging 



Dave Sterba pointed out a sleeping while atomic bug while doing fsync.  This
is because I'm an idiot and didn't realize that rwlock's were spin locks, so
we've been holding this thing while doing allocations and such which is not
good.  This patch fixes this by dropping the write lock before we do
anything heavy and re-acquire it when it is done.  We also need to take a
ref on the em's in case their corresponding pages are evicted and mark them
as being logged so that releasepage does not remove them and doesn't remove
them from our local list.  Thanks,

Reported-by: default avatarDave Sterba <dave@jikos.cz>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
parent 98114659

fs/btrfs/extent_map.c

+2 −1
Original line number Diff line number Diff line
@@ -407,6 +407,7 @@ int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) 


	WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));

	rb_erase(&em->rb_node, &tree->map);

	if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags))

		list_del_init(&em->list);

	em->in_tree = 0;

	return ret;

fs/btrfs/extent_map.h

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#define EXTENT_FLAG_COMPRESSED 1

#define EXTENT_FLAG_VACANCY 2 /* no file extent item found */

#define EXTENT_FLAG_PREALLOC 3 /* pre-allocated extent */

#define EXTENT_FLAG_LOGGING 4 /* Logging this extent */



struct extent_map {

	struct rb_node rb_node;

fs/btrfs/tree-log.c

+17 −4
Original line number Diff line number Diff line
@@ -2945,6 +2945,9 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, 
		list_del_init(&em->list);

		if (em->generation <= test_gen)

			continue;

		/* Need a ref to keep it from getting evicted from cache */

		atomic_inc(&em->refs);

		set_bit(EXTENT_FLAG_LOGGING, &em->flags);

		list_add_tail(&em->list, &extents);

	}
@@ -2954,13 +2957,18 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, 
		em = list_entry(extents.next, struct extent_map, list);



		list_del_init(&em->list);

		clear_bit(EXTENT_FLAG_LOGGING, &em->flags);



		/*

		 * If we had an error we just need to delete everybody from our

		 * private list.

		 */

		if (ret)

		if (ret) {

			free_extent_map(em);

			continue;

		}



		write_unlock(&tree->lock);



		/*

		 * If the previous EM and the last extent we left off on aren't
@@ -2971,21 +2979,26 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, 
			ret = copy_items(trans, inode, dst_path, args.src,

					 args.start_slot, args.nr,

					 LOG_INODE_ALL);

			if (ret)

			if (ret) {

				free_extent_map(em);

				write_lock(&tree->lock);

				continue;

			}

			btrfs_release_path(path);

			args.nr = 0;

		}



		ret = log_one_extent(trans, inode, root, em, path, dst_path, &args);

		free_extent_map(em);

		write_lock(&tree->lock);

	}

	WARN_ON(!list_empty(&extents));

	write_unlock(&tree->lock);



	if (!ret && args.nr)

		ret = copy_items(trans, inode, dst_path, args.src,

				 args.start_slot, args.nr, LOG_INODE_ALL);

	btrfs_release_path(path);

	WARN_ON(!list_empty(&extents));

	write_unlock(&tree->lock);

	return ret;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE