Commit 333db94c authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: Fix snapshot deletion to release the alloc_mutex much more often. 



This lowers the impact of snapshot deletion on the rest of the FS.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 5cd57b2c

fs/btrfs/ctree.c

+1 −1
Original line number Diff line number Diff line
@@ -1255,7 +1255,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root 
	lowest_level = p->lowest_level;

	WARN_ON(lowest_level && ins_len);

	WARN_ON(p->nodes[0] != NULL);

	WARN_ON(root == root->fs_info->extent_root &&

	WARN_ON(cow && root == root->fs_info->extent_root &&

		!mutex_is_locked(&root->fs_info->alloc_mutex));

	WARN_ON(root == root->fs_info->chunk_root &&

		!mutex_is_locked(&root->fs_info->chunk_mutex));

fs/btrfs/disk-io.c

+2 −0
Original line number Diff line number Diff line
@@ -1674,6 +1674,7 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf) 


void btrfs_throttle(struct btrfs_root *root)

{

#if 0

	struct backing_dev_info *bdi;



	bdi = &root->fs_info->bdi;
@@ -1686,6 +1687,7 @@ void btrfs_throttle(struct btrfs_root *root) 
#endif



	}

#endif

}



void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)

fs/btrfs/extent-tree.c

+20 −8
Original line number Diff line number Diff line
@@ -1223,8 +1223,8 @@ printk("space info full %Lu\n", flags); 
	ret = btrfs_make_block_group(trans, extent_root, 0, flags,

		     BTRFS_FIRST_CHUNK_TREE_OBJECTID, start, num_bytes);

	BUG_ON(ret);

	mutex_unlock(&extent_root->fs_info->chunk_mutex);

out:

	mutex_unlock(&extent_root->fs_info->chunk_mutex);

	return 0;

}
@@ -2181,17 +2181,29 @@ static void noinline reada_walk_down(struct btrfs_root *root, 
				continue;

			}

		}

		mutex_unlock(&root->fs_info->alloc_mutex);

		ret = readahead_tree_block(root, bytenr, blocksize,

					   btrfs_node_ptr_generation(node, i));

		last = bytenr + blocksize;

		cond_resched();

		mutex_lock(&root->fs_info->alloc_mutex);

		if (ret)

			break;

	}

}



/*

 * we want to avoid as much random IO as we can with the alloc mutex

 * held, so drop the lock and do the lookup, then do it again with the

 * lock held.

 */

int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,

			      u32 *refs)

{

	mutex_unlock(&root->fs_info->alloc_mutex);

	lookup_extent_ref(NULL, root, start, len, refs);

	mutex_lock(&root->fs_info->alloc_mutex);

	return lookup_extent_ref(NULL, root, start, len, refs);

}



/*

 * helper function for drop_snapshot, this walks down the tree dropping ref

 * counts as it goes.
@@ -2215,8 +2227,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans, 


	WARN_ON(*level < 0);

	WARN_ON(*level >= BTRFS_MAX_LEVEL);

	ret = lookup_extent_ref(trans, root,

				path->nodes[*level]->start,

	ret = drop_snap_lookup_refcount(root, path->nodes[*level]->start,

				path->nodes[*level]->len, &refs);

	BUG_ON(ret);

	if (refs > 1)
@@ -2245,7 +2256,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans, 
		ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);

		blocksize = btrfs_level_size(root, *level - 1);



		ret = lookup_extent_ref(trans, root, bytenr, blocksize, &refs);

		ret = drop_snap_lookup_refcount(root, bytenr, blocksize, &refs);

		BUG_ON(ret);

		if (refs != 1) {

			parent = path->nodes[*level];
@@ -2261,15 +2272,16 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans, 
		next = btrfs_find_tree_block(root, bytenr, blocksize);

		if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {

			free_extent_buffer(next);

			mutex_unlock(&root->fs_info->alloc_mutex);



			reada_walk_down(root, cur, path->slots[*level]);



			mutex_unlock(&root->fs_info->alloc_mutex);

			next = read_tree_block(root, bytenr, blocksize,

					       ptr_gen);

			mutex_lock(&root->fs_info->alloc_mutex);



			/* we've dropped the lock, double check */

			ret = lookup_extent_ref(trans, root, bytenr,

			ret = drop_snap_lookup_refcount(root, bytenr,

						blocksize, &refs);

			BUG_ON(ret);

			if (refs != 1) {