Commit a4c853af authored Nov 16, 2022 by ChenXiaoSong Committed by David Sterba Dec 05, 2022

btrfs: add might_sleep() annotations



Add annotations to functions that might sleep due to allocations or IO
and could be called from various contexts. In case of btrfs_search_slot
it's not obvious why it would sleep:

    btrfs_search_slot
      setup_nodes_for_search
        reada_for_balance
          btrfs_readahead_node_child
            btrfs_readahead_tree_block
              btrfs_find_create_tree_block
                alloc_extent_buffer
                  kmem_cache_zalloc
                    /* allocate memory non-atomically, might sleep */
                    kmem_cache_alloc(GFP_NOFS|__GFP_NOFAIL|__GFP_ZERO)
              read_extent_buffer_pages
                submit_extent_page
                  /* disk IO, might sleep */
                  submit_one_bio

Other examples where the sleeping could happen is in 3 places might
sleep in update_qgroup_limit_item(), as shown below:

  update_qgroup_limit_item
    btrfs_alloc_path
      /* allocate memory non-atomically, might sleep */
      kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS)

Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

parent 054056bd

fs/btrfs/ctree.c

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -184,6 +184,8 @@ size_t __attribute_const__ btrfs_get_num_csums(void)

	struct btrfs_path *btrfs_alloc_path(void)		struct btrfs_path *btrfs_alloc_path(void)
	{		{
			might_sleep();

	return kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);		return kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
	}		}

	@@ -2046,6 +2048,8 @@ int btrfs_search_slot(struct btrfs_trans_handle trans, struct btrfs_root root,
	int min_write_lock_level;		int min_write_lock_level;
	int prev_cmp;		int prev_cmp;

			might_sleep();

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