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Subject[PATCH v6 1/2] btrfs: add might_sleep() to some places in update_qgroup_limit_item()
Date
At least 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)
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

As the potential sleeping under spin lock is hard to spot, we should add
might_sleep() to btrfs_alloc_path() and btrfs_search_slot().

Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
---
fs/btrfs/ctree.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a9543f01184c..1cd0d00ef328 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -78,6 +78,8 @@ size_t __attribute_const__ btrfs_get_num_csums(void)

struct btrfs_path *btrfs_alloc_path(void)
{
+ might_sleep();
+
return kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
}

@@ -1934,6 +1936,8 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
int min_write_lock_level;
int prev_cmp;

+ might_sleep();
+
lowest_level = p->lowest_level;
WARN_ON(lowest_level && ins_len > 0);
WARN_ON(p->nodes[0] != NULL);
--
2.31.1
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