linux-kernel - [PATCH v6 1/2] btrfs: add might_sleep() to some places in update_qgroup_limit

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Date:   Wed, 16 Nov 2022 22:23:53 +0800
From:   ChenXiaoSong <chenxiaosong2@...wei.com>
To:     <clm@...com>, <josef@...icpanda.com>, <dsterba@...e.com>
CC:     <linux-btrfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chenxiaosong2@...wei.com>, <zhangxiaoxu5@...wei.com>,
        <yanaijie@...wei.com>, <quwenruo.btrfs@....com>, <wqu@...e.com>
Subject: [PATCH v6 1/2] btrfs: add might_sleep() to some places in update_qgroup_limit_item()

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@...wei.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