linux-kernel - [PATCH v5 1/2] btrfs: add might_sleep() to btrfs_search

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Date:   Wed, 16 Nov 2022 21:07:15 +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 v5 1/2] btrfs: add might_sleep() to btrfs_search_slot()

At least 2 places might sleep in btrfs_search_slot(), as shown below:

  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_search_slot().

Signed-off-by: ChenXiaoSong <chenxiaosong2@...wei.com>
---
 fs/btrfs/ctree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a9543f01184c..809053e9cfde 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1934,6 +1934,8 @@ 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