linux-kernel - [PATCH v6 0/2] btrfs: fix sleep from invalid context bug in update_qgroup_limit

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Date:   Wed, 16 Nov 2022 22:23:52 +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 0/2] btrfs: fix sleep from invalid context bug 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

Fix this by calling qgroup_dirty() on @dstqgroup, and update limit item in
btrfs_run_qgroups() later.

By the way, add might_sleep() to some places.

ChenXiaoSong (2):
  btrfs: add might_sleep() to some places in update_qgroup_limit_item()
  btrfs: qgroup: fix sleep from invalid context bug in
    update_qgroup_limit_item()

 fs/btrfs/ctree.c  | 4 ++++
 fs/btrfs/qgroup.c | 9 +--------
 2 files changed, 5 insertions(+), 8 deletions(-)

-- 
2.31.1