[v5,0/2] btrfs: fix sleep from invalid context bug in update_qgroup_limit_item()

Message

ChenXiaoSong Nov. 16, 2022, 1:07 p.m. UTC

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 btrfs_search_slot().

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

 fs/btrfs/ctree.c  |  2 ++
 fs/btrfs/qgroup.c | 29 ++++++++++++-----------------
 2 files changed, 14 insertions(+), 17 deletions(-)