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

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Date:   Fri, 18 Nov 2022 17:37:03 +0100
From:   David Sterba <dsterba@...e.cz>
To:     ChenXiaoSong <chenxiaosong2@...wei.com>
Cc:     clm@...com, josef@...icpanda.com, dsterba@...e.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhangxiaoxu5@...wei.com, yanaijie@...wei.com,
        quwenruo.btrfs@....com, wqu@...e.com
Subject: Re: [PATCH v6 0/2] btrfs: fix sleep from invalid context bug in
 update_qgroup_limit_item()

On Wed, Nov 16, 2022 at 10:23:52PM +0800, ChenXiaoSong wrote:
> 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()

Added to misc-next with updated subjects and changelogs, thanks.