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Message-ID: <099a6096-b8b4-947f-681f-7176253d949e@huawei.com>
Date:   Fri, 11 Nov 2022 17:44:46 +0800
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Subject: Re: [PATCH v3] btrfs: qgroup: fix sleep from invalid context bug in
 update_qgroup_limit_item()
To:     <clm@fb.com>, <josef@toxicpanda.com>, <dsterba@suse.com>
CC:     <linux-btrfs@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <zhangxiaoxu5@huawei.com>, <quwenruo.btrfs@gmx.com>
References: <20221111092000.2275068-1-chenxiaosong2@huawei.com>
From:   ChenXiaoSong <chenxiaosong2@huawei.com>
In-Reply-To: <20221111092000.2275068-1-chenxiaosong2@huawei.com>
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Please ignore this v3 patch, I will try to send a new version patch 
according to Qu Wenruo's suggestions: 
https://lore.kernel.org/all/df7ede88-86a2-1c6d-0343-c97a851b9bdf@gmx.com/

在 2022/11/11 17:20, ChenXiaoSong 写道:
> Syzkaller reported BUG as follows:
> 
>    BUG: sleeping function called from invalid context at
>         include/linux/sched/mm.h:274
>    Call Trace:
>     <TASK>
>     dump_stack_lvl+0xcd/0x134
>     __might_resched.cold+0x222/0x26b
>     kmem_cache_alloc+0x2e7/0x3c0
>     update_qgroup_limit_item+0xe1/0x390
>     btrfs_qgroup_inherit+0x147b/0x1ee0
>     create_subvol+0x4eb/0x1710
>     btrfs_mksubvol+0xfe5/0x13f0
>     __btrfs_ioctl_snap_create+0x2b0/0x430
>     btrfs_ioctl_snap_create_v2+0x25a/0x520
>     btrfs_ioctl+0x2a1c/0x5ce0
>     __x64_sys_ioctl+0x193/0x200
>     do_syscall_64+0x35/0x80
> 
> Fix this by delaying the limit item updates until unlock the spin lock.
> 
> Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
> ---
>   fs/btrfs/qgroup.c | 23 ++++++++++++++---------
>   1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 9334c3157c22..0071b2be6785 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -2860,6 +2860,8 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
>   	bool need_rescan = false;
>   	u32 level_size = 0;
>   	u64 nums;
> +	bool update_limit = false;
> +	int err;
>   
>   	/*
>   	 * There are only two callers of this function.
> @@ -2950,15 +2952,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
>   		dstgroup->max_excl = inherit->lim.max_excl;
>   		dstgroup->rsv_rfer = inherit->lim.rsv_rfer;
>   		dstgroup->rsv_excl = inherit->lim.rsv_excl;
> -
> -		ret = update_qgroup_limit_item(trans, dstgroup);
> -		if (ret) {
> -			qgroup_mark_inconsistent(fs_info);
> -			btrfs_info(fs_info,
> -				   "unable to update quota limit for %llu",
> -				   dstgroup->qgroupid);
> -			goto unlock;
> -		}
> +		update_limit = true;
>   	}
>   
>   	if (srcid) {
> @@ -2985,6 +2979,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
>   		dstgroup->max_excl = srcgroup->max_excl;
>   		dstgroup->rsv_rfer = srcgroup->rsv_rfer;
>   		dstgroup->rsv_excl = srcgroup->rsv_excl;
> +		update_limit = true;
>   
>   		qgroup_dirty(fs_info, dstgroup);
>   		qgroup_dirty(fs_info, srcgroup);
> @@ -3053,6 +3048,16 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
>   
>   unlock:
>   	spin_unlock(&fs_info->qgroup_lock);
> +	if (update_limit) {
> +		err = update_qgroup_limit_item(trans, dstgroup);
> +		if (err) {
> +			ret = err;
> +			qgroup_mark_inconsistent(fs_info);
> +			btrfs_info(fs_info,
> +				   "unable to update quota limit for %llu",
> +				   dstgroup->qgroupid);
> +		}
> +	}
>   	if (!ret)
>   		ret = btrfs_sysfs_add_one_qgroup(fs_info, dstgroup);
>   out:
>