linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix deadlock between quota writes and checkpoint

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Message-ID: <054f161c-05db-73b7-3d83-be7addcd6015@kernel.org>
Date:   Wed, 29 Jul 2020 20:42:25 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Cc:     Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix deadlock between quota writes and
 checkpoint

On 2020-7-29 15:02, Jaegeuk Kim wrote:
> f2fs_write_data_pages(quota_mapping)
>  __f2fs_write_data_pages             f2fs_write_checkpoint
>   * blk_start_plug(&plug);
>   * add bio in write_io[DATA]
>                                       - block_operations
>                                       - skip syncing quota by
>                                                 >DEFAULT_RETRY_QUOTA_FLUSH_COUNT
>                                       - down_write(&sbi->node_write);
>   - f2fs_write_single_data_page

After commit 79963d967b49 ("f2fs: shrink node_write lock coverage"),
node_write lock was moved to f2fs_write_single_data_page() and
f2fs_write_compressed_pages().

So it needs to update the callstack.

- down_write(node_write)

Otherwise it looks good to me.

Reviewed-by: Chao Yu <yuchao0@...wei.com>

Thanks,

>     - f2fs_do_write_data_page
>       - f2fs_outplace_write_data
>         - do_write_page
>            - f2fs_allocate_data_block
>             - down_write(node_write)
>                                       - f2fs_wait_on_all_pages(F2FS_WB_CP_DATA);
>
> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
>  fs/f2fs/checkpoint.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 8c782d3f324f0..99c8061da55b9 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1269,6 +1269,8 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
>  		if (type == F2FS_DIRTY_META)
>  			f2fs_sync_meta_pages(sbi, META, LONG_MAX,
>  							FS_CP_META_IO);
> +		else if (type == F2FS_WB_CP_DATA)
> +			f2fs_submit_merged_write(sbi, DATA);
>  		io_schedule_timeout(DEFAULT_IO_TIMEOUT);
>  	}
>  	finish_wait(&sbi->cp_wait, &wait);
>