linux-kernel - Re: [f2fs-dev] [PATCH 1/2] f2fs: fix to add missing sb_{start, end}

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Message-ID: <dfc4a115-9778-49b0-8a11-fd1cfd2272e9@kernel.org>
Date: Mon, 24 Jun 2024 09:58:25 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org, Daeho Jeong <daeho43@...il.com>
Cc: Daeho Jeong <daehojeong@...gle.com>, linux-kernel@...r.kernel.org,
 linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: fix to add missing sb_{start,
 end}_intwrite() for ckpt thread

Hi all,

Please ignore this patch, because during freeze_super(), it will call
sync_fs() to clear all dirty data, there should be no race case after
that.

Thanks,

On 2024/6/10 23:10, Daeho Jeong wrote:
> On Sat, Jun 8, 2024 at 5:36 AM Chao Yu <chao@...nel.org> wrote:
>>
>> On 2024/6/6 17:52, Chao Yu wrote:
>>> After commit 261eeb9c1585 ("f2fs: introduce checkpoint_merge mount
>>> option"), checkpoint can be triggered in background thread, it missed
>>> to cover f2fs inner checkpoint operation w/ sb_{start,end}_intwrite(),
>>> fix it.
>>
>> It needs to use sb_start_intwrite_trylock(), otherwise, it will cause
>> deadlock as below:
>>
>> - freeze_super
>>    - sb_wait_write(SB_FREEZE_WRITE)
>>    - sb_wait_write(SB_FREEZE_PAGEFAULT)
>>    - sb_wait_write(SB_FREEZE_FS)
>>                                          - sync
>>                                           - iterate_supers
>>                                            - super_lock_shared
>>                                             - down_read(&sb->s_umount)
>>                                             - sync_fs_one_sb
>>                                              - f2fs_sync_fs
>>                                               - f2fs_issue_checkpoint
>>                                                - wait_for_completion
>>                                                                          - issue_checkpoint_thread
>>                                                                           - sb_start_intwrite(sbi->sb);
>>
>> - thaw_super
>>    - super_lock_excl
>>     - down_write(&sb->s_umount)
>>
>> Thanks,
>>
>>>
>>> Fixes: 261eeb9c1585 ("f2fs: introduce checkpoint_merge mount option")
>>> Cc: Daeho Jeong <daehojeong@...gle.com>
>>> Signed-off-by: Chao Yu <chao@...nel.org>
>>> ---
>>>    fs/f2fs/checkpoint.c | 5 ++++-
>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>> index 55d444bec5c0..66eaad591b60 100644
>>> --- a/fs/f2fs/checkpoint.c
>>> +++ b/fs/f2fs/checkpoint.c
>>> @@ -1828,8 +1828,11 @@ static int issue_checkpoint_thread(void *data)
>>>        if (kthread_should_stop())
>>>                return 0;
>>>
>>> -     if (!llist_empty(&cprc->issue_list))
>>> +     if (!llist_empty(&cprc->issue_list)) {
>>> +             sb_start_intwrite(sbi->sb);
>>>                __checkpoint_and_complete_reqs(sbi);
>>> +             sb_end_intwrite(sbi->sb);
>>> +     }
>>>
>>>        wait_event_interruptible(*q,
>>>                kthread_should_stop() || !llist_empty(&cprc->issue_list));
>>
>>
> 
> Reviewed-by: Daeho Jeong <daehojeong@...gle.com>
> 
> Thanks.
> 
> 
> 
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@...ts.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel