linux-kernel - Re: 答复: [PATCH] fs-writeback: writeback_sb_inodes: Do not increase 'total

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Date:   Fri, 15 Sep 2023 17:57:09 +0800
From:   Chunhai Guo <guochunhai@...o.com>
To:     Jan Kara <jack@...e.cz>
Cc:     "chao@...nel.org" <chao@...nel.org>,
        "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "brauner@...nel.org" <brauner@...nel.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 答复: [PATCH] fs-writeback: writeback_sb_inodes: Do not increase 'total_wrote' when nothing is written



在 2023/9/14 14:58, Jan Kara 写道:
> On Thu 14-09-23 04:12:31, 郭纯海 wrote:
>>> On Wed 13-09-23 07:15:01, Chunhai Guo wrote:
>>>>  From the dump info, there are only two pages as shown below. One is
>>>> updated and another is under writeback. Maybe f2fs counts the
>>>> writeback page as a dirty one, so get_dirty_pages() got one. As you
>>>> said, maybe this is unreasonable.
>>>>
>>>> Jaegeuk & Chao, what do you think of this?
>>>>
>>>>
>>>> crash_32> files -p 0xE5A44678
>>>>   INODE    NRPAGES
>>>> e5a44678        2
>>>>
>>>>    PAGE    PHYSICAL   MAPPING    INDEX CNT FLAGS
>>>> e8d0e338  641de000  e5a44810         0  5 a095
>>> locked,waiters,uptodate,lru,private,writeback
>>>> e8ad59a0  54528000  e5a44810         1  2 2036
>>> referenced,uptodate,lru,active,private
>>>
>>> Indeed, incrementing pages_skipped when there's no dirty page is a bit odd.
>>> That being said we could also harden requeue_inode() - in particular we could do
>>> there:
>>>
>>>          if (wbc->pages_skipped) {
>>>                  /*
>>>                   * Writeback is not making progress due to locked buffers.
>>>                   * Skip this inode for now. Although having skipped pages
>>>                   * is odd for clean inodes, it can happen for some
>>>                   * filesystems so handle that gracefully.
>>>                   */
>>>                  if (inode->i_state & I_DIRTY_ALL)
>>>                          redirty_tail_locked(inode, wb);
>>>                  else
>>>                          inode_cgwb_move_to_attached(inode, wb);
>>>          }
>>>
>>> Does this fix your problem as well?
>>>
>>>                                                                  Honza
>>
>> Thank you for your reply. Did you forget the 'return' statement? Since I encountered this issue on the 4.19 kernel and there is not inode_cgwb_move_to_attached() yet, I replaced it with inode_io_list_del_locked(). So, below is the test patch I am applying. Please have a check. By the way, the test will take some time. I will provide feedback when it is finished. Thanks.
> 
> Yeah, I forgot about the return.

Hi Jan,
The test is finished and this patch can fix this issue, too.
Thanks,
> 
>> 	if (wbc->pages_skipped) {
>> 		/*
>> 		 * writeback is not making progress due to locked
>> 		 * buffers. Skip this inode for now.
>> 		 */
>> -		redirty_tail_locked(inode, wb);
>> +		if (inode->i_state & I_DIRTY_ALL)
>> +			redirty_tail_locked(inode, wb);
>> +		else
>> +			inode_io_list_del_locked(inode, wb);
>>   		return;
>>   	}
> 
> Looks good. Thanks for testing!
> 
> 								Honza