linux-ext4 - Re: [PATCH 1/2] ext4: let mpage_submit_io works well when blocksize

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Date:	Fri, 2 Dec 2011 09:15:46 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Allison Henderson <achender@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH 1/2] ext4: let mpage_submit_io works well when blocksize < pagesize

On Fri, Dec 2, 2011 at 4:13 AM, Allison Henderson
<achender@...ux.vnet.ibm.com> wrote:
> On 11/23/2011 02:15 AM, Yongqiang Yang wrote:
>>
>> If there is a unwritten but clean buffer in a page and there is a dirty
>> buffer
>> after the buffer, then mpage_submit_io does not write the dirty buffer
>> out.
>> As a result, da_writepages loops forever.
>>
>> This patch fixes the problem by checking dirty flag.
>>
>> Signed-off-by: Yongqiang Yang<xiaoqiangnk@...il.com>
>> ---
>>  fs/ext4/inode.c |    7 +++++--
>>  1 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index 755f6c7..20a1d17 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -1339,8 +1339,11 @@ static int mpage_da_submit_io(struct mpage_da_data
>> *mpd,
>>                                        clear_buffer_unwritten(bh);
>>                                }
>>
>> -                               /* skip page if block allocation undone */
>> -                               if (buffer_delay(bh) ||
>> buffer_unwritten(bh))
>> +                               /*
>> +                                * skip page if block allocation undone
>> and
>> +                                * block is dirty
>> +                                */
>> +                               if (ext4_bh_delay_or_unwritten(NULL, bh))
>>                                        skip_page = 1;
>>                                bh = bh->b_this_page;
>>                                block_start += bh->b_size;
>
> Hi Yongqiang,
>
> Thank you for looking into the punch hole code, I know there's been some
> recent bugs reported, so I am looking at it too.  I've applied your patch
> and ran it through an fsx stress test, and I notice there are some failures,
> but it appears to run longer with the patch then with out it, so it may not
> be the cause of the errors I'm seeing. I think maybe something else may have
> happened between now and the last time it made it through 24hr of fsx (at
> least for me :) ), so I'm continuing to look through the recent code
On the other hand, xfstests have a lot of changes since your last
test.   I am not sure if original xfstests did not discover some
errors.
> changes.  I will keep folks posted on my findings.  Thx!
Did you test it by multi-thread tests or single thread tests?  If
multi-thread, I suggest that we hold the i_mutex in punching hole.


Yongqiang.
>
> Allison Henderson
>
>



-- 
Best Wishes
Yongqiang Yang
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