linux-ext4 - Re: Bug with "fix partial page writes" [3.2-rc regression]

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Date:	Mon, 05 Dec 2011 18:40:46 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	Hugh Dickins <hughd@...gle.com>
CC:	"Ted Ts'o" <tytso@....edu>, Curt Wohlgemuth <curtw@...gle.com>,
	Yongqiang Yang <xiaoqiangnk@...il.com>,
	Surbhi Palande <csurbhi@...il.com>,
	Rafael Wysocki <rjw@...k.pl>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Bug with "fix partial page writes" [3.2-rc regression]

On 12/05/2011 04:38 PM, Hugh Dickins wrote:
> On Mon, 21 Nov 2011, Hugh Dickins wrote:
>> On Mon, 21 Nov 2011, Ted Ts'o wrote:
>>> On Sun, Nov 20, 2011 at 12:59:10PM -0800, Hugh Dickins wrote:
>>>> On Tue, 8 Nov 2011, Curt Wohlgemuth wrote:
>>>> It appears that there's a bug with this patch:
>
> This has been outstanding for a month now, and we've heard no progress:
> please revert commit 02fac1297eb3 "ext4: fix partial page writes" for rc5.
>
> The problems appear on a 1k-blocksize filesystem under memory pressure:
> the hunk in ext4_da_write_end() causes oops, because it's playing with
> a page after generic_write_end() dropped our last reference to it; and
> backing out the hunk in ext4_da_write_begin() is then found to stop
> rare data corruption seen when kbuilding.
>
> Although I earlier reported that backing out the patch caused an fsx
> test to fail earlier, I've since found great variation in how soon it
> fails, and seen it fail just as quickly with 02fac1297eb3 still in.
> I also reported that I had to go back to 2.6.38 for fsx not to fail
> under memory pressure: you won't be surprised that that turned out to
> be because 2.6.38 defaults nomblk_io_submit but 2.6.39 mblk_io_submit.
>
> Thanks,
> Hugh
>


Hi there,

Have you tried Yongqiang's patch "[PATCH 1/2] ext4: let mpage_submit_io 
works well when blocksize < pagesize" ?  I have tried it and it does 
seem to help, but I am still running into some failures that I am trying 
to debug, but let please let us know if it helps the issues that you are 
seeing.  Thx!

Allison Henderson

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