linux-ext4 - Re: [PATCH v4 2/3] ext4: fix races between changing inode journal mode and ext4

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Date:	Wed, 27 Apr 2016 10:30:32 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Daeho Jeong <daeho.jeong@...sung.com>
Cc:	"jack@...e.cz" <jack@...e.cz>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] ext4: fix races between changing inode journal
 mode and ext4_writepages

On Wed, Apr 27, 2016 at 08:04:10AM +0000, Daeho Jeong wrote:
> Oops, sorry about causing the regression.
> 
> But in the version I worked on, we passed the test case and
> we still pass that. I executed the test case as belows.
> 
> kvm-xfstests -c 1k -C 10 generic/231
> 
> I am going to retry the test using GCE with the latest kernel version.

Hi, sorry, it looks like I jumped to conclusions too hastily.

I let the tests finish last night and generic/231 is failing around
10-20% of the time prior to your patch series.  I just didn't notice it
at first because the failure happened at the very end:

xfstests results 201604270033 - 4.6.0-rc4-ext4
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231
Failures: generic/231

With your patches, it remains at about the same level, but when the
tests failed caused me to assume they were the caused by your patches.

xfstests results 201604270044 - 4.6.0-rc4-ext4-00007-g76bee81 (Just before your patches)
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231
Passed all 1 tests

xfstests results 201604270054 - 4.6.0-rc4-ext4-00008-g31cedaa (Your 1/3 patch)
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests

xfstests results 201604270052 - 4.6.0-rc4-ext4-00009-g46ceec9 (Your 2/3 patch)
Failures: generic/231   <=== this is why I thought this commit was the regression
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231

xfstests results 201604270046 - 4.6.0-rc4-ext4-00010-geed525e (Your 3/3 patch)
Failures: generic/231
Failures: generic/231
Failures: generic/231
Failures: generic/231
Failures: generic/231
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Passed all 1 tests
Failures: generic/231   

So enabling per-file data journalling and delalloc is definitely makes
the problem much more visible, but it looks like it was always there.

Apologies for the initial misdiagnosis....

						- Ted
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