linux-ext4 - Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)

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Date:	Sun, 28 Oct 2012 21:09:09 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Andreas Dilger <adilger@...ger.ca>
CC:	Nix <nix@...eri.org.uk>, "Theodore Ts'o" <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3
 (and other stable branches?)

On 10/28/12 12:08 PM, Andreas Dilger wrote:
> On 2012-10-27, at 15:34, Eric Sandeen <sandeen@...hat.com <mailto:sandeen@...hat.com>> wrote:
>> I've been testing with a hacked up devicemapper target which creates
>> a "dirty" snapshot which requires a replay; saves the actual power
>> drop & restore cycle, and I could repro the journal_checksum bug
>> right off.
> 
> Are you using dm-flakey, or something home grown?  I've heard about dm-flakey, but haven't looked into the details to know whether it is actually useful for such testing. 

I just changed DM to not quiesce the fs by hardcoding do_lockfs to "0" in dm_suspend().

>> XFS has an ioctl to make this easy in regression testing, and several
>> tests in xfstests do cover xfs journal recovery.  We need
>> to add such a thing to ext4.  Not being able to programatically
>> test recovery is a problem.
> 
> We have a patch that we used for testing Lustre (and in turn ext4)
> recovery which sits in the block layer and discards writes after a
> trigger is hit. The trigger can be triggered programmatically inside
> the Lustre code, or via ioctl from userspace.
> 
> http://git.whamcloud.com/?p=fs/lustre-release.git;a=blob;f=lustre/kernel_patches/patches/dev_read_only-2.6.32-rhel6.patch
> <http://git.whamcloud.com/?p=fs/lustre-release.git;a=blob;f=lustre/kernel_patches/patches/dev_read_only-2.6.32-rhel6.patch;h=8c79b40b939fccbdb5c3bc4501ee433e23cc7831;hb=HEAD>
>
>
> 
I'd been thinking of moving our testing over to dm-flakey once we get to a new enough kernel (2.6.38+) and/or when it gets back-ported to RHEL6, since this is the last patch to the core kernel that we need for Lustre.

XFS has XFS_IOC_GOINGDOWN to force recovery on the next mount, and several xfstests to exercise it.

-Eric
 
> Cheers, Andreas

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