linux-ext4 - Re: AW: ext4 filesystem bad extent error review

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Date:	Fri, 03 Jan 2014 11:25:30 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Juergens Dirk (CM-AI/ECO2)" <Dirk.Juergens@...bosch.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"Huang Weller (CM/ESW12-CN)" <Weller.Huang@...bosch.com>
CC:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: AW: ext4 filesystem bad extent error review

On 1/3/14, 10:29 AM, Juergens Dirk (CM-AI/ECO2) wrote:
> So, I think there _might_ be a kernel bug, but it could be also a problem 
> related to the particular type of eMMC. We did not observe the same issue
> in previous tests with another type of eMMC from another supplier, but this
> was with an older kernel patch level and with another HW design.
> 
> Regarding a possible kernel bug: Is there any chance that the invalid 
> ee_len or ee_start are returned by, e.g., the block allocator ?
> If so, can we try to instrument the code to get suitable traces ?
> Just to see or to exclude that the corrupted inode is really written
> to the eMMC ?

>From your description it does sound possible that it's a kernel bug.
Adding testcases to the code to catch it before it hits the journal
might be helpful - but then maybe this is something getting overwritten
after the fact - hard to say.

Can you share more details of the test you are running?  Or maybe even
the test itself?

I've used a test framework in the past to simulate resets w/o needing
to reset the box, and do many journal replays very quickly.  It'd be
interesting to run it using your testcase.

Thanks,
-Eric
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