linux-kernel - Re: [BUG]2.6.27.y some contents lost after writing to mmaped file

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Date:	Thu, 19 Nov 2009 15:43:31 +0100
From:	Jan Kara <jack@...e.cz>
To:	JiSheng Zhang <jszhang3@...il.com>
Cc:	Jan Kara <jack@...e.cz>, Chris Mason <chris.mason@...cle.com>,
	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, stable@...nel.org, rmk@....linux.org.uk,
	linux-arm@...ts.infradead.org
Subject: Re: [BUG]2.6.27.y some contents lost after writing to mmaped file

On Wed 18-11-09 22:17:56, JiSheng Zhang wrote:
> On Tue, 17 Nov 2009 20:06:35 +0100
> Jan Kara <jack@...e.cz> wrote:
> 
> > On Tue 17-11-09 07:36:22, Chris Mason wrote:
> > > On Mon, Nov 16, 2009 at 05:56:55PM -0800, Greg KH wrote:
> > > > On Mon, Nov 16, 2009 at 11:38:57AM +0800, JiSheng Zhang wrote:
> > > > > Hi,
> > > > > 
> > > > > I triggered a failure in an fs test with fsx-linux from ltp. It seems that
> > > > > fsx-linux failed at mmap->write sequence.
> > > > > 
> > > > > Tested kernel is 2.6.27.12 and 2.6.27.39
> > > > 
> > > > Does this work on any kernel you have tested?  Or is it a regression?
> > > > 
> > > > > Tested file system: ext3, tmpfs.
> > > > > IMHO, it impacts all file systems.
> > > > > 
> > > > > Some fsx-linux log is:
> > > > > 
> > > > > READ BAD DATA: offset = 0x2771b, size = 0xa28e
> > > > > OFFSET  GOOD    BAD     RANGE
> > > > > 0x287e0 0x35c9  0x15a9     0x80
> > > > > operation# (mod 256) for the bad datamay be 21
> > > > > ...
> > > > > 7828: 1257514978.306753 READ     0x23dba thru 0x25699 (0x18e0 bytes)
> > > > > 7829: 1257514978.306899 MAPWRITE 0x27eeb thru 0x2a516 (0x262c bytes)
> > > > >  ******WWWW
> > > > > 7830: 1257514978.307504 READ     0x2771b thru 0x319a8 (0xa28e bytes)
> > > > >  ***RRRR***
> > > > > Correct content saved for comparison
> > > > > ...
> >   Hmm, how long does it take to reproduce? I'm running fsx-linux on tmpfs
> > for a while on 2.6.27.21 and didn't hit the problem yet.
> 
> I forget to mention that the test were done on an arm board with 64M ram. 
> I have tested fsx-linux again on pc, it seems that failure go away.
>
> > > > Are you sure that the LTP is correct?  It wouldn't be the first time it
> > > > wasn't...
> > > 
> > > I'm afraid fsx usually finds bugs.  I thought Jan Kara recently fixed
> > > something here in ext3, does 2.6.32-rc work?
> >   Yeah, fsx usually finds bugs. Note that he sees the problem also on tmpfs
> > so it's not ext3 problem. Anyway, trying to reproduce with 2.6.32-rc? would
> > be interesting.
> 
> Currently the arm board doesn't support 2.6.32-rc. But I test with 2.6.32-rc7
> On my pc box, there's no failure so far.
  OK, so it's either ARM specific or it's triggered by low amount of
available memory (you might want to try testing your PC with mem=64M).

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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