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

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Date:	Tue, 17 Nov 2009 20:06:35 +0100
From:	Jan Kara <jack@...e.cz>
To:	Chris Mason <chris.mason@...cle.com>
Cc:	Greg KH <gregkh@...e.de>, JiSheng Zhang <jszhang3@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	stable@...nel.org, jack@...e.cz
Subject: Re: [BUG]2.6.27.y some contents lost after writing to mmaped file

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.

> > 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.

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