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Subject: Re: fsck: i_blocks is xxx should be yyy on ext3
From: Mingming Cao <cmm@us.ibm.com>
Reply-To: cmm@us.ibm.com
To: Helge Hafting <helge.hafting@aitel.hist.no>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
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Date: Thu, 16 Feb 2006 11:00:17 -0800
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On Thu, 2006-02-16 at 08:47 +0100, Helge Hafting wrote:
> Mingming Cao wrote:
> 
> >On Wed, 2006-02-08 at 22:53 -0800, Andrew Morton wrote:
> >  
> >
> >>Helge Hafting <helge.hafting@aitel.hist.no> wrote:
> >>    
> >>
> >>> Today I rebooted into 2.6.16-rc2-mm1.  Fsck checked a "clean" ext3 fs,
> >>> because it was many mounts since the last time.
> >>>
> >>> I have seen that many times, but this time I got a lot of
> >>> "i_blocks is xxx, should be yyy fix?"
> >>>
> >>> In all cases, the blocks were fixed to a lower number.
> >>>      
> >>>
> >>Yes, thanks.  It's due to the ext3_getblocks() patches in -mm.  I can't
> >>think of any actual harm which it'll cause.
> >>
> >>To reproduce:
> >>
> >>mkfs
> >>mount
> >>dbench 32
> >><wait 20 seconds>
> >>killall dbench
> >>umount
> >>fsck
> >>-
> >>    
> >>
> >
> >Sorry about the late response.  I failed to reproduce the problem with
> >above instructions. I am running 2.6.16-rc2-mm1 kernel, played dbench
> >32 ,64 and 128, and tried both 8 cpu and 1 cpu, still no luck at last. I
> >am using e2fsck version 1.35 though. What versions you are using?
> >  
> >
> single cpu, e2fsck 1.39-WIP (31-Dec-2005)
>         Using EXT2FS Library version 1.39-WIP, 31-Dec-2005
> 
> I didn't use dbench, only normal use of the machine.
> 
> Helge Hafting
> 
> 

I was able to constantly reproduce this problem on another machine with
1 cpu, and find the bug.  

In the ext3_new_blocks() code, if the # of allocated blocks (num) is
less than the requested # of blocks to allocate (*count), we will need
to free some quota via DQUOT_FREE_BLOCK(), which will eventually adjust
i_blocks value properly. the delta value *count-num is wrong, as we re-
set the *count too early.


The patch seems fixed the bug on my machine, could you please give it a
try?

Thanks.


 linux-2.6.15-cmm/fs/ext3/balloc.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN fs/ext3/balloc.c~ext3-getblocks-i_blocks-fix fs/ext3/balloc.c
--- linux-2.6.15/fs/ext3/balloc.c~ext3-getblocks-i_blocks-fix
2006-02-16 10:19:23.000000000 -0800
+++ linux-2.6.15-cmm/fs/ext3/balloc.c   2006-02-16 10:19:49.000000000
-0800
@@ -1441,8 +1441,8 @@ allocated:

        *errp = 0;
        brelse(bitmap_bh);
-       *count = num;
        DQUOT_FREE_BLOCK(inode, *count-num);
+       *count = num;
        return ret_block;

 io_error:



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