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Re: [PATCH] xfs: superblock buffers need to be sector sized

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: superblock buffers need to be sector sized
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 25 Feb 2015 17:40:38 +1100
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20150224133652.GB45528@xxxxxxxxxxxxxxx>
References: <1424761944-2034-1-git-send-email-david@xxxxxxxxxxxxx> <20150224133652.GB45528@xxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Feb 24, 2015 at 08:36:52AM -0500, Brian Foster wrote:
> On Tue, Feb 24, 2015 at 06:12:24PM +1100, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > 
> > In secondary_sb_wack() we zero the unused portion of both the
> > on-disk superblock and the in-memory copy that we have. When
> > the device sector size is 4k, this causes xfs_repair to crash like
> > so:
> > 
> > # xfs_repair /dev/ram1
> > Phase 1 - find and verify superblock...
> > Phase 2 - using internal log
> >         - zero log...
> >         - scan filesystem freespace and inode maps...
> > bad magic number
> > bad on-disk superblock 3 - bad magic number
> > primary/secondary superblock 3 conflict - AG superblock geometry info 
> > conflicts with filesystem geometry
> > zeroing unused portion of secondary superblock (AG #3)
> > #
> > 
> > The stack trace is indicative:
> > 
> > #0  memset ()
> > #1  0x000000000040404b in secondary_sb_wack
> > #2  verify_set_agheader
> > #3  0x0000000000427b4b in scan_ag
> > #4  0x000000000042a2ca in worker_thread
> > #5  0x00007ffff77ba0a4 in start_thread
> > #6  0x00007ffff74efc2d in clone
> > 
> > Which points at memset overrunning the in memory buffer, as it is
> > only 512 bytes in length.
> > 
> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> > ---
> 
> The patch subject line should probably say 'xfsprogs:' or 'repair:,'
> otherwise this looks good to me:

Right, my mistake.

> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

Thanks,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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