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Date: Tue, 27 Apr 2010 12:14:23 +0200
From: Johannes Stezenbach <js@sig21.net>
To: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: linux-kernel@vger.kernel.org
Subject: Re: fat: excessive log spamming due to corrupted fs
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On Tue, Apr 27, 2010 at 06:48:04PM +0900, OGAWA Hirofumi wrote:
> Johannes Stezenbach <js@sig21.net> writes:
> 
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystem error lidAT: Filesysalid cluster chain (i_pos 34568)
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystem ealid cluster chain (i_pos 3AT: Fiesysalid cluster chain (i_pos 34568)
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystem ealid cluster chain (i_pos 3AT: Fesystalid cluster chain (i_pos 34568)
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystem alid cluster chain (i_pos 3AT: Fiesyalid cluster chain (i_pos 34568)
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystem ealid cluster chain (i_pos AT: Fiesystalid cluster chain (i_pos 34568)
> > Apr 22 16:30:18 zzz kernel: FAT: Filesystealid cluster chain (i_pos 3AT: Fiesystalid cluster chain (i_pos 34568)
> 
> I have no idea about message corruption, vfat just call vprintf() for
> it. I'll see current vprintf() locking stuff.

I think multiple printk per line is prone to corruption on SMP, see the
comment about KERN_CONT in kernel.h.  But maybe it only happens
for /var/log/kern.log and my xconsole when generating too much
output too quickly, "dmesg -s 10000000 | less" did not show
the corruption (but only shows ~2700 lines out of the ~10000).
But I think fat should use vprintf() to a buffer and then one printk()
instead of multiple printk + vprintk.

In xconsole it looks like this:

Apr 27 12:06:45 zzz kernel: <systerrouster chain (i_pos 34568)
Apr 27 12:06:45 zzz kernel: <systeerroruster chain (i_pos 34568)
Apr 27 12:06:45 zzz kernel: <systeerroruster chain (i_pos 34568)
Apr 27 12:06:45 zzz kernel: <3systerroruster chain (i_pos 34568)
Apr 27 12:06:45 zzz kernel: uster chain (i_pos 34568)


Thanks
Johannes
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