linux-kernel - Re: [BUG] reproducable ubifs reboot assert and corruption

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Message-ID: <52E8AB0F.2090905@nod.at>
Date:	Wed, 29 Jan 2014 08:17:35 +0100
From:	Richard Weinberger <richard@....at>
To:	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] reproducable ubifs reboot assert and corruption

Am 29.01.2014 06:32, schrieb Andrew Ruder:
> Ok, I've got some more useful information.  I have been adding
> a multitude of WARN_ON's and prink's all over the remount code and have
> come up with the attached log.
> 
> A little bit of explanation:
> 
> Line 1: sync_filesystem (from do_remount_sb)
> Line 188: sync_filesystem ends
> Line 43, 64, 81, 98, 114, 135, 156, 173: write operations that occur
> during sync_filesystem.  Before each warning I print the inode pointer.
> Line 197: read-only remount has completely finished (this message is
> from userspace post remount)
> Line 199: a sync is called, there are apparently dirty inodes in our
> now-readonly ubifs filesystem
> Line 215: failed assert that occurs because the writeback triggers for
> inode 0xd75b9450 (see line 41, it got in with a sys_write while we were
> running our sync_filesystem in do_remount_sb)
> 
> Does this help?  It looks like there is a race condition between the
> writeback code and the remount read-only.  Nothing is done to lock out
> writes during the first half of the do_remount_sb and some stuff makes
> it into the writeback worker queue while we are busy syncing the
> filesystem only to trigger later when ubifs has decided it is
> read-only...

So you can trigger this by running fsstress on /mnt and then call
mount -o remount,ro /mnt?

Can you also trigger it on nandsim or mtdram?

I did a quick test on my testbed using mtdram and was unable to trigger it.
But I fear my box is too fast.

Thanks,
//richard
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