linux-kernel - Re: remount-ro & umount & quota interaction

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Message-ID: <20080207102815.GB26403@atrey.karlin.mff.cuni.cz>
Date:	Thu, 7 Feb 2008 11:28:15 +0100
From:	Jan Kara <jack@...e.cz>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: remount-ro & umount & quota interaction

> For a long time I'm bitten by a bad interaction
> of mount -o remount,ro and quota operations.
> 
> The sequence is as follows:
> 
>  mount /fs
>  quotaon -ug /fs
>  mount -o remount,ro /fs
>  umount /fs
> 
> At this point, umount never returns.  /proc/$pid/wchan
> shows vfs_quota_off:
> 
> Feb  6 20:53:25 linux kernel: umount        D e5183eb8     0  8646      1
> Feb  6 20:53:25 linux kernel:        e5183ecc 00000086 00000002 e5183eb8 e5183eb0 00000000 c1db2540 c1db2684
> Feb  6 20:53:25 linux kernel:        c1db2684 c1c0dd00 00000000 cfd9f1c0 c0367080 c0367080 f5849000 f7f06880
> Feb  6 20:53:25 linux kernel:        f7e89d80 00000000 c0367080 b7c9795c 005f3997 00000000 000000ff 00000000
> Feb  6 20:53:25 linux kernel: Call Trace:
> Feb  6 20:53:25 linux kernel:  [<c01a2a65>] vfs_quota_off+0x345/0x490
> Feb  6 20:53:25 linux kernel:  [<c013a3a0>] autoremove_wake_function+0x0/0x50
> Feb  6 20:53:25 linux kernel:  [<c0174bf6>] deactivate_super+0x46/0x80
> Feb  6 20:53:25 linux kernel:  [<c0188bba>] sys_umount+0x4a/0x240
> Feb  6 20:53:25 linux kernel:  [<c017637f>] sys_stat64+0xf/0x30
> Feb  6 20:53:25 linux kernel:  [<c0162069>] remove_vma+0x39/0x50
> Feb  6 20:53:25 linux kernel:  [<c0162b67>] do_munmap+0x197/0x1f0
> Feb  6 20:53:25 linux kernel:  [<c0188dc5>] sys_oldumount+0x15/0x20
> Feb  6 20:53:25 linux kernel:  [<c010417e>] sysenter_past_esp+0x5f/0x85
> 
> The filesystem is ext3.  The issue is here for a long time,
> at least since before 2.6.20, and is still present in 2.6.23
> (I'll try 2.6.24 later today).
> 
> Can it be fixed please? :)
  Of course, thanks for report :). The problem is we allow remounting
read only which we should refuse when quota is enabled. I'll fix that in
a minute.

								Honza

-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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