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Date: Sat, 22 May 2010 16:30:40 -0400
From: Andrew Morton <akpm@linux-foundation.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: LKML <linux-kernel@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Eric Paris <eparis@redhat.com>, Dmitry Monakhov <dmonakhov@openvz.org>,
       Jan Kara <jack@ucw.cz>
Subject: Re: [git head f4b87dee9] BUG: using smp_processor_id() in
 preemptible (VFS-related)
Message-Id: <20100522163040.42bbde9d.akpm@linux-foundation.org>
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References: <201005222337.00039.rjw@sisk.pl>
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On Sat, 22 May 2010 23:36:59 +0200 "Rafael J. Wysocki" <rjw@sisk.pl> wrote:

> Hi,
> 
> I get this every time on boot with current -git:
> 
> [    6.906133] EXT4-fs (sda7): mounted filesystem with ordered data mode
> [    7.014359] BUG: using smp_processor_id() in preemptible [00000000] code: mount/1501
> [    7.020570] caller is dqstats_inc+0x19/0x2c
> [    7.026658] Pid: 1501, comm: mount Not tainted 2.6.34-tst #25
> [    7.032792] Call Trace:
> [    7.038859]  [<ffffffff8117c12b>] debug_smp_processor_id+0xcb/0xdc
> [    7.045025]  [<ffffffff8111dfb5>] dqstats_inc+0x19/0x2c
> [    7.051201]  [<ffffffff81120fac>] vfs_quota_sync+0x144/0x210
> [    7.057349]  [<ffffffff810eccfa>] ? __shrink_dcache_sb+0x284/0x293
> [    7.063574]  [<ffffffff810fc48d>] __sync_filesystem+0x3a/0x7e
> [    7.069730]  [<ffffffff810fc552>] sync_filesystem+0x36/0x4c
> [    7.075867]  [<ffffffff810deef0>] do_remount_sb+0x65/0x13c
> [    7.081960]  [<ffffffff810f4359>] do_mount+0x251/0x78a
> [    7.088039]  [<ffffffff810f2c3e>] ? copy_mount_options+0xda/0x146
> [    7.094086]  [<ffffffff810f4911>] sys_mount+0x7f/0xb8
> [    7.100085]  [<ffffffff81002aeb>] system_call_fastpath+0x16/0x1b
> [    7.124208] BUG: using smp_processor_id() in preemptible [00000000] code: mount/1501
> [    7.130307] caller is dqstats_inc+0x19/0x2c
> [    7.136386] Pid: 1501, comm: mount Not tainted 2.6.34-tst #25
> [    7.142512] Call Trace:
> [    7.148629]  [<ffffffff8117c12b>] debug_smp_processor_id+0xcb/0xdc
> [    7.154846]  [<ffffffff8111dfb5>] dqstats_inc+0x19/0x2c
> [    7.161019]  [<ffffffff81120fac>] vfs_quota_sync+0x144/0x210
> [    7.167171]  [<ffffffff810fc48d>] __sync_filesystem+0x3a/0x7e
> [    7.173364]  [<ffffffff810fc563>] sync_filesystem+0x47/0x4c
> [    7.179522]  [<ffffffff810deef0>] do_remount_sb+0x65/0x13c
> [    7.185616]  [<ffffffff810f4359>] do_mount+0x251/0x78a
> [    7.191663]  [<ffffffff810f2c3e>] ? copy_mount_options+0xda/0x146
> [    7.197626]  [<ffffffff810f4911>] sys_mount+0x7f/0xb8
> [    7.203493]  [<ffffffff81002aeb>] system_call_fastpath+0x16/0x1b
> [   11.643596] udev: starting version 153
> 
> This is after reverting commit a7cf4145b (anon_inode: set S_IFREG on the
> anon_inode) that the system is not really useable with.

Caused by "quota: Make quota stat accounting lockless".

Guys, the code this patch adds utterly duplicates the interface
provided by include/linux/percpu_counter.h, only the quota code does it
wrongly and badly.  Please, can we use the nice library code?