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Date: Tue, 28 Apr 2009 20:47:33 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: jan sonnek <ha2nny@gmail.com>, Nick Piggin <npiggin@suse.de>,
       linux-kernel@vger.kernel.org
Subject: Re: oops on 2.6.30-rc3-mm1
Message-Id: <20090428204733.b3c7ee01.akpm@linux-foundation.org>
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On Sun, 26 Apr 2009 13:11:25 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:

> On Mon, 27 Apr 2009, jan sonnek wrote:
> 
> > BUG: unable to handle kernel NULL pointer dereference at 00000040
> > IP: [<c015409c>] balance_dirty_pages_ratelimited_nr+0x10/0x29b
> > *pde = 36b28067 *pte = 00000000
> > Oops: 0000 [#1] PREEMPT SMP
> > last sysfs file: /sys/devices/virtual/dmi/id/chassis_asset_tag
> > Modules linked in: sco bnep l2cap bluetooth coretemp hwmon ipv6 fuse iwl3945
> > iwlcore sdhci_pci sr_mod sg sdhci ohci1394 ieee1394 cdrom mmc_core battery
> > mac80211 led_class ricoh_mmc cfg80211 usb_storage [last unloaded:
> > scsi_wait_scan]
> > 
> > Pid: 2867, comm: X Not tainted (2.6.30-rc3-mm1-hanny #27) F3F
> 
> Where has 2.6.30-rc3-mm1 been released?

I don't bother any more.  Semi-daily snapshots are at
http://userweb.kernel.org/~akpm/mmotm/

I might cc lkml on the announcement emails, actually.  It's only a few-a-week.

> > EIP: 0060:[<c015409c>] EFLAGS: 00213296 CPU: 0
> > EIP is at balance_dirty_pages_ratelimited_nr+0x10/0x29b
> > EAX: 00000000 EBX: 00000008 ECX: 00000000 EDX: 00000001
> > ESI: 00000000 EDI: 5f372067 EBP: f69a1eec ESP: f69a1e84
> >  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> > Process X (pid: 2867, ti=f69a1000 task=f7164380 task.ti=f69a1000)
> > Stack:
> >  f69a1e8c c03691fe f69a1eac 00203292 000000d0 00203292 f7001324 f6ad4474
> >  000f877d 000f877e f69a1ebc c023ea66 f6b003e0 f6b003e0 f69a1ec4 c03691fe
> >  f69a1ed8 c017e704 c1be6e40 f6ad43a8 f6823600 00000000 c049f9c0 c1be6e40
> > Call Trace:
> >  [<c03691fe>] ? _spin_unlock+0x19/0x24
> >  [<c023ea66>] ? drm_vm_open_locked+0x5b/0x94
> >  [<c03691fe>] ? _spin_unlock+0x19/0x24
> >  [<c017e704>] ? mnt_drop_write+0x6d/0xe6
> >  [<c015d26c>] ? __do_fault+0x283/0x2bd
> >  [<c015e784>] ? handle_mm_fault+0x1f7/0x454
> >  [<c0115472>] ? do_page_fault+0x1e0/0x1ef
> >  [<c0115292>] ? do_page_fault+0x0/0x1ef
> >  [<c03694dd>] ? error_code+0x6d/0x74
> >  [<c0115292>] ? do_page_fault+0x0/0x1ef
> 
> This looks like the result of mm-close-page_mkwrite-races-try-3.patch.
> 
> Nick, we lost the check for a non-NULL mapping when calling 
> balance_dirty_pages_ratelimited(mapping) in set_page_dirty_balance() when 
> it was replaced in __do_fault().
> 
> Since we're operating on page->mapping and not dirty_page->mapping here, 
> perhaps this is necessary (against mmotm, not 2.6.30-rc3-mm1)?
> ---
> diff --git a/mm/memory.c b/mm/memory.c
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2905,7 +2905,7 @@ out:
>  			page_mkwrite = 1;
>  		unlock_page(dirty_page);
>  		put_page(dirty_page);
> -		if (page_mkwrite)
> +		if (page_mkwrite && mapping)
>  			balance_dirty_pages_ratelimited(mapping);
>  	} else {
>  		unlock_page(vmf.page);

Yup, this is addressed by mm-close-page_mkwrite-races-try-3-fix.patch
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