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Date: Sat, 20 Jun 2009 20:26:51 +0100
From: Mel Gorman <mel@....ul.ie>
To: Hugh Dickins <hugh.dickins@...cali.co.uk>
Cc: Maxim Levitsky <maximlevitsky@...il.com>,
Johannes Weiner <hannes@...xchg.org>,
linux-kernel@...r.kernel.org
Subject: Re: BUG] Strange oopses in 2.6.30
On Sat, Jun 20, 2009 at 04:40:12PM +0100, Hugh Dickins wrote:
> On Sat, 20 Jun 2009, Maxim Levitsky wrote:
> > On Sat, 2009-06-20 at 00:48 +0300, Maxim Levitsky wrote:
> > > I see lots of following oopses in 2.6.30 and latest -git
> > >
> > > Many different applications shows up, not just reiserfsck
> > > Something in MM I guess, it makes me worry. But system seems to work.
> > >
> > > Is this known?
>
> I think so...
>
Thanks Hugh.
> > >
> > > dmesg attached.
> > >
> > >
> > > [ 34.544040] BUG: Bad page state in process reiserfsck pfn:37d86
> > > [ 34.544044] page:c2a34f38 flags:3650000c count:0 mapcount:0
> > > mapping:(null) index:bffeb
> > > [ 34.544048] Pid: 2654, comm: reiserfsck Tainted: G B
> > > 2.6.30-git #4
> > > [ 34.544051] Call Trace:
> > > [ 34.544055] [<c04cd26a>] ? printk+0x18/0x1e
> > > [ 34.544059] [<c018f065>] bad_page+0xd5/0x140
> > > [ 34.544064] [<c0190097>] free_hot_cold_page+0x1e7/0x280
> > > [ 34.544069] [<c0193682>] ? release_pages+0x92/0x1b0
> > > [ 34.544074] [<c0190155>] __pagevec_free+0x25/0x30
> > > [ 34.544078] [<c0193758>] release_pages+0x168/0x1b0
> > > [ 34.544084] [<c0193cf3>] ? lru_add_drain+0x53/0xd0
> > > [ 34.544088] [<c01ab7d4>] free_pages_and_swap_cache+0x84/0xa0
> > > [ 34.544093] [<c019ff5d>] unmap_vmas+0x73d/0x760
> > > [ 34.544099] [<c016480e>] ? lock_release_non_nested+0x15e/0x270
> > > [ 34.544104] [<c01a43b5>] exit_mmap+0xb5/0x1b0
> > > [ 34.544109] [<c0138666>] mmput+0x36/0xc0
> > > [ 34.544113] [<c013c874>] exit_mm+0xe4/0x120
> > > [ 34.544117] [<c0175539>] ? acct_collect+0x139/0x180
> > > [ 34.544122] [<c013e889>] do_exit+0x6b9/0x720
> > > [ 34.544142] [<c01bcac2>] ? vfs_write+0x122/0x180
> > > [ 34.544146] [<c01bbda0>] ? do_sync_write+0x0/0x110
> > > [ 34.544151] [<c013e920>] do_group_exit+0x30/0x90
> > > [ 34.544156] [<c013e993>] sys_exit_group+0x13/0x20
> > > [ 34.544161] [<c01039e8>] sysenter_do_call+0x12/0x3c
> > > [ 34.544180] BUG: Bad page state in process reiserfsck pfn:37d91
> > > [ 34.544184] page:c2a35174 flags:3650000c count:0 mapcount:0
> > > mapping:(null) index:bfff6
> > > [ 34.544188] Pid: 2654, comm: reiserfsck Tainted: G B
> > > 2.6.30-git #4
> > >
> >
> > This really worries me
>
> I hope it's fixed by this patch Hannes posted yesterday...
>
Does the patch fix the problem up?
> From hannes@...xchg.org Fri Jun 19 19:04:49 2009
> Date: Fri, 19 Jun 2009 19:45:02 +0200
> From: Johannes Weiner <hannes@...xchg.org>
> To: Peter Chubb <peter.chubb@...ta.com.au>
> Cc: <linux-kernel@...r.kernel.org>, <mel@....ul.ie>, <akpm@...ux-foundation.org>
> Subject: Re: [BUG] Bad page flags when process using mlock()ed memory exits
>
> On Fri, Jun 19, 2009 at 02:11:21PM +1000, Peter Chubb wrote:
> >
> > In recent kernels I've been seeing many mesages of the form:
> >
> > BUG: Bad page state in process reiserfsck pfn:79c58
> > page:c3d03b00 flags:8050000c count:0 mapcount:0 mapping:(null) index:8095
> > Pid: 3927, comm: reiserfsck Not tainted 2.6.30-test-05456-gda456f1 #60
> > Call Trace:
> > [<c134a67c>] ? printk+0xf/0x13
> > [<c10774dc>] bad_page+0xc9/0xe2
> > [<c1078041>] free_hot_cold_page+0x5c/0x204
> > [<c1078206>] __pagevec_free+0x1d/0x25
> > [<c107ac3e>] release_pages+0x14e/0x18e)
> > [<c108ef8a>] free_pages_and_swap_cache+0x69/0x82
> > [<c1089458>] exit_mmap+0xf6/0x11f
> > [<c102afcd>] mmput+0x39/0xaf
> > [<c102e534>] exit_mm+0xe5/0xed
> > [<c102fa66>] do_exit+0x13f/0x578
> > [<c102fefd>] do_group_exit+0x5e/0x85
> > [<c102ff37>] sys_exit_group+0x13/0x17
> > [<c10031ef>] sysenter_do_call+0x12/0x3c
> > Disabling lock debugging due to kernel taint
> >
> > This appears to have been introduced by patch
> > da456f14d2f2d7350f2b9440af79c85a34c7eed5
> > page allocator: do not disable interrupts in free_page_mlock()
> >
> > That patch removed the free_page_mlock() from free_pages_check(), so
> > if free_hot_cold_page() is called on an Mlocked page (e.g., if a
> > process that used mlock() calls exit()) free_pages_check() will always
> > barf, whereas before it would just unlock the page.
>
> I prepared a fix, thanks for chasing it down.
>
> Mel, to keep this simple I just used the atomic test-clear, but if I
> am not mistaken we should not need any atomicity here, so we could
> probably add a __TestClearPage version and use this instead...?
>
> ---
> >From 493b74e8615db4e3323b5b169b0b8265dfd7c3f4 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@...xchg.org>
> Date: Fri, 19 Jun 2009 19:30:56 +0200
> Subject: [patch] mm: page_alloc: clear PG_locked before checking flags on free
>
> da456f1 "page allocator: do not disable interrupts in free_page_mlock()" moved
> the PG_mlocked clearing after the flag sanity checking which makes mlocked
> pages always trigger 'bad page'. Fix this by clearing the bit up front.
>
> Reported-by: Peter Chubb <peter.chubb@...ta.com.au>
> Debugged-by: Peter Chubb <peter.chubb@...ta.com.au>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Mel Gorman <mel@....ul.ie>
> ---
> mm/page_alloc.c | 9 ++++-----
> 1 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6f0753f..30d5093 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -488,7 +488,6 @@ static inline void __free_one_page(struct page *page,
> */
> static inline void free_page_mlock(struct page *page)
> {
> - __ClearPageMlocked(page);
> __dec_zone_page_state(page, NR_MLOCK);
> __count_vm_event(UNEVICTABLE_MLOCKFREED);
> }
> @@ -558,7 +557,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
> unsigned long flags;
> int i;
> int bad = 0;
> - int clearMlocked = PageMlocked(page);
> + int wasMlocked = TestClearPageMlocked(page);
>
> kmemcheck_free_shadow(page, order);
>
> @@ -576,7 +575,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
> kernel_map_pages(page, 1 << order, 0);
>
> local_irq_save(flags);
> - if (unlikely(clearMlocked))
> + if (unlikely(wasMlocked))
> free_page_mlock(page);
> __count_vm_events(PGFREE, 1 << order);
> free_one_page(page_zone(page), page, order,
> @@ -1022,7 +1021,7 @@ static void free_hot_cold_page(struct page *page, int cold)
> struct zone *zone = page_zone(page);
> struct per_cpu_pages *pcp;
> unsigned long flags;
> - int clearMlocked = PageMlocked(page);
> + int wasMlocked = TestClearPageMlocked(page);
>
> kmemcheck_free_shadow(page, 0);
>
> @@ -1041,7 +1040,7 @@ static void free_hot_cold_page(struct page *page, int cold)
> pcp = &zone_pcp(zone, get_cpu())->pcp;
> set_page_private(page, get_pageblock_migratetype(page));
> local_irq_save(flags);
> - if (unlikely(clearMlocked))
> + if (unlikely(wasMlocked))
> free_page_mlock(page);
> __count_vm_event(PGFREE);
>
> --
> 1.6.3
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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