This is a note to let you know that I've just added the patch titled mm: vmscan: do not use page_count without a page pin
to the 2.6.39-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-vmscan-do-not-use-page_count-without-a-page-pin.patch and it can be found in the queue-2.6.39 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <sta...@kernel.org> know about it. >From mgor...@suse.de Mon Aug 1 11:42:14 2011 From: Mel Gorman <mgor...@suse.de> Date: Tue, 19 Jul 2011 10:15:50 +0100 Subject: mm: vmscan: do not use page_count without a page pin To: sta...@kernel.org Cc: Andrea Arcangeli <aarca...@redhat.com>, Andrew Morton <a...@linux-foundation.org>, Thomas Sattler <tsatt...@gmx.de>, Mel Gorman <mgor...@suse.de> Message-ID: <1311066951-25546-3-git-send-email-mgor...@suse.de> From: Andrea Arcangeli <aarca...@redhat.com> commit: d179e84ba5da1d0024087d1759a2938817a00f3f upstream It is unsafe to run page_count during the physical pfn scan because compound_head could trip on a dangling pointer when reading page->first_page if the compound page is being freed by another CPU. [mgor...@suse.de: split out patch] Signed-off-by: Andrea Arcangeli <aarca...@redhat.com> Signed-off-by: Mel Gorman <mgor...@suse.de> Reviewed-by: Michal Hocko <mho...@suse.cz> Reviewed-by: Minchan Kim <minchan....@gmail.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@suse.de> --- mm/vmscan.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1114,8 +1114,20 @@ static unsigned long isolate_lru_pages(u nr_lumpy_dirty++; scan++; } else { - /* the page is freed already. */ - if (!page_count(cursor_page)) + /* + * Check if the page is freed already. + * + * We can't use page_count() as that + * requires compound_head and we don't + * have a pin on the page here. If a + * page is tail, we may or may not + * have isolated the head, so assume + * it's not free, it'd be tricky to + * track the head status without a + * page pin. + */ + if (!PageTail(cursor_page) && + !atomic_read(&cursor_page->_count)) continue; break; } Patches currently in stable-queue which might be from mgor...@suse.de are queue-2.6.39/mm-vmscan-evaluate-the-watermarks-against-the-correct.patch queue-2.6.39/mm-compaction-ensure-that-the-compaction-free-scanner-does-not-move-to-the-next-zone.patch queue-2.6.39/mm-vmscan-do-not-apply-pressure-to-slab-if-we-are-not-applying-pressure-to-zone.patch queue-2.6.39/mm-vmscan-do-not-use-page_count-without-a-page-pin.patch queue-2.6.39/vmscan-fix-a-livelock-in-kswapd.patch queue-2.6.39/mm-vmscan-correct-check-for-kswapd-sleeping-in.patch queue-2.6.39/mm-compaction-abort-compaction-if-too-many-pages-are-isolated-and-caller-is-asynchronous-v2.patch queue-2.6.39/mm-vmscan-only-read-new_classzone_idx-from-pgdat-when-reclaiming-successfully.patch _______________________________________________ stable mailing list stable@linux.kernel.org http://linux.kernel.org/mailman/listinfo/stable