Messages in this thread Patch in this message | | | Date | Mon, 23 Apr 2012 11:14:50 -0700 (PDT) | From | Hugh Dickins <> | Subject | [PATCH] mm: fix s390 BUG by __set_page_dirty_no_writeback on swap |
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Mel reports a BUG_ON(slot == NULL) in radix_tree_tag_set() on s390 3.0.13: called from __set_page_dirty_nobuffers() when page_remove_rmap() tries to transfer dirty flag from s390 storage key to struct page and radix_tree.
That would be because of reclaim's shrink_page_list() calling add_to_swap() on this page at the same time: first PageSwapCache is set (causing page_mapping(page) to appear as &swapper_space), then page->private set, then tree_lock taken, then page inserted into radix_tree - so there's an interval before taking the lock when the radix_tree slot is empty.
We could fix this by moving __add_to_swap_cache()'s spin_lock_irq up before the SetPageSwapCache. But a better fix is simply to do what's five years overdue: Ken Chen introduced __set_page_dirty_no_writeback() (if !PageDirty TestSetPageDirty) for tmpfs to skip all the radix_tree overhead, and swap is just the same - it ignores the radix_tree tag, and does not participate in dirty page accounting, so should be using __set_page_dirty_no_writeback() too.
s390 testing now confirms that this does indeed fix the problem.
Reported-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Rik van Riel <riel@redhat.com> Cc: Ken Chen <kenchen@google.com> Cc: stable@vger.kernel.org ---
mm/swap_state.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- 3.4-git/mm/swap_state.c 2012-03-31 17:42:26.949729938 -0700 +++ linux/mm/swap_state.c 2012-04-17 15:34:05.732086663 -0700 @@ -26,7 +26,7 @@ */ static const struct address_space_operations swap_aops = { .writepage = swap_writepage, - .set_page_dirty = __set_page_dirty_nobuffers, + .set_page_dirty = __set_page_dirty_no_writeback, .migratepage = migrate_page, };
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