3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Hugh Dickins <hu...@google.com>
commit aca50bd3b4c4bb5528a1878158ba7abce41de534 upstream.
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 <mgor...@suse.de>
Signed-off-by: Hugh Dickins <hu...@google.com>
Acked-by: Mel Gorman <mgor...@suse.de>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Martin Schwidefsky <schwidef...@de.ibm.com>
Cc: Heiko Carstens <heiko.carst...@de.ibm.com>
Cc: Rik van Riel <r...@redhat.com>
Cc: Ken Chen <kenc...@google.com>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
mm/swap_state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -28,7 +28,7 @@
*/
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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