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From 8afb43e5f076643f012d0267aebb215cc0f0767b Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Mon, 23 Apr 2012 11:14:50 -0700
Subject: [PATCH 022/165] mm: fix s390 BUG by __set_page_dirty_no_writeback on
swap
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 <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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
mm/swap_state.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 78cc4d1..7704d9c 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -27,7 +27,7 @@
*/
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,
};
--
1.7.7.6
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