[ 076/120] mm: fix invalidate_complete_page2() lock ordering

From: Greg Kroah-Hartman
Date: Wed Oct 10 2012 - 21:25:30 EST


3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Hugh Dickins <hughd@xxxxxxxxxx>

commit ec4d9f626d5908b6052c2973f37992f1db52e967 upstream.

In fuzzing with trinity, lockdep protested "possible irq lock inversion
dependency detected" when isolate_lru_page() reenabled interrupts while
still holding the supposedly irq-safe tree_lock:

invalidate_inode_pages2
invalidate_complete_page2
spin_lock_irq(&mapping->tree_lock)
clear_page_mlock
isolate_lru_page
spin_unlock_irq(&zone->lru_lock)

isolate_lru_page() is correct to enable interrupts unconditionally:
invalidate_complete_page2() is incorrect to call clear_page_mlock() while
holding tree_lock, which is supposed to nest inside lru_lock.

Both truncate_complete_page() and invalidate_complete_page() call
clear_page_mlock() before taking tree_lock to remove page from radix_tree.
I guess invalidate_complete_page2() preferred to test PageDirty (again)
under tree_lock before committing to the munlock; but since the page has
already been unmapped, its state is already somewhat inconsistent, and no
worse if clear_page_mlock() moved up.

Reported-by: Sasha Levin <levinsasha928@xxxxxxxxx>
Deciphered-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Mel Gorman <mel@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Ying Han <yinghan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
mm/truncate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -394,11 +394,12 @@ invalidate_complete_page2(struct address
if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
return 0;

+ clear_page_mlock(page);
+
spin_lock_irq(&mapping->tree_lock);
if (PageDirty(page))
goto failed;

- clear_page_mlock(page);
BUG_ON(page_has_private(page));
__delete_from_page_cache(page);
spin_unlock_irq(&mapping->tree_lock);


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