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 <[email protected]>
Deciphered-by: Andrew Morton <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Ying Han <[email protected]>
Cc: [email protected]
---
mm/truncate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- 3.6-rc6.orig/mm/truncate.c 2012-09-18 15:38:08.000000000 -0700
+++ 3.6-rc6/mm/truncate.c 2012-09-18 15:42:17.066731792 -0700
@@ -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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