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SubjectRe: [PATCH 1/4] mm: fix invalidate_complete_page2 lock ordering
On Tue, Sep 18, 2012 at 08:51:47PM -0700, Hugh Dickins wrote:
> 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@gmail.com>
> Deciphered-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: Mel Gorman <mel@csn.ul.ie>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michel Lespinasse <walken@google.com>
> Cc: Ying Han <yinghan@google.com>
> Cc: stable@vger.kernel.org

Acked-by: Mel Gorman <mel@csn.ul.ie>

--
Mel Gorman
SUSE Labs


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