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Date: Wed, 16 Jul 2014 17:36:49 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Andrew Morton <akpm@...ux-foundation.org> cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...e.cz>, Rik van Riel <riel@...hat.com>, stable@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: [patch] mm, writeback: prevent race when calculating dirty limits Setting vm_dirty_bytes and dirty_background_bytes is not protected by any serialization. Therefore, it's possible for either variable to change value after the test in global_dirty_limits() to determine whether available_memory needs to be initialized or not. Always ensure that available_memory is properly initialized. Cc: stable@...r.kernel.org Signed-off-by: David Rientjes <rientjes@...gle.com> --- mm/page-writeback.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -261,14 +261,11 @@ static unsigned long global_dirtyable_memory(void) */ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) { + const unsigned long available_memory = global_dirtyable_memory(); unsigned long background; unsigned long dirty; - unsigned long uninitialized_var(available_memory); struct task_struct *tsk; - if (!vm_dirty_bytes || !dirty_background_bytes) - available_memory = global_dirtyable_memory(); - if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); else -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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