mm, oom: give __GFP_NOFAIL allocations access to memory reserves
__GFP_NOFAIL is a big hammer used to ensure that the allocation request can never fail. This is a strong requirement and as such it also deserves a special treatment when the system is OOM. The primary problem here is that the allocation request might have come with some locks held and the oom victim might be blocked on the same locks. This is basically an OOM deadlock situation. This patch tries to reduce the risk of such a deadlocks by giving __GFP_NOFAIL allocations a special treatment and let them dive into memory reserves after oom killer invocation. This should help them to make a progress and release resources they are holding. The OOM victim should compensate for the reserves consumption. Signed-off-by: Michal Hocko <mhocko@suse.com> Suggested-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Johannes Weiner <hannes@cmpxchg.org> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -2732,8 +2732,21 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
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goto out;
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}
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/* Exhausted what can be done so it's blamo time */
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if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL))
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if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
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*did_some_progress = 1;
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if (gfp_mask & __GFP_NOFAIL) {
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page = get_page_from_freelist(gfp_mask, order,
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ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac);
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/*
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* fallback to ignore cpuset restriction if our nodes
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* are depleted
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*/
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if (!page)
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page = get_page_from_freelist(gfp_mask, order,
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ALLOC_NO_WATERMARKS, ac);
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}
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}
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out:
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mutex_unlock(&oom_lock);
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return page;
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