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Commit 31a6c190 authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
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mm, page_alloc: set alloc_flags only once in slowpath 

In __alloc_pages_slowpath(), alloc_flags doesn't change after it's
initialized, so move the initialization above the retry: label.  Also
make the comment above the initialization more descriptive.

The only exception in the alloc_flags being constant is
ALLOC_NO_WATERMARKS, which may change due to TIF_MEMDIE being set on the
allocating thread.  We can fix this, and make the code simpler and a bit
more effective at the same time, by moving the part that determines
ALLOC_NO_WATERMARKS from gfp_to_alloc_flags() to gfp_pfmemalloc_allowed().

This means we don't have to mask out ALLOC_NO_WATERMARKS in numerous
places in __alloc_pages_slowpath() anymore.  The only two tests for the
flag can instead call gfp_pfmemalloc_allowed().

Link: http://lkml.kernel.org/r/20160721073614.24395-3-vbabka@suse.cz


Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 87cc271d

mm/page_alloc.c

+26 −26
Original line number Diff line number Diff line
@@ -3119,8 +3119,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
	 */

	count_vm_event(COMPACTSTALL);



	page = get_page_from_freelist(gfp_mask, order,

					alloc_flags & ~ALLOC_NO_WATERMARKS, ac);

	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);



	if (page) {

		struct zone *zone = page_zone(page);
@@ -3288,8 +3287,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, 
		return NULL;



retry:

	page = get_page_from_freelist(gfp_mask, order,

					alloc_flags & ~ALLOC_NO_WATERMARKS, ac);

	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);



	/*

	 * If an allocation failed after direct reclaim, it could be because
@@ -3351,16 +3349,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask) 
	} else if (unlikely(rt_task(current)) && !in_interrupt())

		alloc_flags |= ALLOC_HARDER;



	if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {

		if (gfp_mask & __GFP_MEMALLOC)

			alloc_flags |= ALLOC_NO_WATERMARKS;

		else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))

			alloc_flags |= ALLOC_NO_WATERMARKS;

		else if (!in_interrupt() &&

				((current->flags & PF_MEMALLOC) ||

				 unlikely(test_thread_flag(TIF_MEMDIE))))

			alloc_flags |= ALLOC_NO_WATERMARKS;

	}

#ifdef CONFIG_CMA

	if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)

		alloc_flags |= ALLOC_CMA;
@@ -3370,7 +3358,19 @@ gfp_to_alloc_flags(gfp_t gfp_mask) 


bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)

{

	return !!(gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);

	if (unlikely(gfp_mask & __GFP_NOMEMALLOC))

		return false;



	if (gfp_mask & __GFP_MEMALLOC)

		return true;

	if (in_serving_softirq() && (current->flags & PF_MEMALLOC))

		return true;

	if (!in_interrupt() &&

			((current->flags & PF_MEMALLOC) ||

			 unlikely(test_thread_flag(TIF_MEMDIE))))

		return true;



	return false;

}



static inline bool is_thp_gfp_mask(gfp_t gfp_mask)
@@ -3503,36 +3503,36 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
				(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))

		gfp_mask &= ~__GFP_ATOMIC;



retry:

	if (gfp_mask & __GFP_KSWAPD_RECLAIM)

		wake_all_kswapds(order, ac);



	/*

	 * OK, we're below the kswapd watermark and have kicked background

	 * reclaim. Now things get more complex, so set up alloc_flags according

	 * to how we want to proceed.

	 * The fast path uses conservative alloc_flags to succeed only until

	 * kswapd needs to be woken up, and to avoid the cost of setting up

	 * alloc_flags precisely. So we do that now.

	 */

	alloc_flags = gfp_to_alloc_flags(gfp_mask);



retry:

	if (gfp_mask & __GFP_KSWAPD_RECLAIM)

		wake_all_kswapds(order, ac);



	/*

	 * Reset the zonelist iterators if memory policies can be ignored.

	 * These allocations are high priority and system rather than user

	 * orientated.

	 */

	if ((alloc_flags & ALLOC_NO_WATERMARKS) || !(alloc_flags & ALLOC_CPUSET)) {

	if (!(alloc_flags & ALLOC_CPUSET) || gfp_pfmemalloc_allowed(gfp_mask)) {

		ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);

		ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,

					ac->high_zoneidx, ac->nodemask);

	}



	/* This is the last chance, in general, before the goto nopage. */

	page = get_page_from_freelist(gfp_mask, order,

				alloc_flags & ~ALLOC_NO_WATERMARKS, ac);

	page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);

	if (page)

		goto got_pg;



	/* Allocate without watermarks if the context allows */

	if (alloc_flags & ALLOC_NO_WATERMARKS) {

	if (gfp_pfmemalloc_allowed(gfp_mask)) {



		page = get_page_from_freelist(gfp_mask, order,

						ALLOC_NO_WATERMARKS, ac);

		if (page)