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Commit 9cd75558 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm, page_alloc: split alloc_pages_nodemask() 

alloc_pages_nodemask does a number of preperation steps that determine
what zones can be used for the allocation depending on a variety of
factors.  This is fine but a hypothetical caller that wanted multiple
order-0 pages has to do the preparation steps multiple times.  This
patch structures __alloc_pages_nodemask such that it's relatively easy
to build a bulk order-0 page allocator.  There is no functional change.

Link: http://lkml.kernel.org/r/20170123153906.3122-3-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarHillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 066b2393

mm/page_alloc.c

+46 −29
Original line number Diff line number Diff line
@@ -3855,60 +3855,77 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, 
	return page;

}



/*

 * This is the 'heart' of the zoned buddy allocator.

 */

struct page *

__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,

			struct zonelist *zonelist, nodemask_t *nodemask)

static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,

		struct zonelist *zonelist, nodemask_t *nodemask,

		struct alloc_context *ac, gfp_t *alloc_mask,

		unsigned int *alloc_flags)

{

	struct page *page;

	unsigned int alloc_flags = ALLOC_WMARK_LOW;

	gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */

	struct alloc_context ac = {

		.high_zoneidx = gfp_zone(gfp_mask),

		.zonelist = zonelist,

		.nodemask = nodemask,

		.migratetype = gfpflags_to_migratetype(gfp_mask),

	};

	ac->high_zoneidx = gfp_zone(gfp_mask);

	ac->zonelist = zonelist;

	ac->nodemask = nodemask;

	ac->migratetype = gfpflags_to_migratetype(gfp_mask);



	if (cpusets_enabled()) {

		alloc_mask |= __GFP_HARDWALL;

		alloc_flags |= ALLOC_CPUSET;

		if (!ac.nodemask)

			ac.nodemask = &cpuset_current_mems_allowed;

		*alloc_mask |= __GFP_HARDWALL;

		*alloc_flags |= ALLOC_CPUSET;

		if (!ac->nodemask)

			ac->nodemask = &cpuset_current_mems_allowed;

	}



	gfp_mask &= gfp_allowed_mask;



	lockdep_trace_alloc(gfp_mask);



	might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);



	if (should_fail_alloc_page(gfp_mask, order))

		return NULL;

		return false;



	/*

	 * Check the zones suitable for the gfp_mask contain at least one

	 * valid zone. It's possible to have an empty zonelist as a result

	 * of __GFP_THISNODE and a memoryless node

	 */

	if (unlikely(!zonelist->_zonerefs->zone))

		return NULL;

	if (unlikely(!ac->zonelist->_zonerefs->zone))

		return false;



	if (IS_ENABLED(CONFIG_CMA) && ac.migratetype == MIGRATE_MOVABLE)

		alloc_flags |= ALLOC_CMA;

	if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE)

		*alloc_flags |= ALLOC_CMA;



	return true;

}



/* Determine whether to spread dirty pages and what the first usable zone */

static inline void finalise_ac(gfp_t gfp_mask,

		unsigned int order, struct alloc_context *ac)

{

	/* Dirty zone balancing only done in the fast path */

	ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);

	ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);



	/*

	 * The preferred zone is used for statistics but crucially it is

	 * also used as the starting point for the zonelist iterator. It

	 * may get reset for allocations that ignore memory policies.

	 */

	ac.preferred_zoneref = first_zones_zonelist(ac.zonelist,

					ac.high_zoneidx, ac.nodemask);

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

					ac->high_zoneidx, ac->nodemask);

}



/*

 * This is the 'heart' of the zoned buddy allocator.

 */

struct page *

__alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,

			struct zonelist *zonelist, nodemask_t *nodemask)

{

	struct page *page;

	unsigned int alloc_flags = ALLOC_WMARK_LOW;

	gfp_t alloc_mask = gfp_mask; /* The gfp_t that was actually used for allocation */

	struct alloc_context ac = { };



	gfp_mask &= gfp_allowed_mask;

	if (!prepare_alloc_pages(gfp_mask, order, zonelist, nodemask, &ac, &alloc_mask, &alloc_flags))

		return NULL;



	finalise_ac(gfp_mask, order, &ac);

	if (!ac.preferred_zoneref->zone) {

		page = NULL;

		/*