mm: use alloc_flags to record if kswapd can wake

This is a preparation patch that copies the GFP flag __GFP_KSWAPD_RECLAIM
into alloc_flags.  This is a preparation patch only that avoids having to
pass gfp_mask through a long callchain in a future patch.

Note that the setting in the fast path happens in alloc_flags_nofragment()
and it may be claimed that this has nothing to do with ALLOC_NO_FRAGMENT.
That's true in this patch but is not true later so it's done now for
easier review to show where the flag needs to be recorded.

No functional change.

[mgorman@techsingularity.net: ALLOC_KSWAPD flag needs to be applied in the !CONFIG_ZONE_DMA32 case]
Link: http://lkml.kernel.org/r/20181126143503.GO23260@techsingularity.net
Link: http://lkml.kernel.org/r/20181123114528.28802-4-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/internal.h b/mm/internal.h
index 2ffe0cd64c70afb361afa8a49300e1f40dd37c54..f4a7bb02decfea1a5509c0a96cc8aa653ebc816c 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -499,6 +499,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
 #else
 #define ALLOC_NOFRAGMENT         0x0
 #endif
+#define ALLOC_KSWAPD           0x200 /* allow waking of kswapd */
 
 enum ttu_flags;
 struct tlbflush_unmap_batch;

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2046e333ea8fa952adcbc69043b7041cc63c7fac..32b3e121a388b2a4263fd1053a18f07531b3db98 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3268,7 +3268,6 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 }
 #endif /* CONFIG_NUMA */
 
-#ifdef CONFIG_ZONE_DMA32
 /*
  * The restriction on ZONE_DMA32 as being a suitable zone to use to avoid
  * fragmentation is subtle. If the preferred zone was HIGHMEM then
@@ -3278,10 +3277,16 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
  * fragmentation between the Normal and DMA32 zones.
  */
 static inline unsigned int
-alloc_flags_nofragment(struct zone *zone)
+alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
 {
+       unsigned int alloc_flags = 0;
+
+       if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+               alloc_flags |= ALLOC_KSWAPD;
+
+#ifdef CONFIG_ZONE_DMA32
        if (zone_idx(zone) != ZONE_NORMAL)
-               return 0;
+               goto out;
 
        /*
         * If ZONE_DMA32 exists, assume it is the one after ZONE_NORMAL and
@@ -3290,17 +3295,12 @@ alloc_flags_nofragment(struct zone *zone)
         */
        BUILD_BUG_ON(ZONE_NORMAL - ZONE_DMA32 != 1);
        if (nr_online_nodes > 1 && !populated_zone(--zone))
-               return 0;
+               goto out;
 
-       return ALLOC_NOFRAGMENT;
-}
-#else
-static inline unsigned int
-alloc_flags_nofragment(struct zone *zone)
-{
-       return 0;
+out:
+#endif /* CONFIG_ZONE_DMA32 */
+       return alloc_flags;
 }
-#endif
 
 /*
  * get_page_from_freelist goes through the zonelist trying to allocate
@@ -3939,6 +3939,9 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
        } else if (unlikely(rt_task(current)) && !in_interrupt())
                alloc_flags |= ALLOC_HARDER;
 
+       if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+               alloc_flags |= ALLOC_KSWAPD;
+
 #ifdef CONFIG_CMA
        if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
                alloc_flags |= ALLOC_CMA;
@@ -4170,7 +4173,7 @@ retry_cpuset:
        if (!ac->preferred_zoneref->zone)
                goto nopage;
 
-       if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+       if (alloc_flags & ALLOC_KSWAPD)
                wake_all_kswapds(order, gfp_mask, ac);
 
        /*
@@ -4228,7 +4231,7 @@ retry_cpuset:
 
 retry:
        /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
-       if (gfp_mask & __GFP_KSWAPD_RECLAIM)
+       if (alloc_flags & ALLOC_KSWAPD)
                wake_all_kswapds(order, gfp_mask, ac);
 
        reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
@@ -4451,7 +4454,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
         * Forbid the first pass from falling back to types that fragment
         * memory until all local zones are considered.
         */
-       alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone);
+       alloc_flags |= alloc_flags_nofragment(ac.preferred_zoneref->zone, gfp_mask);
 
        /* First allocation attempt */
        page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac);