[PATCH] mm: __alloc_pages cleanup

Clean up of __alloc_pages.

Restoration of previous behaviour, plus further cleanups by introducing an
'alloc_flags', removing the last of should_reclaim_zone.

Signed-off-by: Rohit Seth <rohit.seth@intel.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 85 insertions, 110 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b37dc0f78d07..845b91749a42 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -732,9 +732,7 @@ buffered_rmqueue(struct zone *zone, int order, gfp_t gfp_flags)
                 }
                 local_irq_restore(flags);
                 put_cpu();
-        }
-
-        if (page == NULL) {
+        } else {
                 spin_lock_irqsave(&zone->lock, flags);
                 page = __rmqueue(zone, order);
                 spin_unlock_irqrestore(&zone->lock, flags);
@@ -754,20 +752,25 @@ buffered_rmqueue(struct zone *zone, int order, gfp_t gfp_flags)
         return page;
 }
 
+#define ALLOC_NO_WATERMARKS     0x01 /* don't check watermarks at all */
+#define ALLOC_HARDER            0x02 /* try to alloc harder */
+#define ALLOC_HIGH              0x04 /* __GFP_HIGH set */
+#define ALLOC_CPUSET            0x08 /* check for correct cpuset */
+
 /*
  * Return 1 if free pages are above 'mark'. This takes into account the order
  * of the allocation.
  */
 int zone_watermark_ok(struct zone *z, int order, unsigned long mark,
-                      int classzone_idx, int can_try_harder, gfp_t gfp_high)
+                      int classzone_idx, int alloc_flags)
 {
         /* free_pages my go negative - that's OK */
         long min = mark, free_pages = z->free_pages - (1 << order) + 1;
         int o;
 
-        if (gfp_high)
+        if (alloc_flags & ALLOC_HIGH)
                 min -= min / 2;
-        if (can_try_harder)
+        if (alloc_flags & ALLOC_HARDER)
                 min -= min / 4;
 
         if (free_pages <= min + z->lowmem_reserve[classzone_idx])
@@ -785,14 +788,40 @@ int zone_watermark_ok(struct zone *z, int order, unsigned long mark,
         return 1;
 }
 
-static inline int
-should_reclaim_zone(struct zone *z, gfp_t gfp_mask)
+/*
+ * get_page_from_freeliest goes through the zonelist trying to allocate
+ * a page.
+ */
+static struct page *
+get_page_from_freelist(gfp_t gfp_mask, unsigned int order,
+                struct zonelist *zonelist, int alloc_flags)
 {
-        if (!z->reclaim_pages)
-                return 0;
-        if (gfp_mask & __GFP_NORECLAIM)
-                return 0;
-        return 1;
+        struct zone **z = zonelist->zones;
+        struct page *page = NULL;
+        int classzone_idx = zone_idx(*z);
+
+        /*
+         * Go through the zonelist once, looking for a zone with enough free.
+         * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
+         */
+        do {
+                if ((alloc_flags & ALLOC_CPUSET) &&
+                                !cpuset_zone_allowed(*z, gfp_mask))
+                        continue;
+
+                if (!(alloc_flags & ALLOC_NO_WATERMARKS)) {
+                        if (!zone_watermark_ok(*z, order, (*z)->pages_low,
+                                    classzone_idx, alloc_flags))
+                                continue;
+                }
+
+                page = buffered_rmqueue(*z, order, gfp_mask);
+                if (page) {
+                        zone_statistics(zonelist, *z);
+                        break;
+                }
+        } while (*(++z) != NULL);
+        return page;
 }
 
 /*
@@ -803,92 +832,60 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order,
                 struct zonelist *zonelist)
 {
         const gfp_t wait = gfp_mask & __GFP_WAIT;
-        struct zone **zones, *z;
+        struct zone **z;
         struct page *page;
         struct reclaim_state reclaim_state;
         struct task_struct *p = current;
-        int i;
-        int classzone_idx;
         int do_retry;
-        int can_try_harder;
+        int alloc_flags;
         int did_some_progress;
 
         might_sleep_if(wait);
 
-        /*
-         * The caller may dip into page reserves a bit more if the caller
-         * cannot run direct reclaim, or is the caller has realtime scheduling
-         * policy
-         */
-        can_try_harder = (unlikely(rt_task(p)) && !in_interrupt()) || !wait;
-
-        zones = zonelist->zones;  /* the list of zones suitable for gfp_mask */
+        z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
 
-        if (unlikely(zones[0] == NULL)) {
+        if (unlikely(*z == NULL)) {
                 /* Should this ever happen?? */
                 return NULL;
         }
+restart:
+        page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, order,
+                                zonelist, ALLOC_CPUSET);
+        if (page)
+                goto got_pg;
 
-        classzone_idx = zone_idx(zones[0]);
+        do
+                wakeup_kswapd(*z, order);
+        while (*(++z));
 
-restart:
         /*
-         * Go through the zonelist once, looking for a zone with enough free.
-         * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
+         * 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 caller may dip into page reserves a bit more if the caller
+         * cannot run direct reclaim, or if the caller has realtime scheduling
+         * policy.
          */
-        for (i = 0; (z = zones[i]) != NULL; i++) {
-                int do_reclaim = should_reclaim_zone(z, gfp_mask);
-
-                if (!cpuset_zone_allowed(z, __GFP_HARDWALL))
-                        continue;
-
-                /*
-                 * If the zone is to attempt early page reclaim then this loop
-                 * will try to reclaim pages and check the watermark a second
-                 * time before giving up and falling back to the next zone.
-                 */
-zone_reclaim_retry:
-                if (!zone_watermark_ok(z, order, z->pages_low,
-                                       classzone_idx, 0, 0)) {
-                        if (!do_reclaim)
-                                continue;
-                        else {
-                                zone_reclaim(z, gfp_mask, order);
-                                /* Only try reclaim once */
-                                do_reclaim = 0;
-                                goto zone_reclaim_retry;
-                        }
-                }
-
-                page = buffered_rmqueue(z, order, gfp_mask);
-                if (page)
-                        goto got_pg;
-        }
-
-        for (i = 0; (z = zones[i]) != NULL; i++)
-                wakeup_kswapd(z, order);
+        alloc_flags = 0;
+        if ((unlikely(rt_task(p)) && !in_interrupt()) || !wait)
+                alloc_flags |= ALLOC_HARDER;
+        if (gfp_mask & __GFP_HIGH)
+                alloc_flags |= ALLOC_HIGH;
+        if (wait)
+                alloc_flags |= ALLOC_CPUSET;
 
         /*
          * Go through the zonelist again. Let __GFP_HIGH and allocations
-         * coming from realtime tasks to go deeper into reserves
+         * coming from realtime tasks go deeper into reserves.
          *
          * This is the last chance, in general, before the goto nopage.
          * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
          * See also cpuset_zone_allowed() comment in kernel/cpuset.c.
          */
-        for (i = 0; (z = zones[i]) != NULL; i++) {
-                if (!zone_watermark_ok(z, order, z->pages_min,
-                                       classzone_idx, can_try_harder,
-                                       gfp_mask & __GFP_HIGH))
-                        continue;
-
-                if (wait && !cpuset_zone_allowed(z, gfp_mask))
-                        continue;
-
-                page = buffered_rmqueue(z, order, gfp_mask);
-                if (page)
-                        goto got_pg;
-        }
+        page = get_page_from_freelist(gfp_mask, order, zonelist, alloc_flags);
+        if (page)
+                goto got_pg;
 
         /* This allocation should allow future memory freeing. */
 
@@ -897,13 +894,10 @@ zone_reclaim_retry:
                 if (!(gfp_mask & __GFP_NOMEMALLOC)) {
 nofail_alloc:
                         /* go through the zonelist yet again, ignoring mins */
-                        for (i = 0; (z = zones[i]) != NULL; i++) {
-                                if (!cpuset_zone_allowed(z, gfp_mask))
-                                        continue;
-                                page = buffered_rmqueue(z, order, gfp_mask);
-                                if (page)
-                                        goto got_pg;
-                        }
+                        page = get_page_from_freelist(gfp_mask, order,
+                                zonelist, ALLOC_NO_WATERMARKS|ALLOC_CPUSET);
+                        if (page)
+                                goto got_pg;
                         if (gfp_mask & __GFP_NOFAIL) {
                                 blk_congestion_wait(WRITE, HZ/50);
                                 goto nofail_alloc;
@@ -924,7 +918,7 @@ rebalance:
         reclaim_state.reclaimed_slab = 0;
         p->reclaim_state = &reclaim_state;
 
-        did_some_progress = try_to_free_pages(zones, gfp_mask);
+        did_some_progress = try_to_free_pages(zonelist->zones, gfp_mask);
 
         p->reclaim_state = NULL;
         p->flags &= ~PF_MEMALLOC;
@@ -932,19 +926,10 @@ rebalance:
         cond_resched();
 
         if (likely(did_some_progress)) {
-                for (i = 0; (z = zones[i]) != NULL; i++) {
-                        if (!zone_watermark_ok(z, order, z->pages_min,
-                                               classzone_idx, can_try_harder,
-                                               gfp_mask & __GFP_HIGH))
-                                continue;
-
-                        if (!cpuset_zone_allowed(z, gfp_mask))
-                                continue;
-
-                        page = buffered_rmqueue(z, order, gfp_mask);
-                        if (page)
-                                goto got_pg;
-                }
+                page = get_page_from_freelist(gfp_mask, order,
+                                                zonelist, alloc_flags);
+                if (page)
+                        goto got_pg;
         } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
                 /*
                  * Go through the zonelist yet one more time, keep
@@ -952,18 +937,10 @@ rebalance:
                  * a parallel oom killing, we must fail if we're still
                  * under heavy pressure.
                  */
-                for (i = 0; (z = zones[i]) != NULL; i++) {
-                        if (!zone_watermark_ok(z, order, z->pages_high,
-                                               classzone_idx, 0, 0))
-                                continue;
-
-                        if (!cpuset_zone_allowed(z, __GFP_HARDWALL))
-                                continue;
-
-                        page = buffered_rmqueue(z, order, gfp_mask);
-                        if (page)
-                                goto got_pg;
-                }
+                page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, order,
+                                                zonelist, ALLOC_CPUSET);
+                if (page)
+                        goto got_pg;
 
                 out_of_memory(gfp_mask, order);
                 goto restart;
@@ -996,9 +973,7 @@ nopage:
                 dump_stack();
                 show_mem();
         }
-        return NULL;
 got_pg:
-        zone_statistics(zonelist, z);
         return page;
 }