mm: only set page->pfmemalloc when ALLOC_NO_WATERMARKS was used

__alloc_pages_slowpath() is called when the number of free pages is below
the low watermark.  If the caller is entitled to use ALLOC_NO_WATERMARKS
then the page will be marked page->pfmemalloc.  This protects more pages
than are strictly necessary as we only need to protect pages allocated
below the min watermark (the pfmemalloc reserves).

This patch only sets page->pfmemalloc when ALLOC_NO_WATERMARKS was
required to allocate the page.

[rientjes@google.com: David noticed the problem during review]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 13 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cd5390f2f18d..f9d925451bfd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2116,8 +2116,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 
                 page = get_page_from_freelist(gfp_mask, nodemask,
                                 order, zonelist, high_zoneidx,
-                                alloc_flags, preferred_zone,
-                                migratetype);
+                                alloc_flags & ~ALLOC_NO_WATERMARKS,
+                                preferred_zone, migratetype);
                 if (page) {
                         preferred_zone->compact_considered = 0;
                         preferred_zone->compact_defer_shift = 0;
@@ -2209,8 +2209,8 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
 retry:
         page = get_page_from_freelist(gfp_mask, nodemask, order,
                                         zonelist, high_zoneidx,
-                                        alloc_flags, preferred_zone,
-                                        migratetype);
+                                        alloc_flags & ~ALLOC_NO_WATERMARKS,
+                                        preferred_zone, migratetype);
 
         /*
          * If an allocation failed after direct reclaim, it could be because
@@ -2381,8 +2381,17 @@ rebalance:
                 page = __alloc_pages_high_priority(gfp_mask, order,
                                 zonelist, high_zoneidx, nodemask,
                                 preferred_zone, migratetype);
-                if (page)
+                if (page) {
+                        /*
+                         * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
+                         * necessary to allocate the page. The expectation is
+                         * that the caller is taking steps that will free more
+                         * memory. The caller should avoid the page being used
+                         * for !PFMEMALLOC purposes.
+                         */
+                        page->pfmemalloc = true;
                         goto got_pg;
+                }
         }
 
         /* Atomic allocations - we can't balance anything */
@@ -2499,14 +2508,6 @@ nopage:
         warn_alloc_failed(gfp_mask, order, NULL);
         return page;
 got_pg:
-        /*
-         * page->pfmemalloc is set when the caller had PFMEMALLOC set, is
-         * been OOM killed or specified __GFP_MEMALLOC. The expectation is
-         * that the caller is taking steps that will free more memory. The
-         * caller should avoid the page being used for !PFMEMALLOC purposes.
-         */
-        page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);
-
         if (kmemcheck_enabled)
                 kmemcheck_pagealloc_alloc(page, order, gfp_mask);