mm: page_alloc: generalize the dirty balance reserve

The dirty balance reserve that dirty throttling has to consider is
merely memory not available to userspace allocations.  There is nothing
writeback-specific about it.  Generalize the name so that it's reusable
outside of that context.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 18 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2a6fe377cafc..1e9a56065400 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -114,13 +114,6 @@ static DEFINE_SPINLOCK(managed_page_count_lock);
 unsigned long totalram_pages __read_mostly;
 unsigned long totalreserve_pages __read_mostly;
 unsigned long totalcma_pages __read_mostly;
-/*
- * When calculating the number of globally allowed dirty pages, there
- * is a certain number of per-zone reserves that should not be
- * considered dirtyable memory.  This is the sum of those reserves
- * over all existing zones that contribute dirtyable memory.
- */
-unsigned long dirty_balance_reserve __read_mostly;
 
 int percpu_pagelist_fraction;
 gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
@@ -5942,20 +5935,12 @@ static void calculate_totalreserve_pages(void)
 
                         if (max > zone->managed_pages)
                                 max = zone->managed_pages;
+
+                        zone->totalreserve_pages = max;
+
                         reserve_pages += max;
-                        /*
-                         * Lowmem reserves are not available to
-                         * GFP_HIGHUSER page cache allocations and
-                         * kswapd tries to balance zones to their high
-                         * watermark.  As a result, neither should be
-                         * regarded as dirtyable memory, to prevent a
-                         * situation where reclaim has to clean pages
-                         * in order to balance the zones.
-                         */
-                        zone->dirty_balance_reserve = max;
                 }
         }
-        dirty_balance_reserve = reserve_pages;
         totalreserve_pages = reserve_pages;
 }