mm: vmscan: move swappiness out of scan_control

Swappiness is determined for each scanned memcg individually in
shrink_zone() and is not a parameter that applies throughout the reclaim
scan.  Move it out of struct scan_control to prevent accidental use of a
stale value.

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

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 74a9e0ae09b0f0a8741ca7447df93eded9740ab1..c28b8981e56aba54071963d1f9be2d8007b8bb74 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -89,9 +89,6 @@ struct scan_control {
        /* Scan (total_size >> priority) pages at once */
        int priority;
 
-       /* anon vs. file LRUs scanning "ratio" */
-       int swappiness;
-
        /*
         * The memory cgroup that hit its limit and as a result is the
         * primary target of this reclaim invocation.
@@ -1868,8 +1865,8 @@ enum scan_balance {
  * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
  * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
  */
-static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
-                          unsigned long *nr)
+static void get_scan_count(struct lruvec *lruvec, int swappiness,
+                          struct scan_control *sc, unsigned long *nr)
 {
        struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
        u64 fraction[2];
@@ -1912,7 +1909,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
         * using the memory controller's swap limit feature would be
         * too expensive.
         */
-       if (!global_reclaim(sc) && !sc->swappiness) {
+       if (!global_reclaim(sc) && !swappiness) {
                scan_balance = SCAN_FILE;
                goto out;
        }
@@ -1922,7 +1919,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
         * system is close to OOM, scan both anon and file equally
         * (unless the swappiness setting disagrees with swapping).
         */
-       if (!sc->priority && sc->swappiness) {
+       if (!sc->priority && swappiness) {
                scan_balance = SCAN_EQUAL;
                goto out;
        }
@@ -1965,7 +1962,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
         * With swappiness at 100, anonymous and file have the same priority.
         * This scanning priority is essentially the inverse of IO cost.
         */
-       anon_prio = sc->swappiness;
+       anon_prio = swappiness;
        file_prio = 200 - anon_prio;
 
        /*
@@ -2055,7 +2052,8 @@ out:
 /*
  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
  */
-static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
+static void shrink_lruvec(struct lruvec *lruvec, int swappiness,
+                         struct scan_control *sc)
 {
        unsigned long nr[NR_LRU_LISTS];
        unsigned long targets[NR_LRU_LISTS];
@@ -2066,7 +2064,7 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
        struct blk_plug plug;
        bool scan_adjusted;
 
-       get_scan_count(lruvec, sc, nr);
+       get_scan_count(lruvec, swappiness, sc, nr);
 
        /* Record the original scan target for proportional adjustments later */
        memcpy(targets, nr, sizeof(nr));
@@ -2263,11 +2261,12 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc)
                memcg = mem_cgroup_iter(root, NULL, &reclaim);
                do {
                        struct lruvec *lruvec;
+                       int swappiness;
 
                        lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+                       swappiness = mem_cgroup_swappiness(memcg);
 
-                       sc->swappiness = mem_cgroup_swappiness(memcg);
-                       shrink_lruvec(lruvec, sc);
+                       shrink_lruvec(lruvec, swappiness, sc);
 
                        /*
                         * Direct reclaim and kswapd have to scan all memory
@@ -2714,10 +2713,10 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
                .may_swap = !noswap,
                .order = 0,
                .priority = 0,
-               .swappiness = mem_cgroup_swappiness(memcg),
                .target_mem_cgroup = memcg,
        };
        struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+       int swappiness = mem_cgroup_swappiness(memcg);
 
        sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
                        (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
@@ -2733,7 +2732,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
         * will pick up pages from other mem cgroup's as well. We hack
         * the priority and make it zero.
         */
-       shrink_lruvec(lruvec, &sc);
+       shrink_lruvec(lruvec, swappiness, &sc);
 
        trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);