Merge tag 'module-builtin_driver-v4.1-rc8' of git://git.kernel.org/pub/scm/linux...

[deliverable/linux.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f46339870147fef6604d15f0a540046b4d12e220..e61445dce04e3cc83e9704e84f3d5bf9074b31db 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -154,11 +154,42 @@ static bool global_reclaim(struct scan_control *sc)
 {
        return !sc->target_mem_cgroup;
 }
+
+/**
+ * sane_reclaim - is the usual dirty throttling mechanism operational?
+ * @sc: scan_control in question
+ *
+ * The normal page dirty throttling mechanism in balance_dirty_pages() is
+ * completely broken with the legacy memcg and direct stalling in
+ * shrink_page_list() is used for throttling instead, which lacks all the
+ * niceties such as fairness, adaptive pausing, bandwidth proportional
+ * allocation and configurability.
+ *
+ * This function tests whether the vmscan currently in progress can assume
+ * that the normal dirty throttling mechanism is operational.
+ */
+static bool sane_reclaim(struct scan_control *sc)
+{
+       struct mem_cgroup *memcg = sc->target_mem_cgroup;
+
+       if (!memcg)
+               return true;
+#ifdef CONFIG_CGROUP_WRITEBACK
+       if (cgroup_on_dfl(mem_cgroup_css(memcg)->cgroup))
+               return true;
+#endif
+       return false;
+}
 #else
 static bool global_reclaim(struct scan_control *sc)
 {
        return true;
 }
+
+static bool sane_reclaim(struct scan_control *sc)
+{
+       return true;
+}
 #endif
 
 static unsigned long zone_reclaimable_pages(struct zone *zone)
@@ -941,10 +972,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                 *    note that the LRU is being scanned too quickly and the
                 *    caller can stall after page list has been processed.
                 *
-                * 2) Global reclaim encounters a page, memcg encounters a
-                *    page that is not marked for immediate reclaim or
-                *    the caller does not have __GFP_IO. In this case mark
-                *    the page for immediate reclaim and continue scanning.
+                * 2) Global or new memcg reclaim encounters a page that is
+                *    not marked for immediate reclaim or the caller does not
+                *    have __GFP_IO. In this case mark the page for immediate
+                *    reclaim and continue scanning.
                 *
                 *    __GFP_IO is checked  because a loop driver thread might
                 *    enter reclaim, and deadlock if it waits on a page for
@@ -958,7 +989,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                 *    grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
                 *    may_enter_fs here is liable to OOM on them.
                 *
-                * 3) memcg encounters a page that is not already marked
+                * 3) Legacy memcg encounters a page that is not already marked
                 *    PageReclaim. memcg does not have any dirty pages
                 *    throttling so we could easily OOM just because too many
                 *    pages are in writeback and there is nothing else to
@@ -973,7 +1004,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                                goto keep_locked;
 
                        /* Case 2 above */
-                       } else if (global_reclaim(sc) ||
+                       } else if (sane_reclaim(sc) ||
                            !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) {
                                /*
                                 * This is slightly racy - end_page_writeback()
@@ -1422,7 +1453,7 @@ static int too_many_isolated(struct zone *zone, int file,
        if (current_is_kswapd())
                return 0;
 
-       if (!global_reclaim(sc))
+       if (!sane_reclaim(sc))
                return 0;
 
        if (file) {
@@ -1614,10 +1645,10 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
                set_bit(ZONE_WRITEBACK, &zone->flags);
 
        /*
-        * memcg will stall in page writeback so only consider forcibly
-        * stalling for global reclaim
+        * Legacy memcg will stall in page writeback so avoid forcibly
+        * stalling here.
         */
-       if (global_reclaim(sc)) {
+       if (sane_reclaim(sc)) {
                /*
                 * Tag a zone as congested if all the dirty pages scanned were
                 * backed by a congested BDI and wait_iff_congested will stall.
@@ -2652,7 +2683,8 @@ static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)
 
        for (i = 0; i <= ZONE_NORMAL; i++) {
                zone = &pgdat->node_zones[i];
-               if (!populated_zone(zone))
+               if (!populated_zone(zone) ||
+                   zone_reclaimable_pages(zone) == 0)
                        continue;
 
                pfmemalloc_reserve += min_wmark_pages(zone);
@@ -3602,7 +3634,7 @@ int zone_reclaim_mode __read_mostly;
 #define RECLAIM_OFF 0
 #define RECLAIM_ZONE (1<<0)    /* Run shrink_inactive_list on the zone */
 #define RECLAIM_WRITE (1<<1)   /* Writeout pages during reclaim */
-#define RECLAIM_SWAP (1<<2)    /* Swap pages out during reclaim */
+#define RECLAIM_UNMAP (1<<2)   /* Unmap pages during reclaim */
 
 /*
  * Priority for ZONE_RECLAIM. This determines the fraction of pages
@@ -3644,12 +3676,12 @@ static long zone_pagecache_reclaimable(struct zone *zone)
        long delta = 0;
 
        /*
-        * If RECLAIM_SWAP is set, then all file pages are considered
+        * If RECLAIM_UNMAP is set, then all file pages are considered
         * potentially reclaimable. Otherwise, we have to worry about
         * pages like swapcache and zone_unmapped_file_pages() provides
         * a better estimate
         */
-       if (zone_reclaim_mode & RECLAIM_SWAP)
+       if (zone_reclaim_mode & RECLAIM_UNMAP)
                nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
        else
                nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
@@ -3680,15 +3712,15 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
                .order = order,
                .priority = ZONE_RECLAIM_PRIORITY,
                .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
-               .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+               .may_unmap = !!(zone_reclaim_mode & RECLAIM_UNMAP),
                .may_swap = 1,
        };
 
        cond_resched();
        /*
-        * We need to be able to allocate from the reserves for RECLAIM_SWAP
+        * We need to be able to allocate from the reserves for RECLAIM_UNMAP
         * and we also need to be able to write out pages for RECLAIM_WRITE
-        * and RECLAIM_SWAP.
+        * and RECLAIM_UNMAP.
         */
        p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
        lockdep_set_current_reclaim_state(gfp_mask);