mm: rename and change semantics of nr_indirectly_reclaimable_bytes

The vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES was introduced by
commit eb59254608bc ("mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES") with
the goal of accounting objects that can be reclaimed, but cannot be
allocated via a SLAB_RECLAIM_ACCOUNT cache.  This is now possible via
kmalloc() with __GFP_RECLAIMABLE flag, and the dcache external names user
is converted.

The counter is however still useful for accounting direct page allocations
(i.e.  not slab) with a shrinker, such as the ION page pool.  So keep it,
and:

- change granularity to pages to be more like other counters; sub-page
  allocations should be able to use kmalloc
- rename the counter to NR_KERNEL_MISC_RECLAIMABLE
- expose the counter again in vmstat as "nr_kernel_misc_reclaimable"; we can
  again remove the check for not printing "hidden" counters

Link: http://lkml.kernel.org/r/20180731090649.16028-5-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 14 insertions, 24 deletions

diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c
index 9bc56eb48d2a..0d2a95957ee8 100644
--- a/drivers/staging/android/ion/ion_page_pool.c
+++ b/drivers/staging/android/ion/ion_page_pool.c
@@ -33,8 +33,8 @@ static void ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
                 pool->low_count++;
         }
 
-        mod_node_page_state(page_pgdat(page), NR_INDIRECTLY_RECLAIMABLE_BYTES,
-                            (1 << (PAGE_SHIFT + pool->order)));
+        mod_node_page_state(page_pgdat(page), NR_KERNEL_MISC_RECLAIMABLE,
+                                                        1 << pool->order);
         mutex_unlock(&pool->mutex);
 }
 
@@ -53,8 +53,8 @@ static struct page *ion_page_pool_remove(struct ion_page_pool *pool, bool high)
         }
 
         list_del(&page->lru);
-        mod_node_page_state(page_pgdat(page), NR_INDIRECTLY_RECLAIMABLE_BYTES,
-                            -(1 << (PAGE_SHIFT + pool->order)));
+        mod_node_page_state(page_pgdat(page), NR_KERNEL_MISC_RECLAIMABLE,
+                                                        -(1 << pool->order));
         return page;
 }
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d4b0c79d2924..7bbeba21f6a3 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -180,7 +180,7 @@ enum node_stat_item {
         NR_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
         NR_DIRTIED,             /* page dirtyings since bootup */
         NR_WRITTEN,             /* page writings since bootup */
-        NR_INDIRECTLY_RECLAIMABLE_BYTES, /* measured in bytes */
+        NR_KERNEL_MISC_RECLAIMABLE,     /* reclaimable non-slab kernel pages */
         NR_VM_NODE_STAT_ITEMS
 };
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 747031c2352d..20f25d06c00c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4701,6 +4701,7 @@ long si_mem_available(void)
         unsigned long pagecache;
         unsigned long wmark_low = 0;
         unsigned long pages[NR_LRU_LISTS];
+        unsigned long reclaimable;
         struct zone *zone;
         int lru;
 
@@ -4726,19 +4727,13 @@ long si_mem_available(void)
         available += pagecache;
 
         /*
-         * Part of the reclaimable slab consists of items that are in use,
-         * and cannot be freed. Cap this estimate at the low watermark.
+         * Part of the reclaimable slab and other kernel memory consists of
+         * items that are in use, and cannot be freed. Cap this estimate at the
+         * low watermark.
          */
-        available += global_node_page_state(NR_SLAB_RECLAIMABLE) -
-                     min(global_node_page_state(NR_SLAB_RECLAIMABLE) / 2,
-                         wmark_low);
-
-        /*
-         * Part of the kernel memory, which can be released under memory
-         * pressure.
-         */
-        available += global_node_page_state(NR_INDIRECTLY_RECLAIMABLE_BYTES) >>
-                PAGE_SHIFT;
+        reclaimable = global_node_page_state(NR_SLAB_RECLAIMABLE) +
+                        global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
+        available += reclaimable - min(reclaimable / 2, wmark_low);
 
         if (available < 0)
                 available = 0;
diff --git a/mm/util.c b/mm/util.c
index 470f5cd80b64..f740754f5012 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -678,8 +678,7 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
                  * Part of the kernel memory, which can be released
                  * under memory pressure.
                  */
-                free += global_node_page_state(
-                        NR_INDIRECTLY_RECLAIMABLE_BYTES) >> PAGE_SHIFT;
+                free += global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
 
                 /*
                  * Leave reserved pages. The pages are not for anonymous pages.
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7878da76abf2..2cec2fa4c8ae 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1161,7 +1161,7 @@ const char * const vmstat_text[] = {
         "nr_vmscan_immediate_reclaim",
         "nr_dirtied",
         "nr_written",
-        "", /* nr_indirectly_reclaimable */
+        "nr_kernel_misc_reclaimable",
 
         /* enum writeback_stat_item counters */
         "nr_dirty_threshold",
@@ -1706,10 +1706,6 @@ static int vmstat_show(struct seq_file *m, void *arg)
         unsigned long *l = arg;
         unsigned long off = l - (unsigned long *)m->private;
 
-        /* Skip hidden vmstat items. */
-        if (*vmstat_text[off] == '\0')
-                return 0;
-
         seq_puts(m, vmstat_text[off]);
         seq_put_decimal_ull(m, " ", *l);
         seq_putc(m, '\n');