BACKPORT: 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>

(cherry picked from commit b29940c1abd7a4c3abeb926df0a5ec84d6902d47)

Conflicts:
        drivers/staging/android/ion/ion_page_pool.c

(1. NR_INDIRECTLY_RECLAIMABLE_BYTES accounting is absent, ignore it since
this patch replaces it anyway.)

Bug: 138148041
Test: verify KReclaimable accounting after ION allocation+deallocation
Change-Id: I6196eaa1e72f16dbde7a2894dc42435e75ae156c
Signed-off-by: Suren Baghdasaryan <surenb@google.com>

drivers/staging/android/ion/ion_page_pool.c

@@ -50,6 +50,9 @@ static int ion_page_pool_add(struct ion_page_pool *pool, struct page *page)
 		list_add_tail(&page->lru, &pool->low_items);
 		pool->low_count++;
 	}
+
+	mod_node_page_state(page_pgdat(page), NR_KERNEL_MISC_RECLAIMABLE,
+							1 << pool->order);
 	mutex_unlock(&pool->mutex);
 	return 0;
 }
@@ -69,6 +72,8 @@ 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_KERNEL_MISC_RECLAIMABLE,
+							-(1 << pool->order));
 	return page;
 }
 

include/linux/mmzone.h

@@ -184,7 +184,7 @@ 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
 };
 

mm/page_alloc.c

@@ -4592,6 +4592,7 @@ 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;
 
@@ -4617,19 +4618,13 @@ 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;

mm/util.c

@@ -639,8 +639,7 @@ 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.

mm/vmstat.c

@@ -1094,7 +1094,7 @@ 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",
@@ -1676,10 +1676,6 @@ 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');