Merge branch 'akpm' (patches from Andrew)

Merge misc updates from Andrew Morton:
 "173 patches.

  Subsystems affected by this series: ia64, ocfs2, block, and mm (debug,
  pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
  bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure,
  hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock,
  oom-kill, migration, ksm, percpu, vmstat, and madvise)"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits)
  mm/madvise: add MADV_WILLNEED to process_madvise()
  mm/vmstat: remove unneeded return value
  mm/vmstat: simplify the array size calculation
  mm/vmstat: correct some wrong comments
  mm/percpu,c: remove obsolete comments of pcpu_chunk_populated()
  selftests: vm: add COW time test for KSM pages
  selftests: vm: add KSM merging time test
  mm: KSM: fix data type
  selftests: vm: add KSM merging across nodes test
  selftests: vm: add KSM zero page merging test
  selftests: vm: add KSM unmerge test
  selftests: vm: add KSM merge test
  mm/migrate: correct kernel-doc notation
  mm: wire up syscall process_mrelease
  mm: introduce process_mrelease system call
  memblock: make memblock_find_in_range method private
  mm/mempolicy.c: use in_task() in mempolicy_slab_node()
  mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies
  mm/mempolicy: advertise new MPOL_PREFERRED_MANY
  mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY
  ...

1 files changed, 14 insertions, 14 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index eb57dade6076..81ec192ce067 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -406,6 +406,11 @@ static bool inode_do_switch_wbs(struct inode *inode,
 		inc_wb_stat(new_wb, WB_WRITEBACK);
 	}
 
+	if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) {
+		atomic_dec(&old_wb->writeback_inodes);
+		atomic_inc(&new_wb->writeback_inodes);
+	}
+
 	wb_get(new_wb);
 
 	/*
@@ -1034,20 +1039,20 @@ restart:
  * cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
  * @bdi_id: target bdi id
  * @memcg_id: target memcg css id
- * @nr: number of pages to write, 0 for best-effort dirty flushing
  * @reason: reason why some writeback work initiated
  * @done: target wb_completion
  *
  * Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
  * with the specified parameters.
  */
-int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
+int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
 			   enum wb_reason reason, struct wb_completion *done)
 {
 	struct backing_dev_info *bdi;
 	struct cgroup_subsys_state *memcg_css;
 	struct bdi_writeback *wb;
 	struct wb_writeback_work *work;
+	unsigned long dirty;
 	int ret;
 
 	/* lookup bdi and memcg */
@@ -1076,24 +1081,22 @@ int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
 	}
 
 	/*
-	 * If @nr is zero, the caller is attempting to write out most of
+	 * The caller is attempting to write out most of
 	 * the currently dirty pages.  Let's take the current dirty page
 	 * count and inflate it by 25% which should be large enough to
 	 * flush out most dirty pages while avoiding getting livelocked by
 	 * concurrent dirtiers.
+	 *
+	 * BTW the memcg stats are flushed periodically and this is best-effort
+	 * estimation, so some potential error is ok.
 	 */
-	if (!nr) {
-		unsigned long filepages, headroom, dirty, writeback;
-
-		mem_cgroup_wb_stats(wb, &filepages, &headroom, &dirty,
-				      &writeback);
-		nr = dirty * 10 / 8;
-	}
+	dirty = memcg_page_state(mem_cgroup_from_css(memcg_css), NR_FILE_DIRTY);
+	dirty = dirty * 10 / 8;
 
 	/* issue the writeback work */
 	work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN);
 	if (work) {
-		work->nr_pages = nr;
+		work->nr_pages = dirty;
 		work->sync_mode = WB_SYNC_NONE;
 		work->range_cyclic = 1;
 		work->reason = reason;
@@ -1999,7 +2002,6 @@ static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
 static long wb_writeback(struct bdi_writeback *wb,
 			 struct wb_writeback_work *work)
 {
-	unsigned long wb_start = jiffies;
 	long nr_pages = work->nr_pages;
 	unsigned long dirtied_before = jiffies;
 	struct inode *inode;
@@ -2053,8 +2055,6 @@ static long wb_writeback(struct bdi_writeback *wb,
 			progress = __writeback_inodes_wb(wb, work);
 		trace_writeback_written(wb, work);
 
-		wb_update_bandwidth(wb, wb_start);
-
 		/*
 		 * Did we write something? Try for more
 		 *