Merge branch 'akpm' (patches from Andrew)

Merge misc updates from Andrew Morton:

 - large KASAN update to use arm's "software tag-based mode"

 - a few misc things

 - sh updates

 - ocfs2 updates

 - just about all of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (167 commits)
  kernel/fork.c: mark 'stack_vm_area' with __maybe_unused
  memcg, oom: notify on oom killer invocation from the charge path
  mm, swap: fix swapoff with KSM pages
  include/linux/gfp.h: fix typo
  mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm
  hugetlbfs: Use i_mmap_rwsem to fix page fault/truncate race
  hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization
  memory_hotplug: add missing newlines to debugging output
  mm: remove __hugepage_set_anon_rmap()
  include/linux/vmstat.h: remove unused page state adjustment macro
  mm/page_alloc.c: allow error injection
  mm: migrate: drop unused argument of migrate_page_move_mapping()
  blkdev: avoid migration stalls for blkdev pages
  mm: migrate: provide buffer_migrate_page_norefs()
  mm: migrate: move migrate_page_lock_buffers()
  mm: migrate: lock buffers before migrate_page_move_mapping()
  mm: migration: factor out code to compute expected number of page references
  mm, page_alloc: enable pcpu_drain with zone capability
  kmemleak: add config to select auto scan
  mm/page_alloc.c: don't call kasan_free_pages() at deferred mem init
  ...

1 files changed, 72 insertions, 8 deletions

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 3c1b5ab54bc0..436c5e98e1b6 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -164,11 +164,14 @@ reset             WO    trigger device reset
 mem_used_max      WO    reset the `mem_used_max' counter (see later)
 mem_limit         WO    specifies the maximum amount of memory ZRAM can use
                         to store the compressed data
+writeback_limit   WO    specifies the maximum amount of write IO zram can
+			write out to backing device as 4KB unit
 max_comp_streams  RW    the number of possible concurrent compress operations
 comp_algorithm    RW    show and change the compression algorithm
 compact           WO    trigger memory compaction
 debug_stat        RO    this file is used for zram debugging purposes
 backing_dev	  RW	set up backend storage for zram to write out
+idle		  WO	mark allocated slot as idle
 
 
 User space is advised to use the following files to read the device statistics.
@@ -220,6 +223,17 @@ line of text and contains the following stats separated by whitespace:
  pages_compacted  the number of pages freed during compaction
  huge_pages	  the number of incompressible pages
 
+File /sys/block/zram<id>/bd_stat
+
+The stat file represents device's backing device statistics. It consists of
+a single line of text and contains the following stats separated by whitespace:
+ bd_count	size of data written in backing device.
+		Unit: 4K bytes
+ bd_reads	the number of reads from backing device
+		Unit: 4K bytes
+ bd_writes	the number of writes to backing device
+		Unit: 4K bytes
+
 9) Deactivate:
 	swapoff /dev/zram0
 	umount /dev/zram1
@@ -237,11 +251,60 @@ line of text and contains the following stats separated by whitespace:
 
 = writeback
 
-With incompressible pages, there is no memory saving with zram.
-Instead, with CONFIG_ZRAM_WRITEBACK, zram can write incompressible page
+With CONFIG_ZRAM_WRITEBACK, zram can write idle/incompressible page
 to backing storage rather than keeping it in memory.
-User should set up backing device via /sys/block/zramX/backing_dev
-before disksize setting.
+To use the feature, admin should set up backing device via
+
+	"echo /dev/sda5 > /sys/block/zramX/backing_dev"
+
+before disksize setting. It supports only partition at this moment.
+If admin want to use incompressible page writeback, they could do via
+
+	"echo huge > /sys/block/zramX/write"
+
+To use idle page writeback, first, user need to declare zram pages
+as idle.
+
+	"echo all > /sys/block/zramX/idle"
+
+From now on, any pages on zram are idle pages. The idle mark
+will be removed until someone request access of the block.
+IOW, unless there is access request, those pages are still idle pages.
+
+Admin can request writeback of those idle pages at right timing via
+
+	"echo idle > /sys/block/zramX/writeback"
+
+With the command, zram writeback idle pages from memory to the storage.
+
+If there are lots of write IO with flash device, potentially, it has
+flash wearout problem so that admin needs to design write limitation
+to guarantee storage health for entire product life.
+To overcome the concern, zram supports "writeback_limit".
+The "writeback_limit"'s default value is 0 so that it doesn't limit
+any writeback. If admin want to measure writeback count in a certain
+period, he could know it via /sys/block/zram0/bd_stat's 3rd column.
+
+If admin want to limit writeback as per-day 400M, he could do it
+like below.
+
+    MB_SHIFT=20
+    4K_SHIFT=12
+    echo $((400<<MB_SHIFT>>4K_SHIFT)) > \
+	    /sys/block/zram0/writeback_limit.
+
+If admin want to allow further write again, he could do it like below
+
+    echo 0 > /sys/block/zram0/writeback_limit
+
+If admin want to see remaining writeback budget since he set,
+
+    cat /sys/block/zram0/writeback_limit
+
+The writeback_limit count will reset whenever you reset zram(e.g.,
+system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of
+writeback happened until you reset the zram to allocate extra writeback
+budget in next setting is user's job.
 
 = memory tracking
 
@@ -251,16 +314,17 @@ pages of the process with*pagemap.
 If you enable the feature, you could see block state via
 /sys/kernel/debug/zram/zram0/block_state". The output is as follows,
 
-	  300    75.033841 .wh
-	  301    63.806904 s..
-	  302    63.806919 ..h
+	  300    75.033841 .wh.
+	  301    63.806904 s...
+	  302    63.806919 ..hi
 
 First column is zram's block index.
 Second column is access time since the system was booted
 Third column is state of the block.
 (s: same page
 w: written page to backing store
-h: huge page)
+h: huge page
+i: idle page)
 
 First line of above example says 300th block is accessed at 75.033841sec
 and the block's state is huge so it is written back to the backing