linux.git/mm/page-writeback.c, branch v4.19

notifier: Remove notifier header file wherever not used

2018-08-30T10:56:40+00:00

The conversion of the hotplug notifiers to a state machine left the
notifier.h includes around in some places. Remove them.

Signed-off-by: Mukesh Ojha 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/1535114033-4605-1-git-send-email-mojha@codeaurora.org

mm/page-writeback.c: update stale account_page_redirty() comment

2018-08-17T23:20:30+00:00

Commit 93f78d882865 ("writeback: move backing_dev_info->bdi_stat[] into
bdi_writeback") replaced BDI_DIRTIED with WB_DIRTIED in
account_page_redirty().  Update comment to track that change.

  BDI_DIRTIED => WB_DIRTIED
  BDI_WRITTEN => WB_WRITTEN

Link: http://lkml.kernel.org/r/20180625171526.173483-1-gthelen@google.com
Signed-off-by: Greg Thelen 
Reviewed-by: Jan Kara 
Acked-by: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

writeback: safer lock nesting

2018-04-21T00:18:35+00:00

lock_page_memcg()/unlock_page_memcg() use spin_lock_irqsave/restore() if
the page's memcg is undergoing move accounting, which occurs when a
process leaves its memcg for a new one that has
memory.move_charge_at_immigrate set.

unlocked_inode_to_wb_begin,end() use spin_lock_irq/spin_unlock_irq() if
the given inode is switching writeback domains.  Switches occur when
enough writes are issued from a new domain.

This existing pattern is thus suspicious:
    lock_page_memcg(page);
    unlocked_inode_to_wb_begin(inode, &locked);
    ...
    unlocked_inode_to_wb_end(inode, locked);
    unlock_page_memcg(page);

If both inode switch and process memcg migration are both in-flight then
unlocked_inode_to_wb_end() will unconditionally enable interrupts while
still holding the lock_page_memcg() irq spinlock.  This suggests the
possibility of deadlock if an interrupt occurs before unlock_page_memcg().

    truncate
    __cancel_dirty_page
    lock_page_memcg
    unlocked_inode_to_wb_begin
    unlocked_inode_to_wb_end
    
                                    
                                    end_page_writeback
                                    test_clear_page_writeback
                                    lock_page_memcg
                                    
    unlock_page_memcg

Due to configuration limitations this deadlock is not currently possible
because we don't mix cgroup writeback (a cgroupv2 feature) and
memory.move_charge_at_immigrate (a cgroupv1 feature).

If the kernel is hacked to always claim inode switching and memcg
moving_account, then this script triggers lockup in less than a minute:

  cd /mnt/cgroup/memory
  mkdir a b
  echo 1 > a/memory.move_charge_at_immigrate
  echo 1 > b/memory.move_charge_at_immigrate
  (
    echo $BASHPID > a/cgroup.procs
    while true; do
      dd if=/dev/zero of=/mnt/big bs=1M count=256
    done
  ) &
  while true; do
    sync
  done &
  sleep 1h &
  SLEEP=$!
  while true; do
    echo $SLEEP > a/cgroup.procs
    echo $SLEEP > b/cgroup.procs
  done

The deadlock does not seem possible, so it's debatable if there's any
reason to modify the kernel.  I suggest we should to prevent future
surprises.  And Wang Long said "this deadlock occurs three times in our
environment", so there's more reason to apply this, even to stable.
Stable 4.4 has minor conflicts applying this patch.  For a clean 4.4 patch
see "[PATCH for-4.4] writeback: safer lock nesting"
https://lkml.org/lkml/2018/4/11/146

Wang Long said "this deadlock occurs three times in our environment"

[gthelen@google.com: v4]
  Link: http://lkml.kernel.org/r/20180411084653.254724-1-gthelen@google.com
[akpm@linux-foundation.org: comment tweaks, struct initialization simplification]
Change-Id: Ibb773e8045852978f6207074491d262f1b3fb613
Link: http://lkml.kernel.org/r/20180410005908.167976-1-gthelen@google.com
Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates")
Signed-off-by: Greg Thelen 
Reported-by: Wang Long 
Acked-by: Wang Long 
Acked-by: Michal Hocko 
Reviewed-by: Andrew Morton 
Cc: Johannes Weiner 
Cc: Tejun Heo 
Cc: Nicholas Piggin 
Cc: 	[v4.2+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

page cache: use xa_lock

2018-04-11T17:28:39+00:00

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.

[willy@infradead.org: fix nds32, fs/dax.c]
  Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox 
Acked-by: Jeff Layton 
Cc: Darrick J. Wong 
Cc: Dave Chinner 
Cc: Ryusuke Konishi 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical"

2017-11-30T02:40:43+00:00

This reverts commit 0f6d24f87856 ("mm/page-writeback.c: print a warning
if the vm dirtiness settings are illogical") because it causes false
positive warnings during OOM situations as noticed by Tetsuo Handa:

  Node 0 active_anon:3525940kB inactive_anon:8372kB active_file:216kB inactive_file:1872kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:2504kB dirty:52kB writeback:0kB shmem:8660kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 636928kB writeback_tmp:0kB unstable:0kB all_unreclaimable? yes
  Node 0 DMA free:14848kB min:284kB low:352kB high:420kB active_anon:992kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15988kB managed:15904kB mlocked:0kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
  lowmem_reserve[]: 0 2687 3645 3645
  Node 0 DMA32 free:53004kB min:49608kB low:62008kB high:74408kB active_anon:2712648kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:3129216kB managed:2773132kB mlocked:0kB kernel_stack:96kB pagetables:5096kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
  lowmem_reserve[]: 0 0 958 958
  Node 0 Normal free:17140kB min:17684kB low:22104kB high:26524kB active_anon:812300kB inactive_anon:8372kB active_file:1228kB inactive_file:1868kB unevictable:0kB writepending:52kB present:1048576kB managed:981224kB mlocked:0kB kernel_stack:3520kB pagetables:8552kB bounce:0kB free_pcp:120kB local_pcp:120kB free_cma:0kB
  lowmem_reserve[]: 0 0 0 0
  [...]
  Out of memory: Kill process 8459 (a.out) score 999 or sacrifice child
  Killed process 8459 (a.out) total-vm:4180kB, anon-rss:88kB, file-rss:0kB, shmem-rss:0kB
  oom_reaper: reaped process 8459 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
  vm direct limit must be set greater than background limit.

The problem is that both thresh and bg_thresh will be 0 if
available_memory is less than 4 pages when evaluating
global_dirtyable_memory.

While this might be worked around the whole point of the warning is
dubious at best.  We do rely on admins to do sensible things when
changing tunable knobs.  Dirty memory writeback knobs are not any
special in that regards so revert the warning rather than adding more
hacks to work this around.

Debugged by Yafang Shao.

Link: http://lkml.kernel.org/r/20171127091939.tahb77nznytcxw55@dhcp22.suse.cz
Fixes: 0f6d24f87856 ("mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical")
Signed-off-by: Michal Hocko 
Reported-by: Tetsuo Handa 
Cc: Yafang Shao 
Cc: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

block/laptop_mode: Convert timers to use timer_setup()

2017-11-21T23:46:44+00:00

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Jens Axboe 
Cc: Michal Hocko 
Cc: Andrew Morton 
Cc: Jan Kara 
Cc: Johannes Weiner 
Cc: Nicholas Piggin 
Cc: Vladimir Davydov 
Cc: Matthew Wilcox 
Cc: Jeff Layton 
Cc: linux-block@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook

writeback: remove unused function parameter

2017-11-16T02:21:07+00:00

The parameter `struct bdi_writeback *wb` is not been used in the
function body.  Remove it.

Link: http://lkml.kernel.org/r/1509685485-15278-1-git-send-email-wanglong19@meituan.com
Signed-off-by: Wang Long 
Reviewed-by: Jan Kara 
Acked-by: Tejun Heo 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, pagevec: remove cold parameter for pagevecs

2017-11-16T02:21:06+00:00

Every pagevec_init user claims the pages being released are hot even in
cases where it is unlikely the pages are hot.  As no one cares about the
hotness of pages being released to the allocator, just ditch the
parameter.

No performance impact is expected as the overhead is marginal.  The
parameter is removed simply because it is a bit stupid to have a useless
parameter copied everywhere.

Link: http://lkml.kernel.org/r/20171018075952.10627-6-mgorman@techsingularity.net
Signed-off-by: Mel Gorman 
Acked-by: Vlastimil Babka 
Cc: Andi Kleen 
Cc: Dave Chinner 
Cc: Dave Hansen 
Cc: Jan Kara 
Cc: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: speed up cancel_dirty_page() for clean pages

2017-11-16T02:21:06+00:00

Patch series "Speed up page cache truncation", v1.

When rebasing our enterprise distro to a newer kernel (from 4.4 to 4.12)
we have noticed a regression in bonnie++ benchmark when deleting files.
Eventually we have tracked this down to a fact that page cache
truncation got slower by about 10%.  There were both gains and losses in
the above interval of kernels but we have been able to identify that
commit 83929372f629 ("filemap: prepare find and delete operations for
huge pages") caused about 10% regression on its own.

After some investigation it didn't seem easily possible to fix the
regression while maintaining the THP in page cache functionality so
we've decided to optimize the page cache truncation path instead to make
up for the change.  This series is a result of that effort.

Patch 1 is an easy speedup of cancel_dirty_page().  Patches 2-6 refactor
page cache truncation code so that it is easier to batch radix tree
operations.  Patch 7 implements batching of deletes from the radix tree
which more than makes up for the original regression.

This patch (of 7):

cancel_dirty_page() does quite some work even for clean pages (fetching
of mapping, locking of memcg, atomic bit op on page flags) so it
accounts for ~2.5% of cost of truncation of a clean page.  That is not
much but still dumb for something we don't need at all.  Check whether a
page is actually dirty and avoid any work if not.

Link: http://lkml.kernel.org/r/20171010151937.26984-2-jack@suse.cz
Signed-off-by: Jan Kara 
Acked-by: Mel Gorman 
Reviewed-by: Andi Kleen 
Cc: Dave Hansen 
Cc: Dave Chinner 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page-writeback.c: convert timers to use timer_setup()

2017-11-16T02:21:05+00:00

In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch to using the new timer_setup() and
from_timer() to pass the timer pointer explicitly.

Link: http://lkml.kernel.org/r/20171016225913.GA99214@beast
Signed-off-by: Kees Cook 
Reviewed-by: Jan Kara 
Cc: Johannes Weiner 
Cc: Vladimir Davydov 
Cc: Matthew Wilcox 
Cc: Jeff Layton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds