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  1. 28 8月, 2019 3 次提交
    • N
      raid5 improve too many read errors msg by adding limits · 0009fad0
      由 Nigel Croxon 提交于 
      Often limits can be changed by admin. When discussing such things
it helps if you can provide "self-sustained" facts. Also
sometimes the admin thinks he changed a limit, but it did not
take effect for some reason or he changed the wrong thing.

V3: Only pr_warn when Faulty is 0.
V2: Add read_errors value to pr_warn.
Signed-off-by: NNigel Croxon <ncroxon@redhat.com>
Signed-off-by: NSong Liu <songliubraving@fb.com>
      0009fad0
    • N
      md: don't report active array_state until after revalidate_disk() completes. · 9d4b45d6
      由 NeilBrown 提交于 
      Until revalidate_disk() has completed, the size of a new md array will
appear to be zero.
So we shouldn't report, through array_state, that the array is active
until that time.
udev rules check array_state to see if the array is ready.  As soon as
it appear to be zero, fsck can be run.  If it find the size to be
zero, it will fail.

So add a new flag to provide an interlock between do_md_run() and
array_state_show().  This flag is set while do_md_run() is active and
it prevents array_state_show() from reporting that the array is
active.

Before do_md_run() is called, ->pers will be NULL so array is
definitely not active.
After do_md_run() is called, revalidate_disk() will have run and the
array will be completely ready.

We also move various sysfs_notify*() calls out of md_run() into
do_md_run() after MD_NOT_READY is cleared.  This ensure the
information is ready before the notification is sent.

Prior to v4.12, array_state_show() was called with the
mddev->reconfig_mutex held, which provided exclusion with do_md_run().

Note that MD_NOT_READY cleared twice.  This is deliberate to cover
both success and error paths with minimal noise.

Fixes: b7b17c9b ("md: remove mddev_lock() from md_attr_show()")
Cc: stable@vger.kernel.org (v4.12++)
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NSong Liu <songliubraving@fb.com>
      9d4b45d6
    • N
      md: only call set_in_sync() when it is expected to succeed. · 480523fe
      由 NeilBrown 提交于 
      Since commit 4ad23a97 ("MD: use per-cpu counter for
writes_pending"), set_in_sync() is substantially more expensive: it
can wait for a full RCU grace period which can be 10s of milliseconds.

So we should only call it when the cost is justified.

md_check_recovery() currently calls set_in_sync() every time it finds
anything to do (on non-external active arrays).  For an array
performing resync or recovery, this will be quite often.
Each call will introduce a delay to the md thread, which can noticeable
affect IO submission latency.

In md_check_recovery() we only need to call set_in_sync() if
'safemode' was non-zero at entry, meaning that there has been not
recent IO.  So we save this "safemode was nonzero" state, and only
call set_in_sync() if it was non-zero.

This measurably reduces mean and maximum IO submission latency during
resync/recovery.
Reported-and-tested-by: NJack Wang <jinpu.wang@cloud.ionos.com>
Fixes: 4ad23a97 ("MD: use per-cpu counter for writes_pending")
Cc: stable@vger.kernel.org (v4.12+)
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NSong Liu <songliubraving@fb.com>
      480523fe
  3. 27 8月, 2019 5 次提交
    • T
      writeback, memcg: Implement foreign dirty flushing · 97b27821
      由 Tejun Heo 提交于 
      There's an inherent mismatch between memcg and writeback.  The former
trackes ownership per-page while the latter per-inode.  This was a
deliberate design decision because honoring per-page ownership in the
writeback path is complicated, may lead to higher CPU and IO overheads
and deemed unnecessary given that write-sharing an inode across
different cgroups isn't a common use-case.

Combined with inode majority-writer ownership switching, this works
well enough in most cases but there are some pathological cases.  For
example, let's say there are two cgroups A and B which keep writing to
different but confined parts of the same inode.  B owns the inode and
A's memory is limited far below B's.  A's dirty ratio can rise enough
to trigger balance_dirty_pages() sleeps but B's can be low enough to
avoid triggering background writeback.  A will be slowed down without
a way to make writeback of the dirty pages happen.

This patch implements foreign dirty recording and foreign mechanism so
that when a memcg encounters a condition as above it can trigger
flushes on bdi_writebacks which can clean its pages.  Please see the
comment on top of mem_cgroup_track_foreign_dirty_slowpath() for
details.

A reproducer follows.

write-range.c::

  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <sys/types.h>

  static const char *usage = "write-range FILE START SIZE\n";

  int main(int argc, char **argv)
  {
	  int fd;
	  unsigned long start, size, end, pos;
	  char *endp;
	  char buf[4096];

	  if (argc < 4) {
		  fprintf(stderr, usage);
		  return 1;
	  }

	  fd = open(argv[1], O_WRONLY);
	  if (fd < 0) {
		  perror("open");
		  return 1;
	  }

	  start = strtoul(argv[2], &endp, 0);
	  if (*endp != '\0') {
		  fprintf(stderr, usage);
		  return 1;
	  }

	  size = strtoul(argv[3], &endp, 0);
	  if (*endp != '\0') {
		  fprintf(stderr, usage);
		  return 1;
	  }

	  end = start + size;

	  while (1) {
		  for (pos = start; pos < end; ) {
			  long bread, bwritten = 0;

			  if (lseek(fd, pos, SEEK_SET) < 0) {
				  perror("lseek");
				  return 1;
			  }

			  bread = read(0, buf, sizeof(buf) < end - pos ?
					       sizeof(buf) : end - pos);
			  if (bread < 0) {
				  perror("read");
				  return 1;
			  }
			  if (bread == 0)
				  return 0;

			  while (bwritten < bread) {
				  long this;

				  this = write(fd, buf + bwritten,
					       bread - bwritten);
				  if (this < 0) {
					  perror("write");
					  return 1;
				  }

				  bwritten += this;
				  pos += bwritten;
			  }
		  }
	  }
  }

repro.sh::

  #!/bin/bash

  set -e
  set -x

  sysctl -w vm.dirty_expire_centisecs=300000
  sysctl -w vm.dirty_writeback_centisecs=300000
  sysctl -w vm.dirtytime_expire_seconds=300000
  echo 3 > /proc/sys/vm/drop_caches

  TEST=/sys/fs/cgroup/test
  A=$TEST/A
  B=$TEST/B

  mkdir -p $A $B
  echo "+memory +io" > $TEST/cgroup.subtree_control
  echo $((1<<30)) > $A/memory.high
  echo $((32<<30)) > $B/memory.high

  rm -f testfile
  touch testfile
  fallocate -l 4G testfile

  echo "Starting B"

  (echo $BASHPID > $B/cgroup.procs
   pv -q --rate-limit 70M < /dev/urandom | ./write-range testfile $((2<<30)) $((2<<30))) &

  echo "Waiting 10s to ensure B claims the testfile inode"
  sleep 5
  sync
  sleep 5
  sync
  echo "Starting A"

  (echo $BASHPID > $A/cgroup.procs
   pv < /dev/urandom | ./write-range testfile 0 $((2<<30)))

v2: Added comments explaining why the specific intervals are being used.

v3: Use 0 @nr when calling cgroup_writeback_by_id() to use best-effort
    flushing while avoding possible livelocks.

v4: Use get_jiffies_64() and time_before/after64() instead of raw
    jiffies_64 and arthimetic comparisons as suggested by Jan.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      97b27821
    • T
      writeback, memcg: Implement cgroup_writeback_by_id() · d62241c7
      由 Tejun Heo 提交于 
      Implement cgroup_writeback_by_id() which initiates cgroup writeback
from bdi and memcg IDs.  This will be used by memcg foreign inode
flushing.

v2: Use wb_get_lookup() instead of wb_get_create() to avoid creating
    spurious wbs.

v3: Interpret 0 @nr as 1.25 * nr_dirty to implement best-effort
    flushing while avoding possible livelocks.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      d62241c7
    • T
      writeback: Separate out wb_get_lookup() from wb_get_create() · ed288dc0
      由 Tejun Heo 提交于 
      Separate out wb_get_lookup() which doesn't try to create one if there
isn't already one from wb_get_create().  This will be used by later
patches.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      ed288dc0
    • T
      bdi: Add bdi->id · 34f8fe50
      由 Tejun Heo 提交于 
      There currently is no way to universally identify and lookup a bdi
without holding a reference and pointer to it.  This patch adds an
non-recycling bdi->id and implements bdi_get_by_id() which looks up
bdis by their ids.  This will be used by memcg foreign inode flushing.

I left bdi_list alone for simplicity and because while rb_tree does
support rcu assignment it doesn't seem to guarantee lossless walk when
walk is racing aginst tree rebalance operations.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      34f8fe50
    • T
      writeback: Generalize and expose wb_completion · 5b9cce4c
      由 Tejun Heo 提交于 
      wb_completion is used to track writeback completions.  We want to use
it from memcg side for foreign inode flushes.  This patch updates it
to remember the target waitq instead of assuming bdi->wb_waitq and
expose it outside of fs-writeback.c.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      5b9cce4c
  5. 24 8月, 2019 1 次提交
  7. 23 8月, 2019 6 次提交
  9. 22 8月, 2019 3 次提交
  11. 21 8月, 2019 5 次提交
  13. 20 8月, 2019 3 次提交
  15. 19 8月, 2019 1 次提交
  17. 16 8月, 2019 2 次提交
    • T
      writeback, cgroup: inode_switch_wbs() shouldn't give up on wb_switch_rwsem trylock fail · 6444f47e
      由 Tejun Heo 提交于 
      As inode wb switching may make sync(2) miss some inodes, they're
synchronized using wb_switch_rwsem so that no wb switching happens
while sync(2) is in progress.  In addition to synchronizing the actual
switching, the rwsem is also used to prevent queueing new switch
attempts while sync(2) is in progress.  This is to avoid queueing too
many instances while the rwsem is held by sync(2).  Unfortunately,
this is too agressive and can block wb switching for a long time if
sync(2) is frequent.

The goal is avoiding expolding the number of scheduled switches, not
avoiding scheduling anything.  Let's use wb_switch_rwsem only for
synchronizing the actual switching and sync(2) and use
isw_nr_in_flight instead for limiting the maximum number of scheduled
switches.  The limit is set to 1024 which should be more than enough
while still avoiding extreme situations.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      6444f47e
    • T
      writeback, cgroup: Adjust WB_FRN_TIME_CUT_DIV to accelerate foreign inode switching · 55a694df
      由 Tejun Heo 提交于 
      WB_FRN_TIME_CUT_DIV is used to tell the foreign inode detection logic
to ignore short writeback rounds to prevent getting confused by a
burst of short writebacks.  The parameter is currently 2 meaning that
anything smaller than half of the running average writback duration
will be ignored.

This is unnecessarily aggressive.  The detection logic uses 16 history
slots and is already reasonably protected against some short bursts
confusing it and the current parameter can lead to tens of seconds of
missed detection depending on the writeback pattern.

Let's change the parameter to 8, so that it only ignores writeback
with are smaller than 12.5% of the current running average.

v2: Add comment explaining what's going on with the foreign detection
    parameters.
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      55a694df
  19. 14 8月, 2019 1 次提交
  21. 12 8月, 2019 1 次提交
  23. 09 8月, 2019 3 次提交
  25. 08 8月, 2019 6 次提交