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  1. 03 Oct, 2017 2 commits
    • Joseph Qi's avatar
      blk-throttle: fix possible io stall when upgrade to max · 4f02fb76
      Joseph Qi authored 
      There is a case which will lead to io stall. The case is described as
follows.
/test1
  |-subtest1
/test2
  |-subtest2
And subtest1 and subtest2 each has 32 queued bios already.

Now upgrade to max. In throtl_upgrade_state, it will try to dispatch
bios as follows:
1) tg=subtest1, do nothing;
2) tg=test1, transfer 32 queued bios from subtest1 to test1; no pending
left, no need to schedule next dispatch;
3) tg=subtest2, do nothing;
4) tg=test2, transfer 32 queued bios from subtest2 to test2; no pending
left, no need to schedule next dispatch;
5) tg=/, transfer 8 queued bios from test1 to /, 8 queued bios from
test2 to /, 8 queued bios from test1 to /, and 8 queued bios from test2
to /; note that test1 and test2 each still has 16 queued bios left;
6) tg=/, try to schedule next dispatch, but since disptime is now
(update in tg_update_disptime, wait=0), pending timer is not scheduled
in fact;
7) In throtl_upgrade_state it totally dispatches 32 queued bios and with
32 left. test1 and test2 each has 16 queued bios;
8) throtl_pending_timer_fn sees the left over bios, but could do
nothing, because throtl_select_dispatch returns 0, and test1/test2 has
no pending tg.

The blktrace shows the following:
8,32   0        0     2.539007641     0  m   N throtl upgrade to max
8,32   0        0     2.539072267     0  m   N throtl /test2 dispatch nr_queued=16 read=0 write=16
8,32   7        0     2.539077142     0  m   N throtl /test1 dispatch nr_queued=16 read=0 write=16

So force schedule dispatch if there are pending children.
Reviewed-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJoseph Qi <qijiang.qj@alibaba-inc.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      4f02fb76
    • Wouter Verhelst's avatar
      MAINTAINERS: update list for NBD · 38b249bc
      Wouter Verhelst authored 
      nbd-general@sourceforge.net becomes nbd@other.debian.org, because
sourceforge is just a spamtrap these days.
Signed-off-by: default avatarWouter Verhelst <w@uter.be>
Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      38b249bc
  3. 02 Oct, 2017 1 commit
    • Josef Bacik's avatar
      nbd: fix -ERESTARTSYS handling · 6e60a3bb
      Josef Bacik authored 
      Christoph made it so that if we return'ed BLK_STS_RESOURCE whenever we
got ERESTARTSYS from sending our packets we'd return BLK_STS_OK, which
means we'd never requeue and just hang.  We really need to return the
right value from the upper layer.

Fixes: fc17b653 ("blk-mq: switch ->queue_rq return value to blk_status_t")
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      6e60a3bb
  5. 27 Sep, 2017 1 commit
    • Coly Li's avatar
      bcache: use llist_for_each_entry_safe() in __closure_wake_up() · a5f3d8a5
      Coly Li authored 
      Commit 09b3efec ("bcache: Don't reinvent the wheel but use existing llist
API") replaces the following while loop by llist_for_each_entry(),

-
-	while (reverse) {
-		cl = container_of(reverse, struct closure, list);
-		reverse = llist_next(reverse);
-
+	llist_for_each_entry(cl, reverse, list) {
 		closure_set_waiting(cl, 0);
 		closure_sub(cl, CLOSURE_WAITING + 1);
 	}

This modification introduces a potential race by iterating a corrupted
list. Here is how it happens.

In the above modification, closure_sub() may wake up a process which is
waiting on reverse list. If this process decides to wait again by calling
closure_wait(), its cl->list will be added to another wait list. Then
when llist_for_each_entry() continues to iterate next node, it will travel
on another new wait list which is added in closure_wait(), not the
original reverse list in __closure_wake_up(). It is more probably to
happen on UP machine because the waked up process may preempt the process
which wakes up it.

Use llist_for_each_entry_safe() will fix the issue, the safe version fetch
next node before waking up a process. Then the copy of next node will make
sure list iteration stays on original reverse list.

Fixes: 09b3efec ("bcache: Don't reinvent the wheel but use existing llist API")
Signed-off-by: default avatarColy Li <colyli@suse.de>
Reported-by: default avatarMichael Lyle <mlyle@lyle.org>
Reviewed-by: default avatarByungchul Park <byungchul.park@lge.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      a5f3d8a5
  7. 26 Sep, 2017 4 commits
  9. 25 Sep, 2017 32 commits
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