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Pull in a follow-on commit to resolve a deadlock in ZFS sequential

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resilver (r334844)

MFV/ZoL: Fix deadlock in IO pipeline

commit a76f3d0437
Author: Brian Behlendorf <behlendorf1@llnl.gov>
Date:   Fri Mar 16 16:46:06 2018 -0700

    Fix deadlock in IO pipeline

    In vdev_queue_aggregate() the zio_execute() bypass should not be
    called under the vdev queue lock.  This can result in a deadlock
    as shown in the stack traces below.

    Drop the vdev queue lock then walk the parents of the aggregate IO
    to determine the list of component IOs to be bypassed.  This can
    be done safely without holding the io_lock since the new aggregate
    IO has not yet been returned and its parents cannot change.

    ---  THREAD 1 ---
    arc_read()
      zio_nowait()
        zio_vdev_io_start()
          vdev_queue_io() <--- mutex_enter(vq->vq_lock)
            vdev_queue_io_to_issue()
              vdev_queue_aggregate()
                zio_execute()
            vdev_queue_io_to_issue()
              vdev_queue_aggregate()
                zio_execute()
                  zio_vdev_io_assess()
                    zio_wait_for_children() <- mutex_enter(zio->io_lock)

    --- THREAD 2 --- (inverse order)
    arc_read()
      zio_change_priority() <- mutex_enter(zio->zio_lock)
        vdev_queue_change_io_priority() <- mutex_enter(vq->vq_lock)

    Reviewed-by: Tom Caputi <tcaputi@datto.com>
    Reviewed-by: Don Brady <don.brady@delphix.com>
    Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

Reported by:	ZFS Leadership Meeting
Reviewed by:	mav
Approved by:	re (kib)
Obtained from:	ZFS-on-Linux
MFC after:	2 weeks
Sponsored by:	Klara Systems
Differential Revision:	https://reviews.freebsd.org/D17495
This commit is contained in:
Allan Jude 2018-10-10 22:59:15 +00:00
parent bee8a18986
commit c79b58ccc5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339299
1 changed files with 11 additions and 1 deletions
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12
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
View file

@ -670,6 +670,7 @@ static zio_t *
vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
{
zio_t *first, *last, *aio, *dio, *mandatory, *nio;
zio_link_t *zl = NULL;
uint64_t maxgap = 0;
uint64_t size;
boolean_t stretch;
@ -813,9 +814,18 @@ vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
zio_add_child(dio, aio);
vdev_queue_io_remove(vq, dio);
} while (dio != last);
/*
* We need to drop the vdev queue's lock to avoid a deadlock that we
* could encounter since this I/O will complete immediately.
*/
mutex_exit(&vq->vq_lock);
while ((dio = zio_walk_parents(aio, &zl)) != NULL) {
zio_vdev_io_bypass(dio);
zio_execute(dio);
} while (dio != last);
}
mutex_enter(&vq->vq_lock);
return (aio);
}