Author: allanjude
Date: Wed Oct 10 22:59:15 2018
New Revision: 339299
URL: https://svnweb.freebsd.org/changeset/base/339299
Log:
Pull in a follow-on commit to resolve a deadlock in ZFS sequential
resilver (r334844)
MFV/ZoL: Fix deadlock in IO pipeline
commit a76f3d0437e5e974f0f748f8735af3539443b388
Author: Brian Behlendorf <behlendo...@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 <tcap...@datto.com>
Reviewed-by: Don Brady <don.br...@delphix.com>
Signed-off-by: Brian Behlendorf <behlendo...@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
Modified:
head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c Wed Oct
10 22:55:31 2018 (r339298)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c Wed Oct
10 22:59:15 2018 (r339299)
@@ -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);
}
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