3246 ZFS I/O deadman thread

Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: Eric Schrock <[email protected]>
Reviewed by: Christopher Siden <[email protected]>
Approved by: Garrett D'Amore <[email protected]>

NOTES: This patch has been reworked from the original in the
following ways to accomidate Linux ZFS implementation

*) Usage of the cyclic interface was replaced by the delayed taskq
   interface.  This avoids the need to implement new compatibility
   code and allows us to rely on the existing taskq implementation.

*) An extern for zfs_txg_synctime_ms was added to sys/dsl_pool.h
   because declaring externs in source files as was done in the
   original patch is just plain wrong.

*) Instead of panicing the system when the deadman triggers a
   zevent describing the blocked vdev and the first pending I/O
   is posted.  If the panic behavior is desired Linux provides
   other generic methods to panic the system when threads are
   observed to hang.

*) For reference, to delay zios by 30 seconds for testing you can
   use zinject as follows: 'zinject -d <vdev> -D30 <pool>'

References:
  illumos/illumos-gate@283b84606b6fc326692c03273de1774e8c122f9a
  https://www.illumos.org/issues/3246

Ported-by: Brian Behlendorf <[email protected]>
Closes #1396

1 files changed, 1 insertions, 0 deletions

diff --git a/include/sys/vdev.h b/include/sys/vdev.h
index 8f297a917..f49086a47 100644
--- a/include/sys/vdev.h
+++ b/include/sys/vdev.h
@@ -78,6 +78,7 @@ extern void vdev_metaslab_fini(vdev_t *vd);
 extern void vdev_metaslab_set_size(vdev_t *);
 extern void vdev_expand(vdev_t *vd, uint64_t txg);
 extern void vdev_split(vdev_t *vd);
+extern void vdev_deadman(vdev_t *vd);
 
 
 extern void vdev_get_stats(vdev_t *vd, vdev_stat_t *vs);