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Use a dedicated taskq for vdev_file 

The introduction of parallel zvol prefetch causes deadlock when using
vdev_file.

spa_async->(spa_namespace_lock)->txg_wait_synced->(wait for txg_sync)
txg_sync->zio_wait->(wait for vdev_file_io_fsync on system_taskq)
zvol_prefetch_minors_impl (on system_taskq)->spa_open_common->(wait for spa_namespace_lock)

We fix this by using dedicated taskq for vdev_file.  This same change
was originally made in commit bc25c93 but reverted in commit aa9af22
when dynamic taskqs were added.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <tuxoko@gmail.com>
Closes #5506 
Closes #5495
This commit is contained in:
Chunwei Chen 2016-12-21 10:47:15 -08:00 committed by Brian Behlendorf
parent 5f1346c299
commit da8f51e16a
3 changed files with 24 additions and 2 deletions
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3
include/sys/vdev_file.h
View File

@ -37,6 +37,9 @@ typedef struct vdev_file {
vnode_t *vf_vnode;
} vdev_file_t;
extern void vdev_file_init(void);
extern void vdev_file_fini(void);
#ifdef __cplusplus
}
#endif

2
module/zfs/spa_misc.c
View File

@ -1839,6 +1839,7 @@ spa_init(int mode)
zil_init();
vdev_cache_stat_init();
vdev_raidz_math_init();
vdev_file_init();
zfs_prop_init();
zpool_prop_init();
zpool_feature_init();
@ -1853,6 +1854,7 @@ spa_fini(void)
spa_evict_all();
vdev_file_fini();
vdev_cache_stat_fini();
vdev_raidz_math_fini();
zil_fini();

21
module/zfs/vdev_file.c
View File

@ -37,6 +37,8 @@
* Virtual device vector for files.
*/
static taskq_t *vdev_file_taskq;
static void
vdev_file_hold(vdev_t *vd)
{
@ -212,7 +214,7 @@ vdev_file_io_start(zio_t *zio)
* the sync must be dispatched to a different context.
*/
if (spl_fstrans_check()) {
VERIFY3U(taskq_dispatch(system_taskq,
VERIFY3U(taskq_dispatch(vdev_file_taskq,
vdev_file_io_fsync, zio, TQ_SLEEP), !=,
TASKQID_INVALID);
return;
@ -231,7 +233,7 @@ vdev_file_io_start(zio_t *zio)
zio->io_target_timestamp = zio_handle_io_delay(zio);
VERIFY3U(taskq_dispatch(system_taskq, vdev_file_io_strategy, zio,
VERIFY3U(taskq_dispatch(vdev_file_taskq, vdev_file_io_strategy, zio,
TQ_SLEEP), !=, TASKQID_INVALID);
}
@ -254,6 +256,21 @@ vdev_ops_t vdev_file_ops = {
B_TRUE /* leaf vdev */
};
void
vdev_file_init(void)
{
vdev_file_taskq = taskq_create("z_vdev_file", MAX(boot_ncpus, 16),
minclsyspri, boot_ncpus, INT_MAX, TASKQ_DYNAMIC);
VERIFY(vdev_file_taskq);
}
void
vdev_file_fini(void)
{
taskq_destroy(vdev_file_taskq);
}
/*
* From userland we access disks just like files.
*/