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Add support for asynchronous zvol minor operations

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zfsonlinux issue #2217 - zvol minor operations: check snapdev
property before traversing snapshots of a dataset

zfsonlinux issue #3681 - lock order inversion between zvol_open()
and dsl_pool_sync()...zvol_rename_minors()

Create a per-pool zvol taskq for asynchronous zvol tasks.
There are a few key design decisions to be aware of.

* Each taskq must be single threaded to ensure tasks are always
  processed in the order in which they were dispatched.

* There is a taskq per-pool in order to keep the pools independent.
  This way if one pool is suspended it will not impact another.

* The preferred location to dispatch a zvol minor task is a sync
  task.  In this context there is easy access to the spa_t and
  minimal error handling is required because the sync task must
  succeed.

Support for asynchronous zvol minor operations address issue #3681.

Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2217
Closes #3678
Closes #3681
This commit is contained in:
Boris Protopopov
2014-03-22 05:07:14 -04:00
committed by Brian Behlendorf
parent eb0856779f
commit a0bd735adb
12 changed files with 485 additions and 217 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/spa.c
+30 -7
View File
@@ -24,6 +24,7 @@
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2013, 2014, Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
* Copyright (c) 2016 Actifio, Inc. All rights reserved.
*/
/*
@@ -1136,6 +1137,24 @@ spa_activate(spa_t *spa, int mode)
avl_create(&spa->spa_errlist_last,
spa_error_entry_compare, sizeof (spa_error_entry_t),
offsetof(spa_error_entry_t, se_avl));
/*
* This taskq is used to perform zvol-minor-related tasks
* asynchronously. This has several advantages, including easy
* resolution of various deadlocks (zfsonlinux bug #3681).
*
* The taskq must be single threaded to ensure tasks are always
* processed in the order in which they were dispatched.
*
* A taskq per pool allows one to keep the pools independent.
* This way if one pool is suspended, it will not impact another.
*
* The preferred location to dispatch a zvol minor task is a sync
* task. In this context, there is easy access to the spa_t and minimal
* error handling is required because the sync task must succeed.
*/
spa->spa_zvol_taskq = taskq_create("z_zvol", 1, defclsyspri,
1, INT_MAX, 0);
}
/*
@@ -1154,6 +1173,11 @@ spa_deactivate(spa_t *spa)
spa_evicting_os_wait(spa);
if (spa->spa_zvol_taskq) {
taskq_destroy(spa->spa_zvol_taskq);
spa->spa_zvol_taskq = NULL;
}
txg_list_destroy(&spa->spa_vdev_txg_list);
list_destroy(&spa->spa_config_dirty_list);
@@ -3088,10 +3112,8 @@ spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t *nvpolicy,
mutex_exit(&spa_namespace_lock);
}
#ifdef _KERNEL
if (firstopen)
zvol_create_minors(spa->spa_name);
#endif
zvol_create_minors(spa, spa_name(spa), B_TRUE);
*spapp = spa;
@@ -4211,10 +4233,7 @@ spa_import(char *pool, nvlist_t *config, nvlist_t *props, uint64_t flags)
mutex_exit(&spa_namespace_lock);
spa_history_log_version(spa, "import");
#ifdef _KERNEL
zvol_create_minors(pool);
#endif
zvol_create_minors(spa, pool, B_TRUE);
return (0);
}
@@ -4349,6 +4368,10 @@ spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
spa_open_ref(spa, FTAG);
mutex_exit(&spa_namespace_lock);
spa_async_suspend(spa);
if (spa->spa_zvol_taskq) {
zvol_remove_minors(spa, spa_name(spa), B_TRUE);
taskq_wait(spa->spa_zvol_taskq);
}
mutex_enter(&spa_namespace_lock);
spa_close(spa, FTAG);