Introduce zv_state_lock
The lock is designed to protect internal state of zvol_state_t and to avoid taking spa_namespace_lock (e.g. in dmu_objset_own() code path) while holding zvol_stat_lock. Refactor the code accordingly. Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3484 Closes #6065 Closes #6134
This commit is contained in:
Boris Protopopov
Brian Behlendorf
parent
07783588bc
commit
5559ba094f
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@ -38,6 +38,33 @@
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* Copyright (c) 2016 Actifio, Inc. All rights reserved.
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*/
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/*
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* Note on locking of zvol state structures.
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*
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* These structures are used to maintain internal state used to emulate block
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* devices on top of zvols. In particular, management of device minor number
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* operations - create, remove, rename, and set_snapdev - involves access to
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* these structures. The zvol_state_lock is primarily used to protect the
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* zvol_state_list. The zv->zv_state_lock is used to protect the contents
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* of the zvol_state_t structures, as well as to make sure that when the
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* time comes to remove the structure from the list, it is not in use, and
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* therefore, it can be taken off zvol_state_list and freed.
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*
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* The minor operations are issued to the spa->spa_zvol_taskq quues, that are
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* single-threaded (to preserve order of minor operations), and are executed
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* through the zvol_task_cb that dispatches the specific operations. Therefore,
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* these operations are serialized per pool. Consequently, we can be certain
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* that for a given zvol, there is only one operation at a time in progress.
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* That is why one can be sure that first, zvol_state_t for a given zvol is
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* allocated and placed on zvol_state_list, and then other minor operations
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* for this zvol are going to proceed in the order of issue.
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*
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* It is also worth keeping in mind that once add_disk() is called, the zvol is
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* announced to the world, and zvol_open()/zvol_release() can be called at any
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* time. Incidentally, add_disk() itself calls zvol_open()->zvol_first_open()
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* and zvol_release()->zvol_last_close() directly as well.
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*/
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#include <sys/dbuf.h>
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#include <sys/dmu_traverse.h>
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#include <sys/dsl_dataset.h>
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@ -91,6 +118,7 @@ struct zvol_state {
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list_node_t zv_next; /* next zvol_state_t linkage */
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uint64_t zv_hash; /* name hash */
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struct hlist_node zv_hlink; /* hash link */
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kmutex_t zv_state_lock; /* protects zvol_state_t */
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atomic_t zv_suspend_ref; /* refcount for suspend */
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krwlock_t zv_suspend_lock; /* suspend lock */
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};
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@ -306,8 +334,6 @@ zvol_update_volsize(uint64_t volsize, objset_t *os)
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int error;
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uint64_t txg;
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ASSERT(MUTEX_HELD(&zvol_state_lock));
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tx = dmu_tx_create(os);
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dmu_tx_hold_zap(tx, ZVOL_ZAP_OBJ, TRUE, NULL);
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dmu_tx_mark_netfree(tx);
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@ -367,11 +393,15 @@ zvol_set_volsize(const char *name, uint64_t volsize)
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mutex_enter(&zvol_state_lock);
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zv = zvol_find_by_name(name);
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if (zv != NULL)
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mutex_enter(&zv->zv_state_lock);
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mutex_exit(&zvol_state_lock);
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if (zv == NULL || zv->zv_objset == NULL) {
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if ((error = dmu_objset_own(name, DMU_OST_ZVOL, B_FALSE,
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FTAG, &os)) != 0) {
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mutex_exit(&zvol_state_lock);
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if (zv != NULL)
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mutex_exit(&zv->zv_state_lock);
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return (SET_ERROR(error));
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}
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owned = B_TRUE;
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@ -401,8 +431,10 @@ out:
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} else {
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rw_exit(&zv->zv_suspend_lock);
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}
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mutex_exit(&zvol_state_lock);
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return (error);
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if (zv != NULL)
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mutex_exit(&zv->zv_state_lock);
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return (SET_ERROR(error));
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}
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/*
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@ -456,13 +488,15 @@ zvol_set_volblocksize(const char *name, uint64_t volblocksize)
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zv = zvol_find_by_name(name);
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if (zv == NULL) {
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error = SET_ERROR(ENXIO);
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goto out;
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mutex_exit(&zvol_state_lock);
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return (SET_ERROR(ENXIO));
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}
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mutex_enter(&zv->zv_state_lock);
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mutex_exit(&zvol_state_lock);
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if (zv->zv_flags & ZVOL_RDONLY) {
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error = SET_ERROR(EROFS);
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goto out;
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mutex_exit(&zv->zv_state_lock);
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return (SET_ERROR(EROFS));
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}
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rw_enter(&zv->zv_suspend_lock, RW_READER);
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@ -482,8 +516,8 @@ zvol_set_volblocksize(const char *name, uint64_t volblocksize)
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zv->zv_volblocksize = volblocksize;
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}
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rw_exit(&zv->zv_suspend_lock);
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out:
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mutex_exit(&zvol_state_lock);
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mutex_exit(&zv->zv_state_lock);
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return (SET_ERROR(error));
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}
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@ -1105,8 +1139,12 @@ zvol_suspend(const char *name)
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mutex_enter(&zvol_state_lock);
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zv = zvol_find_by_name(name);
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if (zv == NULL)
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goto out;
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if (zv == NULL) {
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mutex_exit(&zvol_state_lock);
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return (NULL);
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}
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mutex_enter(&zv->zv_state_lock);
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mutex_exit(&zvol_state_lock);
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/* block all I/O, release in zvol_resume. */
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rw_enter(&zv->zv_suspend_lock, RW_WRITER);
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@ -1115,8 +1153,8 @@ zvol_suspend(const char *name)
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if (zv->zv_open_count > 0)
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zvol_shutdown_zv(zv);
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out:
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mutex_exit(&zvol_state_lock);
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mutex_exit(&zv->zv_state_lock);
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return (zv);
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}
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@ -1209,30 +1247,24 @@ static int
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zvol_open(struct block_device *bdev, fmode_t flag)
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{
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zvol_state_t *zv;
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int error = 0, drop_mutex = 0, drop_suspend = 0;
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int error = 0, drop_suspend = 0;
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/*
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* If the caller is already holding the mutex do not take it
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* again, this will happen as part of zvol_create_minor_impl().
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* Once add_disk() is called the device is live and the kernel
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* will attempt to open it to read the partition information.
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*/
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if (!mutex_owned(&zvol_state_lock)) {
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mutex_enter(&zvol_state_lock);
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drop_mutex = 1;
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}
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ASSERT(!mutex_owned(&zvol_state_lock));
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mutex_enter(&zvol_state_lock);
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/*
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* Obtain a copy of private_data under the lock to make sure
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* that either the result of zvol_free() setting
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* that either the result of zvol free code path setting
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* bdev->bd_disk->private_data to NULL is observed, or zvol_free()
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* is not called on this zv because of the positive zv_open_count.
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*/
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zv = bdev->bd_disk->private_data;
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if (zv == NULL) {
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error = -ENXIO;
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goto out_mutex;
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mutex_exit(&zvol_state_lock);
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return (SET_ERROR(-ENXIO));
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}
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mutex_enter(&zv->zv_state_lock);
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mutex_exit(&zvol_state_lock);
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if (zv->zv_open_count == 0) {
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/* make sure zvol is not suspended when first open */
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@ -1259,8 +1291,7 @@ out_open_count:
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out_mutex:
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if (drop_suspend)
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rw_exit(&zv->zv_suspend_lock);
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if (drop_mutex)
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mutex_exit(&zvol_state_lock);
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mutex_exit(&zv->zv_state_lock);
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return (SET_ERROR(error));
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}
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@ -1272,15 +1303,15 @@ static int
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#endif
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zvol_release(struct gendisk *disk, fmode_t mode)
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{
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zvol_state_t *zv = disk->private_data;
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int drop_mutex = 0;
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zvol_state_t *zv;
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ASSERT(!mutex_owned(&zvol_state_lock));
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mutex_enter(&zvol_state_lock);
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zv = disk->private_data;
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ASSERT(zv && zv->zv_open_count > 0);
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if (!mutex_owned(&zvol_state_lock)) {
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mutex_enter(&zvol_state_lock);
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drop_mutex = 1;
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}
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mutex_enter(&zv->zv_state_lock);
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mutex_exit(&zvol_state_lock);
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/* make sure zvol is not suspended when last close */
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if (zv->zv_open_count == 1)
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@ -1292,8 +1323,7 @@ zvol_release(struct gendisk *disk, fmode_t mode)
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rw_exit(&zv->zv_suspend_lock);
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}
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if (drop_mutex)
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mutex_exit(&zvol_state_lock);
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mutex_exit(&zv->zv_state_lock);
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#ifndef HAVE_BLOCK_DEVICE_OPERATIONS_RELEASE_VOID
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return (0);
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@ -1323,9 +1353,9 @@ zvol_ioctl(struct block_device *bdev, fmode_t mode,
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break;
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case BLKZNAME:
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mutex_enter(&zvol_state_lock);
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mutex_enter(&zv->zv_state_lock);
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error = copy_to_user((void *)arg, zv->zv_name, MAXNAMELEN);
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mutex_exit(&zvol_state_lock);
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mutex_exit(&zv->zv_state_lock);
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break;
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default:
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@ -1488,6 +1518,8 @@ zvol_alloc(dev_t dev, const char *name)
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list_link_init(&zv->zv_next);
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mutex_init(&zv->zv_state_lock, NULL, MUTEX_DEFAULT, NULL);
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zv->zv_queue = blk_alloc_queue(GFP_ATOMIC);
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if (zv->zv_queue == NULL)
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goto out_kmem;
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@ -1532,36 +1564,32 @@ out_kmem:
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}
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/*
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* Used for taskq, if used out side zvol_state_lock, you need to clear
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* zv_disk->private_data inside lock first.
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* Cleanup then free a zvol_state_t which was created by zvol_alloc().
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* At this time, the structure is not opened by anyone, is taken off
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* the zvol_state_list, and has its private data set to NULL.
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* The zvol_state_lock is dropped.
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*/
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static void
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zvol_free_impl(void *arg)
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zvol_free(void *arg)
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{
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zvol_state_t *zv = arg;
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ASSERT(!MUTEX_HELD(&zvol_state_lock));
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ASSERT(zv->zv_open_count == 0);
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ASSERT(zv->zv_disk->private_data == NULL);
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rw_destroy(&zv->zv_suspend_lock);
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zfs_rlock_destroy(&zv->zv_range_lock);
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zv->zv_disk->private_data = NULL;
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del_gendisk(zv->zv_disk);
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blk_cleanup_queue(zv->zv_queue);
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put_disk(zv->zv_disk);
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ida_simple_remove(&zvol_ida, MINOR(zv->zv_dev) >> ZVOL_MINOR_BITS);
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kmem_free(zv, sizeof (zvol_state_t));
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}
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/*
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* Cleanup then free a zvol_state_t which was created by zvol_alloc().
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*/
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static void
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zvol_free(zvol_state_t *zv)
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{
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ASSERT(MUTEX_HELD(&zvol_state_lock));
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zvol_free_impl(zv);
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mutex_destroy(&zv->zv_state_lock);
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kmem_free(zv, sizeof (zvol_state_t));
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}
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/*
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@ -1591,10 +1619,12 @@ zvol_create_minor_impl(const char *name)
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zv = zvol_find_by_name_hash(name, hash);
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if (zv) {
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error = SET_ERROR(EEXIST);
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goto out;
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mutex_exit(&zvol_state_lock);
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return (SET_ERROR(EEXIST));
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}
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mutex_exit(&zvol_state_lock);
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doi = kmem_alloc(sizeof (dmu_object_info_t), KM_SLEEP);
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error = dmu_objset_own(name, DMU_OST_ZVOL, B_TRUE, FTAG, &os);
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@ -1666,20 +1696,13 @@ out_dmu_objset_disown:
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dmu_objset_disown(os, FTAG);
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out_doi:
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kmem_free(doi, sizeof (dmu_object_info_t));
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out:
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if (error == 0) {
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mutex_enter(&zvol_state_lock);
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zvol_insert(zv);
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/*
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* Drop the lock to prevent deadlock with sys_open() ->
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* zvol_open(), which first takes bd_disk->bd_mutex and then
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* takes zvol_state_lock, whereas this code path first takes
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* zvol_state_lock, and then takes bd_disk->bd_mutex.
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*/
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mutex_exit(&zvol_state_lock);
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add_disk(zv->zv_disk);
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} else {
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mutex_exit(&zvol_state_lock);
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ida_simple_remove(&zvol_ida, idx);
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}
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@ -1927,10 +1950,14 @@ zvol_remove_minors_impl(const char *name)
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zvol_state_t *zv, *zv_next;
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int namelen = ((name) ? strlen(name) : 0);
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taskqid_t t, tid = TASKQID_INVALID;
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list_t free_list;
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if (zvol_inhibit_dev)
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return;
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list_create(&free_list, sizeof (zvol_state_t),
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offsetof(zvol_state_t, zv_next));
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mutex_enter(&zvol_state_lock);
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for (zv = list_head(&zvol_state_list); zv != NULL; zv = zv_next) {
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@ -1945,22 +1972,36 @@ zvol_remove_minors_impl(const char *name)
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if (zv->zv_open_count > 0 ||
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atomic_read(&zv->zv_suspend_ref))
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continue;
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/*
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* By taking zv_state_lock here, we guarantee that no
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* one is currently using this zv
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*/
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mutex_enter(&zv->zv_state_lock);
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zvol_remove(zv);
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mutex_exit(&zv->zv_state_lock);
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/* clear this so zvol_open won't open it */
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zv->zv_disk->private_data = NULL;
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/* try parallel zv_free, if failed do it in place */
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t = taskq_dispatch(system_taskq, zvol_free_impl, zv,
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t = taskq_dispatch(system_taskq, zvol_free, zv,
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TQ_SLEEP);
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if (t == TASKQID_INVALID)
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zvol_free(zv);
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list_insert_head(&free_list, zv);
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else
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tid = t;
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}
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}
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mutex_exit(&zvol_state_lock);
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/*
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* Drop zvol_state_lock before calling zvol_free()
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*/
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while ((zv = list_head(&free_list)) != NULL) {
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list_remove(&free_list, zv);
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zvol_free(zv);
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}
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if (tid != TASKQID_INVALID)
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taskq_wait_outstanding(system_taskq, tid);
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}
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@ -1987,13 +2028,25 @@ zvol_remove_minor_impl(const char *name)
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if (zv->zv_open_count > 0 ||
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atomic_read(&zv->zv_suspend_ref))
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continue;
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/*
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* By taking zv_state_lock here, we guarantee that no
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* one is currently using this zv
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*/
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mutex_enter(&zv->zv_state_lock);
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zvol_remove(zv);
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zvol_free(zv);
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mutex_exit(&zv->zv_state_lock);
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/* clear this so zvol_open won't open it */
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zv->zv_disk->private_data = NULL;
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break;
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}
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}
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mutex_exit(&zvol_state_lock);
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/*
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* Drop zvol_state_lock before calling zvol_free()
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*/
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zvol_free(zv);
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}
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/*
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