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Simplified the scope of the namespace lock

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If we wait until after we check for no spa references to drop the
namespace lock, then we know that spa consumers will need to call
spa_lookup() and end up waiting on the spa_namespace_cv until we
finish.  This narrows the external checks to spa_lookup and we no
longer need to worry about the spa_vdev_enter case.

Sponsored-By: Klara Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Wilson <gwilson@delphix.com>
Signed-off-by: Don Brady <don.brady@klarasystems.com>
Closes #16153
This commit is contained in:
Don Brady 2024-05-05 14:57:33 +00:00 committed by Brian Behlendorf
parent 975a13259b
commit 89acef992b
2 changed files with 22 additions and 31 deletions
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32
module/zfs/spa.c
View File

@ -6994,15 +6994,11 @@ spa_export_common(const char *pool, int new_state, nvlist_t **oldconfig,
mutex_enter(&spa_namespace_lock);
spa->spa_export_thread = curthread;
spa_close(spa, FTAG);
mutex_exit(&spa_namespace_lock);
/*
* At this point we no longer hold the spa_namespace_lock and
* the spa_export_thread indicates that an export is in progress.
*/
if (spa->spa_state == POOL_STATE_UNINITIALIZED)
if (spa->spa_state == POOL_STATE_UNINITIALIZED) {
mutex_exit(&spa_namespace_lock);
goto export_spa;
}
/*
* The pool will be in core if it's openable, in which case we can
@ -7024,6 +7020,14 @@ spa_export_common(const char *pool, int new_state, nvlist_t **oldconfig,
goto fail;
}
mutex_exit(&spa_namespace_lock);
/*
* At this point we no longer hold the spa_namespace_lock and
* there were no references on the spa. Future spa_lookups will
* notice the spa->spa_export_thread and wait until we signal
* that we are finshed.
*/
if (spa->spa_sync_on) {
vdev_t *rvd = spa->spa_root_vdev;
/*
@ -7035,6 +7039,7 @@ spa_export_common(const char *pool, int new_state, nvlist_t **oldconfig,
if (!force && new_state == POOL_STATE_EXPORTED &&
spa_has_active_shared_spare(spa)) {
error = SET_ERROR(EXDEV);
mutex_enter(&spa_namespace_lock);
goto fail;
}
@ -7102,6 +7107,9 @@ export_spa:
if (new_state == POOL_STATE_EXPORTED)
zio_handle_export_delay(spa, gethrtime() - export_start);
/*
* Take the namespace lock for the actual spa_t removal
*/
mutex_enter(&spa_namespace_lock);
if (new_state != POOL_STATE_UNINITIALIZED) {
if (!hardforce)
@ -7118,20 +7126,20 @@ export_spa:
}
/*
* Wake up any waiters on spa_namespace_lock
* They need to re-attempt a spa_lookup()
* Wake up any waiters in spa_lookup()
*/
cv_broadcast(&spa_namespace_cv);
mutex_exit(&spa_namespace_lock);
return (0);
fail:
mutex_enter(&spa_namespace_lock);
spa->spa_is_exporting = B_FALSE;
spa->spa_export_thread = NULL;
spa_async_resume(spa);
/* Wake up any waiters on spa_namespace_lock */
spa_async_resume(spa);
/*
* Wake up any waiters in spa_lookup()
*/
cv_broadcast(&spa_namespace_cv);
mutex_exit(&spa_namespace_lock);
return (error);

21
module/zfs/spa_misc.c
View File

@ -1240,20 +1240,7 @@ spa_vdev_enter(spa_t *spa)
mutex_enter(&spa->spa_vdev_top_lock);
mutex_enter(&spa_namespace_lock);
/*
* We have a reference on the spa and a spa export could be
* starting but no longer holding the spa_namespace_lock. So
* check if there is an export and if so wait. It will fail
* fast (EBUSY) since we are still holding a spa reference.
*
* Note that we can be woken by a different spa transitioning
* through an import/export, so we must wait for our condition
* to change before proceeding.
*/
while (spa->spa_export_thread != NULL &&
spa->spa_export_thread != curthread) {
cv_wait(&spa_namespace_cv, &spa_namespace_lock);
}
ASSERT0(spa->spa_export_thread);
vdev_autotrim_stop_all(spa);
@ -1272,11 +1259,7 @@ spa_vdev_detach_enter(spa_t *spa, uint64_t guid)
mutex_enter(&spa->spa_vdev_top_lock);
mutex_enter(&spa_namespace_lock);
/* See comment in spa_vdev_enter() */
while (spa->spa_export_thread != NULL &&
spa->spa_export_thread != curthread) {
cv_wait(&spa_namespace_cv, &spa_namespace_lock);
}
ASSERT0(spa->spa_export_thread);
vdev_autotrim_stop_all(spa);