Since transport_clear_lun_ref() already waits until the percpu-refcount
.release() method is called, it is not necessary to wait first until
percpu_ref_kill_and_confirm() has finished transitioning the refcount into
atomic mode. Remove the code that waits for percpu_ref_kill_and_confirm()
to complete and also the completion object that is used by that code.
This patch does not change the behavior of the SCSI target code.
Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: David Disseldorp <ddiss@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/target/target_core_device.c | 1 -
drivers/target/target_core_tpg.c | 1 -
drivers/target/target_core_transport.c | 35 ++++----------------------
include/target/target_core_base.h | 1 -
4 files changed, 5 insertions(+), 33 deletions(-)
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 47b5ef153135..c6b1122ee097 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -822,7 +822,6 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
xcopy_lun = &dev->xcopy_lun;
rcu_assign_pointer(xcopy_lun->lun_se_dev, dev);
- init_completion(&xcopy_lun->lun_ref_comp);
init_completion(&xcopy_lun->lun_shutdown_comp);
INIT_LIST_HEAD(&xcopy_lun->lun_deve_list);
INIT_LIST_HEAD(&xcopy_lun->lun_dev_link);
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index 02e8a5d86658..0cfb9d7b31a3 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -577,7 +577,6 @@ struct se_lun *core_tpg_alloc_lun(
}
lun->unpacked_lun = unpacked_lun;
atomic_set(&lun->lun_acl_count, 0);
- init_completion(&lun->lun_ref_comp);
init_completion(&lun->lun_shutdown_comp);
INIT_LIST_HEAD(&lun->lun_deve_list);
INIT_LIST_HEAD(&lun->lun_dev_link);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index d9e4b736312e..3cd037558957 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -2911,38 +2911,13 @@ void target_wait_for_sess_cmds(struct se_session *se_sess)
}
EXPORT_SYMBOL(target_wait_for_sess_cmds);
-static void target_lun_confirm(struct percpu_ref *ref)
-{
- struct se_lun *lun = container_of(ref, struct se_lun, lun_ref);
-
- complete(&lun->lun_ref_comp);
-}
-
+/*
+ * Prevent that new percpu_ref_tryget_live() calls succeed and wait until
+ * all references to the LUN have been released. Called during LUN shutdown.
+ */
void transport_clear_lun_ref(struct se_lun *lun)
{
- /*
- * Mark the percpu-ref as DEAD, switch to atomic_t mode, drop
- * the initial reference and schedule confirm kill to be
- * executed after one full RCU grace period has completed.
- */
- percpu_ref_kill_and_confirm(&lun->lun_ref, target_lun_confirm);
- /*
- * The first completion waits for percpu_ref_switch_to_atomic_rcu()
- * to call target_lun_confirm after lun->lun_ref has been marked
- * as __PERCPU_REF_DEAD on all CPUs, and switches to atomic_t
- * mode so that percpu_ref_tryget_live() lookup of lun->lun_ref
- * fails for all new incoming I/O.
- */
- wait_for_completion(&lun->lun_ref_comp);
- /*
- * The second completion waits for percpu_ref_put_many() to
- * invoke ->release() after lun->lun_ref has switched to
- * atomic_t mode, and lun->lun_ref.count has reached zero.
- *
- * At this point all target-core lun->lun_ref references have
- * been dropped via transport_lun_remove_cmd(), and it's safe
- * to proceed with the remaining LUN shutdown.
- */
+ percpu_ref_kill(&lun->lun_ref);
wait_for_completion(&lun->lun_shutdown_comp);
}
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index e3bdb0550a59..58a03a094257 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -731,7 +731,6 @@ struct se_lun {
struct scsi_port_stats lun_stats;
struct config_group lun_group;
struct se_port_stat_grps port_stat_grps;
- struct completion lun_ref_comp;
struct completion lun_shutdown_comp;
struct percpu_ref lun_ref;
struct list_head lun_dev_link;
--
2.20.0.rc0.387.gc7a69e6b6c-goog
