From a95be3842c51c9ac32fe17faedf2c156ccf81bd7 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 27 Nov 2018 15:51:57 -0800 Subject: [PATCH] scsi: target/core: Simplify transport_clear_lun_ref() 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 Cc: Mike Christie Cc: Christoph Hellwig Cc: David Disseldorp Cc: Hannes Reinecke Signed-off-by: Bart Van Assche Signed-off-by: Martin K. Petersen --- 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 cffd7430bb99..1d51df2b3e77 100644 --- a/drivers/target/target_core_device.c +++ b/drivers/target/target_core_device.c @@ -823,7 +823,6 @@ 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 16e7a6500be4..e2ace1059437 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 4d1651e46ea9..0c8eca6ae30f 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 53b90cc18902..bb965a355187 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -733,7 +733,6 @@ 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; -- GitLab