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scsi: target/core: Simplify transport_clear_lun_ref()

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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@linux-iscsi.org>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Disseldorp <ddiss@suse.de>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Bart Van Assche 2018-11-27 15:51:57 -08:00 committed by Martin K. Petersen
parent 5d6cd9fe31
commit a95be3842c
4 changed files with 5 additions and 33 deletions
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1
drivers/target/target_core_device.c
View File

@ -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);

1
drivers/target/target_core_tpg.c
View File

@ -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);

35
drivers/target/target_core_transport.c
View File

@ -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);
}

1
include/target/target_core_base.h
View File

@ -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;