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scsi: target: core: Add workqueue based cmd submission 

loop and vhost/scsi do their target cmd submission from driver
workqueues. This allows them to avoid an issue where the backend may block
waiting for resources like tags/requests, mem/locks, etc and that ends up
blocking their entire submission path and for the case of vhost-scsi both
the submission and completion path.

This patch adds a helper drivers can use to submit from a LIO workqueue.
This code will then be extended in the next patches to fix the plugging of
backend devices.

We are only converting vhost/loop initially, but the workqueue based
submission will work for other drivers and have similar benefits where the
main target loops will not end up blocking one some backend resource.

Link: https://lore.kernel.org/r/20210227170006.5077-17-michael.christie@oracle.com
Tested-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mike Christie 2021-02-27 10:59:57 -06:00 committed by Martin K. Petersen
parent 0869419947
commit eb44ce8c8c
5 changed files with 59 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/target/target_core_device.c
View File

@ -735,8 +735,14 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
dev->queue_cnt = nr_cpu_ids;
for (i = 0; i < dev->queue_cnt; i++) {
INIT_LIST_HEAD(&dev->queues[i].state_list);
spin_lock_init(&dev->queues[i].lock);
struct se_device_queue *q;
q = &dev->queues[i];
INIT_LIST_HEAD(&q->state_list);
spin_lock_init(&q->lock);
init_llist_head(&q->sq.cmd_list);
INIT_WORK(&q->sq.work, target_queued_submit_work);
}
dev->se_hba = hba;

1
drivers/target/target_core_internal.h
View File

@ -153,6 +153,7 @@ void target_qf_do_work(struct work_struct *work);
bool target_check_wce(struct se_device *dev);
bool target_check_fua(struct se_device *dev);
void __target_execute_cmd(struct se_cmd *, bool);
void target_queued_submit_work(struct work_struct *work);
/* target_core_stat.c */
void target_stat_setup_dev_default_groups(struct se_device *);

42
drivers/target/target_core_transport.c
View File

@ -41,6 +41,7 @@
#include <trace/events/target.h>
static struct workqueue_struct *target_completion_wq;
static struct workqueue_struct *target_submission_wq;
static struct kmem_cache *se_sess_cache;
struct kmem_cache *se_ua_cache;
struct kmem_cache *t10_pr_reg_cache;
@ -129,8 +130,15 @@ int init_se_kmem_caches(void)
if (!target_completion_wq)
goto out_free_lba_map_mem_cache;
target_submission_wq = alloc_workqueue("target_submission",
WQ_MEM_RECLAIM, 0);
if (!target_submission_wq)
goto out_free_completion_wq;
return 0;
out_free_completion_wq:
destroy_workqueue(target_completion_wq);
out_free_lba_map_mem_cache:
kmem_cache_destroy(t10_alua_lba_map_mem_cache);
out_free_lba_map_cache:
@ -153,6 +161,7 @@ out:
void release_se_kmem_caches(void)
{
destroy_workqueue(target_submission_wq);
destroy_workqueue(target_completion_wq);
kmem_cache_destroy(se_sess_cache);
kmem_cache_destroy(se_ua_cache);
@ -1382,7 +1391,6 @@ void __target_init_cmd(
{
INIT_LIST_HEAD(&cmd->se_delayed_node);
INIT_LIST_HEAD(&cmd->se_qf_node);
INIT_LIST_HEAD(&cmd->se_cmd_list);
INIT_LIST_HEAD(&cmd->state_list);
init_completion(&cmd->t_transport_stop_comp);
cmd->free_compl = NULL;
@ -1799,6 +1807,38 @@ void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
}
EXPORT_SYMBOL(target_submit_cmd);
void target_queued_submit_work(struct work_struct *work)
{
struct se_cmd_queue *sq = container_of(work, struct se_cmd_queue, work);
struct se_cmd *se_cmd, *next_cmd;
struct llist_node *cmd_list;
cmd_list = llist_del_all(&sq->cmd_list);
if (!cmd_list)
/* Previous call took what we were queued to submit */
return;
cmd_list = llist_reverse_order(cmd_list);
llist_for_each_entry_safe(se_cmd, next_cmd, cmd_list, se_cmd_list)
target_submit(se_cmd);
}
/**
* target_queue_submission - queue the cmd to run on the LIO workqueue
* @se_cmd: command descriptor to submit
*/
void target_queue_submission(struct se_cmd *se_cmd)
{
struct se_device *se_dev = se_cmd->se_dev;
int cpu = se_cmd->cpuid;
struct se_cmd_queue *sq;
sq = &se_dev->queues[cpu].sq;
llist_add(&se_cmd->se_cmd_list, &sq->cmd_list);
queue_work_on(cpu, target_submission_wq, &sq->work);
}
EXPORT_SYMBOL_GPL(target_queue_submission);
static void target_complete_tmr_failure(struct work_struct *work)
{
struct se_cmd *se_cmd = container_of(work, struct se_cmd, work);

8
include/target/target_core_base.h
View File

@ -488,7 +488,7 @@ struct se_cmd {
/* Only used for internal passthrough and legacy TCM fabric modules */
struct se_session *se_sess;
struct se_tmr_req *se_tmr_req;
struct list_head se_cmd_list;
struct llist_node se_cmd_list;
struct completion *free_compl;
struct completion *abrt_compl;
const struct target_core_fabric_ops *se_tfo;
@ -765,9 +765,15 @@ struct se_dev_stat_grps {
struct config_group scsi_lu_group;
};
struct se_cmd_queue {
struct llist_head cmd_list;
struct work_struct work;
};
struct se_device_queue {
struct list_head state_list;
spinlock_t lock;
struct se_cmd_queue sq;
};
struct se_device {

2
include/target/target_core_fabric.h
View File

@ -165,6 +165,8 @@ sense_reason_t target_cmd_init_cdb(struct se_cmd *se_cmd, unsigned char *cdb,
sense_reason_t target_cmd_parse_cdb(struct se_cmd *);
void target_submit_cmd(struct se_cmd *, struct se_session *, unsigned char *,
unsigned char *, u64, u32, int, int, int);
void target_queue_submission(struct se_cmd *se_cmd);
int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
unsigned char *sense, u64 unpacked_lun,
void *fabric_tmr_ptr, unsigned char tm_type,