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scst: Free removed LUNs asynchronously

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Instead of waiting until all commands associated with a LUN have finished,
do not wait and free LUN data structures once all associated commands have
finished. This commit should fix https://sourceforge.net/p/scst/tickets/23/.


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@8466 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2019-07-21 01:52:03 +00:00
parent 5b0f9ef0b9
commit cf2167c2b9
4 changed files with 60 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
scst/include/scst.h
View File

@@ -3104,6 +3104,10 @@ struct scst_tgt_dev {
/* List entry in sess->sess_tgt_dev_list */
struct list_head sess_tgt_dev_list_entry;
struct rcu_head rcu;
struct work_struct free_work;
atomic_t *a;
struct scst_device *dev; /* to save extra dereferences */
uint64_t lun; /* to save extra dereferences */
@@ -3259,6 +3263,13 @@ struct scst_acg_dev {
/* sysfs release completion */
struct completion *acg_dev_kobj_release_cmpl;
/*
* Number of deleted tgt_devs associated with this acg_dev. Set if an
* acg_dev is no longer visible and will be freed as soon as all
* associated tgt_dev instances have been freed.
*/
int nr_deleted_tgt_devs;
/* Name of the link to the corresponding LUN */
char acg_dev_link_name[20];
};

93
scst/src/scst_lib.c
View File

@@ -4557,10 +4557,37 @@ out_free:
goto out;
}
static void scst_tgt_dev_free_workfn(struct work_struct *work)
{
struct scst_tgt_dev *tgt_dev = container_of(work, typeof(*tgt_dev),
free_work);
struct scst_acg_dev *acg_dev = tgt_dev->acg_dev;
struct scst_device *dev = tgt_dev->dev;
atomic_t *a = tgt_dev->a;
mutex_lock(&scst_mutex);
scst_free_tgt_dev(tgt_dev);
WARN_ON_ONCE(acg_dev->nr_deleted_tgt_devs <= 0);
if (--acg_dev->nr_deleted_tgt_devs == 0)
scst_free_acg_dev(acg_dev);
mutex_unlock(&scst_mutex);
percpu_ref_put(&dev->refcnt);
scst_put(a);
}
void scst_free_tgt_dev_rcu(struct rcu_head *rcu)
{
struct scst_tgt_dev *tgt_dev = container_of(rcu, typeof(*tgt_dev), rcu);
tgt_dev->a = scst_get();
percpu_ref_get(&tgt_dev->dev->refcnt);
WARN_ON_ONCE(!schedule_work(&tgt_dev->free_work));
}
/* Delete a LUN without generating a unit attention. */
static struct scst_acg_dev *__scst_acg_del_lun(struct scst_acg *acg,
uint64_t lun,
struct list_head *tgt_dev_list,
bool *report_luns_changed)
{
struct scst_acg_dev *acg_dev = NULL, *a;
@@ -4569,8 +4596,6 @@ static struct scst_acg_dev *__scst_acg_del_lun(struct scst_acg *acg,
lockdep_assert_held(&scst_mutex);
INIT_LIST_HEAD(tgt_dev_list);
list_for_each_entry(a, &acg->acg_dev_list, acg_dev_list_entry) {
if (a->lun == lun) {
acg_dev = a;
@@ -4583,17 +4608,17 @@ static struct scst_acg_dev *__scst_acg_del_lun(struct scst_acg *acg,
*report_luns_changed = scst_cm_on_del_lun(acg_dev,
*report_luns_changed);
acg_dev->nr_deleted_tgt_devs = 1;
list_for_each_entry_safe(tgt_dev, tt, &acg_dev->dev->dev_tgt_dev_list,
dev_tgt_dev_list_entry) {
if (tgt_dev->acg_dev == acg_dev) {
sess = tgt_dev->sess;
mutex_lock(&sess->tgt_dev_list_mutex);
acg_dev->nr_deleted_tgt_devs++;
scst_del_tgt_dev(tgt_dev);
mutex_unlock(&sess->tgt_dev_list_mutex);
list_add_tail(&tgt_dev->extra_tgt_dev_list_entry,
tgt_dev_list);
}
}
@@ -4606,37 +4631,17 @@ out:
return acg_dev;
}
static int scst_tgt_devs_cmds(struct list_head *tgt_dev_list)
{
struct scst_tgt_dev *tgt_dev;
int res = 0;
list_for_each_entry(tgt_dev, tgt_dev_list, extra_tgt_dev_list_entry)
res += atomic_read(&tgt_dev->tgt_dev_cmd_count);
return res;
}
static void scst_wait_for_tgt_devs(struct list_head *tgt_dev_list)
{
while (scst_tgt_devs_cmds(tgt_dev_list) > 0)
mdelay(100);
}
int scst_acg_del_lun(struct scst_acg *acg, uint64_t lun,
bool gen_report_luns_changed)
{
int res = 0;
struct scst_acg_dev *acg_dev;
struct scst_tgt_dev *tgt_dev, *tt;
struct list_head tgt_dev_list;
TRACE_ENTRY();
lockdep_assert_held(&scst_mutex);
acg_dev = __scst_acg_del_lun(acg, lun, &tgt_dev_list,
&gen_report_luns_changed);
acg_dev = __scst_acg_del_lun(acg, lun, &gen_report_luns_changed);
if (acg_dev == NULL) {
PRINT_ERROR("Device is not found in group %s", acg->acg_name);
res = -EINVAL;
@@ -4648,16 +4653,11 @@ int scst_acg_del_lun(struct scst_acg *acg, uint64_t lun,
mutex_unlock(&scst_mutex);
scst_wait_for_tgt_devs(&tgt_dev_list);
synchronize_rcu();
mutex_lock(&scst_mutex);
list_for_each_entry_safe(tgt_dev, tt, &tgt_dev_list,
extra_tgt_dev_list_entry) {
scst_free_tgt_dev(tgt_dev);
}
scst_free_acg_dev(acg_dev);
if (--acg_dev->nr_deleted_tgt_devs == 0)
scst_free_acg_dev(acg_dev);
out:
TRACE_EXIT_RES(res);
@@ -4671,13 +4671,12 @@ int scst_acg_repl_lun(struct scst_acg *acg, struct kobject *parent,
{
struct scst_acg_dev *acg_dev;
bool del_gen_ua = false;
struct scst_tgt_dev *tgt_dev, *tt;
struct list_head tgt_dev_list;
struct scst_tgt_dev *tgt_dev;
int res = -EINVAL;
lockdep_assert_held(&scst_mutex);
acg_dev = __scst_acg_del_lun(acg, lun, &tgt_dev_list, &del_gen_ua);
acg_dev = __scst_acg_del_lun(acg, lun, &del_gen_ua);
if (!acg_dev)
flags |= SCST_ADD_LUN_GEN_UA;
res = scst_acg_add_lun(acg, parent, dev, lun, flags, NULL);
@@ -4698,15 +4697,10 @@ int scst_acg_repl_lun(struct scst_acg *acg, struct kobject *parent,
}
mutex_unlock(&scst_mutex);
scst_wait_for_tgt_devs(&tgt_dev_list);
synchronize_rcu();
mutex_lock(&scst_mutex);
list_for_each_entry_safe(tgt_dev, tt, &tgt_dev_list,
extra_tgt_dev_list_entry) {
scst_free_tgt_dev(tgt_dev);
}
if (acg_dev)
if (acg_dev && --acg_dev->nr_deleted_tgt_devs == 0)
scst_free_acg_dev(acg_dev);
out:
@@ -5289,9 +5283,6 @@ void scst_tgt_dev_stop_threads(struct scst_tgt_dev *tgt_dev)
lockdep_assert_held(&scst_mutex);
if (tgt_dev->dev->threads_num < 0)
goto out_deinit;
if (tgt_dev->active_cmd_threads == &scst_main_cmd_threads) {
/* Global async threads */
kref_put(&tgt_dev->aic_keeper->aic_keeper_kref,
@@ -5308,7 +5299,6 @@ void scst_tgt_dev_stop_threads(struct scst_tgt_dev *tgt_dev)
scst_deinit_threads(&tgt_dev->tgt_dev_cmd_threads);
} /* else no threads (not yet initialized, e.g.) */
out_deinit:
tm_dbg_deinit_tgt_dev(tgt_dev);
tgt_dev->active_cmd_threads = NULL;
@@ -5346,6 +5336,8 @@ static int scst_alloc_add_tgt_dev(struct scst_session *sess,
}
INIT_LIST_HEAD(&tgt_dev->sess_tgt_dev_list_entry);
init_rcu_head(&tgt_dev->rcu);
INIT_WORK(&tgt_dev->free_work, scst_tgt_dev_free_workfn);
tgt_dev->dev = dev;
tgt_dev->lun = acg_dev->lun;
tgt_dev->acg_dev = acg_dev;
@@ -5510,6 +5502,8 @@ out_dec_free:
out_free_ua:
scst_free_all_UA(tgt_dev);
destroy_rcu_head(&tgt_dev->rcu);
kmem_cache_free(scst_tgtd_cachep, tgt_dev);
goto out;
}
@@ -5553,7 +5547,8 @@ static void scst_del_tgt_dev(struct scst_tgt_dev *tgt_dev)
scst_tgt_dev_sysfs_del(tgt_dev);
atomic_dec(&tgt_dev->tgt_dev_cmd_count);
if (atomic_dec_return(&tgt_dev->tgt_dev_cmd_count) == 0)
call_rcu(&tgt_dev->rcu, scst_free_tgt_dev_rcu);
}
/*
@@ -5590,6 +5585,8 @@ static void scst_free_tgt_dev(struct scst_tgt_dev *tgt_dev)
scst_tgt_dev_stop_threads(tgt_dev);
destroy_rcu_head(&tgt_dev->rcu);
kmem_cache_free(scst_tgtd_cachep, tgt_dev);
percpu_ref_put(&dev->refcnt);

1
scst/src/scst_priv.h
View File

@@ -382,6 +382,7 @@ void scst_check_reassign_sessions(void);
int scst_sess_alloc_tgt_devs(struct scst_session *sess);
void scst_sess_free_tgt_devs(struct scst_session *sess);
struct scst_tgt_dev *scst_lookup_tgt_dev(struct scst_session *sess, u64 lun);
void scst_free_tgt_dev_rcu(struct rcu_head *rcu);
void scst_nexus_loss(struct scst_tgt_dev *tgt_dev, bool queue_UA);
#define SCST_ADD_LUN_READ_ONLY 1

5
scst/src/scst_targ.c
View File

@@ -4504,7 +4504,8 @@ static int scst_pre_xmit_response1(struct scst_cmd *cmd)
* latency, so we should decrement them after cmd completed.
*/
smp_mb__before_atomic_dec();
atomic_dec(&cmd->tgt_dev->tgt_dev_cmd_count);
if (atomic_dec_return(&cmd->tgt_dev->tgt_dev_cmd_count) == 0)
call_rcu(&cmd->tgt_dev->rcu, scst_free_tgt_dev_rcu);
percpu_ref_put(&cmd->dev->refcnt);
#ifdef CONFIG_SCST_PER_DEVICE_CMD_COUNT_LIMIT
atomic_dec(&cmd->dev->dev_cmd_count);
@@ -5142,7 +5143,7 @@ static int __scst_init_cmd(struct scst_cmd *cmd)
scst_set_cmd_state(cmd, SCST_CMD_STATE_PARSE);
cnt = atomic_inc_return(&tgt_dev->tgt_dev_cmd_count);
cnt = atomic_inc_return(&tgt_dev->tgt_dev_cmd_count) - 1;
if (unlikely(cnt > dev->max_tgt_dev_commands)) {
TRACE(TRACE_FLOW_CONTROL,
"Too many pending commands (%d) in "