On 3/27/2015 11:04 AM, Nicholas A. Bellinger wrote:
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
This patch converts transport_lookup_*_lun() fast-path code to
use RCU read path primitives when looking up se_dev_entry. It
adds a new array of pointers in se_node_acl->lun_entry_hlist
for this purpose.
For transport_lookup_cmd_lun() code, it works with existing per-cpu
se_lun->lun_ref when associating se_cmd with se_lun + se_device.
Also, go ahead and update core_create_device_list_for_node() +
core_free_device_list_for_node() to use ->lun_entry_hlist.
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_device.c | 45 +++++++++++++++++++++++++------------
drivers/target/target_core_tpg.c | 10 +++++----
include/target/target_core_base.h | 2 ++
3 files changed, 39 insertions(+), 18 deletions(-)
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 37449bd..be893c8 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -59,17 +59,24 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u32 unpacked_lun)
{
struct se_lun *se_lun = NULL;
struct se_session *se_sess = se_cmd->se_sess;
+ struct se_node_acl *nacl = se_sess->se_node_acl;
struct se_device *dev;
- unsigned long flags;
+ struct se_dev_entry *deve;
if (unpacked_lun >= TRANSPORT_MAX_LUNS_PER_TPG)
return TCM_NON_EXISTENT_LUN;
- spin_lock_irqsave(&se_sess->se_node_acl->device_list_lock, flags);
- se_cmd->se_deve = se_sess->se_node_acl->device_list[unpacked_lun];
- if (se_cmd->se_deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS) {
- struct se_dev_entry *deve = se_cmd->se_deve;
-
+ rcu_read_lock();
+ deve = rcu_dereference(nacl->lun_entry_hlist[unpacked_lun]);
+ if (deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS) {
+ /*
+ * Make sure that target_enable_device_list_for_node()
+ * has not already cleared the RCU protected pointers.
+ */
+ if (!deve->se_lun) {
+ rcu_read_unlock();
+ goto check_lun;
+ }
deve->total_cmds++;
if ((se_cmd->data_direction == DMA_TO_DEVICE) &&
@@ -78,7 +85,7 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u32 unpacked_lun)
" Access for 0x%08x\n",
se_cmd->se_tfo->get_fabric_name(),
unpacked_lun);
- spin_unlock_irqrestore(&se_sess->se_node_acl->device_list_lock, flags);
+ rcu_read_unlock();
return TCM_WRITE_PROTECTED;
}
@@ -96,8 +103,9 @@ transport_lookup_cmd_lun(struct se_cmd *se_cmd, u32 unpacked_lun)
percpu_ref_get(&se_lun->lun_ref);
se_cmd->lun_ref_active = true;
}
- spin_unlock_irqrestore(&se_sess->se_node_acl->device_list_lock, flags);
+ rcu_read_unlock();
+check_lun:
if (!se_lun) {
/*
* Use the se_portal_group->tpg_virt_lun0 to allow for
@@ -146,25 +154,34 @@ int transport_lookup_tmr_lun(struct se_cmd *se_cmd, u32 unpacked_lun)
struct se_dev_entry *deve;
struct se_lun *se_lun = NULL;
struct se_session *se_sess = se_cmd->se_sess;
+ struct se_node_acl *nacl = se_sess->se_node_acl;
struct se_tmr_req *se_tmr = se_cmd->se_tmr_req;
unsigned long flags;
if (unpacked_lun >= TRANSPORT_MAX_LUNS_PER_TPG)
return -ENODEV;
- spin_lock_irqsave(&se_sess->se_node_acl->device_list_lock, flags);
- se_cmd->se_deve = se_sess->se_node_acl->device_list[unpacked_lun];
- deve = se_cmd->se_deve;
+ rcu_read_lock();
+ deve = rcu_dereference(nacl->lun_entry_hlist[unpacked_lun]);
if (deve->lun_flags & TRANSPORT_LUNFLAGS_INITIATOR_ACCESS) {
+ /*
+ * Make sure that target_enable_device_list_for_node()
+ * has not already cleared the RCU protected pointers.
+ */
+ if (!deve->se_lun) {
+ rcu_read_unlock();
+ goto check_lun;
+ }
se_tmr->tmr_lun = deve->se_lun;
se_cmd->se_lun = deve->se_lun;
se_lun = deve->se_lun;
se_cmd->pr_res_key = deve->pr_res_key;
se_cmd->orig_fe_lun = unpacked_lun;
}
- spin_unlock_irqrestore(&se_sess->se_node_acl->device_list_lock, flags);
+ rcu_read_unlock();
+check_lun:
if (!se_lun) {
pr_debug("TARGET_CORE[%s]: Detected NON_EXISTENT_LUN"
" Access for 0x%08x\n",
@@ -267,8 +284,8 @@ int core_free_device_list_for_node(
}
spin_unlock_irq(&nacl->device_list_lock);
- array_free(nacl->device_list, TRANSPORT_MAX_LUNS_PER_TPG);
- nacl->device_list = NULL;
+ array_free(nacl->lun_entry_hlist, TRANSPORT_MAX_LUNS_PER_TPG);
+ nacl->lun_entry_hlist = NULL;
return 0;
}
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index 0696de9..b2fdba5 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -234,15 +234,15 @@ static int core_create_device_list_for_node(struct se_node_acl *nacl)
struct se_dev_entry *deve;
int i;
- nacl->device_list = array_zalloc(TRANSPORT_MAX_LUNS_PER_TPG,
+ nacl->lun_entry_hlist = array_zalloc(TRANSPORT_MAX_LUNS_PER_TPG,
sizeof(struct se_dev_entry), GFP_KERNEL);
- if (!nacl->device_list) {
+ if (!nacl->lun_entry_hlist) {
pr_err("Unable to allocate memory for"
- " struct se_node_acl->device_list\n");
+ " struct se_node_acl->lun_entry_hlist\n");
return -ENOMEM;
}
for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
- deve = nacl->device_list[i];
+ deve = nacl->lun_entry_hlist[i];
atomic_set(&deve->ua_count, 0);
atomic_set(&deve->pr_ref_count, 0);
@@ -281,6 +281,7 @@ struct se_node_acl *core_tpg_check_initiator_node_acl(
init_completion(&acl->acl_free_comp);
spin_lock_init(&acl->device_list_lock);
spin_lock_init(&acl->nacl_sess_lock);
+ spin_lock_init(&acl->lun_entry_lock);
atomic_set(&acl->acl_pr_ref_count, 0);
acl->queue_depth = tpg->se_tpg_tfo->tpg_get_default_depth(tpg);
snprintf(acl->initiatorname, TRANSPORT_IQN_LEN, "%s", initiatorname);
@@ -408,6 +409,7 @@ struct se_node_acl *core_tpg_add_initiator_node_acl(
init_completion(&acl->acl_free_comp);
spin_lock_init(&acl->device_list_lock);
spin_lock_init(&acl->nacl_sess_lock);
+ spin_lock_init(&acl->lun_entry_lock);
atomic_set(&acl->acl_pr_ref_count, 0);
acl->queue_depth = queue_depth;
snprintf(acl->initiatorname, TRANSPORT_IQN_LEN, "%s", initiatorname);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index fe25a78..06ecd7b 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -595,10 +595,12 @@ struct se_node_acl {
char acl_tag[MAX_ACL_TAG_SIZE];
/* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
atomic_t acl_pr_ref_count;
+ struct se_dev_entry __rcu **lun_entry_hlist;
struct se_dev_entry **device_list;
Shouldn't device_list be removed here?
struct se_session *nacl_sess;
struct se_portal_group *se_tpg;
spinlock_t device_list_lock;
+ spinlock_t lun_entry_lock;
This lock is unused in this patch, it should be
introduced with its usage.
Sagi.
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