[PATCH 04/12] target: Convert UNIT_ATTENTION logic to RCU reader

Nicholas A. Bellinger
2015-05-12T09:36:17Z

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch converts target_core_ua.c code to use RCU read path locks
for se_node_acl->lun_entry_hlist access.

Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
drivers/target/target_core_ua.c | 51 ++++++++++++++++++++++++++++-------------
1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/drivers/target/target_core_ua.c b/drivers/target/target_core_ua.c
index a0bf0d1..6c9616d 100644
--- a/drivers/target/target_core_ua.c
+++ b/drivers/target/target_core_ua.c
@@ -50,9 +50,17 @@ target_scsi3_ua_check(struct se_cmd *cmd)
if (!nacl)
return 0;

- deve = nacl->device_list[cmd->orig_fe_lun];
- if (!atomic_read(&deve->ua_count))
+ rcu_read_lock();
+ deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
+ if (!deve) {
+ rcu_read_unlock();
return 0;
+ }
+ if (!atomic_read(&deve->ua_count)) {
+ rcu_read_unlock();
+ return 0;
+ }
+ rcu_read_unlock();
/*
* From sam4r14, section 5.14 Unit attention condition:
*
@@ -103,9 +111,12 @@ int core_scsi3_ua_allocate(
ua->ua_asc = asc;
ua->ua_ascq = ascq;

- spin_lock_irq(&nacl->device_list_lock);
- deve = nacl->device_list[unpacked_lun];
-
+ rcu_read_lock();
+ deve = target_nacl_find_deve(nacl, unpacked_lun);
+ if (!deve) {
+ rcu_read_unlock();
+ return -EINVAL;
+ }
spin_lock(&deve->ua_lock);
list_for_each_entry_safe(ua_p, ua_tmp, &deve->ua_list, ua_nacl_list) {
/*
@@ -113,7 +124,7 @@ int core_scsi3_ua_allocate(
*/
if ((ua_p->ua_asc == asc) && (ua_p->ua_ascq == ascq)) {
spin_unlock(&deve->ua_lock);
- spin_unlock_irq(&nacl->device_list_lock);
+ rcu_read_unlock();
kmem_cache_free(se_ua_cache, ua);
return 0;
}
@@ -158,14 +169,13 @@ int core_scsi3_ua_allocate(
list_add_tail(&ua->ua_nacl_list,
&deve->ua_list);
spin_unlock(&deve->ua_lock);
- spin_unlock_irq(&nacl->device_list_lock);

atomic_inc_mb(&deve->ua_count);
+ rcu_read_unlock();
return 0;
}
list_add_tail(&ua->ua_nacl_list, &deve->ua_list);
spin_unlock(&deve->ua_lock);
- spin_unlock_irq(&nacl->device_list_lock);

pr_debug("[%s]: Allocated UNIT ATTENTION, mapped LUN: %u, ASC:"
" 0x%02x, ASCQ: 0x%02x\n",
@@ -173,6 +183,7 @@ int core_scsi3_ua_allocate(
asc, ascq);

atomic_inc_mb(&deve->ua_count);
+ rcu_read_unlock();
return 0;
}

@@ -210,10 +221,14 @@ void core_scsi3_ua_for_check_condition(
if (!nacl)
return;

- spin_lock_irq(&nacl->device_list_lock);
- deve = nacl->device_list[cmd->orig_fe_lun];
+ rcu_read_lock();
+ deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
+ if (!deve) {
+ rcu_read_unlock();
+ return;
+ }
if (!atomic_read(&deve->ua_count)) {
- spin_unlock_irq(&nacl->device_list_lock);
+ rcu_read_unlock();
return;
}
/*
@@ -249,7 +264,7 @@ void core_scsi3_ua_for_check_condition(
atomic_dec_mb(&deve->ua_count);
}
spin_unlock(&deve->ua_lock);
- spin_unlock_irq(&nacl->device_list_lock);
+ rcu_read_unlock();

pr_debug("[%s]: %s UNIT ATTENTION condition with"
" INTLCK_CTRL: %d, mapped LUN: %u, got CDB: 0x%02x"
@@ -278,10 +293,14 @@ int core_scsi3_ua_clear_for_request_sense(
if (!nacl)
return -EINVAL;

- spin_lock_irq(&nacl->device_list_lock);
- deve = nacl->device_list[cmd->orig_fe_lun];
+ rcu_read_lock();
+ deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
+ if (!deve) {
+ rcu_read_unlock();
+ return -EINVAL;
+ }
if (!atomic_read(&deve->ua_count)) {
- spin_unlock_irq(&nacl->device_list_lock);
+ rcu_read_unlock();
return -EPERM;
}
/*
@@ -307,7 +326,7 @@ int core_scsi3_ua_clear_for_request_sense(
atomic_dec_mb(&deve->ua_count);
}
spin_unlock(&deve->ua_lock);
- spin_unlock_irq(&nacl->device_list_lock);
+ rcu_read_unlock();

pr_debug("[%s]: Released UNIT ATTENTION condition, mapped"
" LUN: %u, got REQUEST_SENSE reported ASC: 0x%02x,"
--
1.9.1