scsi: target: Remove se_dev_entry.ua_count

se_dev_entry.ua_count is only used to check whether or not
se_dev_entry.ua_list is empty. Use list_empty_careful() instead.  Checking
whether or not ua_list is empty without holding the lock that protects that
list is fine because the code that dequeues from that list will check again
whether or not that list is empty.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_device.c

@@ -336,7 +336,6 @@ int core_enable_device_list_for_node(
 		return -ENOMEM;
 	}
 
-	atomic_set(&new->ua_count, 0);
 	spin_lock_init(&new->ua_lock);
 	INIT_LIST_HEAD(&new->ua_list);
 	INIT_LIST_HEAD(&new->lun_link);

drivers/target/target_core_ua.c

@@ -55,7 +55,7 @@ target_scsi3_ua_check(struct se_cmd *cmd)
 		rcu_read_unlock();
 		return 0;
 	}
-	if (!atomic_read(&deve->ua_count)) {
+	if (list_empty_careful(&deve->ua_list)) {
 		rcu_read_unlock();
 		return 0;
 	}
@@ -154,7 +154,6 @@ int core_scsi3_ua_allocate(
 				&deve->ua_list);
 		spin_unlock(&deve->ua_lock);
 
-		atomic_inc_mb(&deve->ua_count);
 		return 0;
 	}
 	list_add_tail(&ua->ua_nacl_list, &deve->ua_list);
@@ -164,7 +163,6 @@ int core_scsi3_ua_allocate(
 		" 0x%02x, ASCQ: 0x%02x\n", deve->mapped_lun,
 		asc, ascq);
 
-	atomic_inc_mb(&deve->ua_count);
 	return 0;
 }
 
@@ -196,8 +194,6 @@ void core_scsi3_ua_release_all(
 	list_for_each_entry_safe(ua, ua_p, &deve->ua_list, ua_nacl_list) {
 		list_del(&ua->ua_nacl_list);
 		kmem_cache_free(se_ua_cache, ua);
-
-		atomic_dec_mb(&deve->ua_count);
 	}
 	spin_unlock(&deve->ua_lock);
 }
@@ -263,8 +259,6 @@ bool core_scsi3_ua_for_check_condition(struct se_cmd *cmd, u8 *key, u8 *asc,
 		}
 		list_del(&ua->ua_nacl_list);
 		kmem_cache_free(se_ua_cache, ua);
-
-		atomic_dec_mb(&deve->ua_count);
 	}
 	spin_unlock(&deve->ua_lock);
 	rcu_read_unlock();
@@ -304,7 +298,7 @@ int core_scsi3_ua_clear_for_request_sense(
 		rcu_read_unlock();
 		return -EINVAL;
 	}
-	if (!atomic_read(&deve->ua_count)) {
+	if (list_empty_careful(&deve->ua_list)) {
 		rcu_read_unlock();
 		return -EPERM;
 	}
@@ -327,8 +321,6 @@ int core_scsi3_ua_clear_for_request_sense(
 		}
 		list_del(&ua->ua_nacl_list);
 		kmem_cache_free(se_ua_cache, ua);
-
-		atomic_dec_mb(&deve->ua_count);
 	}
 	spin_unlock(&deve->ua_lock);
 	rcu_read_unlock();

include/target/target_core_base.h

@@ -638,7 +638,6 @@ struct se_dev_entry {
 	atomic_long_t		total_cmds;
 	atomic_long_t		read_bytes;
 	atomic_long_t		write_bytes;
-	atomic_t		ua_count;
 	/* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
 	struct kref		pr_kref;
 	struct completion	pr_comp;