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authorNicholas Bellinger <nab@linux-iscsi.org>2015-05-19 00:03:07 -0700
committerNicholas Bellinger <nab@linux-iscsi.org>2015-06-01 00:27:38 -0700
commit4cc987eaff9144182cde88d6d132420c28d3f81b (patch)
tree15cf7d432599e1e09446462968ef01c4d10a087e /drivers/target/target_core_device.c
parentadf653f92f38e80a78bb77e912d49bcc8055330f (diff)
target: Drop lun_sep_lock for se_lun->lun_se_dev RCU usage
With se_port and t10_alua_tg_pt_gp_member being absored into se_lun, there is no need for an extra lock to protect se_lun->lun_se_dev assignment. This patch also converts backend drivers to use call_rcu() release to allow any se_device readers to complete. The call_rcu() instead of kfree_rcu() is required here because se_device is embedded into the backend driver specific structure. Also, convert se_lun->lun_stats to use atomic_long_t within the target_complete_ok_work() completion callback, and add FIXME for transport_lookup_tmr_lun() with se_lun->lun_ref. Finally, update sbp_update_unit_directory() special case usage with proper rcu_dereference_raw() and configfs symlink comment. Reported-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Chris Boot <bootc@bootc.net> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Diffstat (limited to 'drivers/target/target_core_device.c')
-rw-r--r--drivers/target/target_core_device.c47
1 files changed, 31 insertions, 16 deletions
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 8485e9a789fc..3baa6cd7fded 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -61,7 +61,6 @@ 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;
struct se_dev_entry *deve;
if (unpacked_lun >= TRANSPORT_MAX_LUNS_PER_TPG)
@@ -128,16 +127,21 @@ 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;
}
+ /*
+ * RCU reference protected by percpu se_lun->lun_ref taken above that
+ * must drop to zero (including initial reference) before this se_lun
+ * pointer can be kfree_rcu() by the final se_lun->lun_group put via
+ * target_core_fabric_configfs.c:target_fabric_port_release
+ */
+ se_cmd->se_dev = rcu_dereference_raw(se_lun->lun_se_dev);
+ atomic_long_inc(&se_cmd->se_dev->num_cmds);
- /* Directly associate cmd with se_dev */
- se_cmd->se_dev = se_lun->lun_se_dev;
-
- dev = se_lun->lun_se_dev;
- atomic_long_inc(&dev->num_cmds);
if (se_cmd->data_direction == DMA_TO_DEVICE)
- atomic_long_add(se_cmd->data_length, &dev->write_bytes);
+ atomic_long_add(se_cmd->data_length,
+ &se_cmd->se_dev->write_bytes);
else if (se_cmd->data_direction == DMA_FROM_DEVICE)
- atomic_long_add(se_cmd->data_length, &dev->read_bytes);
+ atomic_long_add(se_cmd->data_length,
+ &se_cmd->se_dev->read_bytes);
return 0;
}
@@ -173,10 +177,11 @@ int transport_lookup_tmr_lun(struct se_cmd *se_cmd, u32 unpacked_lun)
unpacked_lun);
return -ENODEV;
}
-
- /* Directly associate cmd with se_dev */
- se_cmd->se_dev = se_lun->lun_se_dev;
- se_tmr->tmr_dev = se_lun->lun_se_dev;
+ /*
+ * XXX: Add percpu se_lun->lun_ref reference count for TMR
+ */
+ se_cmd->se_dev = rcu_dereference_raw(se_lun->lun_se_dev);
+ se_tmr->tmr_dev = rcu_dereference_raw(se_lun->lun_se_dev);
spin_lock_irqsave(&se_tmr->tmr_dev->se_tmr_lock, flags);
list_add_tail(&se_tmr->tmr_list, &se_tmr->tmr_dev->dev_tmr_list);
@@ -390,6 +395,11 @@ void core_disable_device_list_for_node(
struct se_portal_group *tpg)
{
/*
+ * rcu_dereference_raw protected by se_lun->lun_group symlink
+ * reference to se_device->dev_group.
+ */
+ struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev);
+ /*
* If the MappedLUN entry is being disabled, the entry in
* lun->lun_deve_list must be removed now before clearing the
* struct se_dev_entry pointers below as logic in
@@ -426,7 +436,7 @@ void core_disable_device_list_for_node(
kfree_rcu(orig, rcu_head);
- core_scsi3_free_pr_reg_from_nacl(lun->lun_se_dev, nacl);
+ core_scsi3_free_pr_reg_from_nacl(dev, nacl);
}
/* core_clear_lun_from_tpg():
@@ -629,6 +639,11 @@ int core_dev_add_initiator_node_lun_acl(
u32 lun_access)
{
struct se_node_acl *nacl = lacl->se_lun_nacl;
+ /*
+ * rcu_dereference_raw protected by se_lun->lun_group symlink
+ * reference to se_device->dev_group.
+ */
+ struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev);
if (!nacl)
return -EINVAL;
@@ -652,7 +667,7 @@ int core_dev_add_initiator_node_lun_acl(
* Check to see if there are any existing persistent reservation APTPL
* pre-registrations that need to be enabled for this LUN ACL..
*/
- core_scsi3_check_aptpl_registration(lun->lun_se_dev, tpg, lun, nacl,
+ core_scsi3_check_aptpl_registration(dev, tpg, lun, nacl,
lacl->mapped_lun);
return 0;
}
@@ -746,6 +761,7 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
dev->se_hba = hba;
dev->transport = hba->backend->ops;
dev->prot_length = sizeof(struct se_dif_v1_tuple);
+ dev->hba_index = hba->hba_index;
INIT_LIST_HEAD(&dev->dev_list);
INIT_LIST_HEAD(&dev->dev_sep_list);
@@ -802,8 +818,7 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
dev->dev_attrib.max_write_same_len = DA_MAX_WRITE_SAME_LEN;
xcopy_lun = &dev->xcopy_lun;
- xcopy_lun->lun_se_dev = dev;
- spin_lock_init(&xcopy_lun->lun_sep_lock);
+ rcu_assign_pointer(xcopy_lun->lun_se_dev, dev);
init_completion(&xcopy_lun->lun_ref_comp);
INIT_LIST_HEAD(&xcopy_lun->lun_deve_list);
INIT_LIST_HEAD(&xcopy_lun->lun_dev_link);