Commit 4cc987ea authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Boot <bootc@bootc.net>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent adf653f9

drivers/target/sbp/sbp_target.c

+5 −2
Original line number Diff line number Diff line
@@ -1905,8 +1905,11 @@ static int sbp_update_unit_directory(struct sbp_tport *tport) 
	hlist_for_each_entry_rcu(lun, &tport->tpg->se_tpg.tpg_lun_hlist, link) {

		struct se_device *dev;

		int type;



		dev = lun->lun_se_dev;

		/*

		 * rcu_dereference_raw protected by se_lun->lun_group symlink

		 * reference to se_device->dev_group.

		 */

		dev = rcu_dereference_raw(lun->lun_se_dev);

		type = dev->transport->get_device_type(dev);



		/* logical_unit_number */

drivers/target/target_core_alua.c

+10 −2
Original line number Diff line number Diff line
@@ -1935,7 +1935,11 @@ ssize_t core_alua_store_tg_pt_gp_info( 
	size_t count)

{

	struct se_portal_group *tpg = lun->lun_tpg;

	struct se_device *dev = lun->lun_se_dev;

	/*

	 * 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);

	struct t10_alua_tg_pt_gp *tg_pt_gp = NULL, *tg_pt_gp_new = NULL;

	unsigned char buf[TG_PT_GROUP_NAME_BUF];

	int move = 0;
@@ -2189,7 +2193,11 @@ ssize_t core_alua_store_offline_bit( 
	const char *page,

	size_t count)

{

	struct se_device *dev = lun->lun_se_dev;

	/*

	 * 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);

	unsigned long tmp;

	int ret;

drivers/target/target_core_device.c

+31 −16
Original line number Diff line number Diff line
@@ -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);
@@ -389,6 +394,11 @@ void core_disable_device_list_for_node( 
	struct se_node_acl *nacl,

	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
@@ -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);

drivers/target/target_core_file.c

+9 −2
Original line number Diff line number Diff line
@@ -241,6 +241,14 @@ static int fd_configure_device(struct se_device *dev) 
	return ret;

}



static void fd_dev_call_rcu(struct rcu_head *p)

{

	struct se_device *dev = container_of(p, struct se_device, rcu_head);

	struct fd_dev *fd_dev = FD_DEV(dev);



	kfree(fd_dev);

}



static void fd_free_device(struct se_device *dev)

{

	struct fd_dev *fd_dev = FD_DEV(dev);
@@ -249,8 +257,7 @@ static void fd_free_device(struct se_device *dev) 
		filp_close(fd_dev->fd_file, NULL);

		fd_dev->fd_file = NULL;

	}



	kfree(fd_dev);

	call_rcu(&dev->rcu_head, fd_dev_call_rcu);

}



static int fd_do_rw(struct se_cmd *cmd, struct file *fd,

drivers/target/target_core_iblock.c

+9 −1
Original line number Diff line number Diff line
@@ -191,6 +191,14 @@ static int iblock_configure_device(struct se_device *dev) 
	return ret;

}



static void iblock_dev_call_rcu(struct rcu_head *p)

{

	struct se_device *dev = container_of(p, struct se_device, rcu_head);

	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);



	kfree(ib_dev);

}



static void iblock_free_device(struct se_device *dev)

{

	struct iblock_dev *ib_dev = IBLOCK_DEV(dev);
@@ -200,7 +208,7 @@ static void iblock_free_device(struct se_device *dev) 
	if (ib_dev->ibd_bio_set != NULL)

		bioset_free(ib_dev->ibd_bio_set);



	kfree(ib_dev);

	call_rcu(&dev->rcu_head, iblock_dev_call_rcu);

}



static unsigned long long iblock_emulate_read_cap_with_block_size(