target/pr: Use atomic bitop for se_dev_entry->deve_flags reservation check

This patch converts the core_scsi3_pr_seq_non_holder() check for non
reservation holding registrations to use an atomic bitop in ->deve_flags
to determine if a registration is currently active.

It also includes associated a set_bit() in __core_scsi3_add_registration()
and clear_bit() in __core_scsi3_free_registration(), if se_dev_entry still
exists, and has not already been released via se_dev_entry shutdown path
in core_disable_device_list_for_node().

Also, clear_bit in core_disable_device_list_for_node as well to ensure
the read-critical path in core_scsi3_pr_seq_non_holder() picks up the
new state, preceeding the final kfree_rcu() call.

Reported-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index b518523..508528a 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -638,7 +638,6 @@ struct se_lun_acl {
 };
 
 struct se_dev_entry {
-	bool			def_pr_registered;
 	/* See transport_lunflags_table */
 	u32			lun_flags;
 	u32			mapped_lun;
@@ -655,6 +654,8 @@ struct se_dev_entry {
 	struct se_lun_acl __rcu	*se_lun_acl;
 	spinlock_t		ua_lock;
 	struct se_lun __rcu	*se_lun;
+#define DEF_PR_REG_ACTIVE		1
+	unsigned long		deve_flags;
 	struct list_head	alua_port_list;
 	struct list_head	ua_list;
 	struct hlist_node	link;