target: Convert se_node_acl->device_list[] to RCU hlist

This patch converts se_node_acl->device_list[] table for mappedluns
to modern RCU hlist_head usage in order to support an arbitrary number
of node_acl lun mappings.

It converts transport_lookup_*_lun() fast-path code to use RCU read path
primitives when looking up se_dev_entry.  It adds a new hlist_head at
se_node_acl->lun_entry_hlist for this purpose.

For transport_lookup_cmd_lun() code, it works with existing per-cpu
se_lun->lun_ref when associating se_cmd with se_lun + se_device.
Also, go ahead and update core_create_device_list_for_node() +
core_free_device_list_for_node() to use ->lun_entry_hlist.

It also converts se_dev_entry->pr_ref_count access to use modern
struct kref counting, and updates core_disable_device_list_for_node()
to kref_put() and block on se_deve->pr_comp waiting for outstanding PR
special-case PR references to drop, then invoke kfree_rcu() to wait
for the RCU grace period to complete before releasing memory.

So now that se_node_acl->lun_entry_hlist fast path access uses RCU
protected pointers, go ahead and convert remaining non-fast path
RCU updater code using ->lun_entry_lock to struct mutex to allow
callers to block while walking se_node_acl->lun_entry_hlist.

Finally drop the left-over core_clear_initiator_node_from_tpg() that
originally cleared lun_access during se_node_acl shutdown, as post
RCU conversion it now becomes duplicated logic.

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

2 files changed, 16 insertions, 13 deletions

diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index 47fafec556f8..80d9e486e33e 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -101,7 +101,7 @@ int	target_alloc_sgl(struct scatterlist **, unsigned int *, u32, bool);
 sense_reason_t  transport_generic_map_mem_to_cmd(struct se_cmd *,
                 struct scatterlist *, u32, struct scatterlist *, u32);
 
-void    array_free(void *array, int n);
+bool    target_lun_is_rdonly(struct se_cmd *);
 
 /* From target_core_configfs.c to setup default backend config_item_types */
 void    target_core_setup_sub_cits(struct se_subsystem_api *);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 042a73464966..b518523cba7b 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -160,10 +160,8 @@ enum se_cmd_flags_table {
 
 /* struct se_dev_entry->lun_flags and struct se_lun->lun_access */
 enum transport_lunflags_table {
-        TRANSPORT_LUNFLAGS_NO_ACCESS            = 0x00,
-        TRANSPORT_LUNFLAGS_INITIATOR_ACCESS     = 0x01,
-        TRANSPORT_LUNFLAGS_READ_ONLY            = 0x02,
-        TRANSPORT_LUNFLAGS_READ_WRITE           = 0x04,
+        TRANSPORT_LUNFLAGS_READ_ONLY            = 0x01,
+        TRANSPORT_LUNFLAGS_READ_WRITE           = 0x02,
 };
 
 /*
@@ -584,10 +582,10 @@ struct se_node_acl {
         char                    acl_tag[MAX_ACL_TAG_SIZE];
         /* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
         atomic_t                acl_pr_ref_count;
-        struct se_dev_entry     **device_list;
+        struct hlist_head       lun_entry_hlist;
         struct se_session       *nacl_sess;
         struct se_portal_group *se_tpg;
-        spinlock_t              device_list_lock;
+        struct mutex            lun_entry_mutex;
         spinlock_t              nacl_sess_lock;
         struct config_group     acl_group;
         struct config_group     acl_attrib_group;
@@ -644,20 +642,23 @@ struct se_dev_entry {
         /* See transport_lunflags_table */
         u32                     lun_flags;
         u32                     mapped_lun;
-        u32                     total_cmds;
         u64                     pr_res_key;
         u64                     creation_time;
         u32                     attach_count;
-        u64                     read_bytes;
-        u64                     write_bytes;
+        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 */
-        atomic_t                pr_ref_count;
-        struct se_lun_acl       *se_lun_acl;
+        struct kref             pr_kref;
+        struct completion       pr_comp;
+        struct se_lun_acl __rcu *se_lun_acl;
         spinlock_t              ua_lock;
-        struct se_lun           *se_lun;
+        struct se_lun __rcu     *se_lun;
         struct list_head        alua_port_list;
         struct list_head        ua_list;
+        struct hlist_node       link;
+        struct rcu_head         rcu_head;
 };
 
 struct se_dev_attrib {
@@ -703,6 +704,7 @@ struct se_port_stat_grps {
 };
 
 struct se_lun {
+        u16                     lun_rtpi;
 #define SE_LUN_LINK_MAGIC                       0xffff7771
         u32                     lun_link_magic;
         /* See transport_lun_status_table */
@@ -710,6 +712,7 @@ struct se_lun {
         u32                     lun_access;
         u32                     lun_flags;
         u32                     unpacked_lun;
+        u32                     lun_index;
         atomic_t                lun_acl_count;
         spinlock_t              lun_acl_lock;
         spinlock_t              lun_sep_lock;