target: Add transport_init_session_tags using per-cpu ida

This patch adds lib/idr.c based transport_init_session_tags() logic
that allows fabric drivers to setup a per-cpu se_sess->sess_tag_pool
and associated se_sess->sess_cmd_map for basic tagged pre-allocation
of fabric descriptor sized memory.

v5 changes:
  - Convert to percpu_ida.h include

v4 changes:
  - Add transport_alloc_session_tags() for fabrics that need early
    transport_init_session()

v3 changes:
  - Update to percpu-ida usage

Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Asias He <asias@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Asias He <asias@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

3 files changed, 56 insertions, 0 deletions

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 7172d005d063..98ec7110873b 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -232,6 +232,50 @@ struct se_session *transport_init_session(void)
 }
 EXPORT_SYMBOL(transport_init_session);
 
+int transport_alloc_session_tags(struct se_session *se_sess,
+                                 unsigned int tag_num, unsigned int tag_size)
+{
+        int rc;
+
+        se_sess->sess_cmd_map = kzalloc(tag_num * tag_size, GFP_KERNEL);
+        if (!se_sess->sess_cmd_map) {
+                pr_err("Unable to allocate se_sess->sess_cmd_map\n");
+                return -ENOMEM;
+        }
+
+        rc = percpu_ida_init(&se_sess->sess_tag_pool, tag_num);
+        if (rc < 0) {
+                pr_err("Unable to init se_sess->sess_tag_pool,"
+                        " tag_num: %u\n", tag_num);
+                kfree(se_sess->sess_cmd_map);
+                se_sess->sess_cmd_map = NULL;
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL(transport_alloc_session_tags);
+
+struct se_session *transport_init_session_tags(unsigned int tag_num,
+                                               unsigned int tag_size)
+{
+        struct se_session *se_sess;
+        int rc;
+
+        se_sess = transport_init_session();
+        if (IS_ERR(se_sess))
+                return se_sess;
+
+        rc = transport_alloc_session_tags(se_sess, tag_num, tag_size);
+        if (rc < 0) {
+                transport_free_session(se_sess);
+                return ERR_PTR(-ENOMEM);
+        }
+
+        return se_sess;
+}
+EXPORT_SYMBOL(transport_init_session_tags);
+
 /*
  * Called with spin_lock_irqsave(&struct se_portal_group->session_lock called.
  */
@@ -367,6 +411,10 @@ EXPORT_SYMBOL(transport_deregister_session_configfs);
 
 void transport_free_session(struct se_session *se_sess)
 {
+        if (se_sess->sess_cmd_map) {
+                percpu_ida_destroy(&se_sess->sess_tag_pool);
+                kfree(se_sess->sess_cmd_map);
+        }
         kmem_cache_free(se_sess_cache, se_sess);
 }
 EXPORT_SYMBOL(transport_free_session);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index e34fc904f2e1..bd55acd43005 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -5,6 +5,7 @@
 #include <linux/configfs.h>
 #include <linux/dma-mapping.h>
 #include <linux/blkdev.h>
+#include <linux/percpu_ida.h>
 #include <scsi/scsi_cmnd.h>
 #include <net/sock.h>
 #include <net/tcp.h>
@@ -415,6 +416,8 @@ struct se_cmd {
         enum dma_data_direction data_direction;
         /* For SAM Task Attribute */
         int                     sam_task_attr;
+        /* Used for se_sess->sess_tag_pool */
+        unsigned int            map_tag;
         /* Transport protocol dependent state, see transport_state_table */
         enum transport_state_table t_state;
         unsigned                cmd_wait_set:1;
@@ -536,6 +539,8 @@ struct se_session {
         struct list_head        sess_wait_list;
         spinlock_t              sess_cmd_lock;
         struct kref             sess_kref;
+        void                    *sess_cmd_map;
+        struct percpu_ida       sess_tag_pool;
 };
 
 struct se_device;
diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index 7a16178424f9..d559c36692af 100644
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -84,6 +84,9 @@ struct target_core_fabric_ops {
 };
 
 struct se_session *transport_init_session(void);
+int transport_alloc_session_tags(struct se_session *, unsigned int,
+                unsigned int);
+struct se_session *transport_init_session_tags(unsigned int, unsigned int);
 void    __transport_register_session(struct se_portal_group *,
                 struct se_node_acl *, struct se_session *, void *);
 void    transport_register_session(struct se_portal_group *,