Revert "ib_srpt: Convert to percpu_ida tag allocation"

This reverts commit 0fd10721fe3664f7549e74af9d28a509c9a68719.

That patch causes the ib_srpt driver to crash as soon as the first SCSI
command is received:

  kernel BUG at drivers/infiniband/ulp/srpt/ib_srpt.c:1439!
  invalid opcode: 0000 [#1] SMP
  Workqueue: target_completion target_complete_ok_work [target_core_mod]
  RIP: srpt_queue_response+0x437/0x4a0 [ib_srpt]
  Call Trace:
    srpt_queue_data_in+0x9/0x10 [ib_srpt]
    target_complete_ok_work+0x152/0x2b0 [target_core_mod]
    process_one_work+0x197/0x480
    worker_thread+0x49/0x490
    kthread+0xea/0x100
    ret_from_fork+0x22/0x40

Aside from the crash, the shortcomings of that patch are as follows:

 - It makes the ib_srpt driver use I/O contexts allocated by
   transport_alloc_session_tags() but it does not initialize these I/O
   contexts properly.  All the initializations performed by
   srpt_alloc_ioctx() are skipped.

 - It swaps the order of the send ioctx allocation and the transition to
   RTR mode which is wrong.

 - The amount of memory that is needed for I/O contexts is doubled.

 - srpt_rdma_ch.free_list is no longer used but is not removed.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 40 insertions, 17 deletions

diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
index 0bd3cb2f3c67..8b42401d4795 100644
--- a/drivers/infiniband/ulp/srpt/ib_srpt.c
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
@@ -1264,26 +1264,40 @@ free_mem:
  */
 static struct srpt_send_ioctx *srpt_get_send_ioctx(struct srpt_rdma_ch *ch)
 {
-        struct se_session *se_sess;
         struct srpt_send_ioctx *ioctx;
-        int tag;
+        unsigned long flags;
 
         BUG_ON(!ch);
-        se_sess = ch->sess;
 
-        tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
-        if (tag < 0) {
-                pr_err("Unable to obtain tag for srpt_send_ioctx\n");
-                return NULL;
+        ioctx = NULL;
+        spin_lock_irqsave(&ch->spinlock, flags);
+        if (!list_empty(&ch->free_list)) {
+                ioctx = list_first_entry(&ch->free_list,
+                                         struct srpt_send_ioctx, free_list);
+                list_del(&ioctx->free_list);
         }
-        ioctx = &((struct srpt_send_ioctx *)se_sess->sess_cmd_map)[tag];
-        memset(ioctx, 0, sizeof(struct srpt_send_ioctx));
-        ioctx->ch = ch;
+        spin_unlock_irqrestore(&ch->spinlock, flags);
+
+        if (!ioctx)
+                return ioctx;
+
+        BUG_ON(ioctx->ch != ch);
         spin_lock_init(&ioctx->spinlock);
         ioctx->state = SRPT_STATE_NEW;
+        ioctx->n_rbuf = 0;
+        ioctx->rbufs = NULL;
+        ioctx->n_rdma = 0;
+        ioctx->n_rdma_wrs = 0;
+        ioctx->rdma_wrs = NULL;
+        ioctx->mapped_sg_count = 0;
         init_completion(&ioctx->tx_done);
-
-        ioctx->cmd.map_tag = tag;
+        ioctx->queue_status_only = false;
+        /*
+         * transport_init_se_cmd() does not initialize all fields, so do it
+         * here.
+         */
+        memset(&ioctx->cmd, 0, sizeof(ioctx->cmd));
+        memset(&ioctx->sense_data, 0, sizeof(ioctx->sense_data));
 
         return ioctx;
 }
@@ -2021,7 +2035,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
         struct ib_cm_rep_param *rep_param;
         struct srpt_rdma_ch *ch, *tmp_ch;
         u32 it_iu_len;
-        int ret = 0;
+        int i, ret = 0;
         unsigned char *p;
 
         WARN_ON_ONCE(irqs_disabled());
@@ -2143,6 +2157,12 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
         if (!ch->ioctx_ring)
                 goto free_ch;
 
+        INIT_LIST_HEAD(&ch->free_list);
+        for (i = 0; i < ch->rq_size; i++) {
+                ch->ioctx_ring[i]->ch = ch;
+                list_add_tail(&ch->ioctx_ring[i]->free_list, &ch->free_list);
+        }
+
         ret = srpt_create_ch_ib(ch);
         if (ret) {
                 rej->reason = cpu_to_be32(
@@ -2173,8 +2193,7 @@ static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
         p = &ch->sess_name[0];
 
 try_again:
-        ch->sess = target_alloc_session(&sport->port_tpg_1, ch->rq_size,
-                                        sizeof(struct srpt_send_ioctx),
+        ch->sess = target_alloc_session(&sport->port_tpg_1, 0, 0,
                                         TARGET_PROT_NORMAL, p, ch, NULL);
         if (IS_ERR(ch->sess)) {
                 pr_info("Rejected login because no ACL has been"
@@ -2881,7 +2900,7 @@ static void srpt_release_cmd(struct se_cmd *se_cmd)
         struct srpt_send_ioctx *ioctx = container_of(se_cmd,
                                 struct srpt_send_ioctx, cmd);
         struct srpt_rdma_ch *ch = ioctx->ch;
-        struct se_session *se_sess = ch->sess;
+        unsigned long flags;
 
         WARN_ON(ioctx->state != SRPT_STATE_DONE);
         WARN_ON(ioctx->mapped_sg_count != 0);
@@ -2892,7 +2911,9 @@ static void srpt_release_cmd(struct se_cmd *se_cmd)
                 ioctx->n_rbuf = 0;
         }
 
-        percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+        spin_lock_irqsave(&ch->spinlock, flags);
+        list_add(&ioctx->free_list, &ch->free_list);
+        spin_unlock_irqrestore(&ch->spinlock, flags);
 }
 
 /**
diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.h b/drivers/infiniband/ulp/srpt/ib_srpt.h
index ca288f019315..af9b8b527340 100644
--- a/drivers/infiniband/ulp/srpt/ib_srpt.h
+++ b/drivers/infiniband/ulp/srpt/ib_srpt.h
@@ -179,6 +179,7 @@ struct srpt_recv_ioctx {
  * struct srpt_send_ioctx - SRPT send I/O context.
  * @ioctx:       See above.
  * @ch:          Channel pointer.
+ * @free_list:   Node in srpt_rdma_ch.free_list.
  * @n_rbuf:      Number of data buffers in the received SRP command.
  * @rbufs:       Pointer to SRP data buffer array.
  * @single_rbuf: SRP data buffer if the command has only a single buffer.
@@ -201,6 +202,7 @@ struct srpt_send_ioctx {
         struct srp_direct_buf   *rbufs;
         struct srp_direct_buf   single_rbuf;
         struct scatterlist      *sg;
+        struct list_head        free_list;
         spinlock_t              spinlock;
         enum srpt_command_state state;
         struct se_cmd           cmd;