Re: [PATCH RFC v7 11/12] smartpqi: enable host tagset

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On 14/07/2020 14:16, John Garry wrote:
Hi Hannes,

  static struct pqi_io_request *pqi_alloc_io_request(
-    struct pqi_ctrl_info *ctrl_info)
+    struct pqi_ctrl_info *ctrl_info, struct scsi_cmnd *scmd)
  {
      struct pqi_io_request *io_request;
+    unsigned int limit = PQI_RESERVED_IO_SLOTS;
      u16 i = ctrl_info->next_io_request_slot;    /* benignly racy */
-    while (1) {
+    if (scmd) {
+        u32 blk_tag = blk_mq_unique_tag(scmd->request);
+
+        i = blk_mq_unique_tag_to_tag(blk_tag) + limit;
          io_request = &ctrl_info->io_request_pool[i];

This looks ok

-        if (atomic_inc_return(&io_request->refcount) == 1)
-            break;
-        atomic_dec(&io_request->refcount);
-        i = (i + 1) % ctrl_info->max_io_slots;
+        if (WARN_ON(atomic_inc_return(&io_request->refcount) > 1)) {
+            atomic_dec(&io_request->refcount);
+            return NULL;
+        }
+    } else {
+        while (1) {
+            io_request = &ctrl_info->io_request_pool[i];
+            if (atomic_inc_return(&io_request->refcount) == 1)
+                break;
+            atomic_dec(&io_request->refcount);
+            i = (i + 1) % limit;

To me, the range we use here looks incorrect. I would assume we should restrict range to [max_io_slots - PQI_RESERVED_IO_SLOTS, max_io_slots).


Sorry, I missed that you use i = blk_mq_unique_tag_to_tag(blk_tag) + limit for regular command.

But we still set next_io_request_slot for regular command and maybe then read and use it for reserved command.

Thanks



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