Re: [PATCH 37/43] hpsa: use block layer tag for command allocation

[Christoph Hellwig <hch@infradead.org>]

> @@ -4691,27 +4701,31 @@ static int hpsa_scsi_queue_command(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
>  
>  	/* Get the ptr to our adapter structure out of cmd->host. */
>  	h = sdev_to_hba(cmd->device);
> -	dev = cmd->device->hostdata;
> -	if (!dev) {
> +
> +	if (cmd->request->tag < 0) {
> +		dev_crit(&h->pdev->dev,
> +			 "sdev %p scmd %p: bad tag %d -- rejecting\n",
> +			 cmd->device, cmd, cmd->request->tag);
>  		cmd->result = DID_NO_CONNECT << 16;
>  		cmd->scsi_done(cmd);
>  		return 0;

Shouldn't happen with a modern kernel, but if you really want to
assert this I'd recommend a BUG_ON().

> -	if (unlikely(lockup_detected(h))) {
> +	dev = cmd->device->hostdata;
> +	if (!dev) {
>  		cmd->result = DID_NO_CONNECT << 16;
>  		cmd->scsi_done(cmd);
>  		return 0;
>  	}

How could this happen (see my earlier question in one of the first
patches).

> @@ -4838,6 +4852,11 @@ static int hpsa_register_scsi(struct ctlr_info *h)
>  	sh->hostdata[0] = (unsigned long) h;
>  	sh->irq = h->intr[h->intr_mode];
>  	sh->unique_id = sh->irq;
> +	if (!shost_use_blk_mq(sh)) {
> +		error = scsi_init_shared_tag_map(sh, sh->can_queue);
> +		if (error)
> +			goto fail_host_put;
> +	}

scsi_init_shared_tag_map alredy has the blk-mq check, so you can call
it unconditionally.

> +static void hpsa_print_scsi_cmd(struct ctlr_info *h, struct scsi_cmnd *scmd,
> +			   char *prefix)

Maybe just use scsi_print_command?

> +static void cmd_tagged_free(struct ctlr_info *h, struct CommandList *c)
> +{
> +	/*
> +	 * Release our reference to the block.  We don't need to do anything
> +	 * else to free it, because it is accessed by index.  (There's no point
> +	 * in checking the result of the decrement, since we cannot guarantee
> +	 * that there isn't a concurrent abort which is also accessing it.)
> +	 */
> +	(void)atomic_dec_and_test(&c->refcount);

Just use atomic_dec().

Any reason you're implementing your own allocator instead of setting
->cmd_size?