[PATCH 1/4] nvme: fix setting the queue depth in nvme_alloc_io_tag_set

[Sagi Grimberg]

> While the CAP.MQES field in NVMe is a 0s based filed with a natural one
> off, we also need to account for the queue wrap condition and fix undo
> the one off again in nvme_alloc_io_tag_set.  This was never properly
> done by the fabrics drivers, but they don't seem to care because there
> is no actual physical queue that can wrap around, but it became a
> problem when converting over the PCIe driver.  Also add back the
> BLK_MQ_MAX_DEPTH check that was lost in the same commit.
> 
> Fixes: 0da7feaa5913 ("nvme-pci: use the tagset alloc/free helpers")

This looks fine, but does this actually fix anything?
How does nvme-pci ever set sqsize anywhere close to BLK_MQ_MAX_DEPTH ?
NVME_PCI_MAX_QUEUE_SIZE is 4095...

> Reported-by: Hugh Dickins <hughd at google.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>   drivers/nvme/host/core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index e26b085a007aea..cda1361e6d4fbb 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -4897,7 +4897,7 @@ int nvme_alloc_io_tag_set(struct nvme_ctrl *ctrl, struct blk_mq_tag_set *set,
>   
>   	memset(set, 0, sizeof(*set));
>   	set->ops = ops;
> -	set->queue_depth = ctrl->sqsize + 1;
> +	set->queue_depth = min_t(unsigned, ctrl->sqsize, BLK_MQ_MAX_DEPTH - 1);
>   	/*
>   	 * Some Apple controllers requires tags to be unique across admin and
>   	 * the (only) I/O queue, so reserve the first 32 tags of the I/O queue.