nvme: fix setting the queue depth in nvme_alloc_io_tag_set

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: 0da7fea ("nvme-pci: use the tagset alloc/free helpers")
Reported-by: Hugh Dickins <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Tested-by: Hugh Dickins <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Christoph Hellwig

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.