[PATCH] nvme: Fix io_opt limit setting

[Damien Le Moal <damien.lemoal@wdc.com>]

Currently, a namespace io_opt queue limit is set by default to the
physical sector size of the namespace and to the the write optimal
size (NOWS) when the namespace reports this value. This causes problems
with block limits stacking in blk_stack_limits() when a namespace block
device is combined with an HDD which generally do not report any optimal
transfer size (io_opt limit is 0). The code:

/* Optimal I/O a multiple of the physical block size? */
if (t->io_opt & (t->physical_block_size - 1)) {
	t->io_opt = 0;
	t->misaligned = 1;
	ret = -1;
}

results in blk_stack_limits() to return an error when the combined
devices have different but compatible physical sector sizes (e.g. 512B
sector SSD with 4KB sector disks).

Fix this by not setting the optiomal IO size limit if the namespace does
not report an optimal write size value.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 drivers/nvme/host/core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f3c037f5a9ba..0729173053ed 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1809,7 +1809,7 @@ static void nvme_update_disk_info(struct gendisk *disk,
 {
 	sector_t capacity = nvme_lba_to_sect(ns, le64_to_cpu(id->nsze));
 	unsigned short bs = 1 << ns->lba_shift;
-	u32 atomic_bs, phys_bs, io_opt;
+	u32 atomic_bs, phys_bs, io_opt = 0;
 
 	if (ns->lba_shift > PAGE_SHIFT) {
 		/* unsupported block size, set capacity to 0 later */
@@ -1832,12 +1832,11 @@ static void nvme_update_disk_info(struct gendisk *disk,
 		atomic_bs = bs;
 	}
 	phys_bs = bs;
-	io_opt = bs;
 	if (id->nsfeat & (1 << 4)) {
 		/* NPWG = Namespace Preferred Write Granularity */
 		phys_bs *= 1 + le16_to_cpu(id->npwg);
 		/* NOWS = Namespace Optimal Write Size */
-		io_opt *= 1 + le16_to_cpu(id->nows);
+		io_opt = bs * (1 + le16_to_cpu(id->nows));
 	}
 
 	blk_queue_logical_block_size(disk->queue, bs);
@@ -1848,7 +1847,8 @@ static void nvme_update_disk_info(struct gendisk *disk,
 	 */
 	blk_queue_physical_block_size(disk->queue, min(phys_bs, atomic_bs));
 	blk_queue_io_min(disk->queue, phys_bs);
-	blk_queue_io_opt(disk->queue, io_opt);
+	if (io_opt)
+		blk_queue_io_opt(disk->queue, io_opt);
 
 	if (ns->ms && !ns->ext &&
 	    (ns->ctrl->ops->flags & NVME_F_METADATA_SUPPORTED))
-- 
2.25.4