NVMe: Set block queue max sectors

PATCH New Keith Busch 2 participants 2 messages Jul 25, 2012 – Jul 26, 2012

Subsystems (2)

Block layer NVMe

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Keith Busch

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2012-07-25 22:07 UTC #0 lore raw

PATCH 1/1 NVMe: Set block queue max sectors

Set the max hw sectors in a namespace's request queue if the nvme device has a max data transfer size.

Signed-off-by Keith Busch <keith.busch at intel.com>

---
 drivers/block/nvme.c |    6 ++++++
 include/linux/nvme.h |    1 +
 2 files changed, 7 insertions(+), 0 deletions(-)

drivers/block/nvme.c +6 -0

index 38b9c73..3247037 100644
@@ -78,6 +78,7 @@ struct nvme_dev {
 	char serial[20];
 	char model[40];
 	char firmware_rev[8];
+	u32 max_hw_sectors;
 };
 
 /*

@@ -1345,6 +1346,8 @@ static struct nvme_ns *nvme_alloc_ns(struct nvme_dev *dev, int nsid,
 	lbaf = id->flbas & 0xf;
 	ns->lba_shift = id->lbaf[lbaf].ds;
 	blk_queue_logical_block_size(ns->queue, 1 << ns->lba_shift);
+	if (dev->max_hw_sectors) 
+		blk_queue_max_hw_sectors(ns->queue, dev->max_hw_sectors);
 
 	disk->major = nvme_major;
 	disk->minors = NVME_MINORS;

@@ -1486,6 +1489,9 @@ static int __devinit nvme_dev_add(struct nvme_dev *dev)
 	memcpy(dev->serial, ctrl->sn, sizeof(ctrl->sn));
 	memcpy(dev->model, ctrl->mn, sizeof(ctrl->mn));
 	memcpy(dev->firmware_rev, ctrl->fr, sizeof(ctrl->fr));
+	if (ctrl->mdts)
+		dev->max_hw_sectors = ((1 << ctrl->mdts) * (1 << (12 +
+				NVME_CAP_MPSMIN(readq(&dev->bar->cap))))) >> 9;
 
 	id_ns = mem;
 	for (i = 1; i <= nn; i++) {

include/linux/nvme.h +1 -0

index 9490a00..8c71d20 100644
@@ -37,6 +37,7 @@ struct nvme_bar {
 
 #define NVME_CAP_TIMEOUT(cap)	(((cap) >> 24) & 0xff)
 #define NVME_CAP_STRIDE(cap)	(((cap) >> 32) & 0xf)
+#define NVME_CAP_MPSMIN(cap)	(((cap) >> 48) & 0xf)
 
 enum {
 	NVME_CC_ENABLE		= 1 << 0,

Signature · 1 line

1.7.0.4

Matthew Wilcox

2012-07-26 16:22 UTC #1 lore raw

PATCH 1/1 NVMe: Set block queue max sectors

Quoted 2 lines · Keith Busch

Set the max hw sectors in a namespace's request queue if the nvme device has a max data transfer size.

Could I trouble you to reflow your comments in the future? When one types 'git log', it inserts four spaces before the message, so this would look like:

Set the max hw sectors in a namespace's request queue if the nvme device has a max data transfer size.

I find that typing !{fmt in vi does the right thing (it defaults to 75 columns), but I don't know which editor you use.

drivers/block/nvme.c static int __devinit nvme_dev_add(struct nvme_dev *dev) · line 1494

Quoted 5 lines

drivers/block/nvme.c +3 -0

 	memcpy(dev->firmware_rev, ctrl->fr, sizeof(ctrl->fr));
+	if (ctrl->mdts)
+		dev->max_hw_sectors = ((1 << ctrl->mdts) * (1 << (12 +
+				NVME_CAP_MPSMIN(readq(&dev->bar->cap))))) >> 9;

There's something about seeing five close-parens in a row that makes me uncomfortable. Maybe I was molested by a lisp compiler as a child or something, but it tends to indicate an overly complex expression.

Let's see, what might look better ...

	if (ctrl->mdts) {
		int mpsmin = 1 << (NVME_CAP_MPSMIN(readq(&dev->bar->cap)) + 12);
		dev->max_hw_sectors = ((1 << ctrl->mdts) * mpsmin) >> 9;
	}

Alternatively, we could redistribute some of the arithmetic ...

	if (ctrl->mdts)
		dev->max_hw_sectors = 1 << (12 - 9 + ctrl->mdts +
					NVME_CAP_MPSMIN(readq(&dev->bar->cap)));

but that's a little obscure. Perhaps a little less obscure:

	if (ctrl->mdts) {
		int shift = NVME_CAP_MPSMIN(readq(&dev->bar->cap)) + 12;
		dev->max_hw_sectors = 1 << (ctrl->mdts + shift - 9);
	}