[PATCH 1/2] nvme: refactor the atomic write unit detection

[Christoph Hellwig]

Move all the code out of nvme_update_disk_info into the helper, and
rename the helper to have a somewhat less clumsy name.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Luis Chamberlain <mcgrof at kernel.org>
Reviewed-by: John Garry <john.g.garry at oracle.com>
---
 drivers/nvme/host/core.c | 72 +++++++++++++++++++++-------------------
 1 file changed, 38 insertions(+), 34 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 724f5732786c..520fb5f1e214 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2015,21 +2015,51 @@ static void nvme_configure_metadata(struct nvme_ctrl *ctrl,
 }
 
 
-static void nvme_update_atomic_write_disk_info(struct nvme_ns *ns,
-			struct nvme_id_ns *id, struct queue_limits *lim,
-			u32 bs, u32 atomic_bs)
+static u32 nvme_configure_atomic_write(struct nvme_ns *ns,
+		struct nvme_id_ns *id, struct queue_limits *lim, u32 bs)
 {
-	unsigned int boundary = 0;
+	u32 atomic_bs, boundary = 0;
 
-	if (id->nsfeat & NVME_NS_FEAT_ATOMICS && id->nawupf) {
-		if (le16_to_cpu(id->nabspf))
+	/*
+	 * We do not support an offset for the atomic boundaries.
+	 */
+	if (id->nabo)
+		return bs;
+
+	if ((id->nsfeat & NVME_NS_FEAT_ATOMICS) && id->nawupf) {
+		/*
+		 * Use the per-namespace atomic write unit when available.
+		 */
+		atomic_bs = (1 + le16_to_cpu(id->nawupf)) * bs;
+		if (id->nabspf)
 			boundary = (le16_to_cpu(id->nabspf) + 1) * bs;
+	} else {
+		/*
+		 * Use the controller wide atomic write unit.  This sucks
+		 * because the limit is defined in terms of logical blocks while
+		 * namespaces can have different formats, and because there is
+		 * no clear language in the specification prohibiting different
+		 * values for different controllers in the subsystem.
+		 */
+		atomic_bs = (1 + ns->ctrl->awupf) * bs;
+	}
+
+	if (!ns->ctrl->subsys->atomic_bs) {
+		ns->ctrl->subsys->atomic_bs = atomic_bs;
+	} else if (ns->ctrl->subsys->atomic_bs != atomic_bs) {
+		dev_err_ratelimited(ns->ctrl->device,
+			"%s: Inconsistent Atomic Write Size, Namespace will not be added: Subsystem=%d bytes, Controller/Namespace=%d bytes\n",
+			ns->disk ? ns->disk->disk_name : "?",
+			ns->ctrl->subsys->atomic_bs,
+			atomic_bs);
 	}
+
 	lim->atomic_write_hw_max = atomic_bs;
 	lim->atomic_write_hw_boundary = boundary;
 	lim->atomic_write_hw_unit_min = bs;
 	lim->atomic_write_hw_unit_max = rounddown_pow_of_two(atomic_bs);
 	lim->features |= BLK_FEAT_ATOMIC_WRITES;
+	return atomic_bs;
 }
 
 static u32 nvme_max_drv_segments(struct nvme_ctrl *ctrl)
@@ -2067,34 +2097,8 @@ static bool nvme_update_disk_info(struct nvme_ns *ns, struct nvme_id_ns *id,
 		valid = false;
 	}
 
-	atomic_bs = phys_bs = bs;
-	if (id->nabo == 0) {
-		/*
-		 * Bit 1 indicates whether NAWUPF is defined for this namespace
-		 * and whether it should be used instead of AWUPF. If NAWUPF ==
-		 * 0 then AWUPF must be used instead.
-		 */
-		if (id->nsfeat & NVME_NS_FEAT_ATOMICS && id->nawupf)
-			atomic_bs = (1 + le16_to_cpu(id->nawupf)) * bs;
-		else
-			atomic_bs = (1 + ns->ctrl->awupf) * bs;
-
-		/*
-		 * Set subsystem atomic bs.
-		 */
-		if (ns->ctrl->subsys->atomic_bs) {
-			if (atomic_bs != ns->ctrl->subsys->atomic_bs) {
-				dev_err_ratelimited(ns->ctrl->device,
-					"%s: Inconsistent Atomic Write Size, Namespace will not be added: Subsystem=%d bytes, Controller/Namespace=%d bytes\n",
-					ns->disk ? ns->disk->disk_name : "?",
-					ns->ctrl->subsys->atomic_bs,
-					atomic_bs);
-			}
-		} else
-			ns->ctrl->subsys->atomic_bs = atomic_bs;
-
-		nvme_update_atomic_write_disk_info(ns, id, lim, bs, atomic_bs);
-	}
+	phys_bs = bs;
+	atomic_bs = nvme_configure_atomic_write(ns, id, lim, bs);
 
 	if (id->nsfeat & NVME_NS_FEAT_IO_OPT) {
 		/* NPWG = Namespace Preferred Write Granularity */
-- 
2.47.2