nvme: provide num dword helper

Various nvme commands use a zeroes based number of dwords field. Create
a helper function to convert byte lengths to this format.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/core.c

@@ -530,7 +530,7 @@ static int nvme_get_stream_params(struct nvme_ctrl *ctrl,
 
 	c.directive.opcode = nvme_admin_directive_recv;
 	c.directive.nsid = cpu_to_le32(nsid);
-	c.directive.numd = cpu_to_le32((sizeof(*s) >> 2) - 1);
+	c.directive.numd = cpu_to_le32(nvme_bytes_to_numd(sizeof(*s)));
 	c.directive.doper = NVME_DIR_RCV_ST_OP_PARAM;
 	c.directive.dtype = NVME_DIR_STREAMS;
 
@@ -2746,7 +2746,7 @@ int nvme_get_log(struct nvme_ctrl *ctrl, u32 nsid, u8 log_page, u8 lsp,
 		void *log, size_t size, u64 offset)
 {
 	struct nvme_command c = { };
-	unsigned long dwlen = size / 4 - 1;
+	u32 dwlen = nvme_bytes_to_numd(size);
 
 	c.get_log_page.opcode = nvme_admin_get_log_page;
 	c.get_log_page.nsid = cpu_to_le32(nsid);

drivers/nvme/host/nvme.h

@@ -449,6 +449,14 @@ static inline sector_t nvme_lba_to_sect(struct nvme_ns *ns, u64 lba)
 	return lba << (ns->lba_shift - SECTOR_SHIFT);
 }
 
+/*
+ * Convert byte length to nvme's 0-based num dwords
+ */
+static inline u32 nvme_bytes_to_numd(size_t len)
+{
+	return (len >> 2) - 1;
+}
+
 static inline void nvme_end_request(struct request *req, __le16 status,
 		union nvme_result result)
 {