[PATCH] nvme: add a constant for the identify payload size

[willy@linux.intel.com (Matthew Wilcox)]

On Wed, Mar 09, 2016@05:54:37PM +0100, Christoph Hellwig wrote:
> The NVMe spec specifies a hardcoded payload length of 4k for all
> types of Identify commands.  Use a constant instead of hardcoded
> values that can be confused for the page size.

I think the problem here is that we don't have a struct for nvme_ns_list.

Something like this:

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index e2d11d6..a4a7210 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -296,14 +296,16 @@ int nvme_identify_ctrl(struct nvme_ctrl *dev, struct nvme_id_ctrl **id)
 	return error;
 }
 
-static int nvme_identify_ns_list(struct nvme_ctrl *dev, unsigned nsid, __le32 *ns_list)
+static int nvme_identify_ns_list(struct nvme_ctrl *dev, unsigned nsid,
+				struct nvme_id_ns_list *ns_list)
 {
 	struct nvme_command c = { };
 
 	c.identify.opcode = nvme_admin_identify;
 	c.identify.cns = cpu_to_le32(2);
 	c.identify.nsid = cpu_to_le32(nsid);
-	return nvme_submit_sync_cmd(dev->admin_q, &c, ns_list, 0x1000);
+	return nvme_submit_sync_cmd(dev->admin_q, &c, ns_list,
+					sizeof(*ns_list));
 }
 
 int nvme_identify_ns(struct nvme_ctrl *dev, unsigned nsid,
@@ -1296,11 +1298,11 @@ static void nvme_validate_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 static int nvme_scan_ns_list(struct nvme_ctrl *ctrl, unsigned nn)
 {
 	struct nvme_ns *ns;
-	__le32 *ns_list;
+	struct nvme_id_ns_list *ns_list;
 	unsigned i, j, nsid, prev = 0, num_lists = DIV_ROUND_UP(nn, 1024);
 	int ret = 0;
 
-	ns_list = kzalloc(0x1000, GFP_KERNEL);
+	ns_list = kzalloc(sizeof(*ns_list), GFP_KERNEL);
 	if (!ns_list)
 		return -ENOMEM;
 
@@ -1310,7 +1312,7 @@ static int nvme_scan_ns_list(struct nvme_ctrl *ctrl, unsigned nn)
 			goto out;
 
 		for (j = 0; j < min(nn, 1024U); j++) {
-			nsid = le32_to_cpu(ns_list[j]);
+			nsid = le32_to_cpu(ns_list->nsid[j]);
 			if (!nsid)
 				goto out;
 
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index aff71ef..ec2198c 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -175,6 +175,7 @@ static inline void _nvme_check_size(void)
 	BUILD_BUG_ON(sizeof(struct nvme_command) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_id_ctrl) != 4096);
 	BUILD_BUG_ON(sizeof(struct nvme_id_ns) != 4096);
+	BUILD_BUG_ON(sizeof(struct nvme_id_ns_list) != 4096);
 	BUILD_BUG_ON(sizeof(struct nvme_lba_range_type) != 64);
 	BUILD_BUG_ON(sizeof(struct nvme_smart_log) != 512);
 }
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index a55986f..e9122cf 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -183,6 +183,10 @@ struct nvme_id_ns {
 	__u8			vs[3712];
 };
 
+struct nvme_id_ns_list {
+	__le32			nsid[1024];
+};
+
 enum {
 	NVME_NS_FEAT_THIN	= 1 << 0,
 	NVME_NS_FLBAS_LBA_MASK	= 0xf,