nvme: do not scan topology when mmaping registers

For accessing the registers we don't need to scan the topology. With the
device name we already know where to lookup the resource0 file in sysfs.

We also don't need to do the fallback lookup via the namespaces because
Linux kernel v4.0 has introduced the link in /sys/class/nvme/nvme%d. And
nvme-cli 2.x depends on Linux kernel >= 4.15, so it's safe to drop the
fallback.

This avoids all the topology scanning which is excessive and also might
issue an 'id command' via the nuse sysfs entry. So let's not do it.

Signed-off-by: Daniel Wagner <[email protected]>

nvme.c

@@ -190,7 +190,7 @@ static const char space[51] = {[0 ... 49] = ' ', '\0'};
 static char *output_format_val = "normal";
 int verbose_level;
 
-static void *mmap_registers(nvme_root_t r, struct nvme_dev *dev);
+static void *mmap_registers(struct nvme_dev *dev);
 
 const char *nvme_strerror(int errnum)
 {
@@ -984,7 +984,7 @@ static int get_effects_log(int argc, char **argv, struct command *cmd, struct pl
 		__u64 cap;
 
 		r = nvme_scan(NULL);
-		bar = mmap_registers(r, dev);
+		bar = mmap_registers(dev);
 		nvme_free_tree(r);
 
 		if (bar) {
@@ -5249,31 +5249,13 @@ static int nvme_get_properties(int fd, void **pbar)
 	return err;
 }
 
-static void *mmap_registers(nvme_root_t r, struct nvme_dev *dev)
+static void *mmap_registers(struct nvme_dev *dev)
 {
-	nvme_ctrl_t c = NULL;
-	nvme_ns_t n = NULL;
-
 	char path[512];
 	void *membase;
 	int fd;
 
-	c = nvme_scan_ctrl(r, dev->name);
-	if (c) {
-		snprintf(path, sizeof(path), "%s/device/resource0",
-			nvme_ctrl_get_sysfs_dir(c));
-		nvme_free_ctrl(c);
-	} else {
-		n = nvme_scan_namespace(dev->name);
-		if (!n) {
-			nvme_show_error("Unable to find %s", dev->name);
-			return NULL;
-		}
-		snprintf(path, sizeof(path), "%s/device/device/resource0",
-			 nvme_ns_get_sysfs_dir(n));
-		nvme_free_ns(n);
-	}
-
+	sprintf(path, "/sys/class/nvme/%s/device/resource0", dev->name);
 	fd = open(path, O_RDONLY);
 	if (fd < 0) {
 		if (log_level >= LOG_DEBUG)
@@ -5305,7 +5287,6 @@ static int show_registers(int argc, char **argv, struct command *cmd, struct plu
 	_cleanup_nvme_dev_ struct nvme_dev *dev = NULL;
 	enum nvme_print_flags flags;
 	bool fabrics = false;
-	nvme_root_t r;
 	void *bar;
 	int err;
 
@@ -5324,21 +5305,20 @@ static int show_registers(int argc, char **argv, struct command *cmd, struct plu
 	if (err)
 		return err;
 
-	r = nvme_scan(NULL);
 	err = validate_output_format(output_format_val, &flags);
 	if (err < 0) {
 		nvme_show_error("Invalid output format");
-		goto free_tree;
+		return err;
 	}
 
 	if (cfg.human_readable)
 		flags |= VERBOSE;
 
-	bar = mmap_registers(r, dev);
+	bar = mmap_registers(dev);
 	if (!bar) {
 		err = nvme_get_properties(dev_fd(dev), &bar);
 		if (err)
-			goto free_tree;
+			return err;
 		fabrics = true;
 	}
 
@@ -5347,9 +5327,8 @@ static int show_registers(int argc, char **argv, struct command *cmd, struct plu
 		free(bar);
 	else
 		munmap(bar, getpagesize());
-free_tree:
-	nvme_free_tree(r);
-	return err;
+
+	return 0;
 }
 
 static int get_property(int argc, char **argv, struct command *cmd, struct plugin *plugin)