global-ctx: add nvme_sysfs_ctrl_path() for mockable sysfs paths

plugins/micron/micron-utils-linux.c

@@ -25,6 +25,7 @@
 #include "micron-utils.h"
 #include "nvme-print.h"
 #include "src/cleanup.h"
+#include "src/global-ctx.h"
 
 /*
  * Validates that a string is a canonical PCI address in the
@@ -74,6 +75,7 @@ static int get_pcie_bdf(struct libnvme_transport_handle *hdl,
 	char *bdf, size_t bdf_len)
 {
 	__cleanup_free char *ctrl_name = micron_get_ctrl_name(hdl);
+	__cleanup_free char *ctrl_dir = NULL;
 	char path[512];
 	char target[512];
 	ssize_t n;
@@ -84,11 +86,15 @@ static int get_pcie_bdf(struct libnvme_transport_handle *hdl,
 	if (!ctrl_name)
 		return -EINVAL;
 
+	err = nvme_sysfs_ctrl_path(ctrl_name, &ctrl_dir);
+	if (err)
+		return err;
+
 	/*
 	 * If possible, use /sys/class/nvme/<ctrl>/address (kernel >= 4.13).
 	 * On failure, fall back to using the /device symlink.
 	 */
-	snprintf(path, sizeof(path), "/sys/class/nvme/%s/address", ctrl_name);
+	snprintf(path, sizeof(path), "%s/address", ctrl_dir);
 	fd = open(path, O_RDONLY);
 	if (fd >= 0) {
 		n = read(fd, target, sizeof(target) - 1);
@@ -111,7 +117,7 @@ static int get_pcie_bdf(struct libnvme_transport_handle *hdl,
 	 * If unable to use the address file, use the last component of the
 	 * /sys/class/nvme/<ctrl>/device symlink.
 	 */
-	snprintf(path, sizeof(path), "/sys/class/nvme/%s/device", ctrl_name);
+	snprintf(path, sizeof(path), "%s/device", ctrl_dir);
 	n = readlink(path, target, sizeof(target) - 1);
 	if (n < 0) {
 		err = -errno;

src/global-ctx.c

@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
+#include <limits.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -90,6 +91,22 @@ static bool is_true(const char *val)
 		!strncasecmp(val, "enable", 6);
 }
 
+/*
+ * Mirror of libnvme's test sysfs root. libnvme keeps its own copy, set
+ * through libnvme_set_test_sysfs_dir(); this one covers the sysfs
+ * attributes nvme-cli reads by path rather than through libnvme.
+ */
+static char test_sysfs_dir[PATH_MAX];
+
+int nvme_sysfs_ctrl_path(const char *ctrl_name, char **path)
+{
+	if (asprintf(path, "%s/sys/class/nvme/%s", test_sysfs_dir,
+		     ctrl_name) < 0)
+		return -ENOMEM;
+
+	return 0;
+}
+
 /*
  * nvme_apply_option() - apply a single "key=value" pair to @ctx.
  *
@@ -121,6 +138,9 @@ static int nvme_apply_option(struct libnvme_global_ctx *ctx, const char *kv)
 		ret = libnvme_set_test_base_dir(ctx, val);
 	} else if (!strcmp(key, "test-sysfs-dir")) {
 		ret = libnvme_set_test_sysfs_dir(ctx, val);
+		if (!ret)
+			snprintf(test_sysfs_dir, sizeof(test_sysfs_dir), "%s",
+				 val);
 	} else {
 		nvme_show_error("--set-options: unknown key '%s'", key);
 		return -EINVAL;

src/global-ctx.h

@@ -31,6 +31,18 @@ int nvme_create_global_ctx_hostnqn(struct libnvme_global_ctx **ctx,
 
 int nvme_create_global_ctx(struct libnvme_global_ctx **ctx);
 
+/*
+ * nvme_sysfs_ctrl_path() - Build the sysfs directory path of a controller
+ * @ctrl_name: controller name, e.g. "nvme0"
+ * @path: output path, allocated; caller frees
+ *
+ * Prefixed by "--set-options test-sysfs-dir=" when given, so callers reading
+ * sysfs attributes directly stay consistent with libnvme under test.
+ *
+ * Return: 0 on success, -ENOMEM on allocation failure.
+ */
+int nvme_sysfs_ctrl_path(const char *ctrl_name, char **path);
+
 /*
  * parse_and_open - parses arguments and opens the NVMe device, populating @ctx, @hdl
  */

src/nvme-pci-ids-linux.c

@@ -13,6 +13,7 @@
 
 #include <libnvme.h>
 
+#include "global-ctx.h"
 #include "nvme-print.h"
 
 static int read_pci_attr(const char *dir, const char *attr, __u32 *out)
@@ -61,10 +62,7 @@ static int read_pci_attr(const char *dir, const char *attr, __u32 *out)
 int __nvme_get_sysfs_dir(__attribute__((__unused__)) struct libnvme_global_ctx *ctx,
 		const char *ctrl_name, char **sysfs_dir)
 {
-	if (asprintf(sysfs_dir, "/sys/class/nvme/%s", ctrl_name) < 0)
-		return -ENOMEM;
-
-	return 0;
+	return nvme_sysfs_ctrl_path(ctrl_name, sysfs_dir);
 }
 
 int __nvme_get_pci_ids(const char *sysfs_dir,