conditionally remove map_dev from find_free_devnum

map_dev can be slow so it is best to not call it when
not necessary.
The final test in "find_free_devnum" is not relevant when
udev is being used, so remove the test in that case.

Signed-off-by: NeilBrown <neilb@suse.de>

4 files changed, 23 insertions, 8 deletions

diff --git a/lib.c b/lib.c
index 1c856541..8124fa1b 100644
--- a/lib.c
+++ b/lib.c
@@ -390,3 +390,16 @@ void print_escape(char *str)
 		}
 	}
 }
+
+int use_udev(void)
+{
+	static int use = -1;
+	struct stat stb;
+
+	if (use < 0) {
+		use = ((stat("/dev/.udev", &stb) == 0
+			|| stat("/run/udev", &stb) == 0)
+		       && check_env("MDADM_NO_UDEV") == 0);
+	}
+	return use;
+}
diff --git a/mdadm.h b/mdadm.h
index 7adf7d94..be760d26 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -1217,6 +1217,7 @@ extern char *conf_line(FILE *file);
 extern char *conf_word(FILE *file, int allow_key);
 extern void print_quoted(char *str);
 extern void print_escape(char *str);
+extern int use_udev(void);
 extern int conf_name_is_free(char *name);
 extern int conf_verify_devnames(struct mddev_ident *array_list);
 extern int devname_matches(char *name, char *match);
diff --git a/mdopen.c b/mdopen.c
index 24188df6..462743c4 100644
--- a/mdopen.c
+++ b/mdopen.c
@@ -330,8 +330,7 @@ int create_mddev(char *dev, char *name, int autof, int trustworthy,
 	 * If we cannot detect udev, we need to make
 	 * devices and links ourselves.
 	 */
-	if ((stat("/dev/.udev", &stb) != 0 && stat("/run/udev", &stb) != 0) ||
-	    check_env("MDADM_NO_UDEV")) {
+	if (!use_udev()) {
 		/* Make sure 'devname' exists and 'chosen' is a symlink to it */
 		if (lstat(devname, &stb) == 0) {
 			/* Must be the correct device, else error */
diff --git a/util.c b/util.c
index 6c10365e..70ab6f12 100644
--- a/util.c
+++ b/util.c
@@ -839,7 +839,6 @@ int find_free_devnum(int use_partitions)
 	int devnum;
 	for (devnum = 127; devnum != 128;
 	     devnum = devnum ? devnum-1 : (1<<20)-1) {
-		char *dn;
 		int _devnum;
 		char nbuf[50];
 
@@ -849,11 +848,14 @@ int find_free_devnum(int use_partitions)
 		sprintf(nbuf, "%s%d", use_partitions?"mdp":"md", devnum);
 		if (!conf_name_is_free(nbuf))
 			continue;
-		/* make sure it is new to /dev too, at least as a
-		 * non-standard */
-		dn = map_dev(dev2major(_devnum), dev2minor(_devnum), 0);
-		if (dn && ! is_standard(dn, NULL))
-			continue;
+		if (!use_udev()) {
+			/* make sure it is new to /dev too, at least as a
+			 * non-standard */
+			char *dn = map_dev(dev2major(_devnum),
+					   dev2minor(_devnum), 0);
+			if (dn && ! is_standard(dn, NULL))
+				continue;
+		}
 		break;
 	}
 	if (devnum == 128)