Incremental: improve support for "DEVICE" based restriction in mdadm.conf

--incremental currently fails if the device name passed does not
textually match the names permitted by the DEVICE line in mdadm.conf.
This is problematic when "mdadm -I" is run by udev as the name given
can be a temp name.

This patch makes two improvements:
1/ We generate a list of all existing devices that match the names
  in mdadm.conf, and allow rdev based matching
2/ We allows extra aliases to be provided on the command line, and
  perform textual matching on those.  This is particularly suitable
  for udev usages as ${DEVLINKS} can be provided even though the links
  make not yet be created.

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

Incremental.c

@@ -46,7 +46,7 @@ static int try_spare(char *devname, int *dfdp, struct dev_policy *pol,
 static int Incremental_container(struct supertype *st, char *devname,
 				 struct context *c, char *only);
 
-int Incremental(char *devname, struct context *c,
+int Incremental(struct mddev_dev *devlist, struct context *c,
 		struct supertype *st)
 {
 	/* Add this device to an array, creating the array if necessary
@@ -103,6 +103,7 @@ int Incremental(char *devname, struct context *c,
 	struct dev_policy *policy = NULL;
 	struct map_ent target_array;
 	int have_target;
+	char *devname = devlist->devname;
 
 	struct createinfo *ci = conf_get_create_info();
 
@@ -153,7 +154,20 @@ int Incremental(char *devname, struct context *c,
 
 	/* 1/ Check if device is permitted by mdadm.conf */
 
-	if (!conf_test_dev(devname)) {
+	for (;devlist; devlist = devlist->next)
+		if (conf_test_dev(devlist->devname))
+			break;
+	if (!devlist) {
+		devlist = conf_get_devs();
+		for (;devlist; devlist = devlist->next) {
+			struct stat st2;
+			if (stat(devlist->devname, &st2) == 0 &&
+			    (st2.st_mode & S_IFMT) == S_IFBLK &&
+			    st2.st_rdev == stb.st_rdev)
+				break;
+		}
+	}
+	if (!devlist) {
 		if (c->verbose >= 0)
 			pr_err("%s not permitted by mdadm.conf.\n",
 			       devname);

mdadm.8.in

@@ -2676,6 +2676,7 @@ Usage:
 .RB [ \-\-run ]
 .RB [ \-\-quiet ]
 .I component-device
+.RI [ optional-aliases-for-device ]
 .HP 12
 Usage:
 .B mdadm \-\-incremental \-\-fail
@@ -2730,16 +2731,23 @@ That is, is it listed in a
 .B DEVICES
 line in that file.  If
 .B DEVICES
-is absent then the default it to allow any device.  Similar if
+is absent then the default it to allow any device.  Similarly if
 .B DEVICES
 contains the special word
 .B partitions
 then any device is allowed.  Otherwise the device name given to
-.I mdadm
+.IR mdadm ,
+or one of the aliases given, or an alias found in the filesystem,
 must match one of the names or patterns in a
 .B DEVICES
 line.
 
+This is the only context where the aliases are used.  They are
+usually provided by a
+.I udev
+rules mentioning
+.BR ${DEVLINKS} .
+
 .IP +
 Does the device have a valid md superblock?  If a specific metadata
 version is requested with

mdadm.c

@@ -1553,16 +1553,16 @@ int main(int argc, char *argv[])
 			}
 			break;
 		}
-		if (devlist->next) {
-			pr_err("--incremental can only handle one device.\n");
-			rv = 1;
-			break;
-		}
-		if (devmode == 'f')
+		if (devmode == 'f') {
+			if (devlist->next) {
+				pr_err("'--incremental --fail' can only handle one device.\n");
+				rv = 1;
+				break;
+			}
 			rv = IncrementalRemove(devlist->devname, remove_path,
 					       c.verbose);
-		else
-			rv = Incremental(devlist->devname, &c, ss);
+		} else
+			rv = Incremental(devlist, &c, ss);
 		break;
 	case AUTODETECT:
 		autodetect();

mdadm.h

@@ -1235,7 +1235,7 @@ extern int Update_subarray(char *dev, char *subarray, char *update, struct mddev
 extern int Wait(char *dev);
 extern int WaitClean(char *dev, int sock, int verbose);
 
-extern int Incremental(char *devname, struct context *c,
+extern int Incremental(struct mddev_dev *devlist, struct context *c,
 		       struct supertype *st);
 extern void RebuildMap(void);
 extern int IncrementalScan(struct context *c, char *devnm);

udev-md-raid-assembly.rules

@@ -12,7 +12,7 @@ LABEL="md_inc"
 
 # remember you can limit what gets auto/incrementally assembled by
 # mdadm.conf(5)'s 'AUTO' and selectively whitelist using 'ARRAY'
-ACTION=="add", IMPORT{program}="/sbin/mdadm --incremental --export $devnode --offroot"
+ACTION=="add", IMPORT{program}="/sbin/mdadm --incremental --export $devnode --offroot ${DEVLINKS}"
 ACTION=="add", ENV{MD_STARTED}=="*unsafe*", ENV{MD_FOREIGN}=="no", ENV{SYSTEMD_WANTS}+="mdadm-last-resort@$env{MD_DEVICE}.timer"
 ACTION=="remove", ENV{ID_PATH}=="?*", RUN+="/sbin/mdadm -If $name --path $env{ID_PATH}"
 ACTION=="remove", ENV{ID_PATH}!="?*", RUN+="/sbin/mdadm -If $name"