Manage: be more careful about --add attempts.

If an --add is requested and a re-add looks promising but fails or
cannot possibly succeed, then don't try the add.  This avoids
inadvertently turning devices into spares when an array is failed but
the devices seem to actually work.

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

Manage.c

@@ -383,6 +383,7 @@ int Manage_subdevs(char *devname, int fd,
 		char *dnprintable = dv->devname;
 		char *add_dev = dv->devname;
 		int err;
+		int re_add_failed = 0;
 
 		next = dv->next;
 		jnext = 0;
@@ -662,14 +663,20 @@ int Manage_subdevs(char *devname, int fd,
 				    get_linux_version() <= 2006018)
 					;
 				else if (st->sb) {
+					struct mdinfo mdi;
+					st->ss->getinfo_super(st, &mdi);
 					st->ss->uuid_from_super(st, ouuid);
-					if (memcmp(duuid, ouuid, sizeof(ouuid))==0) {
-						/* looks close enough for now.  Kernel
-						 * will worry about whether a bitmap
-						 * based reconstruction is possible.
+					if ((mdi.disk.state & (1<<MD_DISK_ACTIVE)) &&
+					    !(mdi.disk.state & (1<<MD_DISK_FAULTY)) &&
+					    memcmp(duuid, ouuid, sizeof(ouuid))==0) {
+						/* look like it is worth a try.  Need to
+						 * make sure kernel will accept it though.
 						 */
-						struct mdinfo mdi;
-						st->ss->getinfo_super(st, &mdi);
+						disc.number = mdi.disk.number;
+						if (ioctl(fd, GET_DISK_INFO, &disc) != 0
+						    || disc.major != 0 || disc.minor != 0
+						    || !enough_fd(fd))
+							goto skip_re_add;
 						disc.major = major(stb.st_rdev);
 						disc.minor = minor(stb.st_rdev);
 						disc.number = mdi.disk.number;
@@ -684,8 +691,7 @@ int Manage_subdevs(char *devname, int fd,
 						tfd = -1;
 						/* don't even try if disk is marked as faulty */
 						errno = 0;
-						if ((disc.state & 1) == 0 &&
-						    ioctl(fd, ADD_NEW_DISK, &disc) == 0) {
+						if (ioctl(fd, ADD_NEW_DISK, &disc) == 0) {
 							if (verbose >= 0)
 								fprintf(stderr, Name ": re-added %s\n", add_dev);
 							count++;
@@ -698,7 +704,8 @@ int Manage_subdevs(char *devname, int fd,
 								continue;
 							return 1;
 						}
-						/* fall back on normal-add */
+					skip_re_add:
+						re_add_failed = 1;
 					}
 				}
 				if (add_dev != dv->devname) {
@@ -720,6 +727,17 @@ int Manage_subdevs(char *devname, int fd,
 						dv->devname, devname);
 					return 1;
 				}
+				if (re_add_failed) {
+					fprintf(stderr, Name ": %s reports being an active member for %s, but a --re-add fails.\n",
+						dv->devname, devname);
+					fprintf(stderr, Name ": not performing --add as that would convert %s in to a spare.\n",
+						dv->devname);
+					fprintf(stderr, Name ": To make this a spare, use \"mdadm --zero-superblock %s\" first.\n",	
+						dv->devname);
+					if (tfd >= 0)
+						close(tfd);
+					return 1;
+				}
 			} else {
 				/* non-persistent. Must ensure that new drive
 				 * is at least array.size big.

mdadm.h

@@ -986,6 +986,7 @@ extern char *fname_from_uuid(struct supertype *st,
 extern unsigned long calc_csum(void *super, int bytes);
 extern int enough(int level, int raid_disks, int layout, int clean,
 		   char *avail, int avail_disks);
+extern int enough_fd(int fd);
 extern int ask(char *mesg);
 extern unsigned long long get_component_size(int fd);
 extern void remove_partitions(int fd);

tests/01r1fail

@@ -20,6 +20,7 @@ mdadm $md0 --remove $dev2 $dev1
 check nosync
 check state UUU_
 
+mdadm --zero-superblock $dev2
 mdadm $md0 -a $dev2 
 check recovery
 check wait

util.c

@@ -320,6 +320,36 @@ int enough(int level, int raid_disks, int layout, int clean,
 	}
 }
 
+int enough_fd(int fd)
+{
+	struct mdu_array_info_s array;
+	struct mdu_disk_info_s disk;
+	int avail_disks = 0;
+	int i;
+	char *avail;
+
+	if (ioctl(fd, GET_ARRAY_INFO, &array) != 0 ||
+	    array.raid_disks <= 0)
+		return 0;
+	avail = calloc(array.raid_disks, 1);
+	for (i=0; i<array.raid_disks + array.nr_disks; i++) {
+		disk.number = i;
+		if (ioctl(fd, GET_DISK_INFO, &disk) != 0)
+			continue;
+		if (! (disk.state & (1<<MD_DISK_SYNC)))
+			continue;
+		if (disk.raid_disk < 0 || disk.raid_disk >= array.raid_disks)
+			continue;
+		avail_disks++;
+		avail[disk.raid_disk] = 1;
+	}
+	/* This is used on an active array, so assume it is clean */
+	return enough(array.level, array.raid_disks, array.layout,
+		      1,
+		      avail, avail_disks);
+}
+
+
 const int uuid_match_any[4] = { ~0, ~0, ~0, ~0 };
 int same_uuid(int a[4], int b[4], int swapuuid)
 {