On Monday June 26, neilb@xxxxxxx wrote:
> On Sunday June 25, es186@xxxxxxxxxx wrote:
> > Hi!
> >
> > There's a bug in Kernel 2.6.17 and / or mdadm which prevents (re)adding
> > a disk to a degraded RAID5-Array.
>
> Thank you for the detailed report.
> The bug is in the md driver in the kernel (not in mdadm), and only
> affects version-1 superblocks. Debian recently changed the default
> (in /etc/mdadm.conf) to use version-1 superblocks which I thought
> would be OK (I've some testing) but obviously I missed something. :-(
>
> If you remove the "metadata=1" (or whatever it is) from
> /etc/mdadm/mdadm.conf and then create the array, it will be created
> with a version-0.90 superblock has had more testing.
>
> Alternately you can apply the following patch to the kernel and
> version-1 superblocks should work better.
And as a third alternate, you can apply this patch to mdadm-2.5.1
It will work-around the kernel bug.
NeilBrown
diff .prev/Manage.c ./Manage.c
--- .prev/Manage.c 2006-06-20 10:01:17.000000000 +1000
+++ ./Manage.c 2006-06-26 11:46:56.000000000 +1000
@@ -271,8 +271,14 @@ int Manage_subdevs(char *devname, int fd
* If so, we can simply re-add it.
*/
st->ss->uuid_from_super(duuid, dsuper);
-
- if (osuper) {
+
+ /* re-add doesn't work for version-1 superblocks
+ * before 2.6.18 :-(
+ */
+ if (array.major_version == 1 &&
+ get_linux_version() <= 2006018)
+ ;
+ else if (osuper) {
st->ss->uuid_from_super(ouuid, osuper);
if (memcmp(duuid, ouuid, sizeof(ouuid))==0) {
/* look close enough for now. Kernel
@@ -295,7 +301,10 @@ int Manage_subdevs(char *devname, int fd
}
}
}
- for (j=0; j< st->max_devs; j++) {
+ /* due to a bug in 2.6.17 and earlier, we start
+ * looking from raid_disks, not 0
+ */
+ for (j = array.raid_disks ; j< st->max_devs; j++) {
disc.number = j;
if (ioctl(fd, GET_DISK_INFO, &disc))
break;
diff .prev/super1.c ./super1.c
--- .prev/super1.c 2006-06-20 10:01:46.000000000 +1000
+++ ./super1.c 2006-06-26 11:47:12.000000000 +1000
@@ -277,6 +277,18 @@ static void examine_super1(void *sbv, ch
default: break;
}
printf("\n");
+ printf(" Array Slot : %d (", __le32_to_cpu(sb->dev_number));
+ for (i= __le32_to_cpu(sb->max_dev); i> 0 ; i--)
+ if (__le16_to_cpu(sb->dev_roles[i-1]) != 0xffff)
+ break;
+ for (d=0; d < i; d++) {
+ int role = __le16_to_cpu(sb->dev_roles[d]);
+ if (d) printf(", ");
+ if (role == 0xffff) printf("empty");
+ else if(role == 0xfffe) printf("failed");
+ else printf("%d", role);
+ }
+ printf(")\n");
printf(" Array State : ");
for (d=0; d<__le32_to_cpu(sb->raid_disks); d++) {
int cnt = 0;
@@ -767,7 +779,8 @@ static int write_init_super1(struct supe
if (memcmp(sb->set_uuid, refsb->set_uuid, 16)==0) {
/* same array, so preserve events and dev_number */
sb->events = refsb->events;
- sb->dev_number = refsb->dev_number;
+ if (get_linux_version() >= 2006018)
+ sb->dev_number = refsb->dev_number;
}
free(refsb);
}
-
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