Re: Potential mdadm 2.6.7 bug: Cannot grow linear arrays with superblock v1.0, 1.1, or 1.2

[thomas62186218@xxxxxxx]

Hi Neil,

Thank you for the reply and the patch. I patched 2.6.7 (had to tweak 
the patch a little), but this patch seems to have done the trick. I can 
now resize linear arrays of different sizes even with superblock 1.0.

Was this patch already out there? Or is this a new one? If new, will 
this be committed in?

Thanks again!
-Thomas


-----Original Message-----
From: Neil Brown <neilb@xxxxxxx>
To: thomas62186218@xxxxxxx
Cc: linux-raid@xxxxxxxxxxxxxxx
Sent: Tue, 14 Oct 2008 8:32 pm
Subject: Re: Potential mdadm 2.6.7 bug: Cannot grow linear arrays with 
superblock v1.0, 1.1, or 1.2










On Tuesday October 14, thomas62186218@xxxxxxx wrote:
> Hi all,
>
> I have come across what is a potential bug in mdadm 2.6.7. (unless I 
am
> missing something)
>
> Environment:
> Ubuntu Linux 8.0.4 64-bit (Hardy)
> Intel dual socket quad-core server with 16GB RAM
> 10 SATA II 500GB hard drives
> mdadm v2.6.7
>
> Test 1: Attempt to grow linear md device with v1.0 superblock with
> additional hard drive. Failed.
>
> root@localhost:/usr/local/apache2/htdocs# mdadm --grow /dev/md6 --add
> /dev/sdd1
> mdadm: internal error - sb_offset is wrong
> Aborted

Hm, that's bad.
I've tested growing linear devices with 1.0 superblocks and it works.
But I only tested the case where the new device is exactly the same
size as the other devices in the array.  I'm guess this isn't the case
for you.

Are you able to test with the patch below applied?

Thanks.
> Also, any plans on enabling "reshaping" or growth for RAID 0 and RAID
> 10 md's?

Lots of plans.  Not so much time.

NeilBrown


diff --git a/super1.c b/super1.c
index bec0c5e..62a3ab9 100644
--- a/super1.c
+++ b/super1.c
@@ -599,7 +599,7 @@ static int update_super1(struct supertype *st, 
struct mdinfo
*info,
   }
   if (strcmp(update, "linear-grow-new") == 0) {
       int i;
-       int rfd;
+       int rfd, fd;
       int max = __le32_to_cpu(sb->max_dev);

       for (i=0 ; i < max ; i++)
@@ -620,6 +620,25 @@ static int update_super1(struct supertype *st, 
struct
mdinfo *info,

       sb->dev_roles[i] =
           __cpu_to_le16(info->disk.raid_disk);
+
+       fd = open(devname, O_RDONLY);
+       if (fd >= 0) {
+           unsigned long long ds;
+           get_dev_size(fd, devname, &ds);
+           close(fd);
+           ds >>= 9;
+           if (__le64_to_cpu(sb->super_offset) <
+               __le64_to_cpu(sb->data_offset)) {
+               sb->data_size = __cpu_to_le64(
+                   ds - __le64_to_cpu(sb->data_offset));
+           } else {
+               ds -= 8*2;
+               ds &= ~(unsigned long long)(4*2-1);
+               sb->super_offset = __cpu_to_le64(ds);
+               sb->data_size = __cpu_to_le64(
+                   ds - __le64_to_cpu(sb->data_offset));
+           }
+       }
   }
   if (strcmp(update, "linear-grow-update") == 0) {
       sb->raid_disks = __cpu_to_le32(info->array.raid_disks);
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