Comment 37 for bug 992424

I wondered whether ext4_mb_generate_buddy might be related to http://help.lockergnome.com/linux/ext4fs-error-ext4_mb_generate_buddy-741-group-16-8160-cluste--ftopict559576.html
so for a final experiment, I've switched off "discard" once more. That bug seemed confined to scsi_debug, but who knows?

On the other hand, another round of fsck -c -c -k found 3 more bad blocks, once again in the journal.
Note that fsck -c -c -k has got a problem: it adds the blocks to the bad block list, and promptly complains
that there are duplicate blocks in the bad block inode and in the journal. It then asks whether to clone
the multiply-allocated blocks. Unfortunately, it gives no sign how it will clone them: will the bad blocks
remain in the bad block list, with the copies going into the journal, or will the blocks remain in the journal,
with copies uselessly being placed in the bad block list. I decided it was safer to delete the journal, re-run
the check, leaving the blocks only in the bad block list, then recreate the journal, then switch discard off.

The bad blocks were as follows:

(0-2):2277409-2277411
(3-5):2277665-2277667

The pattern is easier to see in hex, I think:
22C021
22C022
22C023
22C121
22C122
22C123

Hmm. 3 in a row each time. 256 might be important in the internal geometry. *Might* be a failing drive.