Some time in early December, disk I/O broke. The EC2 image built from r291495
works fine; the EC2 image built from r292413 is broken.
Symptoms:
1. growfs reports "superblock not recognized"
2. fsck reports lots of "UNKNOWN FILE TYPE"s and after a few seconds provokes
"panic: XEN disk driver
I'm rather suspicious of r292255 here -- royger, hps, kib, can any of you
comment on whether it would be responsible for making non-page-aligned I/Os
no longer get split on page boundaries? The commit message is suggestive,
but I don't know the code very well.
(If I don't hear back I'll
