DragonFly 2.6.2, 2.7.2 tags pushed - fixes for serious HAMMER issue

[Thomas Nikolajsen]

>The corruption can only occur if your HAMMER filesystem became full
>or nearly full sometime in the last 45 days or so with a kernel built
>sometime in the last 45 days.  To check for the corruption you need
>an unmounted or completely idle filesystem and then run (using the
>latest hammer utility):
. .
>    hammer -f <device> show | egrep '^B' | egrep -v '^BM'

I was hit, but think my FS has been under 90% full at all times.
(checked in single user, w/ r/o mount)

Any way to find out which files (history) are affected?

>If using mirror-read to copyoff remember it must be run on every PFS
>individually, and bulk mode (-B) is recommended, and make sure any
>backups are viable before smashing the original filesystem.

Why is -B recommended?
In hammer.8 -B is 'not recommended'; should this just be removed?

Any way to restore root PFS (#0) fully?
Root PFS can not be downgraded to slave, for mirror-write,
so I see no way to get history restored.

Beware of cpdup'ing root PFS; symlinks for already restored PFSs
will be overwritten.

Also remember to copy PFS config (if you use non default).
(I had to restore PFSs twice, as I did 'hammer cleanup' too early)

 -thomas