Lots of new tickets in tracker related to forward scrub, this is a
handly list (mainly for Greg and myself) that maps to the notes from our
design discussion. They're all under the 'fsck' category in tracker.
John
Tagging
prerequisite:
- forward scrub (traverse tree, at least)
#12255
- create "scrub header" or "scrub map" in MDLog, like subtreemap, make
scrub startup wait until this is written before going ahead
#12257
- add recovery of scrub header during MDS replay, and re-start
any scrubs that were ongoing
#12258
- add tagged-scrub command taking <path> <tag>
#12273
- actually apply the tag during the RADOS op for reading something
#12274
- start the process from all subtree roots on all MDSs, and skip
non-auth regions
#12275
- block migration during tagging scrub
OR
- when migrating, look up to parent subtree and send along info about
the scrub if we haven't been scrubbed in this tag yet
- handle MDS rank shutdown vs. ongoing scrub
Backtrace handling
#12277
- during backward scrub, tag our parent with the most recent
backtrace seen, even if we already created it with a less
recent backtrace (set_if_greater on a backtrace xattr) as
a hint to a subsequent forward scrub step
(ready for this now)
#12278
- during forward scrub, look at these hints, and move folders
around if we have more recent linkage information from the backtrace
(maybe wait to do this later, it's a corner)
Backward scrub online
#12279
- Add hooks to MDS to enable backward scrub to lookup_ino and work out
if an "orphaned ino" is actually orphaned or just more recently
created than the last scrub.
- Add hooks to MDS to enable injection to be done online (i.e. inject
linkage RPC)
#12280
- Use hooks from backward scrub in a new mode that is readonly on the
RADOS pools, and mediates all writes through running MDS.
Handling purged strays:
#12281
* StrayManager needs to respect PIN_SCRUBQUEUE (remove it from the scrub
stack before purging it) and the Locker locks that scrubstack uses (don't
purge it until the ongoing scrub RADOS ops are done)
(added a note to #11950)
* if/when we add purgequeue, #11950, backward scrub will also need to
interrogate that to determine non-orphan-ness of an inode, or enforce
that it gets flushed before doing anything.
#11859 - DamageTable
Status & scheduling
#12282
- List/progress/abort/pause commands for ongoing scrub
#12283
- Time of day scheduling for scrub
#12284
- Deprioritise/pause scrub on highly loaded systems (loaded MDS,
loaded RADOS)
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