Ceph » CephFS

Okay, this patch is required to fix the loss of directory layouts issue (#1435) in Bobtail, so I rebased it on that branch, currently in bobtail-layouts.
I then cherry-picked it forward to next, in greg-next.

Yes, this is backwards from normal, but unfortunately the change to using in-inode layouts requires a struct_v change, and those numbers conflict with the mds encoding changes that went into master (and next) recently, so the best solution I or Sage came up with was to let bobtail take the next numbers, and then to pretend like the first revision of the MDS encoding struct_v changes didn't happen (because they were never released).

Needless to say, this all needs a very careful review. Perhaps from more than one person.

Okay, I tested this according to the procedure described below (I wanted to write some scripts, but the non-manual portions of it were only a few lines at a time right now, meh).

It worked, so I've pushed to bobtail (commit:36ed407e0f939a9bca57c3ffc0ee5608d50ab7ed) and next (commit:6bd8781dda524f04bb56bcdac5aa5b13ba61b07d).

Run with bobtail
Set mds_log_max_segments and mds_log_max_expiring to 1, mds_cache_size to 100, then (re)start MDSSet layout on root inode, on child directory "idle_test/dir_with_layout", and on child directory "active_test" (all differently)
drop caches
run pjd test inside of "active_test"
check MDS log to see that idle_test/dir_with_layout was removed from cache, and see that MDS log has expired early segments
upgrade MDS to bobtail-layouts, restart
verify it runs and layouts are present on active_test, missing on idle_test/dir_with_layout
re-apply layouts, run pjd in active_tests
upgrade MDS to greg-next, restart
verify it runs and layouts are correct
repeat with a direct upgrade from bobtail to greg-next and make sure it runs