A specific restriper thread is created for each MDT, it does three
tasks in a loop:
1. If there is directory whose total sub-files exceeds threshold
   (50000 by default, can be changed "lctl set_param
   mdt.*.dir_split_count=N"), split this directory by adding new
   stripes (4 stripes by default, which can be adjusted by
   "lctl set_param mdt.*.dir_split_delta=N").
2. If a directory stripe LMV is marked 'MIGRATION', migrate sub file
   from current offset, and update offset to next file.
3. If a directory master LMV is marked 'RESTRIPING', check whether
   all stripe LMV 'MIGRATION' flag is cleared, if so, clear
   'RESTRIPING' flag and update directory LMV.

In last patch, the first part of manual directory stripe is
implemented, and in this patch, sub file migrations and dir layout
update is done. Directory auto-split is done in similar way, except
that the first step is done by this thread too.

Directory auto-split can be enabled/disabled by "lctl set_param
mdt.*.enable_dir_auto_split=[0|1]", it's turned on by default.

Auto split is triggered at the end of getattr(): since now the attr
contains dirent count, check whether it exceeds threshold, if so,
add this directory into mdr_auto_split list and wake up the dir
restriper thread.

Restripe migration is also triggered in getattr(): if the object is
directory stripe, and LMV 'MIGRATION' flag set, add this object into
mdr_restripe_migrate list and wake up the dir restriper thread.

Directory layout update is similar: if current directory is striped,
and LNV 'RESTRIPING' flag is set, add this directory into
mdr_restripe_update list and wake up restriper thread.

By default restripe migrate dirent only, and leave inode unchanged, it
can be adjusted by "lctl set_param mdt.*.dir_restripe_nsonly=[0|1]".

Currently DoM file inode migration is not supported, migrate dirent
only for such files to avoid leaving dir migration/restripe
unfinished.

Add sanity.sh 230o, 230p and 230q, adjust 230j since DoM files migrate
dirent.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I8c83b42e4acbaab067d0092d0b232de37f956588
Reviewed-on: https://review.whamcloud.com/37284


Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>