New knob for ignoring readonly fss in 340.noid and 310.locate?

[Andre Albsmeier]

I have noticed that "periodic weekly" started to consume more
and more time on some of my machines. The reason is the amount
of snapshots that are used at my site, e.g., on one machine I
have two file systems:

/dev/ccd0           544G    266G    235G    53%    /people
/dev/ccd1           556G    372G    140G    73%    /share

which hold these snapshots:

/dev/md12           544G    241G    259G    48%    /people/.snap/@GMT-2011.04.26-03.15.04
/dev/md13           544G    241G    259G    48%    /people/.snap/@GMT-2011.04.27-03.15.04
/dev/md14           544G    236G    264G    47%    /people/.snap/@GMT-2011.04.28-03.15.03
/dev/md15           544G    240G    260G    48%    /people/.snap/@GMT-2011.04.29-03.15.03
/dev/md16           544G    238G    263G    47%    /people/.snap/@GMT-2011.04.30-03.15.04
/dev/md17           544G    241G    259G    48%    /people/.snap/@GMT-2011.04.23-03.15.01
/dev/md18           544G    239G    261G    48%    /people/.snap/@GMT-2011.04.16-03.15.01
/dev/md22           556G    344G    167G    67%    /share/.snap/@GMT-2011.04.26-03.28.32
/dev/md23           556G    344G    167G    67%    /share/.snap/@GMT-2011.04.27-03.28.26
/dev/md24           556G    344G    167G    67%    /share/.snap/@GMT-2011.04.28-03.28.42
/dev/md25           556G    341G    170G    67%    /share/.snap/@GMT-2011.04.29-03.29.12
/dev/md26           556G    343G    168G    67%    /share/.snap/@GMT-2011.04.30-03.26.48
/dev/md27           556G    344G    167G    67%    /share/.snap/@GMT-2011.04.23-03.27.33
/dev/md28           556G    341G    170G    67%    /share/.snap/@GMT-2011.04.16-03.27.39
/dev/md29           556G    337G    175G    66%    /share/.snap/@GMT-2011.04.09-03.22.01

For our purpose, the weekly maintainance is not desired on
the snapshots. Of course, it might be possible to modify the
behaviour of

310.locate
340.noid

by tweaking /etc/locate.rc or weekly_noid_dirs which would
be rather annoying since this would have to be done on
every machine individually due to their different filesystem
names (and pretty sure will be forgotten when fss are added
or removed).

One condition that would match everything (at least in my case)
would be to restrict the work of 310.locate and 340.noid on
filesystems which are not mounted readonly.

So what would people think about a knob that restricts at least
these two scripts (maybe there are more candidates) from letting
find(1) decend into rdonly filesystems? Of course, this knob would
default to "off" and could be set in periodic.conf and/or locate.rc
individually...

Thanks,

	-Andre