Re: [opensuse-factory] BtrFS Usage/Complaints

9 Jul 2013


      On Sat, Jul 06, 2013 at 06:04:50PM +0200, Jan Ritzerfeld wrote:
...
Am Samstag, 6. Juli 2013, 15:55:23 schrieb Arvin Schnell:
...
On Sat, Jul 06, 2013 at 02:18:44PM +0200, Jan Ritzerfeld wrote:
...
...
...
TIMELINE_LIMIT_* does not:
TIMELINE_LIMIT_HOURLY=5 keeps the last five snapshots and not only five
hourly snapshots per day. And although I set TIMELINE_LIMIT_DAILY=5 and
the rest 0, there are still snapshots made eight days ago (five hourly
and five daily).
Could be because the cleanup algorithm only runs once a day.
[...]
Hmm, no. I manually did a "snapper cleanup timeline".
ATM, I am looking at client/cleanup.cc. And the code indeed does what I 
observed. do_cleanup_timeline fetches a full list of timeline snapshots and 
then removes the ones that should be kept. The remaining snapshots will be 
deleted:
if (num_hourly < limit_hourly && is_first_hourly(it, tmp.end(), *it))
{
    ++num_hourly;
    it = tmp.erase(it);
}
else if (num_daily < limit_daily && is_first_daily(it, tmp.end(), *it))
{
    ++num_daily;
    it = tmp.erase(it);
}
else if...
Obviously, if all snapshots are both the first hourly and the first daily, 
they will be only counted for the hourly limit. This is wrong, because you 
will get "limit_daily" additional snapshots (if there are enough left). The 
same holds true for monthly and yearly.
The correct code would be little bit more complicated:
bool keep = false;
if (num_hourly < limit_hourly && is_first_hourly(it, tmp.end(), *it))
{
    ++num_hourly;
    keep = true;
}
if (num_daily < limit_daily && is_first_daily(it, tmp.end(), *it))
{
    ++num_daily;
    keep = true;
}
if (num_monthly < limit_monthly && is_first_monthly(it, tmp.end(), *it))
{
    ++num_monthly;
    keep = true;
}
if (num_yearly < limit_yearly && is_first_yearly(it, tmp.end(), *it))
{
    ++num_yearly;
    keep = true;
}
if (keep) 
{
    it = tmp.erase(it);
}
else
{
    ++it;
}
The result of the modified code is indeed easier to understand. I
have changed snapper and also added a manpage snapper-configs(5).

Regards,
  Arvin

-- 
Arvin Schnell, <aschnell@suse.de>
Senior Software Engineer, Research & Development
SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg)
Maxfeldstraße 5
90409 Nürnberg
Germany
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