[mythtv-commits] Ticket #2242: Recordings not being deleted fast enough

[MythTV]

#2242: Recordings not being deleted fast enough
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 Reporter:  Martin Ebourne <martin at zepler.org>  |        Owner:  ijr     
     Type:  patch                               |       Status:  reopened
 Priority:  minor                               |    Milestone:          
Component:  mythtv                              |      Version:  head    
 Severity:  medium                              |   Resolution:          
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Changes (by sphery <mtdean at thirdcontact.com>):

  * type:  defect => patch

Comment:

 I was working on this at the same time as Boleslaw and had come up with a
 similar patch, but with a couple of changes.  First, using size_t for
 fsize is unsafe as it will overflow (the overflow happened to create a
 value that was "close enough" to the right value on some systems--
 including the ones on which it was tested), so we need to use off_t.
 Also, the file size we compute is only an estimate (that can be off by a
 lot), so if we decrement the estimate for the initial truncation, it could
 end up being a much larger truncation than desired.

 In my patch, I truncate the file first to the estimated filesize (the file
 is almost definitely not written in the minimum number of blocks possible,
 so the estimate is low).  For example, on a 5.5GiB recording of mine, the
 estimated filesize is 5.5MiB smaller than the size on disk.  Therefore, if
 we don't truncate to the estimate first, the initial truncate would be
 ~9.5MiB instead of the 4MiB/500ms target.  There are obviously several
 other ways of achieving the goal of truncating to the estimated file size
 first, but the approach I used seemed least intrusive to the existing
 code.

 Note that we cannot use st_blocks*512 to determine the size on disk,
 either, as the units of st_blocks is actually undefined.  Only some
 implementations use units of 512bytes (
 http://www.opengroup.org/onlinepubs/000095399/basedefs/sys/stat.h.html ).
 Therefore, an estimate (like Boleslaw's or mine--same idea, just different
 math, but the same result) is probably best.

 Thanks to Anduin for pointing out the blatantly obvious issue that I was
 missing
  while he was helping me with the patch.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/2242#comment:3>
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