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Re: [Bug-tar] Detection of sparse files is broken on btrfs
From: |
Joerg Schilling |
Subject: |
Re: [Bug-tar] Detection of sparse files is broken on btrfs |
Date: |
Thu, 18 Jan 2018 11:25:52 +0100 |
User-agent: |
Heirloom mailx 12.5 7/5/10 |
Andreas Dilger <address@hidden> wrote:
> Given that calling SEEK_HOLE is also going to have some cost, my suggestion
> would be to ignore st_blocks completely for small files (size < 64KB) and
> just read the file in this case, since the overhead of reading will probably
> be about the same as checking if any blocks are allocated. If no blocks are
> allocated, then the read will not do any disk IO, and if there are blocks
> allocated they would have needed to be read from disk anyway and SEEK_HOLE
> would be pure overhead.
If you propose to ignore st_blocks completely for small files that are on
historic (unmaintained) filesystems without SEEK_HOLE support, this is what
star does since years ;-)
> To catch larger files that have been written to cache but haven't flushed
> data to disk yet, it might still make sense to use SEEK_HOLE on larger files
> with st_blocks == 0, especially if they have a recent mtime.
Using mtime does not look like a good idea in this context.
Jörg
--
EMail:address@hidden (home) Jörg Schilling D-13353 Berlin
address@hidden (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.org/private/ http://sf.net/projects/schilytools/files/'
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, (continued)
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/08
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/08
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/08
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/09
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Tim Kientzle, 2018/01/09
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/09
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/10
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Andreas Dilger, 2018/01/17
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Tim Kientzle, 2018/01/17
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Andreas Dilger, 2018/01/18
- Re: [Bug-tar] Detection of sparse files is broken on btrfs,
Joerg Schilling <=
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/09
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/10
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/17
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Ralph Corderoy, 2018/01/17
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Andreas Dilger, 2018/01/17
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/18
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Paul Eggert, 2018/01/18
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/19
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Andreas Dilger, 2018/01/19
- Re: [Bug-tar] Detection of sparse files is broken on btrfs, Joerg Schilling, 2018/01/22