[Gluster-devel] Progress on adding support for SEEK_DATA and SEEK_HOLE

[Niels de Vos]

On Mon, Jul 06, 2015 at 05:42:17AM -0300, Christopher Pereira wrote:
> On 06-07-2015 5:18, Niels de Vos wrote:
> >On Mon, Jul 06, 2015 at 02:46:52AM -0300, J. Christopher Pereira Zimmermann wrote:
> >>Hi Niels,
> >>
> >>Thanks for bouncing.
> >>
> >>I'm not sure if you are asking how to figure out the hole/data offsets from
> >>the underlying fs at once, or about the ec communication.
> >>
> >>There is probably no standard way to query the allocation information with
> >>the hole offsets at once from the fs, so lseeking from hole to hole would
> >>be the only way.
> >>
> >>I quickly checked ext4's SEEK_HOLE implementation [1] and the holes seem to
> >>be marked and sought on "ext4_map_blocks" [2].
> >>There seems to be no standard system call / data structure for getting all
> >>the hole/data offsets at once.
> >>
> >>Is lseeking hole by hole ok?
> >Thanks Christopher!
> >
> >Xavier also responded with details on how EC tracks holes. He is
> >definitely one of the few that should know ;-)
> >
> >Only volumes with EC/stripe/sharding/bd xlators are not straight
> >forward. For the less funky storage methods, lseek() can be used without
> >difficulties.
> >
> >I did put a COPR together for Fedora 22 (x86_64) with a patched kernel
> >and glusterfs packages. If you are eager to test, you can install these
> >on a disposable environment.
> >
> >   https://copr.fedoraproject.org/coprs/devos/glusterfs-SEEK_HOLE
> >   (NOT TESTED AT ALL! But it compiles...)
> >
> >Feedback welcome, but dont have too high expectations from those
> >packages.
> 
> Ok. I will give them a try and provide you feed back.
> Is it possible to generate CentOS 7 builds?

I've added them in the same COPR, building of the kernel will take a
while though. You can check progress here:

  https://copr.fedoraproject.org/coprs/devos/glusterfs-SEEK_HOLE/monitor/

Niels
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