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?
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