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. Cheers, Niels > > [1] : > https://github.com/torvalds/linux/blob/05a8256c586ab75bcd6b793737b2022a1a98cb1e/fs/ext4/file.c > [2] : > https://github.com/torvalds/linux/blob/64e22b86854227b4d13a57fa02f26472bc426812/fs/ext4/ext4.h _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://www.gluster.org/mailman/listinfo/gluster-devel
