Messages in this thread | | | Date | Mon, 27 Apr 2015 15:41:33 +1000 | From | NeilBrown <> | Subject | Re: [PATCH 3/3] btrfs: set FS_SUPPORTS_SEEK_HOLE flag. |
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On Mon, 20 Apr 2015 02:48:55 -0700 Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, Apr 20, 2015 at 10:46:49AM +0100, David Howells wrote: > > NeilBrown <neilb@suse.de> wrote: > > > > > Missing patch 2 of the 3-patch series? > > > > Yes. :-) > > > > Do ext4 and xfs support this, do you know? > > Yes. As do f2fs, ocfs2, gfs2, ceph and NFSv4.2
Are you sure about NFSv4.2?
I see that it *can* report holes, but is there any guarantee that if you create a new file and write only the 5th block, then READ_PLUS will reliably report that the first 4 block are holes??
Because if it doesn't guarantee that, then NFSv4.2 doesn't fit the with the others where SEEK_HOLE reliable reports holes. On the other hand if NFSv4.2 *does* guarantee that then the current READ_PLUS server patches are broken because they just use vfs_llseek and assume that trust what it says.
It would be really nice if SEEK_{DATA,HOLE} either reported holes reliably or returned ENXIO, but I guess there was a goo reason not to do that.
Thanks, NeilBrown [unhandled content-type:application/pgp-signature] | |