On Fri, May 20, 2022 at 7:39 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > On Fri, May 20, 2022 at 6:56 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > On Thu, May 19, 2022 at 04:53:15PM +0300, Amir Goldstein wrote: > > > > > Luis gave up on it, because no maintainer stepped up to take > > > the patch, but I think that is the right way to go. > > > > > > Maybe this bug report can raise awareness to that old patch. > > > > > > Al, could you have a look? > > > > IIRC, you had objections to that variant back then... > > Right. But not about the "main" patch. > The patch had an "also" part: > > The short-circuit code for the case where the copy length is zero has also > been dropped from the VFS code. This is because a zero size copy between > two files shall provide a clear indication on whether or not the > filesystem supports non-zero copies. > > - if (len == 0) > - return 0; > - > > Which would have been a regression for nfs client, because > nfs protocol treats length 0 from ->copy_file_range() as "copy everything": > > https://lore.kernel.org/linux-fsdevel/CAOQ4uxgwcNwWEqYKBg3fMHD3aXOsYUmPeexBe9EVP9Nb53b-Hw@xxxxxxxxxxxxxx/ > > This api impedance should be fixed in the nfs client, but I'm > not sure if that was already done. > > I will test and re-post Luis' patch without removing the short-circuit > unless Luis gets to it first. > Urgh! That old patch passes the fstests -g copy_range group on nfs, but fails almost all of them on xfs/btrfs. The reason is that when we allow to perform copy_range with remap_file_range() it fails for sizes smaller than block size and returning short read of 0 from copy_range is not an option. So what I am going to do is to keep the basic restriction in this patch of: "copy_range allowed for fs that implement either ->copy_file_range() or ->remap_file_range() (for same sb copy)" But will change the logic of: "try clone and then copy then fail" to: - try ->copy_file_range() - try ->remap_file_range() - fall back to kernel copy Patch coming shortly. Thanks, Amir.
