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. BTW, IIRC, there were already LTP tests and man page fixes posted for the copt_file_range() behavior change. Thanks, Amir.
