Re: [PATCH v4 1/5] generic/392: Add copy to new file test

[Eryu Guan <eguan@redhat.com>]

On Mon, Dec 19, 2016 at 02:34:47PM -0800, Darrick J. Wong wrote:
> > 
> > And seems copy_range -l option doesn't work well with xfs reflink
> > enabled? I saw many EINVALs when testing reflink enabled xfs, all these
> > 5 tests failed. Kernel bug or xfs_io bug or we just want to _notrun on
> > reflink xfs?
> 
> Ugggggggghhhhhhhhh...
> 
> Prior to hch's vfs patch reorganizing vfs_copy_file_range to try clone first,
> this happened[1]:
> 
> ret = -EOPNOTSUPP;
> if (file_out->f_op->copy_file_range)
> 	ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out,
> 					      pos_out, len, flags);
> if (ret == -EOPNOTSUPP)
> 	ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> 			len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> 
> Note that copy_file_range pointed to XFS's clone_range implementation,
> so if you pass in an offset/length that aren't block aligned, the clone
> code returns EINVAL and ... we pass that out to userspace instead of
> falling back.
> 
> Now it does this[2]:
> 
> if (file_in->f_op->clone_file_range) {
> 	ret = file_in->f_op->clone_file_range(file_in, pos_in,
> 			file_out, pos_out, len);
> 	if (ret == 0) {
> 		ret = len;
> 		goto done;
> 	}
> }
> 
> if (file_out->f_op->copy_file_range) {
> 	ret = file_out->f_op->copy_file_range(file_in, pos_in, file_out,
> 					      pos_out, len, flags);
> 	if (ret != -EOPNOTSUPP)
> 		goto done;
> }
> 
> ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> 		len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> 
> XFS removed the copy_file_range pointer, so therefore we'll try to
> reflink the range and if that doesn't succeed we'll fall back to
> whatever do_splice_direct does.  All those EINVALs should go away
> shortly, at least on reflink-XFS.

Good to know, thanks for the explanation!

Eryu

> 
> --D
> 
> [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/read_write.c?id=ffecee4f2442bb8cb6b34c3335fef4eb50c22fdd#n1545
> [2] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/read_write.c#n1543
> 
> > 
> > Thanks,
> > Eryu
> > --
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