On Sun, Oct 18, 2015 at 11:30:13AM -0700, Christoph Hellwig wrote: > Just commenting on the man page here as the comment is about sematics. > All the infrastructure in the patch looks reasonable to me, but this > is something we need to get right. > > > +.B COPY_FR_REFLINK > > +Create a lightweight "reflink", where data is not copied until > > +one of the files is modified. > > +.PP > > +The default behavior > > +.RI ( flags > > +== 0) is to perform a full data copy of the requested range. > > +.SH RETURN VALUE > > +Upon successful completion, > > +.BR copy_file_range () > > +will return the number of bytes copied between files. > > +This could be less than the length originally requested. > > As mentioned in the previous discussion I fundamentally disagree with > the way your word the flags here. > > flags = 0 gives you the data from source at dest, period. How it's > implemented is up to the file system as a user cannot observe how data > actually is stored underneath. > > Additionaly I think the 'clone' option with it's stronger guarantees > should be a separate system call. So for now just have no supported > flag and leave it up to the file system and storage device how to > implement it. So, continue to include a "flags" field but just error out if it's anything but zero for now? Sounds fine by me. We can always implement the other stuff later. --b. > > For the future a COPY_FALLOC flag taht guaranatees you do not get ENOSPC > on the copied range will be very useful, but given the complexity I > think it's not something we should add now. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
