vfs: move the clone/dedupe/remap helpers to a single file I would like to move the generic helper functions that support the file remap range operations (aka clone and dedupe) to a separate file under fs/. For the moment, I have a few goals here: one is to declutter fs/read_write.c and mm/filemap.c. The second goal is to be able to deselect all the remap code if no filesystems require it. The third (and much more long term) goal is to have a place to land the generic code for the atomic file extent swap functionality, since it will reuse some of the functionality. Someday. Whenever I get around to submitting that again. AFAICT, nobody is attempting to land any major changes in any of the vfs remap functions during the 5.10 window -- for-next showed conflicts only in the Makefile, so it seems like a quiet enough time to do this. There are no functional changes here, it's just moving code blocks around. v2: move a few more things