On Thu, Aug 30, 2018 at 11:10:05AM -0500, Eric Sandeen wrote: > We disabled FIBMAP/bmap calls for reflinked files because swap will then > writes directly to the blocks, bypassing COW mechanisms, and breaking > copy on write. As noted in commit db1327b, this restriction also breaks > bootloaders that want to use the FIBMAP ioctl. > > Rather than disabling the entire mapping interface for everyone just > because swapon may abuse the info, teach xfs_iomap_swapfile_activate() > to reject activation for reflinked files, and re-enable the FIBMAP > interface. Every use of the feature is an abuse, and that includes bootloaders. By the time you've obtained the information it can (and often will) be stale.
