I know there's work on this for xfs, but could this be done in generic mm code? What are the obstacles? page->mapping and page->index are the obvious ones. If that's too difficult is it maybe enough to share mappings between files while they are completely identical and clone the mapping when necessary? All COW filesystems would benefit, as well as layered ones: lots of fuse fs, and in some cases overlayfs too. Related: what can DAX do in the presence of cloned block? Thanks, Miklos -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>