On Sun, Aug 13, 2017 at 2:25 AM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > On Sat, Aug 12, 2017 at 07:44:14PM -0700, Dan Williams wrote: >> How about MAP_SYNC == (MAP_SHARED|MAP_PRIVATE)? On older kernels that >> should get -EINVAL, and on new kernels it means SYNC+SHARED. > > Cute trick, but I'd hate to waster it just for our little flag. > > How about: > > #define __MAP_VALIDATE MAP_SHARED|MAP_PRIVATE > #define MAP_SYNC 0x??? | __MAP_VALIDATE > > so that we can reuse that trick for any new flag? Yes, even better. I think that effectively kicks the need for mmap3() down the road a bit.
