On Tue 19-12-17 12:40:16, David Laight wrote: > From: Edward Napierala > > Sent: 14 December 2017 14:55 > > > > On 1214T1415, Michal Hocko wrote: > > > On Thu 14-12-17 12:44:17, Edward Napierala wrote: > > > > Regarding the name - how about adopting MAP_EXCL? It was introduced in > > > > FreeBSD, > > > > and seems to do exactly this; quoting mmap(2): > > > > > > > > MAP_FIXED Do not permit the system to select a different address > > > > than the one specified. If the specified address > > > > cannot be used, mmap() will fail. If MAP_FIXED is > > > > specified, addr must be a multiple of the page size. > > > > If MAP_EXCL is not specified, a successful MAP_FIXED > > > > request replaces any previous mappings for the > > > > process' pages in the range from addr to addr + len. > > > > In contrast, if MAP_EXCL is specified, the request > > > > will fail if a mapping already exists within the > > > > range. > > > > > > I am not familiar with the FreeBSD implementation but from the above it > > > looks like MAP_EXCL is a MAP_FIXED mofifier which is not how we are > > > going to implement it in linux due to reasons mentioned in this cover > > > letter. Using the same name would be more confusing than helpful I am > > > afraid. > > > > Sorry, missed that. Indeed, reusing a name with a different semantics > > would be a bad idea. > > I don't remember any discussion about using MAP_FIXED | MAP_EXCL ? > > Why not match the prior art?? See the cover letter which explains why an extension is not backward compatible. -- Michal Hocko SUSE Labs
