Matthew Wilcox <willy@xxxxxxxxxxxxx> writes: > On Tue, Dec 05, 2017 at 08:54:35PM -0800, Matthew Wilcox wrote: >> On Wed, Dec 06, 2017 at 03:51:44PM +1100, Michael Ellerman wrote: >> > Cyril Hrubis <chrubis@xxxxxxx> writes: >> > >> > > Hi! >> > >> > MAP_FIXED_UNIQUE >> > >> > MAP_FIXED_ONCE >> > >> > MAP_FIXED_FRESH >> > >> >> > >> Well, I can open a poll for the best name, but none of those you are >> > >> proposing sound much better to me. Yeah, naming sucks... >> > > >> > > Given that MAP_FIXED replaces the previous mapping MAP_FIXED_NOREPLACE >> > > would probably be a best fit. >> > >> > Yeah that could work. >> > >> > I prefer "no clobber" as I just suggested, because the existing >> > MAP_FIXED doesn't politely "replace" a mapping, it destroys the current >> > one - which you or another thread may be using - and clobbers it with >> > the new one. >> >> It's longer than MAP_FIXED_WEAK :-P >> >> You'd have to be pretty darn strong to clobber an existing mapping. > > I think we're thinking about this all wrong. We shouldn't document it as > "This is a variant of MAP_FIXED". We should document it as "Here's an > alternative to MAP_FIXED". > > So, just like we currently say "exactly one of MAP_SHARED or MAP_PRIVATE", > we could add a new paragraph saying "at most one of MAP_FIXED or > MAP_REQUIRED" and "any of the following values". > > Now, we should implement MAP_REQUIRED as having each architecture > define _MAP_NOT_A_HINT, and then #define MAP_REQUIRED (MAP_FIXED | > _MAP_NOT_A_HINT), but that's not information to confuse users with. > > Also, that lets us add a third option at some point that is Yet Another > Way to interpret the 'addr' argument, by having MAP_FIXED clear and > _MAP_NOT_A_HINT set. > > I'm not set on MAP_REQUIRED. I came up with some awful names > (MAP_TODDLER, MAP_TANTRUM, MAP_ULTIMATUM, MAP_BOSS, MAP_PROGRAM_MANAGER, > etc). But I think we should drop FIXED from the middle of the name. MAP_REQUIRED doesn't immediately grab me, but I don't actively dislike it either :) What about MAP_AT_ADDR ? It's short, and says what it does on the tin. The first argument to mmap is actually called "addr" too. cheers
