On Fri 11-08-17 17:24:29, Florian Weimer wrote: > On 08/11/2017 04:24 PM, Michal Hocko wrote: > > On Fri 11-08-17 16:11:44, Florian Weimer wrote: > >> On 08/11/2017 04:06 PM, Michal Hocko wrote: > >> > >>> I am sorry to look too insisting here (I have still hard time to reconcile > >>> myself with the madvise (ab)use) but if we in fact want minherit like > >>> interface why don't we simply add minherit and make the code which wants > >>> to use that interface easier to port? Is the only reason that hooking > >>> into madvise is less code? If yes is that a sufficient reason to justify > >>> the (ab)use of madvise? If there is a general consensus on that part I > >>> will shut up and won't object anymore. Arguably MADV_DONTFORK would fit > >>> into minherit API better as well. > >> > >> It does, OpenBSD calls it MAP_INHERIT_NONE. > >> > >> Could you implement MAP_INHERIT_COPY and MAP_INHERIT_SHARE as well? Or > >> is changing from MAP_SHARED to MAP_PRIVATE and back impossible? > > > > I haven't explored those two very much. Their semantic seems rather > > awkward, especially map_inherit_share one. I guess MAP_INHERIT_COPY > > would be doable. Do we have to support all modes or a missing support > > would disqualify the syscall completely? > > I think it would be a bit awkward if we implemented MAP_INHERIT_ZERO and > it would not turn a shared mapping into a private mapping in the child, > or would not work on shared mappings at all, or deviate in any way from > the OpenBSD implementation. If we go with minherit API then I think we should adhere with the BSD semantic and alloc MAP_INHERIT_ZERO for shared mappings as well > MAP_INHERIT_SHARE for a MAP_PRIVATE mapping which has been modified is a > bit bizarre, and I don't know how OpenBSD implements any of this. It > could well be that the exact behavior implemented in OpenBSD is a poor > fit for the Linux VM implementation. yeah, it would be MAP_INHERIT_SHARE that I would consider problematic and rather go with ENOSUPP or even EINVAL. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
