From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Subject: RE: [PATCH v2 0/2] mm: introduce MAP_FIXED_SAFE Date: Tue, 19 Dec 2017 12:40:16 +0000 Message-ID: <0ca2620ce7534c5491e69416621ac41b@AcuMS.aculab.com> References: <20171213092550.2774-1-mhocko@kernel.org> <20171213163210.6a16ccf8753b74a6982ef5b6@linux-foundation.org> <20171214131526.GM16951@dhcp22.suse.cz> <20171214145443.GA2202@brick> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20171214145443.GA2202@brick> Content-Language: en-US Sender: owner-linux-mm@kvack.org To: 'Edward Napierala' , Michal Hocko Cc: Andrew Morton , "linux-api@vger.kernel.org" , Khalid Aziz , Michael Ellerman , Russell King - ARM Linux , Andrea Arcangeli , "linux-mm@kvack.org" , LKML , "linux-arch@vger.kernel.org" , Florian Weimer , John Hubbard , Matthew Wilcox , Abdul Haleem , Joel Stanley , Kees Cook , "jasone@google.com" , "davidtgoldblatt@gmail.com" List-Id: linux-api@vger.kernel.org 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 add= ress > > > cannot be used, mmap() will fail. If MAP_FIX= ED is > > > specified, addr must be a multiple of the pag= e size. > > > If MAP_EXCL is not specified, a successful MA= P_FIXED > > > request replaces any previous mappings for th= e > > > process' pages in the range from addr to addr= + len. > > > In contrast, if MAP_EXCL is specified, the re= quest > > > 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. >=20 > 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?? David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org