From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kirill A. Shutemov" Subject: Re: [RFC, PATCHv2 29/29] mm, x86: introduce RLIMIT_VADDR Date: Thu, 5 Jan 2017 23:11:53 +0300 Message-ID: <20170105201153.GA27928@node.shutemov.name> References: <20161227015413.187403-1-kirill.shutemov@linux.intel.com> <20161227015413.187403-30-kirill.shutemov@linux.intel.com> <5a3dcc25-b264-37c7-c090-09981b23940d@intel.com> <20170105192910.q26ozg4ci4i3j2ai@black.fi.intel.com> <161ece66-fbf4-cb89-3da6-91b4851af69f@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <161ece66-fbf4-cb89-3da6-91b4851af69f@intel.com> Sender: owner-linux-mm@kvack.org To: Dave Hansen Cc: "Kirill A. Shutemov" , Linus Torvalds , Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , Arnd Bergmann , "H. Peter Anvin" , Andi Kleen , Andy Lutomirski , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org List-Id: linux-api@vger.kernel.org On Thu, Jan 05, 2017 at 11:39:16AM -0800, Dave Hansen wrote: > On 01/05/2017 11:29 AM, Kirill A. Shutemov wrote: > > On Thu, Jan 05, 2017 at 11:13:57AM -0800, Dave Hansen wrote: > >> On 12/26/2016 05:54 PM, Kirill A. Shutemov wrote: > >>> MM would use min(RLIMIT_VADDR, TASK_SIZE) as upper limit of virtual > >>> address available to map by userspace. > >> > >> What happens to existing mappings above the limit when this upper limit > >> is dropped? > > > > Nothing: we only prevent creating new mappings. All existing are not > > affected. > > > > The semantics here the same as with other resource limits. > > > >> Similarly, why do we do with an application running with something > >> incompatible with the larger address space that tries to raise the > >> limit? Say, legacy MPX. > > > > It has to know what it does. Yes, it can change limit to the point where > > application is unusable. But you can to the same with other limits. > > I'm not sure I'm comfortable with this. Do other rlimit changes cause > silent data corruption? I'm pretty sure doing this to MPX would. Maybe it's too ugly, but MPX can set rlim_max to rlim_cur on enabling. -- Kirill A. Shutemov -- 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