From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out4.electric.net (smtp-out4.electric.net [192.162.216.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vj9g75L3HzDqGb for ; Tue, 14 Mar 2017 21:18:26 +1100 (AEDT) From: David Laight To: 'Till Smejkal' , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Russell King , Catalin Marinas , "Will Deacon" , Steven Miao , Richard Kuo , Tony Luck , Fenghua Yu , James Hogan , Ralf Baechle , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , "Michael Ellerman" , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , Rich Felker , "David S. Miller" , Chris Metcalf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "x86@kernel.org" , "Andy Lutomirski" , Chris Zankel , "Max Filippov" , Arnd Bergmann , "Greg Kroah-Hartman" , Laurent Pinchart , Mauro Carvalho Chehab , Pawel Osciak , Marek Szyprowski , Kyungmin Park , David Woodhouse , Brian Norris , Boris Brezillon , Marek Vasut , Richard Weinberger , Cyrille Pitchen , Felipe Balbi , Alexander Viro , Benjamin LaHaise , "Nadia Yvette Chambers" , Jeff Layton , "J. Bruce Fields" , Peter Zijlstra , Hugh Dickins , Arnaldo Carvalho de Melo , Alexander Shishkin , Jaroslav Kysela , Takashi Iwai CC: "linux-mips@linux-mips.org" , "alsa-devel@alsa-project.org" , "linux-ia64@vger.kernel.org" , "linux-aio@kvack.org" , "linux-mm@kvack.org" , "linux-mtd@lists.infradead.org" , "sparclinux@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-hexagon@vger.kernel.org" , "linux-sh@vger.kernel.org" , "linux-snps-arc@lists.infradead.org" , "linux-media@vger.kernel.org" , "linux-xtensa@linux-xtensa.org" , "adi-buildroot-devel@lists.sourceforge.net" , "linux-metag@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-parisc@vger.kernel.org" , "linux-api@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-alpha@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Subject: RE: [RFC PATCH 07/13] kernel/fork: Split and export 'mm_alloc' and 'mm_init' Date: Tue, 14 Mar 2017 10:18:03 +0000 Message-ID: <063D6719AE5E284EB5DD2968C1650D6DCFFB03F4@AcuExch.aculab.com> References: <20170313221415.9375-1-till.smejkal@gmail.com> <20170313221415.9375-8-till.smejkal@gmail.com> In-Reply-To: <20170313221415.9375-8-till.smejkal@gmail.com> Content-Type: text/plain; charset="Windows-1252" MIME-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Linuxppc-dev Till Smejkal > Sent: 13 March 2017 22:14 > The only way until now to create a new memory map was via the exported > function 'mm_alloc'. Unfortunately, this function not only allocates a ne= w > memory map, but also completely initializes it. However, with the > introduction of first class virtual address spaces, some initialization > steps done in 'mm_alloc' are not applicable to the memory maps needed for > this feature and hence would lead to errors in the kernel code. >=20 > Instead of introducing a new function that can allocate and initialize > memory maps for first class virtual address spaces and potentially > duplicate some code, I decided to split the mm_alloc function as well as > the 'mm_init' function that it uses. >=20 > Now there are four functions exported instead of only one. The new > 'mm_alloc' function only allocates a new mm_struct and zeros it out. If o= ne > want to have the old behavior of mm_alloc one can use the newly introduce= d > function 'mm_alloc_and_setup' which not only allocates a new mm_struct bu= t > also fully initializes it. ... That looks like bugs waiting to happen. You need unchanged code to fail to compile. David