From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 16 Oct 2007 14:02:38 -0400 Message-Id: <200710161802.l9GI2ca6012758@agora.fsl.cs.sunysb.edu> From: Erez Zadok Subject: Re: msync(2) bug(?), returns AOP_WRITEPAGE_ACTIVATE to userland In-reply-to: Your message of "Mon, 15 Oct 2007 14:47:52 +0300." <84144f020710150447o94b1babo8b6e6a647828465f@mail.gmail.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Pekka Enberg Cc: Erez Zadok , Hugh Dickins , Ryan Finnie , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, cjwatson@ubuntu.com, linux-mm@kvack.org List-ID: In message <84144f020710150447o94b1babo8b6e6a647828465f@mail.gmail.com>, "Pekka Enberg" writes: > Hi, > > On 10/15/07, Erez Zadok wrote: > > Pekka, with a small change to your patch (to handle time-based cache > > coherency), your patch worked well and passed all my tests. Thanks. > > > > So now I wonder if we still need the patch to prevent AOP_WRITEPAGE_ACTIVATE > > from being returned to userland. I guess we still need it, b/c even with > > your patch, generic_writepages() can return AOP_WRITEPAGE_ACTIVATE back to > > the VFS and we need to ensure that doesn't "leak" outside the kernel. > > I wonder whether _not setting_ BDI_CAP_NO_WRITEBACK implies that > ->writepage() will never return AOP_WRITEPAGE_ACTIVATE for > !wbc->for_reclaim case which would explain why we haven't hit this bug > before. Hugh, Andrew? > > And btw, I think we need to fix ecryptfs too. Yes, ecryptfs needs this fix too (and probably a couple of other mmap fixes I've made to unionfs recently -- Mike Halcrow already knows :-) Of course, running ecryptfs on top of tmpfs is somewhat odd and uncommon; but with unionfs, users use tmpfs as the copyup branch very often. > Pekka Erez. -- 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