From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH -v8 3/4] Enable the MS_ASYNC functionality in sys_msync() From: Matt Mackall In-Reply-To: <200801241236.01114.nickpiggin@yahoo.com.au> References: <12010440803930-git-send-email-salikhmetov@gmail.com> <1201044083504-git-send-email-salikhmetov@gmail.com> <200801241236.01114.nickpiggin@yahoo.com.au> Content-Type: text/plain Date: Thu, 24 Jan 2008 12:56:13 -0600 Message-Id: <1201200973.3897.31.camel@cinder.waste.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Linus Torvalds , Anton Salikhmetov , linux-mm@kvack.org, jakob@unthought.net, linux-kernel@vger.kernel.org, valdis.kletnieks@vt.edu, riel@redhat.com, ksm@42.dk, staubach@redhat.com, jesper.juhl@gmail.com, a.p.zijlstra@chello.nl, akpm@linux-foundation.org, protasnb@gmail.com, miklos@szeredi.hu, r.e.wolff@bitwizard.nl, hidave.darkstar@gmail.com, hch@infradead.org List-ID: On Thu, 2008-01-24 at 12:36 +1100, Nick Piggin wrote: > On Thursday 24 January 2008 04:05, Linus Torvalds wrote: > > On Wed, 23 Jan 2008, Anton Salikhmetov wrote: > > > + > > > + if (pte_dirty(*pte) && pte_write(*pte)) { > > > > Not correct. > > > > You still need to check "pte_present()" before you can test any other > > bits. For a non-present pte, none of the other bits are defined, and for > > all we know there might be architectures out there that require them to > > be non-dirty. > > > > As it is, you just possibly randomly corrupted the pte. > > > > Yeah, on all architectures I know of, it the pte is clear, neither of > > those tests will trigger, so it just happens to work, but it's still > > wrong. > > Probably it can fail for !present nonlinear mappings on many > architectures. Definitely. -- Mathematics is the supreme nostalgia of our time. -- 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