From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 15 Feb 2008 19:37:36 -0800 From: Andrew Morton Subject: Re: [patch 3/6] mmu_notifier: invalidate_page callbacks Message-Id: <20080215193736.9d6e7da3.akpm@linux-foundation.org> In-Reply-To: <20080215064932.918191502@sgi.com> References: <20080215064859.384203497@sgi.com> <20080215064932.918191502@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andrea Arcangeli , Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , general@lists.openfabrics.org, Steve Wise , Roland Dreier , Kanoj Sarcar , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com List-ID: On Thu, 14 Feb 2008 22:49:02 -0800 Christoph Lameter wrote: > Two callbacks to remove individual pages as done in rmap code > > invalidate_page() > > Called from the inner loop of rmap walks to invalidate pages. > > age_page() > > Called for the determination of the page referenced status. > > If we do not care about page referenced status then an age_page callback > may be be omitted. PageLock and pte lock are held when either of the > functions is called. The age_page mystery shallows. It would be useful to have some rationale somewhere in the patchset for the existence of this callback. > #include > > @@ -287,7 +288,8 @@ static int page_referenced_one(struct pa > if (vma->vm_flags & VM_LOCKED) { > referenced++; > *mapcount = 1; /* break early from loop */ > - } else if (ptep_clear_flush_young(vma, address, pte)) > + } else if (ptep_clear_flush_young(vma, address, pte) | > + mmu_notifier_age_page(mm, address)) > referenced++; The "|" is obviously deliberate. But no explanation is provided telling us why we still call the callback if ptep_clear_flush_young() said the page was recently referenced. People who read your code will want to understand this. > /* Pretend the page is referenced if the task has the > @@ -455,6 +457,7 @@ static int page_mkclean_one(struct page > > flush_cache_page(vma, address, pte_pfn(*pte)); > entry = ptep_clear_flush(vma, address, pte); > + mmu_notifier(invalidate_page, mm, address); I just don't see how ths can be done if the callee has another thread in the middle of establishing IO against this region of memory. ->invalidate_page() _has_ to be able to block. Confused. -- 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