From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 2B6326B003D for ; Wed, 1 Apr 2009 09:25:20 -0400 (EDT) Message-ID: <49D36B4E.7000702@redhat.com> Date: Wed, 01 Apr 2009 09:25:34 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [patch 4/6] Guest page hinting: writable page table entries. References: <20090327150905.819861420@de.ibm.com> <20090327151012.398894143@de.ibm.com> In-Reply-To: <20090327151012.398894143@de.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Martin Schwidefsky Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.osdl.org, frankeh@watson.ibm.com, akpm@osdl.org, nickpiggin@yahoo.com.au, hugh@veritas.com List-ID: Martin Schwidefsky wrote: This code has me stumped. Does it mean that if a page already has the PageWritable bit set (and count_ok stays 0), we will always mark the page as volatile? How does that work out on !s390? > /** > + * __page_check_writable() - check page state for new writable pte > + * > + * @page: the page the new writable pte refers to > + * @pte: the new writable pte > + */ > +void __page_check_writable(struct page *page, pte_t pte, unsigned int offset) > +{ > + int count_ok = 0; > + > + preempt_disable(); > + while (page_test_set_state_change(page)) > + cpu_relax(); > + > + if (!TestSetPageWritable(page)) { > + count_ok = check_counts(page, offset); > + if (check_bits(page) && count_ok) > + page_set_volatile(page, 1); > + else > + /* > + * If two processes create a write mapping at the > + * same time check_counts will return false or if > + * the page is currently isolated from the LRU > + * check_bits will return false but the page might > + * be in volatile state. > + * We have to take care about the dirty bit so the > + * only option left is to make the page stable but > + * we can try to make it volatile a bit later. > + */ > + page_set_stable_if_present(page); > + } > + page_clear_state_change(page); > + if (!count_ok) > + page_make_volatile(page, 1); > + preempt_enable(); > +} > +EXPORT_SYMBOL(__page_check_writable); -- All rights reversed. -- 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