Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752676Ab0LTDb5 (ORCPT ); Sun, 19 Dec 2010 22:31:57 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:55440 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752374Ab0LTDb4 convert rfc822-to-8bit (ORCPT ); Sun, 19 Dec 2010 22:31:56 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=PeIYlx4DAz711pBod4ljXk4+LFaMxDzlRCyayQPAut26yLr7THCB6SFWVuOtFC1TKf FogA8vjAzwPnAmKDa7SJHJbbJi8wnC1MPEpThBq8A6qOAt7gV3C6nZf6Ul287ChaxAYf +ebc3xl/VNjD3kYbgicwjIqnRyunkydMZH56Q= MIME-Version: 1.0 In-Reply-To: <20101220120218.E56F.A69D9226@jp.fujitsu.com> References: <20101220113239.E56C.A69D9226@jp.fujitsu.com> <20101220120218.E56F.A69D9226@jp.fujitsu.com> Date: Mon, 20 Dec 2010 12:31:55 +0900 Message-ID: Subject: Re: [RFC 5/5] truncate: Remove unnecessary page release From: Minchan Kim To: KOSAKI Motohiro Cc: Andrew Morton , linux-mm , LKML , Nick Piggin , Al Viro , Andi Kleen Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2834 Lines: 83 On Mon, Dec 20, 2010 at 12:03 PM, KOSAKI Motohiro wrote: >> On Mon, Dec 20, 2010 at 11:32 AM, KOSAKI Motohiro >> wrote: >> >> On Mon, Dec 20, 2010 at 11:21 AM, KOSAKI Motohiro >> >> wrote: >> >> >> This patch series changes remove_from_page_cache's page ref counting >> >> >> rule. page cache ref count is decreased in remove_from_page_cache. >> >> >> So we don't need call again in caller context. >> >> >> >> >> >> Cc: Nick Piggin >> >> >> Cc: Al Viro >> >> >> Cc: linux-mm@kvack.org >> >> >> Signed-off-by: Minchan Kim >> >> >> --- >> >> >> ?mm/truncate.c | ? ?1 - >> >> >> ?1 files changed, 0 insertions(+), 1 deletions(-) >> >> >> >> >> >> diff --git a/mm/truncate.c b/mm/truncate.c >> >> >> index 9ee5673..8decb93 100644 >> >> >> --- a/mm/truncate.c >> >> >> +++ b/mm/truncate.c >> >> >> @@ -114,7 +114,6 @@ truncate_complete_page(struct address_space *mapping, struct page *page) >> >> >> ? ? ? ?* calls cleancache_put_page (and note page->mapping is now NULL) >> >> >> ? ? ? ?*/ >> >> >> ? ? ? cleancache_flush_page(mapping, page); >> >> >> - ? ? page_cache_release(page); ? ? ? /* pagecache ref */ >> >> >> ? ? ? return 0; >> >> > >> >> > Do we _always_ have stable page reference here? IOW, I can assume >> >> >> >> I think so. >> >> Because the page is locked so caller have to hold a ref to unlock it. >> > >> > Hmm... >> > >> > Perhaps, I'm missing something. But I think ?__memory_failure() only lock >> > compaund_head page. not all. example. >> >> The page passed truncate_complete_page is only head page? >> Is it possible to pass the page which isn't head of compound in >> truncate_complete_page? > > I dunno, really. My five miniture grep found following logic. therefore I asked you. > > > > __memory_failure() > { > ? ? ? ?p = pfn_to_page(pfn); > ? ? ? ?hpage = compound_head(p); > (snip) > ? ? ? ?res = -EBUSY; > ? ? ? ?for (ps = error_states;; ps++) { > ? ? ? ? ? ? ? ?if ((p->flags & ps->mask) == ps->res) { > ? ? ? ? ? ? ? ? ? ? ? ?res = page_action(ps, p, pfn); ?// call truncate here > ? ? ? ? ? ? ? ? ? ? ? ?break; > ? ? ? ? ? ? ? ?} > ? ? ? ?} > out: > ? ? ? ?unlock_page(hpage); > } > > AFAIK, We have to handle head page when we handle compound page. Internal page handling logic about tail pages is hidden by compound page internal. So I think memory_failure also don't have a problem. For needing double check, Cced Andi. Thanks for the review, KOSAKI. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/