From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751949Ab0JAFFO (ORCPT ); Fri, 1 Oct 2010 01:05:14 -0400 Received: from smtp-out.google.com ([74.125.121.35]:17105 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751388Ab0JAFFM (ORCPT ); Fri, 1 Oct 2010 01:05:12 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=AE3R2kLN6V0ARIcNpK9Ma9DBlsAd9ldUeXjmMlmgOa9o3qKdGUxvLqB+p+IYF+leZu 56mq9dVefNHKplqMlRoA== From: Michel Lespinasse To: linux-mm@kvack.org, Linus Torvalds , Ying Han Cc: linux-kernel@vger.kernel.org, Andrew Morton , Rik van Riel , Nick Piggin , Peter Zijlstra , Hugh Dickins Subject: [PATCH 1/2] Unique path for locking page in filemap_fault() Date: Thu, 30 Sep 2010 22:04:43 -0700 Message-Id: <1285909484-30958-2-git-send-email-walken@google.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1285909484-30958-1-git-send-email-walken@google.com> References: <1285909484-30958-1-git-send-email-walken@google.com> X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Note that if the file got truncated before we locked the page, we retry at find_get_page(). This is similar to what find_lock_page() would do. Linus's commit ef00e08e introduced a goto no_cached_page in that simuation, which seems correct as well but possibly less efficient ? ----------------------- >8 ------------------------ This change introduces a single location where filemap_fault() locks the desired page. There used to be two such places, depending if the initial find_get_page() was successful or not. Signed-off-by: Michel Lespinasse --- mm/filemap.c | 20 +++++++++++--------- 1 files changed, 11 insertions(+), 9 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 3d4df44..8ed709a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1539,25 +1539,27 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) * waiting for the lock. */ do_async_mmap_readahead(vma, ra, file, page, offset); - lock_page(page); - - /* Did it get truncated? */ - if (unlikely(page->mapping != mapping)) { - unlock_page(page); - put_page(page); - goto no_cached_page; - } } else { /* No page in the page cache at all */ do_sync_mmap_readahead(vma, ra, file, offset); count_vm_event(PGMAJFAULT); ret = VM_FAULT_MAJOR; retry_find: - page = find_lock_page(mapping, offset); + page = find_get_page(mapping, offset); if (!page) goto no_cached_page; } + lock_page(page); + + /* Did it get truncated? */ + if (unlikely(page->mapping != mapping)) { + unlock_page(page); + put_page(page); + goto retry_find; + } + VM_BUG_ON(page->index != offset); + /* * We have a locked page in the page cache, now we need to check * that it's up-to-date. If not, it is going to be due to an error. -- 1.7.1