From: Nick Piggin Subject: Re: [PATCH]: ufs: ufs_get_locked_patch race fix Date: Tue, 01 Aug 2006 17:18:14 +1000 Message-ID: <44CF0036.9080701@yahoo.com.au> References: <20060731125702.GA5094@rain> <20060731230251.3b149902.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: Evgeniy Dushistov , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Return-path: Received: from smtp107.mail.mud.yahoo.com ([209.191.85.217]:21852 "HELO smtp107.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S932536AbWHAHSS (ORCPT ); Tue, 1 Aug 2006 03:18:18 -0400 To: Andrew Morton In-Reply-To: <20060731230251.3b149902.akpm@osdl.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Andrew Morton wrote: >On Mon, 31 Jul 2006 16:57:02 +0400 >Evgeniy Dushistov wrote: > > >>As discussed earlier: >>http://lkml.org/lkml/2006/6/28/136 >>this patch fixes such issue: >>`ufs_get_locked_page' takes page from cache >>after that `vmtruncate' takes page and deletes it from cache >>`ufs_get_locked_page' locks page, and reports about EIO error. >> >>Also because of find_lock_page always return valid page or NULL, >>we have no need check it if page not NULL. >> >>Signed-off-by: Evgeniy Dushistov >> >> >>--- >> >> >>Index: linux-2.6.18-rc2-mm1/fs/ufs/util.c >>=================================================================== >>--- linux-2.6.18-rc2-mm1.orig/fs/ufs/util.c >>+++ linux-2.6.18-rc2-mm1/fs/ufs/util.c >>@@ -257,6 +257,7 @@ try_again: >> page = read_cache_page(mapping, index, >> (filler_t*)mapping->a_ops->readpage, >> NULL); >>+ >> if (IS_ERR(page)) { >> printk(KERN_ERR "ufs_change_blocknr: " >> "read_cache_page error: ino %lu, index: %lu\n", >>@@ -266,6 +267,13 @@ try_again: >> >> lock_page(page); >> >>+ if (unlikely(page->mapping != mapping || >>+ page->index != index)) { >>+ unlock_page(page); >>+ page_cache_release(page); >>+ goto try_again; >>+ } >>+ >> if (!PageUptodate(page) || PageError(page)) { >> unlock_page(page); >> page_cache_release(page); >> > >Looks good to me. > >Is there any need to be checking ->index? Normally we simply use the >sequence: > > lock_page(page); > if (page->mapping == NULL) > /* truncate got there first */ > >to handle this case. > If you already have a reference on the page, I believe no. We have to be a bit careful about it in the core vm now that splice can move pages between different parts of the same mapping, but any code outside mm/ shouldn't need to worry (exactly because they should have a ref before doing the lock_page). -- Send instant messages to your online friends http://au.messenger.yahoo.com