Return-Path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:40716 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752366Ab0LAWnn (ORCPT ); Wed, 1 Dec 2010 17:43:43 -0500 Date: Wed, 1 Dec 2010 14:43:14 -0800 From: Andrew Morton To: Neil Brown Cc: Trond Myklebust , Hugh Dickins , Linus Torvalds , Nick Bowler , Linux Kernel Mailing List , linux-nfs@vger.kernel.org, Rik van Riel , Christoph Hellwig , Al Viro , Nick Piggin Subject: Re: [PATCH v2 3/3] NFS: Fix a memory leak in nfs_readdir Message-Id: <20101201144314.6a827f8d.akpm@linux-foundation.org> In-Reply-To: <20101202082913.7cb98444@notabene.brown> References: <1291217804-11257-1-git-send-email-Trond.Myklebust@netapp.com> <1291217804-11257-2-git-send-email-Trond.Myklebust@netapp.com> <20101201150428.GA2879@elliptictech.com> <1291217804-11257-3-git-send-email-Trond.Myklebust@netapp.com> <1291217804-11257-4-git-send-email-Trond.Myklebust@netapp.com> <1291229669.6609.24.camel@heimdal.trondhjem.org> <1291233938.6609.37.camel@heimdal.trondhjem.org> <20101201123929.ab7cef1d.akpm@linux-foundation.org> <20101202082913.7cb98444@notabene.brown> Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Thu, 2 Dec 2010 08:29:13 +1100 Neil Brown wrote: > > > > > > However, while reading Documentation/filesystems/vfs.txt (in order to > > > add documentation for freepage) I was surprised to read that the > > > ->releasepage() is itself supposed to be allowed to actually remove the > > > page from the address space if it so desires. > > > > That doesn't sound right. It came from Neil in 2006. > > > > Neil, what were you thinking there? Did you find such a ->releasepage()? > > Nope, no idea, sorry. > > No releasepage functions do anything like that, and no call sites suggest it > could be a possibility. Quite the reverse - they are likely to remove the > page from the mapping without checking that it is still in the mapping. > > So that sentence should be deleted. This? From: Andrew Morton ->releasepage() does not remove the page from the mapping. Cc: Neil Brown Cc: Trond Myklebust Signed-off-by: Andrew Morton --- Documentation/filesystems/vfs.txt | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff -puN Documentation/filesystems/vfs.txt~documentation-filesystems-vfstxt-fix-repeasepage-description Documentation/filesystems/vfs.txt --- a/Documentation/filesystems/vfs.txt~documentation-filesystems-vfstxt-fix-repeasepage-description +++ a/Documentation/filesystems/vfs.txt @@ -660,11 +660,10 @@ struct address_space_operations { releasepage: releasepage is called on PagePrivate pages to indicate that the page should be freed if possible. ->releasepage should remove any private data from the page and clear the - PagePrivate flag. It may also remove the page from the - address_space. If this fails for some reason, it may indicate - failure with a 0 return value. - This is used in two distinct though related cases. The first - is when the VM finds a clean page with no active users and + PagePrivate flag. If releasepage() fails for some reason, it must + indicate failure with a 0 return value. + releasepage() is used in two distinct though related cases. The + first is when the VM finds a clean page with no active users and wants to make it a free page. If ->releasepage succeeds, the page will be removed from the address_space and become free. _