From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753022Ab0KHPcR (ORCPT ); Mon, 8 Nov 2010 10:32:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51924 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752222Ab0KHPcO convert rfc822-to-8bit (ORCPT ); Mon, 8 Nov 2010 10:32:14 -0500 From: Jeff Moyer To: Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] dio: track and serialise unaligned direct IO References: <1289202023-15102-1-git-send-email-david@fromorbit.com> <1289202023-15102-2-git-send-email-david@fromorbit.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Mon, 08 Nov 2010 10:28:29 -0500 In-Reply-To: <1289202023-15102-2-git-send-email-david@fromorbit.com> (Dave Chinner's message of "Mon, 8 Nov 2010 18:40:21 +1100") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave Chinner writes: > +struct dio_zero_block { > + struct list_head dio_list; /* list of io in progress */ > + sector_t zero_block; /* block being zeroed */ > + struct dio *dio; /* owner dio */ > + wait_queue_head_t wq; /* New IO block here */ New IOs block here, or new IO blocks here? > +/* > + * Add a filesystem block to the list of blocks we are tracking. > + */ > +static void > +dio_start_zero_block(struct dio *dio, sector_t zero_block) > +{ > + struct dio_zero_block *zb; > + > + zb = kmalloc(sizeof(*zb), GFP_NOIO); > + if (!zb) > + return; > + INIT_LIST_HEAD(&zb->dio_list); > + init_waitqueue_head(&zb->wq); > + zb->zero_block = zero_block; > + zb->dio = dio; > + atomic_set(&zb->ref, 1); > + > + spin_lock(&dio_zero_block_lock); > + list_add(&zb->dio_list, &dio_zero_block_list); > + spin_unlock(&dio_zero_block_lock); What protects from two processes getting here at the same time, and hence adding the same block to the list? i_mutex? > @@ -1210,6 +1343,13 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, > */ > memset(dio, 0, offsetof(struct dio, pages)); > > + /* > + * zero_blocks need to initialised to largeѕt value to avoid ^ be