From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Moyer Subject: Re: [PATCH 1/3] dio: track and serialise unaligned direct IO Date: Mon, 08 Nov 2010 10:28:29 -0500 Message-ID: References: <1289202023-15102-1-git-send-email-david@fromorbit.com> <1289202023-15102-2-git-send-email-david@fromorbit.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Dave Chinner Return-path: 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") Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.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 =3D kmalloc(sizeof(*zb), GFP_NOIO); > + if (!zb) > + return; > + INIT_LIST_HEAD(&zb->dio_list); > + init_waitqueue_head(&zb->wq); > + zb->zero_block =3D zero_block; > + zb->dio =3D 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 *ioc= b, struct inode *inode, > */ > memset(dio, 0, offsetof(struct dio, pages)); > =20 > + /* > + * zero_blocks need to initialised to large=D1=95t value to avoid ^ be