From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9488CC3A5A7 for ; Mon, 2 Sep 2019 16:41:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77CA521744 for ; Mon, 2 Sep 2019 16:41:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726341AbfIBQlO (ORCPT ); Mon, 2 Sep 2019 12:41:14 -0400 Received: from verein.lst.de ([213.95.11.211]:51590 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbfIBQlN (ORCPT ); Mon, 2 Sep 2019 12:41:13 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 31E29227A8A; Mon, 2 Sep 2019 18:41:09 +0200 (CEST) Date: Mon, 2 Sep 2019 18:41:08 +0200 From: Christoph Hellwig To: Goldwyn Rodrigues Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, darrick.wong@oracle.com, hch@lst.de, david@fromorbit.com, riteshh@linux.ibm.com, Goldwyn Rodrigues Subject: Re: [PATCH 12/15] iomap: use a function pointer for dio submits Message-ID: <20190902164108.GD6263@lst.de> References: <20190901200836.14959-1-rgoldwyn@suse.de> <20190901200836.14959-13-rgoldwyn@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190901200836.14959-13-rgoldwyn@suse.de> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sun, Sep 01, 2019 at 03:08:33PM -0500, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > This helps filesystems to perform tasks on the bio while > submitting for I/O. Since btrfs requires the position > we are working on, pass pos to iomap_dio_submit_bio() Please avoid passing function pointers in mutable data structures. I think the best idea here is to move the end_io handler into a structure that can be marked const, and to which we can add the submit handler later. Something like this: --- >From d17419b6b4124e95088858d3dcea486db6be9ffa Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 2 Sep 2019 18:39:34 +0200 Subject: iomap: move the direct I/O ->end_io callback into a structure Add a new iomap_dio_ops structure that for now just contains the end_io handler. This avoid storing the function pointer in a mutable structure, which is a possible exploit vector for kernel code execution, and prepares for adding a submit_io handler that btrfs needs. Signed-off-by: Christoph Hellwig --- fs/iomap/direct-io.c | 17 +++++++++-------- fs/xfs/xfs_file.c | 6 +++++- include/linux/iomap.h | 9 ++++++--- 3 files changed, 20 insertions(+), 12 deletions(-) diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 10517cea9682..cfe5f6a88945 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -24,7 +24,7 @@ struct iomap_dio { struct kiocb *iocb; - iomap_dio_end_io_t *end_io; + const struct iomap_dio_ops *dops; loff_t i_size; loff_t size; atomic_t ref; @@ -72,13 +72,14 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap, static ssize_t iomap_dio_complete(struct iomap_dio *dio) { + const struct iomap_dio_ops *dops = dio->dops; struct kiocb *iocb = dio->iocb; struct inode *inode = file_inode(iocb->ki_filp); loff_t offset = iocb->ki_pos; ssize_t ret; - if (dio->end_io) { - ret = dio->end_io(iocb, + if (dops && dops->end_io) { + ret = dops->end_io(iocb, dio->error ? dio->error : dio->size, dio->flags); } else { @@ -101,9 +102,9 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio) * one is a pretty crazy thing to do, so we don't support it 100%. If * this invalidation fails, tough, the write still worked... * - * And this page cache invalidation has to be after dio->end_io(), as - * some filesystems convert unwritten extents to real allocations in - * end_io() when necessary, otherwise a racing buffer read would cache + * And this page cache invalidation has to be after ->end_io(), as some + * filesystems convert unwritten extents to real allocations in + * ->end_io() when necessary, otherwise a racing buffer read would cache * zeros from unwritten extents. */ if (!dio->error && @@ -396,7 +397,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length, */ ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, - const struct iomap_ops *ops, iomap_dio_end_io_t end_io) + const struct iomap_ops *ops, const struct iomap_dio_ops *dops) { struct address_space *mapping = iocb->ki_filp->f_mapping; struct inode *inode = file_inode(iocb->ki_filp); @@ -421,7 +422,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, atomic_set(&dio->ref, 1); dio->size = 0; dio->i_size = i_size_read(inode); - dio->end_io = end_io; + dio->dops = dops; dio->error = 0; dio->flags = 0; diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 28101bbc0b78..0a2dc6b71c3c 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -440,6 +440,10 @@ xfs_dio_write_end_io( return error; } +static const struct iomap_dio_ops xfs_dio_write_ops = { + .end_io = xfs_dio_write_end_io, +}; + /* * xfs_file_dio_aio_write - handle direct IO writes * @@ -540,7 +544,7 @@ xfs_file_dio_aio_write( } trace_xfs_file_direct_write(ip, count, iocb->ki_pos); - ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, xfs_dio_write_end_io); + ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops); /* * If unaligned, this is the only IO in-flight. If it has not yet diff --git a/include/linux/iomap.h b/include/linux/iomap.h index bc499ceae392..d8c0769bb360 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -188,10 +188,13 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno, */ #define IOMAP_DIO_UNWRITTEN (1 << 0) /* covers unwritten extent(s) */ #define IOMAP_DIO_COW (1 << 1) /* covers COW extent(s) */ -typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t ret, - unsigned flags); + +struct iomap_dio_ops { + int (*end_io)(struct kiocb *iocb, ssize_t ret, unsigned flags); +}; + ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, - const struct iomap_ops *ops, iomap_dio_end_io_t end_io); + const struct iomap_ops *ops, const struct iomap_dio_ops *dops); int iomap_dio_iopoll(struct kiocb *kiocb, bool spin); #ifdef CONFIG_SWAP -- 2.20.1