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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 11F06C432C0 for ; Tue, 26 Nov 2019 17:49:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C96492075C for ; Tue, 26 Nov 2019 17:49:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Jh9MUTMx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726036AbfKZRtN (ORCPT ); Tue, 26 Nov 2019 12:49:13 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:60976 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725870AbfKZRrw (ORCPT ); Tue, 26 Nov 2019 12:47:52 -0500 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xAQHiE6g008010; Tue, 26 Nov 2019 17:47:34 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2019-08-05; bh=VLb/YMJCsrWhkvFIIjrbjJTaLfIayBXhXUM0yEnRDWo=; b=Jh9MUTMxEOm/dG3iFRfvsYLovnV1zqT4f07gIo4HvvCmRIeQGo7Cui9Qh2qlmOqNQHuZ qXkPiZU07/d7vp7nctgUHrm/gHHTqJIZhnR+JPvf+K2tpDNePStwdTK6/u2PNaHBNVla KrhNmsiPCTrcqYvODaU8CG1dZ1BvkswwWwjEvrXODclRVJ2xhuSHYi/EvWyKNVjnNwWF KPqxLCH5q9czNMNzl1QuVBSqDCsn8D3KL4k/2yGvWvPPQ4RQN/cr4uAoF7U6Nkiym609 cxVL8y6umD5WduoWuudIJ4aZQITft44ojo9nw/fVnya9Mx4XT7lCt2nYaPbR6xqLemYG Fg== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by userp2120.oracle.com with ESMTP id 2wewdr8bt0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Nov 2019 17:47:33 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xAQHdT4B014627; Tue, 26 Nov 2019 17:47:33 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 2wgvfjwm9t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 26 Nov 2019 17:47:33 +0000 Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id xAQHlVFd025458; Tue, 26 Nov 2019 17:47:32 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 26 Nov 2019 09:47:31 -0800 Date: Tue, 26 Nov 2019 09:47:30 -0800 From: "Darrick J. Wong" To: Jan Kara Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, Eric Biggers , Matthew Bobrowski Subject: Re: [PATCH] iomap: Do not create fake iter in iomap_dio_bio_actor() Message-ID: <20191126174730.GT6211@magnolia> References: <20191125083930.11854-1-jack@suse.cz> <20191125111901.11910-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191125111901.11910-1-jack@suse.cz> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9453 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911260148 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9453 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-1911260149 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org n Mon, Nov 25, 2019 at 12:18:57PM +0100, Jan Kara wrote: > iomap_dio_bio_actor() copies iter to a local variable and then limits it > to a file extent we have mapped. When IO is submitted, > iomap_dio_bio_actor() advances the original iter while the copied iter > is advanced inside bio_iov_iter_get_pages(). This logic is non-obvious > especially because both iters still point to same shared structures > (such as pipe info) so if iov_iter_advance() changes anything in the > shared structure, this scheme breaks. Let's just truncate and reexpand > the original iter as needed instead of playing games with copying iters > and keeping them in sync. > > Signed-off-by: Jan Kara Looks ok, seems to test ok too Reviewed-by: Darrick J. Wong --D > --- > fs/iomap/direct-io.c | 31 ++++++++++++++++++------------- > 1 file changed, 18 insertions(+), 13 deletions(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 420c0c82f0ac..b75cd0b0609b 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -201,12 +201,12 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev)); > unsigned int fs_block_size = i_blocksize(inode), pad; > unsigned int align = iov_iter_alignment(dio->submit.iter); > - struct iov_iter iter; > struct bio *bio; > bool need_zeroout = false; > bool use_fua = false; > int nr_pages, ret = 0; > size_t copied = 0; > + size_t orig_count; > > if ((pos | length | align) & ((1 << blkbits) - 1)) > return -EINVAL; > @@ -236,15 +236,18 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > } > > /* > - * Operate on a partial iter trimmed to the extent we were called for. > - * We'll update the iter in the dio once we're done with this extent. > + * Save the original count and trim the iter to just the extent we > + * are operating on right now. The iter will be re-expanded once > + * we are done. > */ > - iter = *dio->submit.iter; > - iov_iter_truncate(&iter, length); > + orig_count = iov_iter_count(dio->submit.iter); > + iov_iter_truncate(dio->submit.iter, length); > > - nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES); > - if (nr_pages <= 0) > - return nr_pages; > + nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); > + if (nr_pages <= 0) { > + ret = nr_pages; > + goto out; > + } > > if (need_zeroout) { > /* zero out from the start of the block to the write offset */ > @@ -257,7 +260,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > size_t n; > if (dio->error) { > iov_iter_revert(dio->submit.iter, copied); > - return 0; > + copied = ret = 0; > + goto out; > } > > bio = bio_alloc(GFP_KERNEL, nr_pages); > @@ -268,7 +272,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > bio->bi_private = dio; > bio->bi_end_io = iomap_dio_bio_end_io; > > - ret = bio_iov_iter_get_pages(bio, &iter); > + ret = bio_iov_iter_get_pages(bio, dio->submit.iter); > if (unlikely(ret)) { > /* > * We have to stop part way through an IO. We must fall > @@ -294,13 +298,11 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > bio_set_pages_dirty(bio); > } > > - iov_iter_advance(dio->submit.iter, n); > - > dio->size += n; > pos += n; > copied += n; > > - nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES); > + nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); > iomap_dio_submit_bio(dio, iomap, bio); > } while (nr_pages); > > @@ -318,6 +320,9 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, > if (pad) > iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); > } > +out: > + /* Undo iter limitation to current extent */ > + iov_iter_reexpand(dio->submit.iter, orig_count - copied); > if (copied) > return copied; > return ret; > -- > 2.16.4 >