From patchwork Tue Aug 8 08:45:12 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9886921 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 57FDD60352 for ; Tue, 8 Aug 2017 08:49:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4A43E22BF1 for ; Tue, 8 Aug 2017 08:49:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3E81F26E1A; Tue, 8 Aug 2017 08:49:15 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B7C0822BF1 for ; Tue, 8 Aug 2017 08:49:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752590AbdHHIsb (ORCPT ); Tue, 8 Aug 2017 04:48:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45306 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752170AbdHHIs2 (ORCPT ); Tue, 8 Aug 2017 04:48:28 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 07201356F0; Tue, 8 Aug 2017 08:48:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 07201356F0 Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=ming.lei@redhat.com Received: from localhost (ovpn-12-24.pek2.redhat.com [10.72.12.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 581BB908D8; Tue, 8 Aug 2017 08:48:21 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , Huang Ying , Andrew Morton , Alexander Viro Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ming Lei , Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org Subject: [PATCH v3 13/49] btrfs: comment on direct access bvec table Date: Tue, 8 Aug 2017 16:45:12 +0800 Message-Id: <20170808084548.18963-14-ming.lei@redhat.com> In-Reply-To: <20170808084548.18963-1-ming.lei@redhat.com> References: <20170808084548.18963-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 08 Aug 2017 08:48:28 +0000 (UTC) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba Cc: linux-btrfs@vger.kernel.org Acked: David Sterba Signed-off-by: Ming Lei --- fs/btrfs/compression.c | 4 ++++ fs/btrfs/inode.c | 12 ++++++++++++ 2 files changed, 16 insertions(+) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index d2ef9ac2a630..f795d0a6d176 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -542,6 +542,10 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, /* we need the actual starting offset of this extent in the file */ read_lock(&em_tree->lock); + /* + * It is still safe to retrieve the 1st page of the bio + * in this way after supporting multipage bvec. + */ em = lookup_extent_mapping(em_tree, page_offset(bio->bi_io_vec->bv_page), PAGE_SIZE); diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5cf320ee7ea0..084ed99dd308 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8051,6 +8051,12 @@ static void btrfs_retry_endio_nocsum(struct bio *bio) if (bio->bi_status) goto end; + /* + * WARNING: + * + * With multipage bvec, the following way of direct access to + * bvec table is only safe if the bio includes single page. + */ ASSERT(bio->bi_vcnt == 1); io_tree = &BTRFS_I(inode)->io_tree; failure_tree = &BTRFS_I(inode)->io_failure_tree; @@ -8143,6 +8149,12 @@ static void btrfs_retry_endio(struct bio *bio) uptodate = 1; + /* + * WARNING: + * + * With multipage bvec, the following way of direct access to + * bvec table is only safe if the bio includes single page. + */ ASSERT(bio->bi_vcnt == 1); ASSERT(bio->bi_io_vec->bv_len == btrfs_inode_sectorsize(done->inode));