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 7C842C34022 for ; Wed, 19 Feb 2020 03:29:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D45B24658 for ; Wed, 19 Feb 2020 03:29:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726739AbgBSD3H (ORCPT ); Tue, 18 Feb 2020 22:29:07 -0500 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:56365 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726667AbgBSD3H (ORCPT ); Tue, 18 Feb 2020 22:29:07 -0500 Received: from dread.disaster.area (pa49-179-138-28.pa.nsw.optusnet.com.au [49.179.138.28]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id C4ADA7EB4FD; Wed, 19 Feb 2020 14:29:02 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1j4G2m-0005Wz-JP; Wed, 19 Feb 2020 14:29:00 +1100 Date: Wed, 19 Feb 2020 14:29:00 +1100 From: Dave Chinner To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org Subject: Re: [PATCH v6 17/19] iomap: Restructure iomap_readpages_actor Message-ID: <20200219032900.GE10776@dread.disaster.area> References: <20200217184613.19668-1-willy@infradead.org> <20200217184613.19668-31-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200217184613.19668-31-willy@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=X6os11be c=1 sm=1 tr=0 a=zAxSp4fFY/GQY8/esVNjqw==:117 a=zAxSp4fFY/GQY8/esVNjqw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=l697ptgUJYAA:10 a=JfrnYn6hAAAA:8 a=7-415B0cAAAA:8 a=D_ITGRzz0ucxF3CW0B0A:9 a=m4Eakf-3O-CBJR1D:21 a=uIsSIQHDIO17Gszz:21 a=CjuIK1q_8ugA:10 a=1CNFftbPRP8L7MoqJWF3:22 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Feb 17, 2020 at 10:46:11AM -0800, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > By putting the 'have we reached the end of the page' condition at the end > of the loop instead of the beginning, we can remove the 'submit the last > page' code from iomap_readpages(). Also check that iomap_readpage_actor() > didn't return 0, which would lead to an endless loop. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > fs/iomap/buffered-io.c | 25 ++++++++++++------------- > 1 file changed, 12 insertions(+), 13 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index cb3511eb152a..44303f370b2d 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -400,15 +400,9 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length, > void *data, struct iomap *iomap, struct iomap *srcmap) > { > struct iomap_readpage_ctx *ctx = data; > - loff_t done, ret; > + loff_t ret, done = 0; > > - for (done = 0; done < length; done += ret) { > - if (ctx->cur_page && offset_in_page(pos + done) == 0) { > - if (!ctx->cur_page_in_bio) > - unlock_page(ctx->cur_page); > - put_page(ctx->cur_page); > - ctx->cur_page = NULL; > - } > + while (done < length) { > if (!ctx->cur_page) { > ctx->cur_page = iomap_next_page(inode, ctx->pages, > pos, length, &done); > @@ -418,6 +412,15 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length, > } > ret = iomap_readpage_actor(inode, pos + done, length - done, > ctx, iomap, srcmap); > + if (WARN_ON(ret == 0)) > + break; This error case now leaks ctx->cur_page.... > + done += ret; > + if (offset_in_page(pos + done) == 0) { > + if (!ctx->cur_page_in_bio) > + unlock_page(ctx->cur_page); > + put_page(ctx->cur_page); > + ctx->cur_page = NULL; > + } > } > > return done; > @@ -451,11 +454,7 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages, > done: > if (ctx.bio) > submit_bio(ctx.bio); > - if (ctx.cur_page) { > - if (!ctx.cur_page_in_bio) > - unlock_page(ctx.cur_page); > - put_page(ctx.cur_page); > - } > + BUG_ON(ctx.cur_page); And so will now trigger both a warn and a bug.... Cheers, Dave. -- Dave Chinner david@fromorbit.com