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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 1398DC433ED for ; Mon, 3 May 2021 14:28:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C733B61139 for ; Mon, 3 May 2021 14:28:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229697AbhECO25 (ORCPT ); Mon, 3 May 2021 10:28:57 -0400 Received: from mx2.suse.de ([195.135.220.15]:45828 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229687AbhECO25 (ORCPT ); Mon, 3 May 2021 10:28:57 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4699CAFCC; Mon, 3 May 2021 14:28:03 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 45C20DA7A1; Mon, 3 May 2021 16:25:36 +0200 (CEST) Date: Mon, 3 May 2021 16:25:36 +0200 From: David Sterba To: "tiantao (H)" Cc: dsterba@suse.cz, Tian Tao , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: delete unneeded assignments in btrfs_defrag_file Message-ID: <20210503142536.GM7604@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, "tiantao (H)" , Tian Tao , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org References: <1619488221-29490-1-git-send-email-tiantao6@hisilicon.com> <20210428180243.GS7604@twin.jikos.cz> <0c116d82-3334-ed4e-fb69-76c1c6c8343a@huawei.com> <20210429132233.GV7604@twin.jikos.cz> <64eef0c6-4353-7738-124a-8ddfe4edda66@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <64eef0c6-4353-7738-124a-8ddfe4edda66@huawei.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Apr 30, 2021 at 09:27:21AM +0800, tiantao (H) wrote: > > 在 2021/4/29 21:22, David Sterba 写道: > > On Thu, Apr 29, 2021 at 09:16:53AM +0800, tiantao (H) wrote: > >> 在 2021/4/29 2:02, David Sterba 写道: > >>> On Tue, Apr 27, 2021 at 09:50:21AM +0800, Tian Tao wrote: > >>>> ret is assigned -EAGAIN at line 1455 and then reassigned defrag_count > >>>> at line 1547 after exiting the while loop, but the btrfs_defrag_file > >>>> function returns a negative number indicating that the execution failed > >>>> because it does not make sense to reassign defrag_count to ret, so > >>>> delete it. > >>> The line references are fragile, so the 1455 is after defrag is > >>> cancelled. > >>> > >>>> Signed-off-by: Tian Tao > >>>> --- > >>>> fs/btrfs/ioctl.c | 2 -- > >>>> 1 file changed, 2 deletions(-) > >>>> > >>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > >>>> index ee1dbab..2b3b228 100644 > >>>> --- a/fs/btrfs/ioctl.c > >>>> +++ b/fs/btrfs/ioctl.c > >>>> @@ -1544,8 +1544,6 @@ int btrfs_defrag_file(struct inode *inode, struct file *file, > >>>> btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD); > >>>> } > >>>> > >>>> - ret = defrag_count; > >>> But this would change semantics of the whole function, after deleting > >>> this line any stale value of 'ret' would be returned, it's used for some > >>> intermediate return values in the whole while loop. > >>> > >>> 1597 if (btrfs_defrag_cancelled(fs_info)) { > >>> 1598 btrfs_debug(fs_info, "defrag_file cancelled"); > >>> 1599 ret = -EAGAIN; > >>> 1600 break; > >>> 1601 } > >>> > >>> Jumping to the 'out_ra' label looks like a candidate fix but that also > >>> jumps around all the incompat bit setting, so that could in some cases > >>> miss to set them properly. And actually this is a problem with all the > >>> other error cases. > >>> > >>> I'm not yet sure what's the proper fix, but the errors from within the > >>> while loop should be returned and incompat bits set. > >> How does the following change look? > >> > >> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > >> index ee1dbab..b8e496e 100644 > >> --- a/fs/btrfs/ioctl.c > >> +++ b/fs/btrfs/ioctl.c > >> @@ -1453,7 +1453,7 @@ int btrfs_defrag_file(struct inode *inode, struct > >> file *file, > >>                 if (btrfs_defrag_cancelled(fs_info)) { > >>                         btrfs_debug(fs_info, "defrag_file cancelled"); > >>                         ret = -EAGAIN; > >> -                       break; > >> +                      goto error; > >>                 } > >> > >>                 if (!should_defrag_range(inode, (u64)i << PAGE_SHIFT, > >> @@ -1531,6 +1531,9 @@ int btrfs_defrag_file(struct inode *inode, struct > >> file *file, > >>                 } > >>         } > >> > >> +       ret = defrag_count; > >> + > >> +error: > >>         if ((range->flags & BTRFS_DEFRAG_RANGE_START_IO)) { > >>                 filemap_flush(inode->i_mapping); > >>                 if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT, > >> @@ -1544,8 +1547,6 @@ int btrfs_defrag_file(struct inode *inode, struct > >> file *file, > >>                 btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD); > >>         } > >> > >> -       ret = defrag_count; > >> - > >>  out_ra: > >>         if (do_compress) { > >>                 btrfs_inode_lock(inode, 0); > > Yes that looks like covering all the issues. One more thing is the change on > > the userspace where the cancelled defrag returns non-error, but now it would be > > EAGAIN. So far I haven't found anything that would go wrong, all errors > > are reported and the whole defrag loop continues. Pressing ctrl-c should > > cancel it completely. > > . > Would you give ack-by if v2 was sent according to this code above? Yes, thanks.