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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 BDB79C35DF5 for ; Tue, 25 Feb 2020 09:21:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 990DE21744 for ; Tue, 25 Feb 2020 09:21:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726916AbgBYJVa (ORCPT ); Tue, 25 Feb 2020 04:21:30 -0500 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:59746 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726867AbgBYJVa (ORCPT ); Tue, 25 Feb 2020 04:21:30 -0500 Received: from dread.disaster.area (pa49-195-202-68.pa.nsw.optusnet.com.au [49.195.202.68]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id DC8223A2B2D; Tue, 25 Feb 2020 20:21:22 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1j6WP4-0007us-5L; Tue, 25 Feb 2020 20:21:22 +1100 Date: Tue, 25 Feb 2020 20:21:22 +1100 From: Dave Chinner To: Allison Collins Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH v7 16/19] xfs: Simplify xfs_attr_set_iter Message-ID: <20200225092122.GK10776@dread.disaster.area> References: <20200223020611.1802-1-allison.henderson@oracle.com> <20200223020611.1802-17-allison.henderson@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200223020611.1802-17-allison.henderson@oracle.com> 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=mqTaRPt+QsUAtUurwE173Q==:117 a=mqTaRPt+QsUAtUurwE173Q==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=l697ptgUJYAA:10 a=yPCof4ZbAAAA:8 a=7-415B0cAAAA:8 a=NbAEnV_rIWBo99No2akA:9 a=sF15wFxuq4E-j2l5:21 a=LxOBVDF-yqvvc8_b:21 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Sat, Feb 22, 2020 at 07:06:08PM -0700, Allison Collins wrote: > Delayed attribute mechanics make frequent use of goto statements. We can use this > to further simplify xfs_attr_set_iter. Because states tend to fall between if > conditions, we can invert the if logic and jump to the goto. This helps to reduce > indentation and simplify things. > > Signed-off-by: Allison Collins > --- > fs/xfs/libxfs/xfs_attr.c | 71 ++++++++++++++++++++++++++++-------------------- > 1 file changed, 42 insertions(+), 29 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c > index 30a16fe..dd935ff 100644 > --- a/fs/xfs/libxfs/xfs_attr.c > +++ b/fs/xfs/libxfs/xfs_attr.c > @@ -254,6 +254,19 @@ xfs_attr_try_sf_addname( > } > > /* > + * Check to see if the attr should be upgraded from non-existent or shortform to > + * single-leaf-block attribute list. > + */ > +static inline bool > +xfs_attr_fmt_needs_update( > + struct xfs_inode *dp) Can we use *ip for the inode in newly factored code helpers like this? > +{ > + return dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL || > + (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS && > + dp->i_d.di_anextents == 0); > +} > + > +/* > * Set the attribute specified in @args. > */ > int > @@ -342,40 +355,40 @@ xfs_attr_set_iter( > } > > /* > - * If the attribute list is non-existent or a shortform list, > - * upgrade it to a single-leaf-block attribute list. > + * If the attribute list is already in leaf format, jump straight to > + * leaf handling. Otherwise, try to add the attribute to the shortform > + * list; if there's no room then convert the list to leaf format and try > + * again. > */ > - if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL || > - (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS && > - dp->i_d.di_anextents == 0)) { > + if (!xfs_attr_fmt_needs_update(dp)) > + goto add_leaf; The logic seems inverted to me here, but that really indicates a sub-optimal function name. It's really checking if the attribute fork is empty or in shortform format. Hence: if (!xfs_attr_is_shortform(dp)) goto add_leaf; > - /* > - * Try to add the attr to the attribute list in the inode. > - */ > - error = xfs_attr_try_sf_addname(dp, args); > + /* > + * Try to add the attr to the attribute list in the inode. > + */ > + error = xfs_attr_try_sf_addname(dp, args); > > - /* Should only be 0, -EEXIST or ENOSPC */ > - if (error != -ENOSPC) > - return error; > + /* Should only be 0, -EEXIST or ENOSPC */ > + if (error != -ENOSPC) > + return error; > > - /* > - * It won't fit in the shortform, transform to a leaf block. > - * GROT: another possible req'mt for a double-split btree op. > - */ > - error = xfs_attr_shortform_to_leaf(args, leaf_bp); > - if (error) > - return error; > + /* > + * It won't fit in the shortform, transform to a leaf block. > + * GROT: another possible req'mt for a double-split btree op. > + */ > + error = xfs_attr_shortform_to_leaf(args, leaf_bp); > + if (error) > + return error; > > - /* > - * Prevent the leaf buffer from being unlocked so that a > - * concurrent AIL push cannot grab the half-baked leaf > - * buffer and run into problems with the write verifier. > - */ > - xfs_trans_bhold(args->trans, *leaf_bp); > - args->dac.flags |= XFS_DAC_FINISH_TRANS; > - args->dac.dela_state = XFS_DAS_ADD_LEAF; > - return -EAGAIN; > - } > + /* > + * Prevent the leaf buffer from being unlocked so that a > + * concurrent AIL push cannot grab the half-baked leaf > + * buffer and run into problems with the write verifier. > + */ > + xfs_trans_bhold(args->trans, *leaf_bp); > + args->dac.flags |= XFS_DAC_FINISH_TRANS; > + args->dac.dela_state = XFS_DAS_ADD_LEAF; > + return -EAGAIN; Heh. This is an example of exactly why I think this should be factored into functions first. Move all the code you just re-indented into xfs_attr_set_shortform(), and the goto disappears because this code becomes: if (xfs_attr_is_shortform(dp)) return xfs_attr_set_shortform(dp, args); add_leaf: That massively improves the readability of the code - it separates the operation implementation from the decision logic nice and cleanly, and lends itself to being implemented in the delayed attr state machine without needing gotos at all. Cheers, Dave. -- Dave Chinner david@fromorbit.com