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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 E5AB0C47404 for ; Wed, 9 Oct 2019 13:06:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7367206B6 for ; Wed, 9 Oct 2019 13:06:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731237AbfJINGN (ORCPT ); Wed, 9 Oct 2019 09:06:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:34158 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730858AbfJINGN (ORCPT ); Wed, 9 Oct 2019 09:06:13 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 5F941AE55; Wed, 9 Oct 2019 13:06:10 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B732B1E4851; Wed, 9 Oct 2019 15:06:09 +0200 (CEST) Date: Wed, 9 Oct 2019 15:06:09 +0200 From: Jan Kara To: Matthew Bobrowski Cc: Jan Kara , tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com Subject: Re: [PATCH v4 1/8] ext4: move out iomap field population into separate helper Message-ID: <20191009130609.GD5050@quack2.suse.cz> References: <8b4499e47bea3841194850e1b3eeb924d87e69a5.1570100361.git.mbobrowski@mbobrowski.org> <20191008102709.GD5078@quack2.suse.cz> <20191009085721.GA1534@poseidon.bobrowski.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191009085721.GA1534@poseidon.bobrowski.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed 09-10-19 19:57:23, Matthew Bobrowski wrote: > On Tue, Oct 08, 2019 at 12:27:09PM +0200, Jan Kara wrote: > > On Thu 03-10-19 21:33:09, Matthew Bobrowski wrote: > > > +static int ext4_set_iomap(struct inode *inode, struct iomap *iomap, u16 type, > > > + unsigned long first_block, struct ext4_map_blocks *map) > > > +{ > > > + u8 blkbits = inode->i_blkbits; > > > + > > > + iomap->flags = 0; > > > + if (ext4_inode_datasync_dirty(inode)) > > > + iomap->flags |= IOMAP_F_DIRTY; > > > + iomap->bdev = inode->i_sb->s_bdev; > > > + iomap->dax_dev = EXT4_SB(inode->i_sb)->s_daxdev; > > > + iomap->offset = (u64) first_block << blkbits; > > > + iomap->length = (u64) map->m_len << blkbits; > > > + > > > + if (type) { > > > + iomap->type = type; > > > + iomap->addr = IOMAP_NULL_ADDR; > > > + } else { > > > + if (map->m_flags & EXT4_MAP_MAPPED) { > > > + iomap->type = IOMAP_MAPPED; > > > + } else if (map->m_flags & EXT4_MAP_UNWRITTEN) { > > > + iomap->type = IOMAP_UNWRITTEN; > > > + } else { > > > + WARN_ON_ONCE(1); > > > + return -EIO; > > > + } > > > + iomap->addr = (u64) map->m_pblk << blkbits; > > > + } > > > > Looking at this function now, the 'type' argument looks a bit weird. Can we > > perhaps just remove the 'type' argument and change the above to: > > We can, but refer to the point below. > > > if (map->m_flags & (EXT4_MAP_MAPPED | EXT4_MAP_UNWRITTEN)) { > > if (map->m_flags & EXT4_MAP_MAPPED) > > iomap->type = IOMAP_MAPPED; > > else if (map->m_flags & EXT4_MAP_UNWRITTEN) > > iomap->type = IOMAP_UNWRITTEN; > > iomap->addr = (u64) map->m_pblk << blkbits; > > } else { > > iomap->type = IOMAP_HOLE; > > iomap->addr = IOMAP_NULL_ADDR; > > } > > > > And then in ext4_iomap_begin() we overwrite the type to: > > > > if (delalloc && iomap->type == IOMAP_HOLE) > > iomap->type = IOMAP_DELALLOC; > > > > That would IMO make ext4_set_iomap() arguments harder to get wrong. > > I was thinking about this while doing a bunch of other things at work > today. I'm kind of aligned with what Christoph mentioned around > possibly duplicating some of the post 'iomap->type' setting from both > current and any future ext4_set_iomap() callers. In addition to this, > my thought was that if we're populating the iomap structure with > values respectively, then it would make most sense to encapsulate > those routines, if possible, within the ext4_set_iomap() as that's the > sole purpose of the function. Well, what I dislike about 'type' argument is the inconsistency in it's handling. It is useful only for HOLE/DELALLOC, anything else will just give you invalid iomap and you have to be careful to pass 0 in that case. I understand the concern about possible duplication but since only IOMAP_REPORT cares about IOMAP_DELALLOC, I'm not much concerned about it. But another sensible API would be to optionally pass 'struct extent_status *es' argument to ext4_set_iomap() and if this argument is non-NULL, ext4_set_iomap() will handle the intersection of ext4_map_blocks and extent_status and deduce appropriate resulting type from that. Honza -- Jan Kara SUSE Labs, CR