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Thu, 10 Oct 2019 01:39:32 -0400 Received: by mail-pf1-f195.google.com with SMTP id q5so3123038pfg.13 for ; Wed, 09 Oct 2019 22:39:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mbobrowski-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=CQ8qLkYxE3s0aj/7O2LxSmHAT6SGLjMyMlog3ylNc2I=; b=nf3VoIshCTmDpZ0oex/t5ARoB3VgkbQuNWiDByqqqC//+0GDmW/7qKTuiv9Py8F8oO 6+pdWDVOp1zrT9x99x1szhVN2H3SbfQMqRYIQBtK1XzYSy+z/znzKPP7edXgzcDSRNSO AO8CchB7kaot693N5W81/j3mqPT/bR4eqCV1McMLmWdvNsF4tkZ41xmMcWF5xiZkT7Y1 KtTodBivEBrK2f7pehC8jAWkd/+jFVI9H7VF3YbLhrIsLj9pjUXNaWDNMfmgObVJ5W9D BA8yLQUR0AaflJVIpjTHybWJ4XC6bZX6lfVzcsvm+Y4z23r74p5/LzCsnAimeNKhXMAq ruUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=CQ8qLkYxE3s0aj/7O2LxSmHAT6SGLjMyMlog3ylNc2I=; 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charset=us-ascii Content-Disposition: inline In-Reply-To: <20191009130609.GD5050@quack2.suse.cz> 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, Oct 09, 2019 at 03:06:09PM +0200, Jan Kara wrote: > 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. I see and thank you for sharing your view point. Let's go with what you originally proposed, which is dropping the 'type' argument and then handling IOMAP_DELALLOC within ext4_set_iomap(). No real hard objections. :) ----