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Date: Thu, 13 Nov 2025 07:50:55 +0100
From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>, Christian Brauner <brauner@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Darrick J. Wong" <djwong@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	Avi Kivity <avi@scylladb.com>, Damien Le Moal <dlemoal@kernel.org>,
	Naohiro Aota <naohiro.aota@wdc.com>,
	Johannes Thumshirn <jth@kernel.org>, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org
Subject: Re: [PATCH 4/5] iomap: support write completions from interrupt
 context
Message-ID: <20251113065055.GA29641@lst.de>
References: <20251112072214.844816-1-hch@lst.de> <20251112072214.844816-5-hch@lst.de> <nujtqnweb7jfbyk4ov3a7z5tdtl24xljntzbpecgv6l7aoeytd@nkxsilt6w7d3>
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On Wed, Nov 12, 2025 at 09:25:58PM +0100, Jan Kara wrote:
> > +
> > +		/*
> > +		 * We can only do inline completion for pure overwrites that
> > +		 * don't require additional I/O at completion time.
> > +		 *
> > +		 * This rules out writes that need zeroing or extent conversion,
> > +		 * or extend the file size.
> > +		 */
> > +		if (!iomap_dio_is_overwrite(iomap))
> > +			dio->flags &= ~IOMAP_DIO_INLINE_COMP;
> >  	} else {
> >  		bio_opf |= REQ_OP_READ;
> >  	}
> 
> OK, now I see why you wrote iomap_dio_is_overwrite() the way you did. You
> still want to keep completions inline for overwrites of possibly
> uncommitted extents.

Yes.

> But I have to admit it all seems somewhat fragile and
> difficult to follow. Can't we just check for IOMAP_DIO_UNWRITTEN |
> IOMAP_DIO_COW | IOMAP_DIO_NEED_SYNC in flags (plus the i_size check) and be
> done with it?

You mean drop the common helper?  How would that be better and less
fragile?   Note that I care strongly, but I don't really see the point.