Re: [PATCH v7 12/12] iomap: Put struct iomap_ops into struct iomap

From: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
	cluster-devel <cluster-devel@redhat.com>,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v7 12/12] iomap: Put struct iomap_ops into struct iomap
Date: Mon, 4 Jun 2018 19:00:21 +0200	[thread overview]
Message-ID: <CAHpGcMJiEhpVkdgOSkO_2tqSpYW5QmM3vqkJHmDgLZ9qBcFHpw@mail.gmail.com> (raw)
In-Reply-To: <20180604125227.GC30780@lst.de>

2018-06-04 14:52 GMT+02:00 Christoph Hellwig <hch@lst.de>:
> On Mon, Jun 04, 2018 at 02:37:29PM +0200, Andreas Gruenbacher wrote:
>> We need access to the struct iomap_ops in iomap_write_end to call the
>> (optional) page_write_end hook, so instead of passing the operators to
>> iomap_write_end differently depending on the code path, add an ops field
>> to struct iomap.
>
> I don't really like this.  We already pass the iomap_ops to the
> function we call from iomap.c, and in fact ->iomap_begin is called
> through the ops.

There's no duplicate ops passing going on if that's what you mean.

> But what we could do is to move the page_write_end callback out of
> iomap_ops and just attached it to the iomap, especially given that
> it isn't really as generic as the other ops.

Given that struct iomap is allocated inside iomap_apply(), if
page_write_end is moved to struct iomap, how would the filesystem set
it?

> Can't say I like the implications of this callback in general, but
> the use case is real, so..

Yes, it's not very pretty.

Thanks,
Andreas