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Date: Mon, 28 May 2018 15:02:06 +0200
From: Christoph Hellwig <hch@lst.de>
To: Andreas =?iso-8859-1?Q?Gr=FCnbacher?=
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Cc: Christoph Hellwig <hch@lst.de>,
        Andreas Gruenbacher <agruenba@redhat.com>,
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        Dave Chinner <dchinner@redhat.com>
Subject: Re: [PATCH v4 06/11] iomap: Add write_{begin,end} iomap operations
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References: <20180514153624.29598-1-agruenba@redhat.com> <20180514153624.29598-7-agruenba@redhat.com> <20180515011147.GF23861@dastard> <20180515072252.GA23202@lst.de> <CAHc6FU6kwz4ZsKUdTHjNX5BsLb3Z0csqwP-UV0fHbLNsm70cDg@mail.gmail.com> <20180518160458.GA3503@lst.de> <CAHpGcM+m=Ar=_WO31J3OqdvGPHq3Ozq-QtAYKt0y8WL6+ybWtQ@mail.gmail.com>
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On Fri, May 25, 2018 at 07:58:14PM +0200, Andreas Gr�nbacher wrote:
> > The right way to deal with that is to make
> > inline data an explicit iomap type (done in my next posting of the
> > buffer head removal series), and then have iomap_begin find the data,
> > kmap it and return it in the iomap, with iomap_end doing any fixups.
> 
> I see what you mean. How would iomap_write_actor deal with
> IOMAP_INLINE -- just skip iomap_write_begin and iomap_write_end and
> grab the page from the iomap?

I would add a data pointer to struct iomap and pass the data back
from there.  We'll still need most of iomap_write_begin / iomap_write_end,
but just copy the data from the iomap instead of reading it from disk.
Note that the block_write_begin code already handles that case for
the get_blocks path.