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From:   David Howells <dhowells@redhat.com>
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To:     Christoph Hellwig <hch@infradead.org>
Cc:     dhowells@redhat.com, Jens Axboe <axboe@kernel.dk>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Hillf Danton <hdanton@sina.com>,
        Christian Brauner <brauner@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v20 03/32] splice: Make direct_read_splice() limit to eof where appropriate
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Date:   Fri, 19 May 2023 09:43:34 +0100
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Christoph Hellwig <hch@infradead.org> wrote:

> I'm really not sure if this is a good idea.  Right now
> direct_read_splice (which also appears a little misnamed) really is
> a splice by calling ->read_iter helper.

It can be renamed if you want a different name.  copy_splice_read() or
copy_splice_read_iter()?

> I we don't do any of this validtion we can just call it directly from
> splice.c instead of calling into ->splice_read for direct I/O and DAX and
> remove a ton of boilerplate code.

There's a couple of places where we might not want to do that - at least for
non-DAX.  shmem and f2fs for example.  f2fs calls back to buffered reading
under some circumstances.  shmem ignores O_DIRECT and always splices from the
pagecache.

David