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Date:   Wed, 23 Dec 2020 12:52:59 +0000
From:   Pavel Begunkov <>
To:     Christoph Hellwig <>
Cc:     Ming Lei <>,,
        Jens Axboe <>,
        Matthew Wilcox <>,
        Johannes Weiner <>,
        Alexander Viro <>,
        "Darrick J . Wong" <>,
        "Martin K . Petersen" <>,
        Jonathan Corbet <>,,,,,,,
Subject: Re: [PATCH v1 0/6] no-copy bvec

On 22/12/2020 14:11, Christoph Hellwig wrote:
> On Tue, Dec 15, 2020 at 02:05:35PM +0000, Pavel Begunkov wrote:
>>> You may find clue from the following link:
>> Thanks for the link!
>> Al, you mentioned "Zero-length segments are not disallowed", do you have
>> a strong opinion on that? Apart from already diverged behaviour from the
>> block layer and getting in the way of this series, without it we'd also be
>> able to remove some extra ifs, e.g. in iterate_bvec()
> I'd prefer not to support zero-length ITER_BVEC and catching them
> early, as the block layer can't deal with them either.  From a quick
> look at iter_file_splice_write it should be pretty trivial to fix there,
> although we'll need to audit other callers as well (even if I don't
> expect them to submit this degenerate case).

Can scatterlist have 0-len entries? Those are directly translated into
bvecs, e.g. in nvme/target/io-cmd-file.c and target/target_core_file.c.
I've audited most of others by this moment, they're fine.

Thanks for other nits, they will go into next version.

Pavel Begunkov

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