linux-kernel - Re: [PATCH v1 0/6] no-copy bvec

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Date:   Tue, 15 Dec 2020 09:41:14 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Pavel Begunkov <asml.silence@...il.com>
Cc:     linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Jonathan Corbet <corbet@....net>, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, target-devel@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v1 0/6] no-copy bvec

On Tue, Dec 15, 2020 at 12:20:19AM +0000, Pavel Begunkov wrote:
> Instead of creating a full copy of iter->bvec into bio in direct I/O,
> the patchset makes use of the one provided. It changes semantics and
> obliges users of asynchronous kiocb to track bvec lifetime, and [1/6]
> converts the only place that doesn't.

Just think of one corner case: iov_iter(BVEC) may pass bvec table with zero
length bvec, which may not be supported by block layer or driver, so
this patchset has to address this case first.

Please see 7e24969022cb ("block: allow for_each_bvec to support zero len bvec").


thanks,
Ming