linux-kernel - Re: [PATCH 3/9 next] lib/iov_iter: Improved function for importing iovec[] from userpace.

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Message-ID: <20200921141051.GC24515@infradead.org>
Date:   Mon, 21 Sep 2020 15:10:51 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>,
        "David S. Miller" <davem@...emloft.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 3/9 next] lib/iov_iter: Improved function for importing
 iovec[] from userpace.

On Tue, Sep 15, 2020 at 02:55:17PM +0000, David Laight wrote:
> 
> import_iovec() has a 'pointer by reference' parameter to pass in the
> (on-stack) iov[] cache and return the address of a larger copy that
> the caller must free.
> This is non-intuitive, faffy to setup, and not that efficient.
> Instead just pass in the address of the cache and return the address
> to free (on success) or PTR_ERR() (on error).

To me it seems pretty sensible, and in fact the conversions to your
new API seem to add more lines than they remove.