Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <YTrQuvqvJHd9IObe@zeniv-ca.linux.org.uk> <f02eae7c-f636-c057-4140-2e688393f79d@kernel.dk>
 <YTrSqvkaWWn61Mzi@zeniv-ca.linux.org.uk> <9855f69b-e67e-f7d9-88b8-8941666ab02f@kernel.dk>
 <4b26d8cd-c3fa-8536-a295-850ecf052ecd@kernel.dk> <1a61c333-680d-71a0-3849-5bfef555a49f@kernel.dk>
 <YTuOPAFvGpayTBpp@zeniv-ca.linux.org.uk> <CAHk-=wiPEZypYDnoDF7mRE=u1y6E_etmCTuOx3v2v6a_Wj=z3g@mail.gmail.com>
 <b1944570-0e72-fd64-a453-45f17e7c1e56@kernel.dk> <CAHk-=wjWQtXmtOK9nMdM68CKavejv=p-0B81WazbjxaD-e3JXw@mail.gmail.com>
 <YTuogsGTH5pQLKo7@zeniv-ca.linux.org.uk>
In-Reply-To: <YTuogsGTH5pQLKo7@zeniv-ca.linux.org.uk>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 10 Sep 2021 12:04:28 -0700
Message-ID: <CAHk-=wg8O4NBTUr9GvNo=vnUmONUGYypN4dFr7QNEGUFcN=tBw@mail.gmail.com>
Subject: Re: [git pull] iov_iter fixes
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Pavel Begunkov <asml.silence@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Sep 10, 2021 at 11:50 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> I think that sizeof(struct bio_vec) != sizeof(struct iovec):

Ooh, very good catch.

That would cause some *very* odd and subtle errors, since it just
happens to work on 64-bit, and then causes very confusing pointer
arithmetic errors on 32-bit.

So yeah, that

        i->iov -= state->nr_segs - i->nr_segs;

doesn't work after all, comment or not.

So only 'struct iovec' and 'struct kvec' actually have the same format
and can be used interchangeably.

            Linus