linux-kernel - Re: [PATCH v2] vfs: add RWF

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Message-ID: <f20a786f-156a-4772-8633-66518bd09a02@oracle.com>
Date: Mon, 22 Jul 2024 10:28:27 +0100
From: John Garry <john.g.garry@...cle.com>
To: Rich Felker <dalias@...c.org>, Jann Horn <jannh@...gle.com>
Cc: linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: Re: [PATCH v2] vfs: add RWF_NOAPPEND flag for pwritev2

On 31/08/2020 16:32, Rich Felker wrote:
> The pwrite function, originally defined by POSIX (thus the "p"), is
> defined to ignore O_APPEND and write at the offset passed as its
> argument. However, historically Linux honored O_APPEND if set and
> ignored the offset. This cannot be changed due to stability policy,
> but is documented in the man page as a bug.
> 
> Now that there's a pwritev2 syscall providing a superset of the pwrite
> functionality that has a flags argument, the conforming behavior can
> be offered to userspace via a new flag. Since pwritev2 checks flag
> validity (in kiocb_set_rw_flags) and reports unknown ones with
> EOPNOTSUPP, callers will not get wrong behavior on old kernels that
> don't support the new flag; the error is reported and the caller can
> decide how to handle it.
> 
> Signed-off-by: Rich Felker <dalias@...c.org>

What about updating the linux man pages for this flag?

If someone gives me a description of RWF_NOAPPEND for 
rehttps://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man/man2/readv.2, 
then I can do it.