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

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Message-ID: <20240119191053.GT22081@brightrain.aerifal.cx>
Date: Fri, 19 Jan 2024 14:10:54 -0500
From: Rich Felker <dalias@...c.org>
To: Christian Brauner <brauner@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>,
	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>,
	Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH v2] vfs: add RWF_NOAPPEND flag for pwritev2

On Fri, Jan 19, 2024 at 03:33:32PM +0100, Christian Brauner wrote:
> On Mon, 31 Aug 2020 11:32:08 -0400, 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.
> > 
> > [...]
> 
> The RWF_* and IOCB_* flags were
> aligned so they could be set in one operation. So there was a merge
> conflict when applying. I've resolved it. Please take a look and make
> sure that it's all correct.
> 
> ---
> 
> Applied to the vfs.misc branch of the vfs/vfs.git tree.
> Patches in the vfs.misc branch should appear in linux-next soon.
> 
> Please report any outstanding bugs that were missed during review in a
> new review to the original patch series allowing us to drop it.
> 
> It's encouraged to provide Acked-bys and Reviewed-bys even though the
> patch has now been applied. If possible patch trailers will be updated.
> 
> Note that commit hashes shown below are subject to change due to rebase,
> trailer updates or similar. If in doubt, please check the listed branch.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
> branch: vfs.misc
> 
> [1/1] vfs: add RWF_NOAPPEND flag for pwritev2
>       https://git.kernel.org/vfs/vfs/c/31081ab305a1

LGTM. Thanks!