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

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Date: Fri, 19 Jan 2024 15:33:32 +0100
From: Christian Brauner <brauner@...nel.org>
To: Rich Felker <dalias@...c.org>,
	Jens Axboe <axboe@...nel.dk>
Cc: Christian Brauner <brauner@...nel.org>,
	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 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