Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5728ebda22a723b0eb209ae078e8f132d7b4ac7b.camel@kernel.org>
Subject: Re: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD_GETLK
From:   Jeff Layton <jlayton@kernel.org>
To:     Stas Sergeev <stsp2@yandex.ru>, linux-kernel@vger.kernel.org
Cc:     Chuck Lever <chuck.lever@oracle.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        linux-fsdevel@vger.kernel.org
Date:   Tue, 20 Jun 2023 06:51:41 -0400
In-Reply-To: <20230620095507.2677463-3-stsp2@yandex.ru>
References: <20230620095507.2677463-1-stsp2@yandex.ru>
         <20230620095507.2677463-3-stsp2@yandex.ru>
Content-Type: text/plain; charset="ISO-8859-15"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.48.3 (3.48.3-1.fc38) 
MIME-Version: 1.0
Precedence: bulk

On Tue, 2023-06-20 at 14:55 +0500, Stas Sergeev wrote:
> Currently F_OFD_GETLK sets the pid of the lock owner to -1.
> Remove such behavior to allow getting the proper owner's pid.
> This may be helpful when you want to send some message (like SIGKILL)
> to the offending locker.
>=20
> Signed-off-by: Stas Sergeev <stsp2@yandex.ru>
>=20
> CC: Jeff Layton <jlayton@kernel.org>
> CC: Chuck Lever <chuck.lever@oracle.com>
> CC: Alexander Viro <viro@zeniv.linux.org.uk>
> CC: Christian Brauner <brauner@kernel.org>
> CC: linux-fsdevel@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
>=20
> ---
>  fs/locks.c | 2 --
>  1 file changed, 2 deletions(-)
>=20
> diff --git a/fs/locks.c b/fs/locks.c
> index 210766007e63..ee265e166542 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2158,8 +2158,6 @@ static pid_t locks_translate_pid(struct file_lock *=
fl, struct pid_namespace *ns)
>  	pid_t vnr;
>  	struct pid *pid;
> =20
> -	if (IS_OFDLCK(fl))
> -		return -1;
>  	if (IS_REMOTELCK(fl))
>  		return fl->fl_pid;
>  	/*

NACK on this one.

OFD locks are not owned by processes. They are owned by the file
description (hence the name). Because of this, returning a pid here is
wrong.

This precedent comes from BSD, where flock() and POSIX locks can
conflict. BSD returns -1 for the pid if you call F_GETLK on a file
locked with flock(). Since OFD locks have similar ownership semantics to
flock() locks, we use the same convention here.

Cheers,=20
--=20
Jeff Layton <jlayton@kernel.org>