linux-kernel - Re: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD

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Message-ID: <ZJG5ZOK8HKl/eWmM@casper.infradead.org>
Date:   Tue, 20 Jun 2023 15:36:20 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     stsp <stsp2@...dex.ru>
Cc:     Jeff Layton <jlayton@...nel.org>, linux-kernel@...r.kernel.org,
        Chuck Lever <chuck.lever@...cle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] fd/locks: allow get the lock owner by F_OFD_GETLK

On Tue, Jun 20, 2023 at 06:47:31PM +0500, stsp wrote:
> 
> 20.06.2023 18:46, Matthew Wilcox пишет:
> > On Tue, Jun 20, 2023 at 06:39:07PM +0500, stsp wrote:
> > > Though it will, for sure, represent the
> > > task that _owns_ the lock.
> > No, it *DOESN'T*.  I can open a file, SCM_RIGHTS pass it to another task
> > and then exit.  Now the only owner of that lock is the recipient ...
> Won't I get the recipient's pid in an
> l_pid then?

You snipped the part where I pointed out that at times there can be
_no_ task that owns it.  open a fd, set the lock, pass the fd to another
task, exit.  until that task calls recvmsg(), no task owns it.