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

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Date:   Tue, 20 Jun 2023 17:34:00 +0500
From:   stsp <stsp2@...dex.ru>
To:     Jeff Layton <jlayton@...nel.org>, linux-kernel@...r.kernel.org
Cc:     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


20.06.2023 17:02, Jeff Layton пишет:
> Suppose I start a process (call it pid 100), and then spawn a thread
> (101). I then have 101 open a file and set an OFD lock on it (such that
> the resulting fl_pid field in the file_lock is set to 101).

How come?
There are multiple places in locks.c
with this line:
fl->fl_pid = current->tgid;

And I've yet to see the line like:
fl->fl_pid = current->pid;
Its simply not there.

No, we put tgid into l_pid!
tgid will still be 100, no matter how
many threads you spawn or destroy.
Or what am I misseng?


> That's just one example, of course. The underlying problem is that OFD
> locks are not owned by processes in the same way that traditional POSIX
> locks are, so reporting a pid there is unreliable, at best.
But we report tgid.
It doesn't depend on threads.
I don't understand. :)