linux-kernel - Re: fs_struct refcounting: spinlock vs atomic

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Message-ID: <20180215185204.GD30522@ZenIV.linux.org.uk>
Date:   Thu, 15 Feb 2018 18:52:04 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Enrico Weigelt <lkml@...ux.net>
Cc:     Richard Weinberger <richard.weinberger@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: fs_struct refcounting: spinlock vs atomic

On Thu, Feb 15, 2018 at 06:39:57PM +0000, Al Viro wrote:

> Not true.  We also assume that once fs_struct has been locked, the number of
> tasks with reference to it won't change.  See fs/exec.c:check_unsafe_exec(),
> for example.

PS: any discussion of VFS and filesystems stuff belongs on fsdevel; Cc to l-k
is fine, but don't expect anyone to be able to reliably spot it there.

l-k is far too high volume (and low S/N) to keep up with it; some of us have
entirely given up on it (Linus is certainly not the only one who'd unsubscribed
from l-k many years ago), some try to scan it for something relevant, but
latency and reliability of such scans inevitably sucks.