From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
To: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>
Cc: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org,
linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
hch-jcswGhMUV9g@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [RFC PATCH v8 2/2] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags
Date: Mon, 11 Sep 2017 13:10:30 +0200 [thread overview]
Message-ID: <20170911111030.GA20127@lst.de> (raw)
In-Reply-To: <20170911094714.GD8503-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
On Mon, Sep 11, 2017 at 11:47:14AM +0200, Jan Kara wrote:
> On Fri 08-09-17 12:35:13, Dan Williams wrote:
> > The mmap(2) syscall suffers from the ABI anti-pattern of not validating
> > unknown flags. However, proposals like MAP_SYNC and MAP_DIRECT need a
> > mechanism to define new behavior that is known to fail on older kernels
> > without the support. Define a new MAP_SHARED_VALIDATE flag pattern that
> > is guaranteed to fail on all legacy mmap implementations.
> >
> > With this in place new flags can be defined as:
> >
> > #define MAP_new (MAP_SHARED_VALIDATE | val)
>
> Is this changelog stale? Given MAP_SHARED_VALIDATE will be new mapping
> type, I'd expect we define new flags just as any other mapping flags...
> I see no reason why MAP_SHARED_VALIDATE should be or'ed to that.
Btw, I still think it should be a new hidden flag and not a new mapping
type. I brought this up last time, so maybe I missed the answer
to my concern.
next prev parent reply other threads:[~2017-09-11 11:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-08 19:35 [RFC PATCH v8 0/2] mmap: safely enable support for new flags Dan Williams
[not found] ` <150489930202.29460.5141541423730649272.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-09-08 19:35 ` [RFC PATCH v8 1/2] vfs: add flags parameter to all ->mmap() handlers Dan Williams
2017-09-11 9:50 ` Jan Kara
2017-09-08 19:35 ` [RFC PATCH v8 2/2] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags Dan Williams
[not found] ` <150489931339.29460.8760855724603300792.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-09-11 9:47 ` Jan Kara
[not found] ` <20170911094714.GD8503-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2017-09-11 11:10 ` Christoph Hellwig [this message]
[not found] ` <20170911111030.GA20127-jcswGhMUV9g@public.gmane.org>
2017-09-11 11:45 ` Jan Kara
2017-09-11 17:01 ` Dan Williams
2017-09-11 17:21 ` Dan Williams
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