From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andy Lutomirski <luto@amacapital.net>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>,
Michel Lespinasse <walken@google.com>,
Hugh Dickins <hughd@google.com>, J??rn Engel <joern@logfs.org>
Subject: Re: [PATCH] mm: Downgrade mmap_sem before locking or populating on mmap
Date: Fri, 14 Dec 2012 14:49:27 +0000 [thread overview]
Message-ID: <20121214144927.GS4939@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CALCETrVw9Pc1sUZBL=wtLvsnBnkW5LAO5iu-i=T2oMOdwQfjHg@mail.gmail.com>
On Fri, Dec 14, 2012 at 03:14:50AM -0800, Andy Lutomirski wrote:
> > Wait a minute. get_user_pages() relies on ->mmap_sem being held. Unless
> > I'm seriously misreading your patch it removes that protection. And yes,
> > I'm aware of execve-related exception; it's in special circumstances -
> > bprm->mm is guaranteed to be not shared (and we need to rearchitect that
> > area anyway, but that's a separate story).
>
> Unless I completely screwed up the patch, ->mmap_sem is still held for
> read (it's downgraded from write). It's just not held for write
> anymore.
Huh? I'm talking about the call of get_user_pages() in aio_setup_ring().
With your patch it's done completely outside of ->mmap_sem, isn't it?
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next prev parent reply other threads:[~2012-12-14 14:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-14 5:49 [PATCH] mm: Downgrade mmap_sem before locking or populating on mmap Andy Lutomirski
2012-12-14 7:27 ` Al Viro
2012-12-14 11:14 ` Andy Lutomirski
2012-12-14 14:49 ` Al Viro [this message]
2012-12-14 16:12 ` Andy Lutomirski
2012-12-16 8:41 ` Ingo Molnar
2012-12-16 17:04 ` Al Viro
2012-12-16 17:48 ` Al Viro
2012-12-16 18:49 ` Johannes Weiner
2012-12-16 19:53 ` Al Viro
2012-12-16 20:16 ` Al Viro
2012-12-15 2:17 ` [PATCH v2] " Andy Lutomirski
2012-12-16 9:00 ` Ingo Molnar
2012-12-16 17:52 ` Andy Lutomirski
2012-12-17 9:52 ` Ingo Molnar
2012-12-18 0:54 ` [PATCH v3] " Andy Lutomirski
2012-12-20 2:22 ` Simon Jeons
2012-12-16 12:39 ` [PATCH v2] " Michel Lespinasse
2012-12-16 18:05 ` Andy Lutomirski
2012-12-17 3:29 ` Michel Lespinasse
2012-12-17 22:01 ` Andy Lutomirski
2012-12-16 19:58 ` Linus Torvalds
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