Date: Wed, 9 Mar 2011 02:33:04 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Stephen Wilson <wilsons@start.ca>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@redhat.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Roland McGrath <roland@redhat.com>, Matt Mackall <mpm@selenic.com>,
        David Rientjes <rientjes@google.com>, Nick Piggin <npiggin@kernel.dk>,
        Andrea Arcangeli <aarcange@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
        Ingo Molnar <mingo@elte.hu>, Michel Lespinasse <walken@google.com>,
        Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/6] enable writing to /proc/pid/mem
Message-ID: <20110309023303.GZ22723@ZenIV.linux.org.uk>
References: <1299631343-4499-1-git-send-email-wilsons@start.ca>
 <20110309013017.GY22723@ZenIV.linux.org.uk>
 <20110309021524.GA4838@fibrous.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20110309021524.GA4838@fibrous.localdomain>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 748
Lines: 15

On Tue, Mar 08, 2011 at 09:15:25PM -0500, Stephen Wilson wrote:

> I think we could also remove the intermediate copy in both mem_read() and
> mem_write() as well, but I think such optimizations could be left for
> follow on patches.

How?  We do copy_.._user() in there; it can trigger page faults and
that's not something you want while holding mmap_sem on some mm.
Looks like a deadlock country...  So we can't do that from inside
access_process_vm() or its analogs, which means buffering in caller.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/