Date: Wed, 19 Oct 2016 11:23:51 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Jan Kara <jack@suse.cz>, linux-mm@kvack.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Rik van Riel <riel@redhat.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        adi-buildroot-devel@lists.sourceforge.net, ceph-devel@vger.kernel.org,
        dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        kvm@vger.kernel.org, linux-alpha@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-cris-kernel@axis.com,
        linux-fbdev@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org, linux-mips@linux-mips.org,
        linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org,
        linux-samsung-soc@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-sh@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org,
        sparclinux@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 08/10] mm: replace __access_remote_vm() write parameter
 with gup_flags
Message-ID: <20161019092350.GF7517@dhcp22.suse.cz>
References: <20161013002020.3062-1-lstoakes@gmail.com>
 <20161013002020.3062-9-lstoakes@gmail.com>
 <20161019075903.GP29967@quack2.suse.cz>
 <20161019081352.GB7562@dhcp22.suse.cz>
 <20161019084045.GA19441@lucifer>
 <20161019085204.GD7517@dhcp22.suse.cz>
 <20161019090646.GA24243@lucifer>
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On Wed 19-10-16 10:06:46, Lorenzo Stoakes wrote:
> On Wed, Oct 19, 2016 at 10:52:05AM +0200, Michal Hocko wrote:
> > yes this is the desirable and expected behavior.
> >
> > > wonder if this is desirable behaviour or whether this ought to be limited to
> > > ptrace system calls. Regardless, by making the flag more visible it makes it
> > > easier to see that this is happening.
> >
> > mem_open already enforces PTRACE_MODE_ATTACH
> 
> Ah I missed this, that makes a lot of sense, thanks!
> 
> I still wonder whether other invocations of access_remote_vm() in fs/proc/base.c
> (the principle caller of this function) need FOLL_FORCE, for example the various
> calls that simply read data from other processes, so I think the point stands
> about keeping this explicit.

I do agree. Making them explicit will help to clean them up later,
should there be a need.

-- 
Michal Hocko
SUSE Labs