From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: vDSO vs. mm : problems with ppc vdso From: Benjamin Herrenschmidt In-Reply-To: References: <1141105154.3767.27.camel@localhost.localdomain> <20060227215416.2bfc1e18.akpm@osdl.org> <1141106896.3767.34.camel@localhost.localdomain> <20060227222055.4d877f16.akpm@osdl.org> <1141108220.3767.43.camel@localhost.localdomain> <440424CA.5070206@yahoo.com.au> Content-Type: text/plain Date: Wed, 01 Mar 2006 04:55:54 +1100 Message-Id: <1141149355.3767.57.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: Nick Piggin , Andrew Morton , linux-mm@kvack.org, paulus@samba.org, davem@davemloft.net List-ID: On Tue, 2006-02-28 at 12:32 +0000, Hugh Dickins wrote: > On Tue, 28 Feb 2006, Nick Piggin wrote: > > > > You should be OK. VM_RESERVED itself is something of an anachronism > > these days. If you're not getting your page from the page allocator > > then you'll want to make sure each of their count, and mapcount is > > reset before allowing them to be mapped. > > Yes, it's fine that VM_RESERVED isn't set on it. > But I don't understand your remarks about count and mapcount at all: > perhaps you meant to say something else? Ah thanks , I was worried there too ;) > If I ignore what you actually said, and think of what problems there > might be in that area, then yes, if the pages come from kernel memory > (they do) rather than page allocator, we'd better make sure page_count > starts above 0, so it doesn't go down to zero on last free from userspace: > and indeed, Ben's vdso_init does a get_page on each to ensure that. Yup, I took care of that and that part seems to work. I don't touch mapcount at all. Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org