From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Thu, 1 Dec 2011 21:18:27 +0100 Subject: flatmem broken for nommu? [Was: Re: does non-continuous RAM means I need to select the sparse memory model?] In-Reply-To: <4ED7A6EF.1000705@the2masters.de> References: <20111129203010.GA26618@pengutronix.de> <20111201105718.GJ26618@pengutronix.de> <20111201153933.GL26618@pengutronix.de> <4ED7A6EF.1000705@the2masters.de> Message-ID: <20111201201827.GN26618@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello Stefan, On Thu, Dec 01, 2011 at 05:10:23PM +0100, Stefan Hellermann wrote: > Am 01.12.2011 16:39, schrieb Uwe Kleine-K?nig: > > The problem is that the memory for mem_map is allocated using: > > > > map = alloc_bootmem_node_nopanic(pgdat, size); > > > > without any error checking. The _nopanic was introduced by commit > > > > 8f389a99 (mm: use alloc_bootmem_node_nopanic() on really needed path) > > > > I don't understand the commit's log and don't really see why it should > > be allowed to not panic if the allocation failes here but use a NULL > > pointer instead. > > I put the people involved in 8f389a99 on Cc, maybe someone can comment? > > > > Apart from that it seems I cannot use flatmem as is on my machine. It > > has only 128kiB at 0x10000000 + 1MiB at 0x80000000 and needs 14MiB to hold the > > table of "struct page"s. :-( > > > > Best regards > > Uwe > > > The commit was made after an bug report from me. I have an old x86 > tablet pc with only 8Mb Ram. This machine fails early on bootup without > this commit. I found an archived message of the bug report here: > http://comments.gmane.org/gmane.linux.kernel/1135909 I saw that, too, but still I think that at least the last hunk in this patch is wrong. (I didn't check the others.) For me the allocation for mem_map failed and instead of handling the error somehow (be it a panic or not) just using NULL isn't nice. Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |