[PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Tue, Oct 19, 2010 at 01:13:36AM -0700, Colin Cross wrote:
> On Mon, Oct 11, 2010 at 8:25 AM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> > On Sun, Oct 10, 2010 at 04:52:36AM +0300, Felipe Contreras wrote:
> > Here's a different approach which will work. ?This pushes ARM further
> > towards using memblock for everything relating to memory init (although
> > we still have the old membank stuff around.)
> >
> > The advantage with this is that memblock is now used as the basis for
> > determining where memory is, setting up the maps, freeing memory into
> > the pools, etc.
> >
> > What this also means is that this code in the ->reserve callback:
> >
> > ? ? ? ?size = min(size, SZ_2M);
> > ? ? ? ?base = memblock_alloc(size, min(align, SZ_2M));
> > ? ? ? ?memblock_free(base, size);
> > ? ? ? ?memblock_remove(base, size);
> >
> > will result in [base+size] being removed from the available memory,
> > using highmem if available, if not from lowmem and removing it from
> > the lowmem memory map - which is exactly the behaviour we want.
> >
> > ?arch/arm/mm/init.c | ?160 +++++++++++++++++++++++++++++++++++-----------------
> > ?arch/arm/mm/mmu.c ?| ? 43 ++++++++------
> > ?mm/memblock.c ? ? ?| ? ?4 +
> > ?3 files changed, 138 insertions(+), 69 deletions(-)
> 
> If memblock_remove is used on the end of memory with this patch,
> mem_init accesses off the end of the array of page structures because
> of the discrepancy between memblock.memory and membank on the number
> of the last pfn.   memblock.memory is used to determine the memory
> zones in arm_bootmem_free, which eventually  is used to create the
> array of page structures, but mem_init iterates over membank and calls
> pfn_to_page on pfns up to bank_pfn_end.

BTW, reverting the change to find_limits() should resolve this problem.
Please confirm.