ARM: 7113/1: mm: Align bank start to MAX_ORDER_NR_PAGES

The VM subsystem assumes that there are valid memmap entries from
the bank start aligned to MAX_ORDER_NR_PAGES.

On the Ux500 we have a lot of mem=N arguments on the commandline
triggering this bug several times over and causing kernel
oops messages.

Cc: stable@kernel.org
Cc: Michael Bohan <mbohan@codeaurora.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Johan Palsson <johan.palsson@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/init.c

@@ -496,6 +496,13 @@ static void __init free_unused_memmap(struct meminfo *mi)
 		 */
 		bank_start = min(bank_start,
 				 ALIGN(prev_bank_end, PAGES_PER_SECTION));
+#else
+		/*
+		 * Align down here since the VM subsystem insists that the
+		 * memmap entries are valid from the bank start aligned to
+		 * MAX_ORDER_NR_PAGES.
+		 */
+		bank_start = round_down(bank_start, MAX_ORDER_NR_PAGES);
 #endif
 		/*
 		 * If we had a previous bank, and there is a space