[PATCH v2] MIPS: Kernel crashes on boot with SPARSEMEM + HIGHMEM enabled

[Kevin Cernekee <cernekee@gmail.com>]

From: Michael Sundius <msundius@cisco.com>

Fix 3 problems in the MIPS SPARSEMEM implementation:

1) mem_init() sets/clears PG_reserved on all pages in the HIGHMEM range
without checking to see whether the page descriptor actually exists.

2) bootmem_init() never calls memory_present() on HIGHMEM pages, so
page descriptors are never created for them if SPARSEMEM is enabled.

3) bootmem_init() calls memory_present() on lowmem pages before bootmem
is fully set up.  This is bad because memory_present() can allocate
bootmem in some circumstances (e.g. if SPARSEMEM_EXTREME ever got
enabled).

Signed-off-by: Michael Sundius <msundius@cisco.com>
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: stable@kernel.org
---
 arch/mips/kernel/setup.c |   18 +++++++++++++++++-
 arch/mips/mm/init.c      |    3 +++
 2 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 8ad1d56..1f9f902 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -390,7 +390,6 @@ static void __init bootmem_init(void)
 
 		/* Register lowmem ranges */
 		free_bootmem(PFN_PHYS(start), size << PAGE_SHIFT);
-		memory_present(0, start, end);
 	}
 
 	/*
@@ -402,6 +401,23 @@ static void __init bootmem_init(void)
 	 * Reserve initrd memory if needed.
 	 */
 	finalize_initrd();
+
+	/*
+	 * Call memory_present() on all valid ranges, for SPARSEMEM.
+	 * This must be done after setting up bootmem, since memory_present()
+	 * may allocate bootmem.
+	 */
+	for (i = 0; i < boot_mem_map.nr_map; i++) {
+		unsigned long start, end;
+
+		if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
+			continue;
+
+		start = PFN_UP(boot_mem_map.map[i].addr);
+		end   = PFN_DOWN(boot_mem_map.map[i].addr
+				    + boot_mem_map.map[i].size);
+		memory_present(0, start, end);
+	}
 }
 
 #endif	/* CONFIG_SGI_IP27 */
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 279599e..78a4cf2 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -392,6 +392,9 @@ void __init mem_init(void)
 	for (tmp = highstart_pfn; tmp < highend_pfn; tmp++) {
 		struct page *page = pfn_to_page(tmp);
 
+		if (!pfn_valid(tmp))
+			continue;
+
 		if (!page_is_ram(tmp)) {
 			SetPageReserved(page);
 			continue;
-- 
1.7.4.2