[PATCH] MIPS: bootmem: Fix mapstart calculation for contiguous maps

[PATCH] MIPS: bootmem: Fix mapstart calculation for contiguous maps

[Alexander Sverdlin]

Commit a6335fa1 fixed the case with gap between initrd and next usable PFN zone,
but broken the case when initrd is combined with usable memory into one region
(in add_memory_region()). Restore the fixup initially brought in by f9a7febd.

---- error message ----
Unpacking initramfs...
Initramfs unpacking failed: junk in compressed archive
BUG: Bad page state in process swapper  pfn:00261
page:81004c20 count:0 mapcount:-127 mapping:  (null) index:0x2
flags: 0x0()
page dumped because: nonzero mapcount
CPU: 0 PID: 1 Comm: swapper Not tainted 4.2.0+ #1782
-----------------------

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Reported-by: Tony Wu <tung7970@gmail.com>
Tested-by: Tony Wu <tung7970@gmail.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Joe Perches <joe@perches.com>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: stable@vger.kernel.org
---
 arch/mips/kernel/setup.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 008b337..4ceac5c 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -338,7 +338,7 @@ static void __init bootmem_init(void)
 		if (end <= reserved_end)
 			continue;
 #ifdef CONFIG_BLK_DEV_INITRD
-		/* mapstart should be after initrd_end */
+		/* Skip zones before initrd and initrd itself */
 		if (initrd_end && end <= (unsigned long)PFN_UP(__pa(initrd_end)))
 			continue;
 #endif
@@ -371,6 +371,14 @@ static void __init bootmem_init(void)
 		max_low_pfn = PFN_DOWN(HIGHMEM_START);
 	}

+#ifdef CONFIG_BLK_DEV_INITRD
+	/*
+	 * mapstart should be after initrd_end
+	 */
+	if (initrd_end)
+		mapstart = max(mapstart, (unsigned long)PFN_UP(__pa(initrd_end)));
+#endif
+
 	/*
 	 * Initialize the boot-time allocator with low memory only.
 	 */