[PATCH] Do not round per_cpu_ptr_to_phys to page boundary

[Petr Tesarik]

The phys_addr_t per_cpu_ptr_to_phys() function ignores the offset within a 
page, whenever not using a simple translation using __pa().

Without this patch /sys/devices/system/cpu/cpu*/crash_notes shows incorrect 
values, which breaks kdump. Other things may also be broken.

Signed-off-by: Petr Tesarik <ptesarik@xxxxxxx>

diff --git a/mm/percpu.c b/mm/percpu.c
index 3bb810a..1a1b5ac 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -998,6 +998,7 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
 	bool in_first_chunk = false;
 	unsigned long first_low, first_high;
 	unsigned int cpu;
+	phys_addr_t page_addr;
 
 	/*
 	 * The following test on unit_low/high isn't strictly
@@ -1023,9 +1024,10 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
 		if (!is_vmalloc_addr(addr))
 			return __pa(addr);
 		else
-			return page_to_phys(vmalloc_to_page(addr));
+			page_addr = page_to_phys(vmalloc_to_page(addr));
 	} else
-		return page_to_phys(pcpu_addr_to_page(addr));
+		page_addr = page_to_phys(pcpu_addr_to_page(addr));
+	return page_addr + offset_in_page(addr);
 }
 
 /**
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