mm/memblock: introduce PHYS_ADDR_MAX

So far code was using ULLONG_MAX and type casting to obtain a
phys_addr_t with all bits set.  The typecast is necessary to silence
compiler warnings on 32-bit platforms.

Use the simpler but still type safe approach "~(phys_addr_t)0" to create a
preprocessor define for all bits set.

Link: http://lkml.kernel.org/r/20180406213809.566-1-stefan@agner.ch
Signed-off-by: Stefan Agner <stefan@agner.ch>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/kernel.h

@@ -29,6 +29,7 @@
 #define LLONG_MIN	(-LLONG_MAX - 1)
 #define ULLONG_MAX	(~0ULL)
 #define SIZE_MAX	(~(size_t)0)
+#define PHYS_ADDR_MAX	(~(phys_addr_t)0)
 
 #define U8_MAX		((u8)~0U)
 #define S8_MAX		((s8)(U8_MAX>>1))

mm/memblock.c

@@ -68,7 +68,7 @@ ulong __init_memblock choose_memblock_flags(void)
 /* adjust *@size so that (@base + *@size) doesn't overflow, return new size */
 static inline phys_addr_t memblock_cap_size(phys_addr_t base, phys_addr_t *size)
 {
-	return *size = min(*size, (phys_addr_t)ULLONG_MAX - base);
+	return *size = min(*size, PHYS_ADDR_MAX - base);
 }
 
 /*
@@ -925,7 +925,7 @@ void __init_memblock __next_mem_range(u64 *idx, int nid, ulong flags,
 			r = &type_b->regions[idx_b];
 			r_start = idx_b ? r[-1].base + r[-1].size : 0;
 			r_end = idx_b < type_b->cnt ?
-				r->base : (phys_addr_t)ULLONG_MAX;
+				r->base : PHYS_ADDR_MAX;
 
 			/*
 			 * if idx_b advanced past idx_a,
@@ -1041,7 +1041,7 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 			r = &type_b->regions[idx_b];
 			r_start = idx_b ? r[-1].base + r[-1].size : 0;
 			r_end = idx_b < type_b->cnt ?
-				r->base : (phys_addr_t)ULLONG_MAX;
+				r->base : PHYS_ADDR_MAX;
 			/*
 			 * if idx_b advanced past idx_a,
 			 * break out to advance idx_a
@@ -1516,13 +1516,13 @@ phys_addr_t __init_memblock memblock_end_of_DRAM(void)
 
 static phys_addr_t __init_memblock __find_max_addr(phys_addr_t limit)
 {
-	phys_addr_t max_addr = (phys_addr_t)ULLONG_MAX;
+	phys_addr_t max_addr = PHYS_ADDR_MAX;
 	struct memblock_region *r;
 
 	/*
 	 * translate the memory @limit size into the max address within one of
 	 * the memory memblock regions, if the @limit exceeds the total size
-	 * of those regions, max_addr will keep original value ULLONG_MAX
+	 * of those regions, max_addr will keep original value PHYS_ADDR_MAX
 	 */
 	for_each_memblock(memory, r) {
 		if (limit <= r->size) {
@@ -1537,22 +1537,22 @@ static phys_addr_t __init_memblock __find_max_addr(phys_addr_t limit)
 
 void __init memblock_enforce_memory_limit(phys_addr_t limit)
 {
-	phys_addr_t max_addr = (phys_addr_t)ULLONG_MAX;
+	phys_addr_t max_addr = PHYS_ADDR_MAX;
 
 	if (!limit)
 		return;
 
 	max_addr = __find_max_addr(limit);
 
 	/* @limit exceeds the total size of the memory, do nothing */
-	if (max_addr == (phys_addr_t)ULLONG_MAX)
+	if (max_addr == PHYS_ADDR_MAX)
 		return;
 
 	/* truncate both memory and reserved regions */
 	memblock_remove_range(&memblock.memory, max_addr,
-			      (phys_addr_t)ULLONG_MAX);
+			      PHYS_ADDR_MAX);
 	memblock_remove_range(&memblock.reserved, max_addr,
-			      (phys_addr_t)ULLONG_MAX);
+			      PHYS_ADDR_MAX);
 }
 
 void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
@@ -1580,7 +1580,7 @@ void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
 	/* truncate the reserved regions */
 	memblock_remove_range(&memblock.reserved, 0, base);
 	memblock_remove_range(&memblock.reserved,
-			base + size, (phys_addr_t)ULLONG_MAX);
+			base + size, PHYS_ADDR_MAX);
 }
 
 void __init memblock_mem_limit_remove_map(phys_addr_t limit)
@@ -1593,7 +1593,7 @@ void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 	max_addr = __find_max_addr(limit);
 
 	/* @limit exceeds the total size of the memory, do nothing */
-	if (max_addr == (phys_addr_t)ULLONG_MAX)
+	if (max_addr == PHYS_ADDR_MAX)
 		return;
 
 	memblock_cap_memory_range(0, max_addr);