lib/stackdepot: rename handle and pool constants

Change the "STACK_ALLOC_" prefix to "DEPOT_" for the constants that
define the number of bits in stack depot handles and the maximum number
of pools.

The old prefix is unclear and makes wonder about how these constants
are related to stack allocations. The new prefix is also shorter.

Also simplify the comment for DEPOT_POOL_ORDER.

No functional changes.

Link: https://lkml.kernel.org/r/84fcceb0acc261a356a0ad4bdfab9ff04bea2445.1676063693.git.andreyknvl@google.comSigned-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/stackdepot.c

@@ -36,30 +36,28 @@
 #include <linux/memblock.h>
 #include <linux/kasan-enabled.h>
 
-#define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8)
-
-#define STACK_ALLOC_NULL_PROTECTION_BITS 1
-#define STACK_ALLOC_ORDER 2 /* Pool size order for stack depot, 4 pages */
-#define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER))
-#define STACK_ALLOC_ALIGN 4
-#define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \
-					STACK_ALLOC_ALIGN)
-#define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \
-		STACK_ALLOC_NULL_PROTECTION_BITS - \
-		STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
-#define STACK_ALLOC_POOLS_CAP 8192
-#define STACK_ALLOC_MAX_POOLS \
-	(((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_POOLS_CAP) ? \
-	 (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_POOLS_CAP)
+#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8)
+
+#define DEPOT_VALID_BITS 1
+#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */
+#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER))
+#define DEPOT_STACK_ALIGN 4
+#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN)
+#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_VALID_BITS - \
+			       DEPOT_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
+#define DEPOT_POOLS_CAP 8192
+#define DEPOT_MAX_POOLS \
+	(((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \
+	 (1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP)
 
 /* The compact structure to store the reference to stacks. */
 union handle_parts {
 	depot_stack_handle_t handle;
 	struct {
-		u32 pool_index : STACK_ALLOC_INDEX_BITS;
-		u32 offset : STACK_ALLOC_OFFSET_BITS;
-		u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS;
-		u32 extra : STACK_DEPOT_EXTRA_BITS;
+		u32 pool_index	: DEPOT_POOL_INDEX_BITS;
+		u32 offset	: DEPOT_OFFSET_BITS;
+		u32 valid	: DEPOT_VALID_BITS;
+		u32 extra	: STACK_DEPOT_EXTRA_BITS;
 	};
 };
 
@@ -91,7 +89,7 @@ static unsigned int stack_bucket_number_order;
 static unsigned int stack_hash_mask;
 
 /* Array of memory regions that store stack traces. */
-static void *stack_pools[STACK_ALLOC_MAX_POOLS];
+static void *stack_pools[DEPOT_MAX_POOLS];
 /* Currently used pool in stack_pools. */
 static int pool_index;
 /* Offset to the unused space in the currently used pool. */
@@ -235,7 +233,7 @@ static bool init_stack_pool(void **prealloc)
 		*prealloc = NULL;
 	} else {
 		/* If this is the last depot pool, do not touch the next one. */
-		if (pool_index + 1 < STACK_ALLOC_MAX_POOLS) {
+		if (pool_index + 1 < DEPOT_MAX_POOLS) {
 			stack_pools[pool_index + 1] = *prealloc;
 			*prealloc = NULL;
 		}
@@ -255,10 +253,10 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 	struct stack_record *stack;
 	size_t required_size = struct_size(stack, entries, size);
 
-	required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
+	required_size = ALIGN(required_size, 1 << DEPOT_STACK_ALIGN);
 
-	if (unlikely(pool_offset + required_size > STACK_ALLOC_SIZE)) {
-		if (unlikely(pool_index + 1 >= STACK_ALLOC_MAX_POOLS)) {
+	if (unlikely(pool_offset + required_size > DEPOT_POOL_SIZE)) {
+		if (unlikely(pool_index + 1 >= DEPOT_MAX_POOLS)) {
 			WARN_ONCE(1, "Stack depot reached limit capacity");
 			return NULL;
 		}
@@ -269,7 +267,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 		 * |next_pool_inited| in stack_depot_save() and
 		 * init_stack_pool().
 		 */
-		if (pool_index + 1 < STACK_ALLOC_MAX_POOLS)
+		if (pool_index + 1 < DEPOT_MAX_POOLS)
 			smp_store_release(&next_pool_inited, 0);
 	}
 	init_stack_pool(prealloc);
@@ -281,7 +279,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 	stack->hash = hash;
 	stack->size = size;
 	stack->handle.pool_index = pool_index;
-	stack->handle.offset = pool_offset >> STACK_ALLOC_ALIGN;
+	stack->handle.offset = pool_offset >> DEPOT_STACK_ALIGN;
 	stack->handle.valid = 1;
 	stack->handle.extra = 0;
 	memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
@@ -412,7 +410,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 		alloc_flags &= ~GFP_ZONEMASK;
 		alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
 		alloc_flags |= __GFP_NOWARN;
-		page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
+		page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
 		if (page)
 			prealloc = page_address(page);
 	}
@@ -444,7 +442,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 exit:
 	if (prealloc) {
 		/* Nobody used this memory, ok to free it. */
-		free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
+		free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER);
 	}
 	if (found)
 		retval.handle = found->handle.handle;
@@ -489,7 +487,7 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 {
 	union handle_parts parts = { .handle = handle };
 	void *pool;
-	size_t offset = parts.offset << STACK_ALLOC_ALIGN;
+	size_t offset = parts.offset << DEPOT_STACK_ALIGN;
 	struct stack_record *stack;
 
 	*entries = NULL;