mm/vmacache, sched/headers: Introduce 'struct vmacache' and move it from <linux/sched.h> to <linux/mm_types>

The <linux/sched.h> header includes various vmacache related defines,
which are arguably misplaced.

Move them to mm_types.h and minimize the sched.h impact by putting
all task vmacache state into a new 'struct vmacache' structure.

No change in functionality.

Acked-by: Linus Torvalds <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

include/linux/mm_types.h

···
 	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 };
 
+/*
+ * The per task VMA cache array:
+ */
+#define VMACACHE_BITS 2
+#define VMACACHE_SIZE (1U << VMACACHE_BITS)
+#define VMACACHE_MASK (VMACACHE_SIZE - 1)
+
+struct vmacache {
+	u32 seqnum;
+	struct vm_area_struct *vmas[VMACACHE_SIZE];
+};
+
 struct core_thread {
 	struct task_struct *task;
 	struct core_thread *next;

include/linux/sched.h

···
 struct filename;
 struct nameidata;
 
-#define VMACACHE_BITS 2
-#define VMACACHE_SIZE (1U << VMACACHE_BITS)
-#define VMACACHE_MASK (VMACACHE_SIZE - 1)
-
 /*
  * These are the constant used to fake the fixed-point load-average
  * counting. Some notes:
···
 #endif
 
 	struct mm_struct *mm, *active_mm;
-	/* per-thread vma caching */
-	u32 vmacache_seqnum;
-	struct vm_area_struct *vmacache[VMACACHE_SIZE];
+
+	/* Per-thread vma caching: */
+	struct vmacache vmacache;
+
 #if defined(SPLIT_RSS_COUNTING)
 	struct task_rss_stat	rss_stat;
 #endif

include/linux/vmacache.h

···
 
 static inline void vmacache_flush(struct task_struct *tsk)
 {
-	memset(tsk->vmacache, 0, sizeof(tsk->vmacache));
+	memset(tsk->vmacache.vmas, 0, sizeof(tsk->vmacache.vmas));
 }
 
 extern void vmacache_flush_all(struct mm_struct *mm);

kernel/debug/debug_core.c

···
 		int i;
 
 		for (i = 0; i < VMACACHE_SIZE; i++) {
-			if (!current->vmacache[i])
+			if (!current->vmacache.vmas[i])
 				continue;
-			flush_cache_range(current->vmacache[i],
+			flush_cache_range(current->vmacache.vmas[i],
 					  addr, addr + BREAK_INSTR_SIZE);
 		}
 	}

mm/nommu.c

···
 	mm->map_count--;
 	for (i = 0; i < VMACACHE_SIZE; i++) {
 		/* if the vma is cached, invalidate the entire cache */
-		if (curr->vmacache[i] == vma) {
+		if (curr->vmacache.vmas[i] == vma) {
 			vmacache_invalidate(mm);
 			break;
 		}

mm/vmacache.c

···
 void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
 {
 	if (vmacache_valid_mm(newvma->vm_mm))
-		current->vmacache[VMACACHE_HASH(addr)] = newvma;
+		current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
 }
 
 static bool vmacache_valid(struct mm_struct *mm)
···
 		return false;
 
 	curr = current;
-	if (mm->vmacache_seqnum != curr->vmacache_seqnum) {
+	if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
 		/*
 		 * First attempt will always be invalid, initialize
 		 * the new cache for this task here.
 		 */
-		curr->vmacache_seqnum = mm->vmacache_seqnum;
+		curr->vmacache.seqnum = mm->vmacache_seqnum;
 		vmacache_flush(curr);
 		return false;
 	}
···
 		return NULL;
 
 	for (i = 0; i < VMACACHE_SIZE; i++) {
-		struct vm_area_struct *vma = current->vmacache[i];
+		struct vm_area_struct *vma = current->vmacache.vmas[i];
 
 		if (!vma)
 			continue;
···
 		return NULL;
 
 	for (i = 0; i < VMACACHE_SIZE; i++) {
-		struct vm_area_struct *vma = current->vmacache[i];
+		struct vm_area_struct *vma = current->vmacache.vmas[i];
 
 		if (vma && vma->vm_start == start && vma->vm_end == end) {
 			count_vm_vmacache_event(VMACACHE_FIND_HITS);