percpu: generalize bitmap (un)populated iterators

The area map allocator only used a bitmap for the backing page state.
The new bitmap allocator will use bitmaps to manage the allocation
region in addition to this.

This patch generalizes the bitmap iterators so they can be reused with
the bitmap allocator.
Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/percpu.c

@@ -253,35 +253,32 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
 	       pcpu_unit_page_offset(cpu, page_idx);
 }
 
-static void __maybe_unused pcpu_next_unpop(struct pcpu_chunk *chunk,
-					   int *rs, int *re, int end)
+static void pcpu_next_unpop(unsigned long *bitmap, int *rs, int *re, int end)
 {
-	*rs = find_next_zero_bit(chunk->populated, end, *rs);
-	*re = find_next_bit(chunk->populated, end, *rs + 1);
+	*rs = find_next_zero_bit(bitmap, end, *rs);
+	*re = find_next_bit(bitmap, end, *rs + 1);
 }
 
-static void __maybe_unused pcpu_next_pop(struct pcpu_chunk *chunk,
-					 int *rs, int *re, int end)
+static void pcpu_next_pop(unsigned long *bitmap, int *rs, int *re, int end)
 {
-	*rs = find_next_bit(chunk->populated, end, *rs);
-	*re = find_next_zero_bit(chunk->populated, end, *rs + 1);
+	*rs = find_next_bit(bitmap, end, *rs);
+	*re = find_next_zero_bit(bitmap, end, *rs + 1);
 }
 
 /*
- * (Un)populated page region iterators.  Iterate over (un)populated
- * page regions between @start and @end in @chunk.  @rs and @re should
- * be integer variables and will be set to start and end page index of
- * the current region.
+ * Bitmap region iterators.  Iterates over the bitmap between
+ * [@start, @end) in @chunk.  @rs and @re should be integer variables
+ * and will be set to start and end index of the current free region.
  */
-#define pcpu_for_each_unpop_region(chunk, rs, re, start, end)		    \
-	for ((rs) = (start), pcpu_next_unpop((chunk), &(rs), &(re), (end)); \
+#define pcpu_for_each_unpop_region(bitmap, rs, re, start, end)		     \
+	for ((rs) = (start), pcpu_next_unpop((bitmap), &(rs), &(re), (end)); \
 	     (rs) < (re);						     \
-	     (rs) = (re) + 1, pcpu_next_unpop((chunk), &(rs), &(re), (end)))
+	     (rs) = (re) + 1, pcpu_next_unpop((bitmap), &(rs), &(re), (end)))
 
-#define pcpu_for_each_pop_region(chunk, rs, re, start, end)		    \
-	for ((rs) = (start), pcpu_next_pop((chunk), &(rs), &(re), (end));   \
+#define pcpu_for_each_pop_region(bitmap, rs, re, start, end)		     \
+	for ((rs) = (start), pcpu_next_pop((bitmap), &(rs), &(re), (end));   \
 	     (rs) < (re);						     \
-	     (rs) = (re) + 1, pcpu_next_pop((chunk), &(rs), &(re), (end)))
+	     (rs) = (re) + 1, pcpu_next_pop((bitmap), &(rs), &(re), (end)))
 
 /**
  * pcpu_mem_zalloc - allocate memory
@@ -521,7 +518,8 @@ static int pcpu_fit_in_area(struct pcpu_chunk *chunk, int off, int this_size,
 		page_end = PFN_UP(head + off + size);
 
 		rs = page_start;
-		pcpu_next_unpop(chunk, &rs, &re, PFN_UP(off + this_size));
+		pcpu_next_unpop(chunk->populated, &rs, &re,
+				PFN_UP(off + this_size));
 		if (rs >= page_end)
 			return head;
 		cand_off = re * PAGE_SIZE;
@@ -1071,7 +1069,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 		page_start = PFN_DOWN(off);
 		page_end = PFN_UP(off + size);
 
-		pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
+		pcpu_for_each_unpop_region(chunk->populated, rs, re,
+					   page_start, page_end) {
 			WARN_ON(chunk->immutable);
 
 			ret = pcpu_populate_chunk(chunk, rs, re);
@@ -1221,7 +1220,8 @@ static void pcpu_balance_workfn(struct work_struct *work)
 	list_for_each_entry_safe(chunk, next, &to_free, list) {
 		int rs, re;
 
-		pcpu_for_each_pop_region(chunk, rs, re, 0, chunk->nr_pages) {
+		pcpu_for_each_pop_region(chunk->populated, rs, re, 0,
+					 chunk->nr_pages) {
 			pcpu_depopulate_chunk(chunk, rs, re);
 			spin_lock_irq(&pcpu_lock);
 			pcpu_chunk_depopulated(chunk, rs, re);
@@ -1288,7 +1288,8 @@ static void pcpu_balance_workfn(struct work_struct *work)
 			continue;
 
 		/* @chunk can't go away while pcpu_alloc_mutex is held */
-		pcpu_for_each_unpop_region(chunk, rs, re, 0, chunk->nr_pages) {
+		pcpu_for_each_unpop_region(chunk->populated, rs, re, 0,
+					   chunk->nr_pages) {
 			int nr = min(re - rs, nr_to_pop);
 
 			ret = pcpu_populate_chunk(chunk, rs, rs + nr);