percpu: move region iterations out of pcpu_[de]populate_chunk()

Previously, pcpu_[de]populate_chunk() were called with the range which
may contain multiple target regions in it and
pcpu_[de]populate_chunk() iterated over the regions.  This has the
benefit of batching up cache flushes for all the regions; however,
we're planning to add more bookkeeping logic around [de]population to
support atomic allocations and this delegation of iterations gets in
the way.

This patch moves the region iterations out of
pcpu_[de]populate_chunk() into its callers - pcpu_alloc() and
pcpu_reclaim() - so that we can later add logic to track more states
around them.  This change may make cache and tlb flushes more frequent
but multi-region [de]populations are rare anyway and if this actually
becomes a problem, it's not difficult to factor out cache flushes as
separate callbacks which are directly invoked from percpu.c.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 8 insertions, 11 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index 6087384f6ef01..fe5de97d7caad 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -807,20 +807,17 @@ area_found:
 	page_start = PFN_DOWN(off);
 	page_end = PFN_UP(off + size);
 
-	rs = page_start;
-	pcpu_next_pop(chunk, &rs, &re, page_end);
-
-	if (rs != page_start || re != page_end) {
+	pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
 		WARN_ON(chunk->immutable);
 
-		if (pcpu_populate_chunk(chunk, off, size)) {
+		if (pcpu_populate_chunk(chunk, rs, re)) {
 			spin_lock_irqsave(&pcpu_lock, flags);
 			pcpu_free_area(chunk, off);
 			err = "failed to populate";
 			goto fail_unlock;
 		}
 
-		bitmap_set(chunk->populated, page_start, page_end - page_start);
+		bitmap_set(chunk->populated, rs, re - rs);
 	}
 
 	mutex_unlock(&pcpu_alloc_mutex);
@@ -919,12 +916,12 @@ static void pcpu_reclaim(struct work_struct *work)
 	spin_unlock_irq(&pcpu_lock);
 
 	list_for_each_entry_safe(chunk, next, &todo, list) {
-		int rs = 0, re;
-
-		pcpu_next_unpop(chunk, &rs, &re, PFN_UP(pcpu_unit_size));
-		if (rs || re != PFN_UP(pcpu_unit_size))
-			pcpu_depopulate_chunk(chunk, 0, pcpu_unit_size);
+		int rs, re;
 
+		pcpu_for_each_pop_region(chunk, rs, re, 0, pcpu_unit_pages) {
+			pcpu_depopulate_chunk(chunk, rs, re);
+			bitmap_clear(chunk->populated, rs, re - rs);
+		}
 		pcpu_destroy_chunk(chunk);
 	}