md/md-bitmap: add a new helper md_bitmap_set_pages()

Currently md-cluster will set bitmap->counts.pages directly, add a
helper to do this to avoid dereferencing bitmap directly.

Noted that after this patch bitmap is not dereferenced directly anymore
and following patches will move the structure inside md-bitmap.c.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-11-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>

drivers/md/md-bitmap.c

@@ -2094,6 +2094,12 @@ int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
 }
 EXPORT_SYMBOL_GPL(md_bitmap_copy_from_slot);
 
+void md_bitmap_set_pages(struct bitmap *bitmap, unsigned long pages)
+{
+	bitmap->counts.pages = pages;
+}
+EXPORT_SYMBOL_GPL(md_bitmap_set_pages);
+
 int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
 {
 	struct bitmap_storage *storage;

drivers/md/md-bitmap.h

@@ -285,6 +285,7 @@ int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot);
 int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
 			     sector_t *lo, sector_t *hi, bool clear_bits);
+void md_bitmap_set_pages(struct bitmap *bitmap, unsigned long pages);
 void md_bitmap_free(struct bitmap *bitmap);
 void md_bitmap_wait_behind_writes(struct mddev *mddev);
 

drivers/md/md-cluster.c

@@ -1163,7 +1163,6 @@ static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsiz
 
 	for (i = 0; i < mddev->bitmap_info.nodes; i++) {
 		struct dlm_lock_resource *bm_lockres;
-		struct bitmap_counts *counts;
 		char str[64];
 
 		if (i == md_cluster_ops->slot_number(mddev))
@@ -1175,7 +1174,6 @@ static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsiz
 			bitmap = NULL;
 			goto out;
 		}
-		counts = &bitmap->counts;
 
 		rv = md_bitmap_get_stats(bitmap, &stats);
 		if (rv)
@@ -1193,7 +1191,7 @@ static int resize_bitmaps(struct mddev *mddev, sector_t newsize, sector_t oldsiz
 		bm_lockres->flags |= DLM_LKF_NOQUEUE;
 		rv = dlm_lock_sync(bm_lockres, DLM_LOCK_PW);
 		if (!rv)
-			counts->pages = my_pages;
+			md_bitmap_set_pages(bitmap, my_pages);
 		lockres_free(bm_lockres);
 
 		if (my_pages != stats.pages)