md/md-bitmap: add 'file_pages' into struct md_bitmap_stats

There are no functional changes, avoid dereferencing bitmap directly to
prepare inventing a new bitmap.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-8-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>

drivers/md/md-bitmap.c

@@ -2096,6 +2096,7 @@ EXPORT_SYMBOL_GPL(md_bitmap_copy_from_slot);
 
 int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
 {
+	struct bitmap_storage *storage;
 	struct bitmap_counts *counts;
 	bitmap_super_t *sb;
 
@@ -2110,9 +2111,11 @@ int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
 	stats->missing_pages = counts->missing_pages;
 	stats->pages = counts->pages;
 
-	stats->events_cleared = bitmap->events_cleared;
-	stats->file = bitmap->storage.file;
+	storage = &bitmap->storage;
+	stats->file_pages = storage->file_pages;
+	stats->file = storage->file;
 
+	stats->events_cleared = bitmap->events_cleared;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(md_bitmap_get_stats);

drivers/md/md-bitmap.h

@@ -237,6 +237,7 @@ struct bitmap {
 struct md_bitmap_stats {
 	u64		events_cleared;
 	unsigned long	missing_pages;
+	unsigned long	file_pages;
 	unsigned long	sync_size;
 	unsigned long	pages;
 	struct file	*file;

drivers/md/md.c

@@ -2335,7 +2335,6 @@ super_1_allow_new_offset(struct md_rdev *rdev,
 			 unsigned long long new_offset)
 {
 	/* All necessary checks on new >= old have been done */
-	struct bitmap *bitmap;
 	if (new_offset >= rdev->data_offset)
 		return 1;
 
@@ -2352,11 +2351,17 @@ super_1_allow_new_offset(struct md_rdev *rdev,
 	 */
 	if (rdev->sb_start + (32+4)*2 > new_offset)
 		return 0;
-	bitmap = rdev->mddev->bitmap;
-	if (bitmap && !rdev->mddev->bitmap_info.file &&
-	    rdev->sb_start + rdev->mddev->bitmap_info.offset +
-	    bitmap->storage.file_pages * (PAGE_SIZE>>9) > new_offset)
+
+	if (!rdev->mddev->bitmap_info.file) {
+		struct md_bitmap_stats stats;
+		int err;
+
+		err = md_bitmap_get_stats(rdev->mddev->bitmap, &stats);
+		if (!err && rdev->sb_start + rdev->mddev->bitmap_info.offset +
+		    stats.file_pages * (PAGE_SIZE >> 9) > new_offset)
 			return 0;
+	}
+
 	if (rdev->badblocks.sector + rdev->badblocks.size > new_offset)
 		return 0;