md/md-bitmap: replace md_bitmap_status() with a new helper md_bitmap_get_stats()

There are no functional changes, and the new helper will be used in
multiple places in following patches to avoid dereferencing bitmap
directly.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-3-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>

drivers/md/md-bitmap.c

@@ -2094,32 +2094,19 @@ int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
 }
 EXPORT_SYMBOL_GPL(md_bitmap_copy_from_slot);
 
-
-void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap)
+int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats)
 {
-	unsigned long chunk_kb;
 	struct bitmap_counts *counts;
 
 	if (!bitmap)
-		return;
+		return -ENOENT;
 
 	counts = &bitmap->counts;
+	stats->missing_pages = counts->missing_pages;
+	stats->pages = counts->pages;
+	stats->file = bitmap->storage.file;
 
-	chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10;
-	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], "
-		   "%lu%s chunk",
-		   counts->pages - counts->missing_pages,
-		   counts->pages,
-		   (counts->pages - counts->missing_pages)
-		   << (PAGE_SHIFT - 10),
-		   chunk_kb ? chunk_kb : bitmap->mddev->bitmap_info.chunksize,
-		   chunk_kb ? "KB" : "B");
-	if (bitmap->storage.file) {
-		seq_printf(seq, ", file: ");
-		seq_file_path(seq, bitmap->storage.file, " \t\n");
-	}
-
-	seq_printf(seq, "\n");
+	return 0;
 }
 
 int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,

drivers/md/md-bitmap.h

@@ -234,6 +234,12 @@ struct bitmap {
 	int cluster_slot;		/* Slot offset for clustered env */
 };
 
+struct md_bitmap_stats {
+	unsigned long	missing_pages;
+	unsigned long	pages;
+	struct file	*file;
+};
+
 /* the bitmap API */
 
 /* these are used only by md/bitmap */
@@ -244,7 +250,7 @@ void md_bitmap_destroy(struct mddev *mddev);
 
 void md_bitmap_print_sb(struct bitmap *bitmap);
 void md_bitmap_update_sb(struct bitmap *bitmap);
-void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap);
+int md_bitmap_get_stats(struct bitmap *bitmap, struct md_bitmap_stats *stats);
 
 int  md_bitmap_setallbits(struct bitmap *bitmap);
 void md_bitmap_write_all(struct bitmap *bitmap);

drivers/md/md.c

@@ -8370,6 +8370,33 @@ static void md_seq_stop(struct seq_file *seq, void *v)
 	spin_unlock(&all_mddevs_lock);
 }
 
+static void md_bitmap_status(struct seq_file *seq, struct mddev *mddev)
+{
+	struct md_bitmap_stats stats;
+	unsigned long used_pages;
+	unsigned long chunk_kb;
+	int err;
+
+	err = md_bitmap_get_stats(mddev->bitmap, &stats);
+	if (err)
+		return;
+
+	chunk_kb = mddev->bitmap_info.chunksize >> 10;
+	used_pages = stats.pages - stats.missing_pages;
+
+	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], %lu%s chunk",
+		   used_pages, stats.pages, used_pages << (PAGE_SHIFT - 10),
+		   chunk_kb ? chunk_kb : mddev->bitmap_info.chunksize,
+		   chunk_kb ? "KB" : "B");
+
+	if (stats.file) {
+		seq_puts(seq, ", file: ");
+		seq_file_path(seq, stats.file, " \t\n");
+	}
+
+	seq_putc(seq, '\n');
+}
+
 static int md_seq_show(struct seq_file *seq, void *v)
 {
 	struct mddev *mddev;
@@ -8453,7 +8480,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
 		} else
 			seq_printf(seq, "\n       ");
 
-		md_bitmap_status(seq, mddev->bitmap);
+		md_bitmap_status(seq, mddev);
 
 		seq_printf(seq, "\n");
 	}