md-cluster: introduce cluster_check_sync_size

Support resize is a little complex for clustered
raid, since we need to ensure all the nodes share
the same knowledge about the size of raid.

We achieve the goal by check the sync_size which
is in each node's bitmap, we can only change the
capacity after cluster_check_sync_size returns 0.

Also, get_bitmap_from_slot is added to get a slot's
bitmap. And we exported some funcs since they are
used in cluster_check_sync_size().

We can also reuse get_bitmap_from_slot to remove
redundant code existed in bitmap_copy_from_slot.

Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/bitmap.c

@@ -471,6 +471,7 @@ void bitmap_update_sb(struct bitmap *bitmap)
 	kunmap_atomic(sb);
 	write_page(bitmap, bitmap->storage.sb_page, 1);
 }
+EXPORT_SYMBOL(bitmap_update_sb);
 
 /* print out the bitmap file superblock */
 void bitmap_print_sb(struct bitmap *bitmap)
@@ -1727,7 +1728,7 @@ void bitmap_flush(struct mddev *mddev)
 /*
  * free memory that was allocated
  */
-static void bitmap_free(struct bitmap *bitmap)
+void bitmap_free(struct bitmap *bitmap)
 {
 	unsigned long k, pages;
 	struct bitmap_page *bp;
@@ -1761,6 +1762,7 @@ static void bitmap_free(struct bitmap *bitmap)
 	kfree(bp);
 	kfree(bitmap);
 }
+EXPORT_SYMBOL(bitmap_free);
 
 void bitmap_destroy(struct mddev *mddev)
 {
@@ -1920,6 +1922,27 @@ out:
 }
 EXPORT_SYMBOL_GPL(bitmap_load);
 
+struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot)
+{
+	int rv = 0;
+	struct bitmap *bitmap;
+
+	bitmap = bitmap_create(mddev, slot);
+	if (IS_ERR(bitmap)) {
+		rv = PTR_ERR(bitmap);
+		return ERR_PTR(rv);
+	}
+
+	rv = bitmap_init_from_disk(bitmap, 0);
+	if (rv) {
+		bitmap_free(bitmap);
+		return ERR_PTR(rv);
+	}
+
+	return bitmap;
+}
+EXPORT_SYMBOL(get_bitmap_from_slot);
+
 /* Loads the bitmap associated with slot and copies the resync information
  * to our bitmap
  */
@@ -1929,14 +1952,13 @@ int bitmap_copy_from_slot(struct mddev *mddev, int slot,
 	int rv = 0, i, j;
 	sector_t block, lo = 0, hi = 0;
 	struct bitmap_counts *counts;
-	struct bitmap *bitmap = bitmap_create(mddev, slot);
-
-	if (IS_ERR(bitmap))
-		return PTR_ERR(bitmap);
+	struct bitmap *bitmap;
 
-	rv = bitmap_init_from_disk(bitmap, 0);
-	if (rv)
-		goto err;
+	bitmap = get_bitmap_from_slot(mddev, slot);
+	if (IS_ERR(bitmap)) {
+		pr_err("%s can't get bitmap from slot %d\n", __func__, slot);
+		return -1;
+	}
 
 	counts = &bitmap->counts;
 	for (j = 0; j < counts->chunks; j++) {
@@ -1963,8 +1985,7 @@ int bitmap_copy_from_slot(struct mddev *mddev, int slot,
 	bitmap_unplug(mddev->bitmap);
 	*low = lo;
 	*high = hi;
-err:
-	bitmap_free(bitmap);
+
 	return rv;
 }
 EXPORT_SYMBOL_GPL(bitmap_copy_from_slot);

drivers/md/bitmap.h

@@ -267,8 +267,10 @@ void bitmap_daemon_work(struct mddev *mddev);
 
 int bitmap_resize(struct bitmap *bitmap, sector_t blocks,
 		  int chunksize, int init);
+struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot);
 int bitmap_copy_from_slot(struct mddev *mddev, int slot,
 				sector_t *lo, sector_t *hi, bool clear_bits);
+void bitmap_free(struct bitmap *bitmap);
 #endif
 
 #endif

drivers/md/md-cluster.c

@@ -1091,6 +1091,66 @@ static void metadata_update_cancel(struct mddev *mddev)
 	unlock_comm(cinfo);
 }
 
+/*
+ * return 0 if all the bitmaps have the same sync_size
+ */
+int cluster_check_sync_size(struct mddev *mddev)
+{
+	int i, rv;
+	bitmap_super_t *sb;
+	unsigned long my_sync_size, sync_size = 0;
+	int node_num = mddev->bitmap_info.nodes;
+	int current_slot = md_cluster_ops->slot_number(mddev);
+	struct bitmap *bitmap = mddev->bitmap;
+	char str[64];
+	struct dlm_lock_resource *bm_lockres;
+
+	sb = kmap_atomic(bitmap->storage.sb_page);
+	my_sync_size = sb->sync_size;
+	kunmap_atomic(sb);
+
+	for (i = 0; i < node_num; i++) {
+		if (i == current_slot)
+			continue;
+
+		bitmap = get_bitmap_from_slot(mddev, i);
+		if (IS_ERR(bitmap)) {
+			pr_err("can't get bitmap from slot %d\n", i);
+			return -1;
+		}
+
+		/*
+		 * If we can hold the bitmap lock of one node then
+		 * the slot is not occupied, update the sb.
+		 */
+		snprintf(str, 64, "bitmap%04d", i);
+		bm_lockres = lockres_init(mddev, str, NULL, 1);
+		if (!bm_lockres) {
+			pr_err("md-cluster: Cannot initialize %s\n", str);
+			lockres_free(bm_lockres);
+			return -1;
+		}
+		bm_lockres->flags |= DLM_LKF_NOQUEUE;
+		rv = dlm_lock_sync(bm_lockres, DLM_LOCK_PW);
+		if (!rv)
+			bitmap_update_sb(bitmap);
+		lockres_free(bm_lockres);
+
+		sb = kmap_atomic(bitmap->storage.sb_page);
+		if (sync_size == 0)
+			sync_size = sb->sync_size;
+		else if (sync_size != sb->sync_size) {
+			kunmap_atomic(sb);
+			bitmap_free(bitmap);
+			return -1;
+		}
+		kunmap_atomic(sb);
+		bitmap_free(bitmap);
+	}
+
+	return (my_sync_size == sync_size) ? 0 : -1;
+}
+
 static int resync_start(struct mddev *mddev)
 {
 	struct md_cluster_info *cinfo = mddev->cluster_info;