Btrfs: Fix chunk allocation when some devices don't have enough room for stripes

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/volumes.c

@@ -664,7 +664,7 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	struct extent_map_tree *em_tree;
 	struct map_lookup *map;
 	struct extent_map *em;
-	int min_chunk_size = 8 * 1024 * 1024;
+	int min_stripe_size = 1 * 1024 * 1024;
 	u64 physical;
 	u64 calc_size = 1024 * 1024 * 1024;
 	u64 max_chunk_size = calc_size;
@@ -673,6 +673,7 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	u64 max_avail = 0;
 	u64 percent_max;
 	int num_stripes = 1;
+	int min_stripes = 1;
 	int sub_stripes = 0;
 	int looped = 0;
 	int ret;
@@ -683,15 +684,20 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	if (list_empty(dev_list))
 		return -ENOSPC;
 
-	if (type & (BTRFS_BLOCK_GROUP_RAID0))
+	if (type & (BTRFS_BLOCK_GROUP_RAID0)) {
 		num_stripes = btrfs_super_num_devices(&info->super_copy);
-	if (type & (BTRFS_BLOCK_GROUP_DUP))
+		min_stripes = 2;
+	}
+	if (type & (BTRFS_BLOCK_GROUP_DUP)) {
 		num_stripes = 2;
+		min_stripes = 2;
+	}
 	if (type & (BTRFS_BLOCK_GROUP_RAID1)) {
 		num_stripes = min_t(u64, 2,
 				  btrfs_super_num_devices(&info->super_copy));
 		if (num_stripes < 2)
 			return -ENOSPC;
+		min_stripes = 2;
 	}
 	if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
 		num_stripes = btrfs_super_num_devices(&info->super_copy);
@@ -699,22 +705,26 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 			return -ENOSPC;
 		num_stripes &= ~(u32)1;
 		sub_stripes = 2;
+		min_stripes = 4;
 	}
 
 	if (type & BTRFS_BLOCK_GROUP_DATA) {
 		max_chunk_size = 10 * calc_size;
-		min_chunk_size = 256 * 1024 * 1024;
+		min_stripe_size = 64 * 1024 * 1024;
 	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
 		max_chunk_size = 4 * calc_size;
-		min_chunk_size = 64 * 1024 * 1024;
-	} else {
-		min_chunk_size = 32 * 1024 * 1024;
+		min_stripe_size = 32 * 1024 * 1024;
+	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
+		calc_size = 8 * 1024 * 1024;
+		max_chunk_size = calc_size * 2;
+		min_stripe_size = 1 * 1024 * 1024;
 	}
 
 	/* we don't want a chunk larger than 10% of the FS */
 	percent_max = div_factor(btrfs_super_total_bytes(&info->super_copy), 1);
 	max_chunk_size = min(percent_max, max_chunk_size);
 
+again:
 	if (calc_size * num_stripes > max_chunk_size) {
 		calc_size = max_chunk_size;
 		do_div(calc_size, num_stripes);
@@ -722,12 +732,8 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		calc_size *= stripe_len;
 	}
 	/* we don't want tiny stripes */
-	*num_bytes = chunk_bytes_by_type(type, calc_size,
-					 num_stripes, sub_stripes);
-	calc_size = max_t(u64, chunk_bytes_by_type(type, min_chunk_size,
-		          num_stripes, sub_stripes), calc_size);
+	calc_size = max_t(u64, min_stripe_size, calc_size);
 
-again:
 	do_div(calc_size, stripe_len);
 	calc_size *= stripe_len;
 
@@ -746,19 +752,27 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 
 		avail = device->total_bytes - device->bytes_used;
 		cur = cur->next;
-		if (avail > max_avail)
-			max_avail = avail;
 		if (avail >= min_free) {
 			list_move_tail(&device->dev_list, &private_devs);
 			index++;
 			if (type & BTRFS_BLOCK_GROUP_DUP)
 				index++;
-		}
+		} else if (avail > max_avail)
+			max_avail = avail;
 		if (cur == dev_list)
 			break;
 	}
 	if (index < num_stripes) {
 		list_splice(&private_devs, dev_list);
+		if (index >= min_stripes) {
+			num_stripes = index;
+			if (type & (BTRFS_BLOCK_GROUP_RAID10)) {
+				num_stripes /= sub_stripes;
+				num_stripes *= sub_stripes;
+			}
+			looped = 1;
+			goto again;
+		}
 		if (!looped && max_avail > 0) {
 			looped = 1;
 			calc_size = max_avail;
@@ -766,7 +780,6 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		}
 		return -ENOSPC;
 	}
-
 	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
 	key.type = BTRFS_CHUNK_ITEM_KEY;
 	ret = find_next_chunk(chunk_root, BTRFS_FIRST_CHUNK_TREE_OBJECTID,