btrfs: on unknown chunk allocation policy fallback to regular

We have only two chunk allocation policies right now and the
switch/cases don't handle an unknown one properly. The error is in the
impossible category (the policy is stored only in memory), we don't have
to BUG(), falling back to regular policy should be safe.

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

fs/btrfs/volumes.c

@@ -1528,6 +1528,9 @@ static bool contains_pending_extent(struct btrfs_device *device, u64 *start,
 static u64 dev_extent_search_start(struct btrfs_device *device)
 {
 	switch (device->fs_devices->chunk_alloc_policy) {
+	default:
+		btrfs_warn_unknown_chunk_allocation(device->fs_devices->chunk_alloc_policy);
+		fallthrough;
 	case BTRFS_CHUNK_ALLOC_REGULAR:
 		return BTRFS_DEVICE_RANGE_RESERVED;
 	case BTRFS_CHUNK_ALLOC_ZONED:
@@ -1537,8 +1540,6 @@ static u64 dev_extent_search_start(struct btrfs_device *device)
 		 * for superblock logging.
 		 */
 		return 0;
-	default:
-		BUG();
 	}
 }
 
@@ -1618,6 +1619,9 @@ static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,
 		}
 
 		switch (device->fs_devices->chunk_alloc_policy) {
+		default:
+			btrfs_warn_unknown_chunk_allocation(device->fs_devices->chunk_alloc_policy);
+			fallthrough;
 		case BTRFS_CHUNK_ALLOC_REGULAR:
 			/* No extra check */
 			break;
@@ -1632,8 +1636,6 @@ static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,
 				continue;
 			}
 			break;
-		default:
-			BUG();
 		}
 
 		break;
@@ -5199,14 +5201,15 @@ static void init_alloc_chunk_ctl(struct btrfs_fs_devices *fs_devices,
 	ctl->ndevs = 0;
 
 	switch (fs_devices->chunk_alloc_policy) {
+	default:
+		btrfs_warn_unknown_chunk_allocation(fs_devices->chunk_alloc_policy);
+		fallthrough;
 	case BTRFS_CHUNK_ALLOC_REGULAR:
 		init_alloc_chunk_ctl_policy_regular(fs_devices, ctl);
 		break;
 	case BTRFS_CHUNK_ALLOC_ZONED:
 		init_alloc_chunk_ctl_policy_zoned(fs_devices, ctl);
 		break;
-	default:
-		BUG();
 	}
 }
 
@@ -5395,12 +5398,13 @@ static int decide_stripe_size(struct btrfs_fs_devices *fs_devices,
 	ctl->ndevs = min(ctl->ndevs, ctl->devs_max);
 
 	switch (fs_devices->chunk_alloc_policy) {
+	default:
+		btrfs_warn_unknown_chunk_allocation(fs_devices->chunk_alloc_policy);
+		fallthrough;
 	case BTRFS_CHUNK_ALLOC_REGULAR:
 		return decide_stripe_size_regular(ctl, devices_info);
 	case BTRFS_CHUNK_ALLOC_ZONED:
 		return decide_stripe_size_zoned(ctl, devices_info);
-	default:
-		BUG();
 	}
 }
 

fs/btrfs/volumes.h

@@ -846,6 +846,11 @@ static inline const char *btrfs_dev_name(const struct btrfs_device *device)
 		return rcu_str_deref(device->name);
 }
 
+static inline void btrfs_warn_unknown_chunk_allocation(enum btrfs_chunk_allocation_policy pol)
+{
+	WARN_ONCE(1, "unknown allocation policy %d, fallback to regular", pol);
+}
+
 void btrfs_commit_device_sizes(struct btrfs_transaction *trans);
 
 struct list_head * __attribute_const__ btrfs_get_fs_uuids(void);