bcachefs: struct bch_extent_rebalance

This adds the extent entry for extents that rebalance needs to do
something with.

We're adding this ahead of the main rebalance_work patchset, because
adding new extent entries can't be done in a forwards-compatible way.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs_format.h

@@ -488,8 +488,9 @@ struct bch_csum {
 	x(crc32,		1)		\
 	x(crc64,		2)		\
 	x(crc128,		3)		\
-	x(stripe_ptr,		4)
-#define BCH_EXTENT_ENTRY_MAX	5
+	x(stripe_ptr,		4)		\
+	x(rebalance,		5)
+#define BCH_EXTENT_ENTRY_MAX	6
 
 enum bch_extent_entry_type {
 #define x(f, n) BCH_EXTENT_ENTRY_##f = n,
@@ -624,6 +625,20 @@ struct bch_extent_reservation {
 #endif
 };
 
+struct bch_extent_rebalance {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	__u64			type:7,
+				unused:33,
+				compression:8,
+				target:16;
+#elif defined (__BIG_ENDIAN_BITFIELD)
+	__u64			target:16,
+				compression:8,
+				unused:33,
+				type:7;
+#endif
+};
+
 union bch_extent_entry {
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ ||  __BITS_PER_LONG == 64
 	unsigned long			type;

fs/bcachefs/extents.c

@@ -1202,6 +1202,8 @@ int bch2_bkey_ptrs_invalid(const struct bch_fs *c, struct bkey_s_c k,
 			}
 			have_ec = true;
 			break;
+		case BCH_EXTENT_ENTRY_rebalance:
+			break;
 		}
 	}
 
@@ -1260,6 +1262,8 @@ void bch2_ptr_swab(struct bkey_s k)
 			break;
 		case BCH_EXTENT_ENTRY_stripe_ptr:
 			break;
+		case BCH_EXTENT_ENTRY_rebalance:
+			break;
 		}
 	}
 }
@@ -1310,6 +1314,8 @@ int bch2_cut_front_s(struct bpos where, struct bkey_s k)
 				break;
 			case BCH_EXTENT_ENTRY_stripe_ptr:
 				break;
+			case BCH_EXTENT_ENTRY_rebalance:
+				break;
 			}
 
 			if (extent_entry_is_crc(entry))

fs/bcachefs/extents.h

@@ -318,6 +318,9 @@ static inline struct bkey_ptrs bch2_bkey_ptrs(struct bkey_s k)
 			(_ptr).ec = _entry->stripe_ptr;			\
 			(_ptr).has_ec	= true;				\
 			break;						\
+		default:						\
+			/* nothing */					\
+			break;						\
 		}							\
 out:									\
 	_entry < (_end);						\