bcachefs: extents no longer require special handling for packing

Extent overwrite used to  be handled differently, underneath the
journaling layer and within the core btree code. This imposed
restrictions on bkey packing/packed formats, which no longer apply.

This patch deletes those restrictions.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey.c

@@ -323,15 +323,6 @@ bool bch2_bkey_pack_key(struct bkey_packed *out, const struct bkey *in,
 #define x(id, field)	if (!set_inc_field(&state, id, in->field)) return false;
 	bkey_fields()
 #undef x
-
-	/*
-	 * Extents - we have to guarantee that if an extent is packed, a trimmed
-	 * version will also pack:
-	 */
-	if (bkey_start_offset(in) <
-	    le64_to_cpu(format->field_offset[BKEY_FIELD_OFFSET]))
-		return false;
-
 	pack_state_finish(&state, out);
 	out->u64s	= format->key_u64s + in->u64s - BKEY_U64s;
 	out->format	= KEY_FORMAT_LOCAL_BTREE;

fs/bcachefs/bkey.h

@@ -689,7 +689,6 @@ static inline void bch2_bkey_format_add_key(struct bkey_format_state *s, const s
 #define x(id, field) __bkey_format_add(s, id, k->field);
 	bkey_fields()
 #undef x
-	__bkey_format_add(s, BKEY_FIELD_OFFSET, bkey_start_offset(k));
 }
 
 void bch2_bkey_format_add_pos(struct bkey_format_state *, struct bpos);