bcachefs: Fix range in bch2_lookup_indirect_extent() error path

Before calling bch2_indirect_extent_missing_error(), we have to
calculate the missing range, which is the intersection of the reflink
pointer and the non-indirect-extent we found.

The calculation didn't take into account that the returned extent may
span the iter position, leading to an infinite loop when we
(unnecessarily) resized the extent we were returning to one that didn't
extend past the offset we were looking up.

Signed-off-by: Kent Overstreet <[email protected]>

Author: Kent Overstreet

fs/bcachefs/reflink.c

@@ -64,6 +64,9 @@ void bch2_reflink_p_to_text(struct printbuf *out, struct bch_fs *c,
 	       REFLINK_P_IDX(p.v),
 	       le32_to_cpu(p.v->front_pad),
 	       le32_to_cpu(p.v->back_pad));
+
+	if (REFLINK_P_ERROR(p.v))
+		prt_str(out, " error");
 }
 
 bool bch2_reflink_p_merge(struct bch_fs *c, struct bkey_s _l, struct bkey_s_c _r)
@@ -269,13 +272,12 @@ struct bkey_s_c bch2_lookup_indirect_extent(struct btree_trans *trans,
 		return k;
 
 	if (unlikely(!bkey_extent_is_reflink_data(k.k))) {
-		unsigned size = min((u64) k.k->size,
-				    REFLINK_P_IDX(p.v) + p.k->size + le32_to_cpu(p.v->back_pad) -
-				    reflink_offset);
-		bch2_key_resize(&iter->k, size);
+		u64 missing_end = min(k.k->p.offset,
+				      REFLINK_P_IDX(p.v) + p.k->size + le32_to_cpu(p.v->back_pad));
+		BUG_ON(reflink_offset == missing_end);
 
 		int ret = bch2_indirect_extent_missing_error(trans, p, reflink_offset,
-							     k.k->p.offset, should_commit);
+							     missing_end, should_commit);
 		if (ret) {
 			bch2_trans_iter_exit(trans, iter);
 			return bkey_s_c_err(ret);