bcachefs: Handle race between stripe reuse, invalidate_stripe_to_dev

When creating a new stripe, we may reuse an existing stripe that has
some empty and some nonempty blocks.

Generally, the existing stripe won't change underneath us - except for
block sector counts, which we copy to the new key in
ec_stripe_key_update.

But the device removal path can now invalidate stripe pointers to a
device, and that can race with stripe reuse.

Change ec_stripe_key_update() to check for and resolve this
inconsistency.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/ec.c

@@ -1206,47 +1206,62 @@ void bch2_do_stripe_deletes(struct bch_fs *c)
 /* stripe creation: */
 
 static int ec_stripe_key_update(struct btree_trans *trans,
-				struct bkey_i_stripe *new,
-				bool create)
+				struct bkey_i_stripe *old,
+				struct bkey_i_stripe *new)
 {
 	struct bch_fs *c = trans->c;
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
+	bool create = !old;
 
-	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_stripes,
-			       new->k.p, BTREE_ITER_intent);
-	ret = bkey_err(k);
+	struct btree_iter iter;
+	struct bkey_s_c k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_stripes,
+					       new->k.p, BTREE_ITER_intent);
+	int ret = bkey_err(k);
 	if (ret)
 		goto err;
 
-	if (k.k->type != (create ? KEY_TYPE_deleted : KEY_TYPE_stripe)) {
-		bch2_fs_inconsistent(c, "error %s stripe: got existing key type %s",
-				     create ? "creating" : "updating",
-				     bch2_bkey_types[k.k->type]);
+	if (bch2_fs_inconsistent_on(k.k->type != (create ? KEY_TYPE_deleted : KEY_TYPE_stripe),
+				    c, "error %s stripe: got existing key type %s",
+				    create ? "creating" : "updating",
+				    bch2_bkey_types[k.k->type])) {
 		ret = -EINVAL;
 		goto err;
 	}
 
 	if (k.k->type == KEY_TYPE_stripe) {
-		const struct bch_stripe *old = bkey_s_c_to_stripe(k).v;
-		unsigned i;
+		const struct bch_stripe *v = bkey_s_c_to_stripe(k).v;
 
-		if (old->nr_blocks != new->v.nr_blocks) {
-			bch_err(c, "error updating stripe: nr_blocks does not match");
-			ret = -EINVAL;
-			goto err;
-		}
+		BUG_ON(old->v.nr_blocks != new->v.nr_blocks);
+		BUG_ON(old->v.nr_blocks != v->nr_blocks);
+
+		for (unsigned i = 0; i < new->v.nr_blocks; i++) {
+			unsigned sectors = stripe_blockcount_get(v, i);
+
+			if (!bch2_extent_ptr_eq(old->v.ptrs[i], new->v.ptrs[i]) && sectors) {
+				struct printbuf buf = PRINTBUF;
 
-		for (i = 0; i < new->v.nr_blocks; i++) {
-			unsigned v = stripe_blockcount_get(old, i);
+				prt_printf(&buf, "stripe changed nonempty block %u", i);
+				prt_str(&buf, "\nold: ");
+				bch2_bkey_val_to_text(&buf, c, k);
+				prt_str(&buf, "\nnew: ");
+				bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&new->k_i));
+				bch2_fs_inconsistent(c, "%s", buf.buf);
+				printbuf_exit(&buf);
+				ret = -EINVAL;
+				goto err;
+			}
 
-			BUG_ON(v &&
-			       (old->ptrs[i].dev != new->v.ptrs[i].dev ||
-				old->ptrs[i].gen != new->v.ptrs[i].gen ||
-				old->ptrs[i].offset != new->v.ptrs[i].offset));
+			/*
+			 * If the stripe ptr changed underneath us, it must have
+			 * been dev_remove_stripes() -> * invalidate_stripe_to_dev()
+			 */
+			if (!bch2_extent_ptr_eq(old->v.ptrs[i], v->ptrs[i])) {
+				BUG_ON(v->ptrs[i].dev != BCH_SB_MEMBER_INVALID);
+
+				if (bch2_extent_ptr_eq(old->v.ptrs[i], new->v.ptrs[i]))
+					new->v.ptrs[i].dev = BCH_SB_MEMBER_INVALID;
+			}
 
-			stripe_blockcount_set(&new->v, i, v);
+			stripe_blockcount_set(&new->v, i, sectors);
 		}
 	}
 
@@ -1508,8 +1523,10 @@ static void ec_stripe_create(struct ec_stripe_new *s)
 			    BCH_TRANS_COMMIT_no_check_rw|
 			    BCH_TRANS_COMMIT_no_enospc,
 			    ec_stripe_key_update(trans,
-					bkey_i_to_stripe(&s->new_stripe.key),
-					!s->have_existing_stripe));
+					s->have_existing_stripe
+					? bkey_i_to_stripe(&s->existing_stripe.key)
+					: NULL,
+					bkey_i_to_stripe(&s->new_stripe.key)));
 	bch_err_msg(c, ret, "creating stripe key");
 	if (ret) {
 		goto err;

fs/bcachefs/extents.h

@@ -695,6 +695,16 @@ void bch2_bkey_ptrs_to_text(struct printbuf *, struct bch_fs *,
 int bch2_bkey_ptrs_validate(struct bch_fs *, struct bkey_s_c,
 			    enum bch_validate_flags);
 
+static inline bool bch2_extent_ptr_eq(struct bch_extent_ptr ptr1,
+				      struct bch_extent_ptr ptr2)
+{
+	return (ptr1.cached	== ptr2.cached &&
+		ptr1.unwritten	== ptr2.unwritten &&
+		ptr1.offset	== ptr2.offset &&
+		ptr1.dev	== ptr2.dev &&
+		ptr1.dev	== ptr2.dev);
+}
+
 void bch2_ptr_swab(struct bkey_s);
 
 const struct bch_extent_rebalance *bch2_bkey_rebalance_opts(struct bkey_s_c);