bcachefs: bch2_btree_delete_range_trans() now returns -BCH_ERR_transaction_restart_nested

The new convention is that functions that handle transaction restarts
within an existing transaction context should return
-BCH_ERR_transaction_restart_nested when they did so, since they
invalidated the outer transaction context.

This also means bch2_btree_delete_range_trans() is changed to only call
bch2_trans_begin() after a transaction restart, not on every loop
iteration.

This is to fix a bug in fsck, in check_inode() when we truncate an inode
with BCH_INODE_I_SIZE_DIRTY set.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_update_leaf.c

@@ -1713,15 +1713,16 @@ int bch2_btree_delete_range_trans(struct btree_trans *trans, enum btree_id id,
 				  unsigned update_flags,
 				  u64 *journal_seq)
 {
+	u32 restart_count = trans->restart_count;
 	struct btree_iter iter;
 	struct bkey_s_c k;
 	int ret = 0;
 
 	bch2_trans_iter_init(trans, &iter, id, start, BTREE_ITER_INTENT);
 retry:
-	while ((bch2_trans_begin(trans),
-	       (k = bch2_btree_iter_peek(&iter)).k) &&
-	       !(ret = bkey_err(k)) &&
+	while ((k = bch2_btree_iter_peek(&iter)).k &&
+	       !(ret = bkey_err(k) ?:
+		 btree_trans_too_many_iters(trans)) &&
 	       bkey_cmp(iter.pos, end) < 0) {
 		struct disk_reservation disk_res =
 			bch2_disk_reservation_init(trans->c, 0);
@@ -1767,11 +1768,15 @@ int bch2_btree_delete_range_trans(struct btree_trans *trans, enum btree_id id,
 	}
 
 	if (bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+		bch2_trans_begin(trans);
 		ret = 0;
 		goto retry;
 	}
 
 	bch2_trans_iter_exit(trans, &iter);
+
+	if (!ret && trans_was_restarted(trans, restart_count))
+		ret = -BCH_ERR_transaction_restart_nested;
 	return ret;
 }
 
@@ -1785,8 +1790,12 @@ int bch2_btree_delete_range(struct bch_fs *c, enum btree_id id,
 			    unsigned update_flags,
 			    u64 *journal_seq)
 {
-	return bch2_trans_run(c,
-			bch2_btree_delete_range_trans(&trans, id, start, end, update_flags, journal_seq));
+	int ret = bch2_trans_run(c,
+			bch2_btree_delete_range_trans(&trans, id, start, end,
+						      update_flags, journal_seq));
+	if (ret == -BCH_ERR_transaction_restart_nested)
+		ret = 0;
+	return ret;
 }
 
 int bch2_trans_log_msg(struct btree_trans *trans, const char *msg)

fs/bcachefs/fsck.c

@@ -19,6 +19,10 @@
 
 #define QSTR(n) { { { .len = strlen(n) } }, .name = n }
 
+/*
+ * XXX: this is handling transaction restarts without returning
+ * -BCH_ERR_transaction_restart_nested, this is not how we do things anymore:
+ */
 static s64 bch2_count_inode_sectors(struct btree_trans *trans, u64 inum,
 				    u32 snapshot)
 {
@@ -239,18 +243,20 @@ static int fsck_inode_rm(struct btree_trans *trans, u64 inum, u32 snapshot)
 	struct bkey_s_c k;
 	int ret;
 
-	ret   = bch2_btree_delete_range_trans(trans, BTREE_ID_extents,
-					      SPOS(inum, 0, snapshot),
-					      SPOS(inum, U64_MAX, snapshot),
-					      0, NULL) ?:
-		bch2_btree_delete_range_trans(trans, BTREE_ID_dirents,
-					      SPOS(inum, 0, snapshot),
-					      SPOS(inum, U64_MAX, snapshot),
-					      0, NULL) ?:
-		bch2_btree_delete_range_trans(trans, BTREE_ID_xattrs,
-					      SPOS(inum, 0, snapshot),
-					      SPOS(inum, U64_MAX, snapshot),
-					      0, NULL);
+	do {
+		ret   = bch2_btree_delete_range_trans(trans, BTREE_ID_extents,
+						      SPOS(inum, 0, snapshot),
+						      SPOS(inum, U64_MAX, snapshot),
+						      0, NULL) ?:
+			bch2_btree_delete_range_trans(trans, BTREE_ID_dirents,
+						      SPOS(inum, 0, snapshot),
+						      SPOS(inum, U64_MAX, snapshot),
+						      0, NULL) ?:
+			bch2_btree_delete_range_trans(trans, BTREE_ID_xattrs,
+						      SPOS(inum, 0, snapshot),
+						      SPOS(inum, U64_MAX, snapshot),
+						      0, NULL);
+	} while (ret == -BCH_ERR_transaction_restart_nested);
 	if (ret)
 		goto err;
 retry: