bcachefs: Run bch2_check_dirent_target() at lookup time

More on the "full online self healing" project:

We now run most of the dirent <-> inode consistency checks, with repair
code, at runtime - the exact same check and repair code that fsck runs.

This will allow us to repair the "dirent points to inode that does not
point back" inconsistencies that have been popping up at runtime.

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

Author: Kent Overstreet

fs/bcachefs/fs.c

@@ -641,7 +641,9 @@ static struct bch_inode_info *bch2_lookup_trans(struct btree_trans *trans,
 	if (ret)
 		return ERR_PTR(ret);
 
-	ret = bch2_dirent_read_target(trans, dir, bkey_s_c_to_dirent(k), &inum);
+	struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
+
+	ret = bch2_dirent_read_target(trans, dir, d, &inum);
 	if (ret > 0)
 		ret = -ENOENT;
 	if (ret)
@@ -651,30 +653,30 @@ static struct bch_inode_info *bch2_lookup_trans(struct btree_trans *trans,
 	if (inode)
 		goto out;
 
+	/*
+	 * Note: if check/repair needs it, we commit before
+	 * bch2_inode_hash_init_insert(), as after that point we can't take a
+	 * restart - not in the top level loop with a commit_do(), like we
+	 * usually do:
+	 */
+
 	struct bch_subvolume subvol;
 	struct bch_inode_unpacked inode_u;
 	ret =   bch2_subvolume_get(trans, inum.subvol, true, &subvol) ?:
 		bch2_inode_find_by_inum_nowarn_trans(trans, inum, &inode_u) ?:
+		bch2_check_dirent_target(trans, &dirent_iter, d, &inode_u, false) ?:
+		bch2_trans_commit(trans, NULL, NULL, BCH_TRANS_COMMIT_no_enospc) ?:
 		PTR_ERR_OR_ZERO(inode = bch2_inode_hash_init_insert(trans, inum, &inode_u, &subvol));
 
+	/*
+	 * don't remove it: check_inodes might find another inode that points
+	 * back to this dirent
+	 */
 	bch2_fs_inconsistent_on(bch2_err_matches(ret, ENOENT),
 				c, "dirent to missing inode:\n  %s",
-				(bch2_bkey_val_to_text(&buf, c, k), buf.buf));
+				(bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf));
 	if (ret)
 		goto err;
-
-	/* regular files may have hardlinks: */
-	if (bch2_fs_inconsistent_on(bch2_inode_should_have_single_bp(&inode_u) &&
-				    !bkey_eq(k.k->p, POS(inode_u.bi_dir, inode_u.bi_dir_offset)),
-				    c,
-				    "dirent points to inode that does not point back:\n  %s",
-				    (bch2_bkey_val_to_text(&buf, c, k),
-				     prt_printf(&buf, "\n  "),
-				     bch2_inode_unpacked_to_text(&buf, &inode_u),
-				     buf.buf))) {
-		ret = -ENOENT;
-		goto err;
-	}
 out:
 	bch2_trans_iter_exit(trans, &dirent_iter);
 	printbuf_exit(&buf);