1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Copyright (c) 2021-2024 Oracle.  All Rights Reserved.
4 * Author: Darrick J. Wong <djwong@kernel.org>
5 */
6#ifndef __XFS_SCRUB_NLINKS_H__
7#define __XFS_SCRUB_NLINKS_H__
8
9/* Live link count control structure. */
10struct xchk_nlink_ctrs {
11	struct xfs_scrub	*sc;
12
13	/* Shadow link count data and its mutex. */
14	struct xfarray		*nlinks;
15	struct mutex		lock;
16
17	/*
18	 * The collection step uses a separate iscan context from the compare
19	 * step because the collection iscan coordinates live updates to the
20	 * observation data while this scanner is running.  The compare iscan
21	 * is secondary and can be reinitialized as needed.
22	 */
23	struct xchk_iscan	collect_iscan;
24	struct xchk_iscan	compare_iscan;
25
26	/*
27	 * Hook into directory updates so that we can receive live updates
28	 * from other writer threads.
29	 */
30	struct xfs_dir_hook	dhook;
31
32	/* Orphanage reparenting request. */
33	struct xrep_adoption	adoption;
34
35	/* Directory entry name, plus the trailing null. */
36	struct xfs_name		xname;
37	char			namebuf[MAXNAMELEN];
38};
39
40/*
41 * In-core link counts for a given inode in the filesystem.
42 *
43 * For an empty rootdir, the directory entries and the field to which they are
44 * accounted are as follows:
45 *
46 * Root directory:
47 *
48 * . points to self		(root.child)
49 * .. points to self		(root.parent)
50 * f1 points to a child file	(f1.parent)
51 * d1 points to a child dir	(d1.parent, root.child)
52 *
53 * Subdirectory d1:
54 *
55 * . points to self		(d1.child)
56 * .. points to root dir	(root.backref)
57 * f2 points to child file	(f2.parent)
58 * f3 points to root.f1		(f1.parent)
59 *
60 * root.nlink == 3 (root.dot, root.dotdot, root.d1)
61 * d1.nlink == 2 (root.d1, d1.dot)
62 * f1.nlink == 2 (root.f1, d1.f3)
63 * f2.nlink == 1 (d1.f2)
64 */
65struct xchk_nlink {
66	/* Count of forward links from parent directories to this file. */
67	xfs_nlink_t		parents;
68
69	/*
70	 * Count of back links to this parent directory from child
71	 * subdirectories.
72	 */
73	xfs_nlink_t		backrefs;
74
75	/*
76	 * Count of forward links from this directory to all child files and
77	 * the number of dot entries.  Should be zero for non-directories.
78	 */
79	xfs_nlink_t		children;
80
81	/* Record state flags */
82	unsigned int		flags;
83};
84
85/*
86 * This incore link count has been written at least once.  We never want to
87 * store an xchk_nlink that looks uninitialized.
88 */
89#define XCHK_NLINK_WRITTEN		(1U << 0)
90
91/* Already checked this link count record. */
92#define XCHK_NLINK_COMPARE_SCANNED	(1U << 1)
93
94/* Already made a repair with this link count record. */
95#define XREP_NLINK_DIRTY		(1U << 2)
96
97/* Compute total link count, using large enough variables to detect overflow. */
98static inline uint64_t
99xchk_nlink_total(struct xfs_inode *ip, const struct xchk_nlink *live)
100{
101	uint64_t	ret = live->parents;
102
103	/* Add one link count for the dot entry of any linked directory. */
104	if (ip && S_ISDIR(VFS_I(ip)->i_mode) && VFS_I(ip)->i_nlink)
105		ret++;
106	return ret + live->children;
107}
108
109#endif /* __XFS_SCRUB_NLINKS_H__ */
110