nlinks.h

  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__ */