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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright (c) 2021-2024 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <djwong@kernel.org>
*/
#ifndef __XFS_SCRUB_NLINKS_H__
#define __XFS_SCRUB_NLINKS_H__
/* Live link count control structure. */
struct xchk_nlink_ctrs {
struct xfs_scrub *sc;
/* Shadow link count data and its mutex. */
struct xfarray *nlinks;
struct mutex lock;
/*
* The collection step uses a separate iscan context from the compare
* step because the collection iscan coordinates live updates to the
* observation data while this scanner is running. The compare iscan
* is secondary and can be reinitialized as needed.
*/
struct xchk_iscan collect_iscan;
struct xchk_iscan compare_iscan;
/*
* Hook into directory updates so that we can receive live updates
* from other writer threads.
*/
struct xfs_dir_hook dhook;
};
/*
* In-core link counts for a given inode in the filesystem.
*
* For an empty rootdir, the directory entries and the field to which they are
* accounted are as follows:
*
* Root directory:
*
* . points to self (root.child)
* .. points to self (root.parent)
* f1 points to a child file (f1.parent)
* d1 points to a child dir (d1.parent, root.child)
*
* Subdirectory d1:
*
* . points to self (d1.child)
* .. points to root dir (root.backref)
* f2 points to child file (f2.parent)
* f3 points to root.f1 (f1.parent)
*
* root.nlink == 3 (root.dot, root.dotdot, root.d1)
* d1.nlink == 2 (root.d1, d1.dot)
* f1.nlink == 2 (root.f1, d1.f3)
* f2.nlink == 1 (d1.f2)
*/
struct xchk_nlink {
/* Count of forward links from parent directories to this file. */
xfs_nlink_t parents;
/*
* Count of back links to this parent directory from child
* subdirectories.
*/
xfs_nlink_t backrefs;
/*
* Count of forward links from this directory to all child files and
* the number of dot entries. Should be zero for non-directories.
*/
xfs_nlink_t children;
/* Record state flags */
unsigned int flags;
};
/*
* This incore link count has been written at least once. We never want to
* store an xchk_nlink that looks uninitialized.
*/
#define XCHK_NLINK_WRITTEN (1U << 0)
/* Already checked this link count record. */
#define XCHK_NLINK_COMPARE_SCANNED (1U << 1)
/* Already made a repair with this link count record. */
#define XREP_NLINK_DIRTY (1U << 2)
/* Compute total link count, using large enough variables to detect overflow. */
static inline uint64_t
xchk_nlink_total(struct xfs_inode *ip, const struct xchk_nlink *live)
{
uint64_t ret = live->parents;
/* Add one link count for the dot entry of any linked directory. */
if (ip && S_ISDIR(VFS_I(ip)->i_mode) && VFS_I(ip)->i_nlink)
ret++;
return ret + live->children;
}
#endif /* __XFS_SCRUB_NLINKS_H__ */
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