fs/xfs/scrub/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. */
  10 struct 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  */
  65 struct 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. */
  98 static inline uint64_t
  99 xchk_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__ */