fs/overlayfs/ovl_entry.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *
   4  * Copyright (C) 2011 Novell Inc.
   5  * Copyright (C) 2016 Red Hat, Inc.
   6  */
   7
   8 struct ovl_config {
   9         char *upperdir;
  10         char *workdir;
  11         bool default_permissions;
  12         int redirect_mode;
  13         int verity_mode;
  14         bool index;
  15         int uuid;
  16         bool nfs_export;
  17         int xino;
  18         bool metacopy;
  19         bool userxattr;
  20         bool ovl_volatile;
  21 };
  22
  23 struct ovl_sb {
  24         struct super_block *sb;
  25         dev_t pseudo_dev;
  26         /* Unusable (conflicting) uuid */
  27         bool bad_uuid;
  28         /* Used as a lower layer (but maybe also as upper) */
  29         bool is_lower;
  30 };
  31
  32 struct ovl_layer {
  33         /* ovl_free_fs() relies on @mnt being the first member! */
  34         struct vfsmount *mnt;
  35         /* Trap in ovl inode cache */
  36         struct inode *trap;
  37         struct ovl_sb *fs;
  38         /* Index of this layer in fs root (upper idx == 0) */
  39         int idx;
  40         /* One fsid per unique underlying sb (upper fsid == 0) */
  41         int fsid;
  42         char *name;
  43 };
  44
  45 /*
  46  * ovl_free_fs() relies on @mnt being the first member when unmounting
  47  * the private mounts created for each layer. Let's check both the
  48  * offset and type.
  49  */
  50 static_assert(offsetof(struct ovl_layer, mnt) == 0);
  51 static_assert(__same_type(typeof_member(struct ovl_layer, mnt), struct vfsmount *));
  52
  53 struct ovl_path {
  54         const struct ovl_layer *layer;
  55         struct dentry *dentry;
  56 };
  57
  58 struct ovl_entry {
  59         unsigned int __numlower;
  60         struct ovl_path __lowerstack[];
  61 };
  62
  63 /* private information held for overlayfs's superblock */
  64 struct ovl_fs {
  65         unsigned int numlayer;
  66         /* Number of unique fs among layers including upper fs */
  67         unsigned int numfs;
  68         /* Number of data-only lower layers */
  69         unsigned int numdatalayer;
  70         const struct ovl_layer *layers;
  71         struct ovl_sb *fs;
  72         /* workbasedir is the path at workdir= mount option */
  73         struct dentry *workbasedir;
  74         /* workdir is the 'work' directory under workbasedir */
  75         struct dentry *workdir;
  76         /* index directory listing overlay inodes by origin file handle */
  77         struct dentry *indexdir;
  78         long namelen;
  79         /* pathnames of lower and upper dirs, for show_options */
  80         struct ovl_config config;
  81         /* creds of process who forced instantiation of super block */
  82         const struct cred *creator_cred;
  83         bool tmpfile;
  84         bool noxattr;
  85         bool nofh;
  86         /* Did we take the inuse lock? */
  87         bool upperdir_locked;
  88         bool workdir_locked;
  89         /* Traps in ovl inode cache */
  90         struct inode *workbasedir_trap;
  91         struct inode *workdir_trap;
  92         struct inode *indexdir_trap;
  93         /* -1: disabled, 0: same fs, 1..32: number of unused ino bits */
  94         int xino_mode;
  95         /* For allocation of non-persistent inode numbers */
  96         atomic_long_t last_ino;
  97         /* Shared whiteout cache */
  98         struct dentry *whiteout;
  99         bool no_shared_whiteout;
 100         /* r/o snapshot of upperdir sb's only taken on volatile mounts */
 101         errseq_t errseq;
 102 };
 103
 104 /* Number of lower layers, not including data-only layers */
 105 static inline unsigned int ovl_numlowerlayer(struct ovl_fs *ofs)
 106 {
 107         return ofs->numlayer - ofs->numdatalayer - 1;
 108 }
 109
 110 static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
 111 {
 112         return ofs->layers[0].mnt;
 113 }
 114
 115 static inline struct mnt_idmap *ovl_upper_mnt_idmap(struct ovl_fs *ofs)
 116 {
 117         return mnt_idmap(ovl_upper_mnt(ofs));
 118 }
 119
 120 extern struct file_system_type ovl_fs_type;
 121
 122 static inline struct ovl_fs *OVL_FS(struct super_block *sb)
 123 {
 124         if (IS_ENABLED(CONFIG_OVERLAY_FS_DEBUG))
 125                 WARN_ON_ONCE(sb->s_type != &ovl_fs_type);
 126
 127         return (struct ovl_fs *)sb->s_fs_info;
 128 }
 129
 130 static inline bool ovl_should_sync(struct ovl_fs *ofs)
 131 {
 132         return !ofs->config.ovl_volatile;
 133 }
 134
 135 static inline unsigned int ovl_numlower(struct ovl_entry *oe)
 136 {
 137         return oe ? oe->__numlower : 0;
 138 }
 139
 140 static inline struct ovl_path *ovl_lowerstack(struct ovl_entry *oe)
 141 {
 142         return ovl_numlower(oe) ? oe->__lowerstack : NULL;
 143 }
 144
 145 static inline struct ovl_path *ovl_lowerpath(struct ovl_entry *oe)
 146 {
 147         return ovl_lowerstack(oe);
 148 }
 149
 150 static inline struct ovl_path *ovl_lowerdata(struct ovl_entry *oe)
 151 {
 152         struct ovl_path *lowerstack = ovl_lowerstack(oe);
 153
 154         return lowerstack ? &lowerstack[oe->__numlower - 1] : NULL;
 155 }
 156
 157 /* May return NULL if lazy lookup of lowerdata is needed */
 158 static inline struct dentry *ovl_lowerdata_dentry(struct ovl_entry *oe)
 159 {
 160         struct ovl_path *lowerdata = ovl_lowerdata(oe);
 161
 162         return lowerdata ? READ_ONCE(lowerdata->dentry) : NULL;
 163 }
 164
 165 /* private information held for every overlayfs dentry */
 166 static inline unsigned long *OVL_E_FLAGS(struct dentry *dentry)
 167 {
 168         return (unsigned long *) &dentry->d_fsdata;
 169 }
 170
 171 struct ovl_inode {
 172         union {
 173                 struct ovl_dir_cache *cache;    /* directory */
 174                 const char *lowerdata_redirect; /* regular file */
 175         };
 176         const char *redirect;
 177         u64 version;
 178         unsigned long flags;
 179         struct inode vfs_inode;
 180         struct dentry *__upperdentry;
 181         struct ovl_entry *oe;
 182
 183         /* synchronize copy up and more */
 184         struct mutex lock;
 185 };
 186
 187 static inline struct ovl_inode *OVL_I(struct inode *inode)
 188 {
 189         return container_of(inode, struct ovl_inode, vfs_inode);
 190 }
 191
 192 static inline struct ovl_entry *OVL_I_E(struct inode *inode)
 193 {
 194         return inode ? OVL_I(inode)->oe : NULL;
 195 }
 196
 197 static inline struct ovl_entry *OVL_E(struct dentry *dentry)
 198 {
 199         return OVL_I_E(d_inode(dentry));
 200 }
 201
 202 static inline struct dentry *ovl_upperdentry_dereference(struct ovl_inode *oi)
 203 {
 204         return READ_ONCE(oi->__upperdentry);
 205 }