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