fs/overlayfs/util.c

   1 /*
   2  * Copyright (C) 2011 Novell Inc.
   3  * Copyright (C) 2016 Red Hat, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  */
   9
  10 #include <linux/fs.h>
  11 #include <linux/mount.h>
  12 #include <linux/slab.h>
  13 #include <linux/xattr.h>
  14 #include "overlayfs.h"
  15 #include "ovl_entry.h"
  16
  17 int ovl_want_write(struct dentry *dentry)
  18 {
  19         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  20         return mnt_want_write(ofs->upper_mnt);
  21 }
  22
  23 void ovl_drop_write(struct dentry *dentry)
  24 {
  25         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  26         mnt_drop_write(ofs->upper_mnt);
  27 }
  28
  29 struct dentry *ovl_workdir(struct dentry *dentry)
  30 {
  31         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  32         return ofs->workdir;
  33 }
  34
  35 const struct cred *ovl_override_creds(struct super_block *sb)
  36 {
  37         struct ovl_fs *ofs = sb->s_fs_info;
  38
  39         return override_creds(ofs->creator_cred);
  40 }
  41
  42 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  43 {
  44         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  45         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  46
  47         if (oe)
  48                 oe->numlower = numlower;
  49
  50         return oe;
  51 }
  52
  53 bool ovl_dentry_remote(struct dentry *dentry)
  54 {
  55         return dentry->d_flags &
  56                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
  57                  DCACHE_OP_REAL);
  58 }
  59
  60 bool ovl_dentry_weird(struct dentry *dentry)
  61 {
  62         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
  63                                   DCACHE_MANAGE_TRANSIT |
  64                                   DCACHE_OP_HASH |
  65                                   DCACHE_OP_COMPARE);
  66 }
  67
  68 enum ovl_path_type ovl_path_type(struct dentry *dentry)
  69 {
  70         struct ovl_entry *oe = dentry->d_fsdata;
  71         enum ovl_path_type type = 0;
  72
  73         if (oe->__upperdentry) {
  74                 type = __OVL_PATH_UPPER;
  75
  76                 /*
  77                  * Non-dir dentry can hold lower dentry from previous
  78                  * location.
  79                  */
  80                 if (oe->numlower && d_is_dir(dentry))
  81                         type |= __OVL_PATH_MERGE;
  82         } else {
  83                 if (oe->numlower > 1)
  84                         type |= __OVL_PATH_MERGE;
  85         }
  86         return type;
  87 }
  88
  89 void ovl_path_upper(struct dentry *dentry, struct path *path)
  90 {
  91         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  92         struct ovl_entry *oe = dentry->d_fsdata;
  93
  94         path->mnt = ofs->upper_mnt;
  95         path->dentry = ovl_upperdentry_dereference(oe);
  96 }
  97
  98 void ovl_path_lower(struct dentry *dentry, struct path *path)
  99 {
 100         struct ovl_entry *oe = dentry->d_fsdata;
 101
 102         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
 103 }
 104
 105 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 106 {
 107         enum ovl_path_type type = ovl_path_type(dentry);
 108
 109         if (!OVL_TYPE_UPPER(type))
 110                 ovl_path_lower(dentry, path);
 111         else
 112                 ovl_path_upper(dentry, path);
 113
 114         return type;
 115 }
 116
 117 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 118 {
 119         struct ovl_entry *oe = dentry->d_fsdata;
 120
 121         return ovl_upperdentry_dereference(oe);
 122 }
 123
 124 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
 125 {
 126         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 127 }
 128
 129 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 130 {
 131         struct ovl_entry *oe = dentry->d_fsdata;
 132
 133         return __ovl_dentry_lower(oe);
 134 }
 135
 136 struct dentry *ovl_dentry_real(struct dentry *dentry)
 137 {
 138         struct ovl_entry *oe = dentry->d_fsdata;
 139         struct dentry *realdentry;
 140
 141         realdentry = ovl_upperdentry_dereference(oe);
 142         if (!realdentry)
 143                 realdentry = __ovl_dentry_lower(oe);
 144
 145         return realdentry;
 146 }
 147
 148 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 149 {
 150         struct ovl_entry *oe = dentry->d_fsdata;
 151
 152         return oe->cache;
 153 }
 154
 155 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 156 {
 157         struct ovl_entry *oe = dentry->d_fsdata;
 158
 159         oe->cache = cache;
 160 }
 161
 162 bool ovl_dentry_is_opaque(struct dentry *dentry)
 163 {
 164         struct ovl_entry *oe = dentry->d_fsdata;
 165         return oe->opaque;
 166 }
 167
 168 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 169 {
 170         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 171 }
 172
 173 void ovl_dentry_set_opaque(struct dentry *dentry)
 174 {
 175         struct ovl_entry *oe = dentry->d_fsdata;
 176
 177         oe->opaque = true;
 178 }
 179
 180 bool ovl_redirect_dir(struct super_block *sb)
 181 {
 182         struct ovl_fs *ofs = sb->s_fs_info;
 183
 184         return ofs->config.redirect_dir;
 185 }
 186
 187 void ovl_clear_redirect_dir(struct super_block *sb)
 188 {
 189         struct ovl_fs *ofs = sb->s_fs_info;
 190
 191         ofs->config.redirect_dir = false;
 192 }
 193
 194 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 195 {
 196         struct ovl_entry *oe = dentry->d_fsdata;
 197
 198         return oe->redirect;
 199 }
 200
 201 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 202 {
 203         struct ovl_entry *oe = dentry->d_fsdata;
 204
 205         kfree(oe->redirect);
 206         oe->redirect = redirect;
 207 }
 208
 209 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 210 {
 211         struct ovl_entry *oe = dentry->d_fsdata;
 212
 213         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
 214         WARN_ON(oe->__upperdentry);
 215         /*
 216          * Make sure upperdentry is consistent before making it visible to
 217          * ovl_upperdentry_dereference().
 218          */
 219         smp_wmb();
 220         oe->__upperdentry = upperdentry;
 221 }
 222
 223 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
 224 {
 225         WRITE_ONCE(inode->i_private, (unsigned long) realinode |
 226                    (is_upper ? OVL_ISUPPER_MASK : 0));
 227 }
 228
 229 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
 230 {
 231         WARN_ON(!upperinode);
 232         WARN_ON(!inode_unhashed(inode));
 233         WRITE_ONCE(inode->i_private,
 234                    (unsigned long) upperinode | OVL_ISUPPER_MASK);
 235         if (!S_ISDIR(upperinode->i_mode))
 236                 __insert_inode_hash(inode, (unsigned long) upperinode);
 237 }
 238
 239 void ovl_dentry_version_inc(struct dentry *dentry)
 240 {
 241         struct ovl_entry *oe = dentry->d_fsdata;
 242
 243         WARN_ON(!inode_is_locked(dentry->d_inode));
 244         oe->version++;
 245 }
 246
 247 u64 ovl_dentry_version_get(struct dentry *dentry)
 248 {
 249         struct ovl_entry *oe = dentry->d_fsdata;
 250
 251         WARN_ON(!inode_is_locked(dentry->d_inode));
 252         return oe->version;
 253 }
 254
 255 bool ovl_is_whiteout(struct dentry *dentry)
 256 {
 257         struct inode *inode = dentry->d_inode;
 258
 259         return inode && IS_WHITEOUT(inode);
 260 }
 261
 262 struct file *ovl_path_open(struct path *path, int flags)
 263 {
 264         return dentry_open(path, flags | O_NOATIME, current_cred());
 265 }