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/cred.h>
  14 #include <linux/xattr.h>
  15 #include "overlayfs.h"
  16 #include "ovl_entry.h"
  17
  18 int ovl_want_write(struct dentry *dentry)
  19 {
  20         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  21         return mnt_want_write(ofs->upper_mnt);
  22 }
  23
  24 void ovl_drop_write(struct dentry *dentry)
  25 {
  26         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  27         mnt_drop_write(ofs->upper_mnt);
  28 }
  29
  30 struct dentry *ovl_workdir(struct dentry *dentry)
  31 {
  32         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  33         return ofs->workdir;
  34 }
  35
  36 const struct cred *ovl_override_creds(struct super_block *sb)
  37 {
  38         struct ovl_fs *ofs = sb->s_fs_info;
  39
  40         return override_creds(ofs->creator_cred);
  41 }
  42
  43 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  44 {
  45         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  46         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  47
  48         if (oe)
  49                 oe->numlower = numlower;
  50
  51         return oe;
  52 }
  53
  54 bool ovl_dentry_remote(struct dentry *dentry)
  55 {
  56         return dentry->d_flags &
  57                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
  58                  DCACHE_OP_REAL);
  59 }
  60
  61 bool ovl_dentry_weird(struct dentry *dentry)
  62 {
  63         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
  64                                   DCACHE_MANAGE_TRANSIT |
  65                                   DCACHE_OP_HASH |
  66                                   DCACHE_OP_COMPARE);
  67 }
  68
  69 enum ovl_path_type ovl_path_type(struct dentry *dentry)
  70 {
  71         struct ovl_entry *oe = dentry->d_fsdata;
  72         enum ovl_path_type type = 0;
  73
  74         if (oe->__upperdentry) {
  75                 type = __OVL_PATH_UPPER;
  76
  77                 /*
  78                  * Non-dir dentry can hold lower dentry from previous
  79                  * location.
  80                  */
  81                 if (oe->numlower && d_is_dir(dentry))
  82                         type |= __OVL_PATH_MERGE;
  83         } else {
  84                 if (oe->numlower > 1)
  85                         type |= __OVL_PATH_MERGE;
  86         }
  87         return type;
  88 }
  89
  90 void ovl_path_upper(struct dentry *dentry, struct path *path)
  91 {
  92         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  93         struct ovl_entry *oe = dentry->d_fsdata;
  94
  95         path->mnt = ofs->upper_mnt;
  96         path->dentry = ovl_upperdentry_dereference(oe);
  97 }
  98
  99 void ovl_path_lower(struct dentry *dentry, struct path *path)
 100 {
 101         struct ovl_entry *oe = dentry->d_fsdata;
 102
 103         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
 104 }
 105
 106 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 107 {
 108         enum ovl_path_type type = ovl_path_type(dentry);
 109
 110         if (!OVL_TYPE_UPPER(type))
 111                 ovl_path_lower(dentry, path);
 112         else
 113                 ovl_path_upper(dentry, path);
 114
 115         return type;
 116 }
 117
 118 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 119 {
 120         struct ovl_entry *oe = dentry->d_fsdata;
 121
 122         return ovl_upperdentry_dereference(oe);
 123 }
 124
 125 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
 126 {
 127         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 128 }
 129
 130 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 131 {
 132         struct ovl_entry *oe = dentry->d_fsdata;
 133
 134         return __ovl_dentry_lower(oe);
 135 }
 136
 137 struct dentry *ovl_dentry_real(struct dentry *dentry)
 138 {
 139         struct ovl_entry *oe = dentry->d_fsdata;
 140         struct dentry *realdentry;
 141
 142         realdentry = ovl_upperdentry_dereference(oe);
 143         if (!realdentry)
 144                 realdentry = __ovl_dentry_lower(oe);
 145
 146         return realdentry;
 147 }
 148
 149 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 150 {
 151         struct ovl_entry *oe = dentry->d_fsdata;
 152
 153         return oe->cache;
 154 }
 155
 156 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 157 {
 158         struct ovl_entry *oe = dentry->d_fsdata;
 159
 160         oe->cache = cache;
 161 }
 162
 163 bool ovl_dentry_is_opaque(struct dentry *dentry)
 164 {
 165         struct ovl_entry *oe = dentry->d_fsdata;
 166         return oe->opaque;
 167 }
 168
 169 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 170 {
 171         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 172 }
 173
 174 void ovl_dentry_set_opaque(struct dentry *dentry)
 175 {
 176         struct ovl_entry *oe = dentry->d_fsdata;
 177
 178         oe->opaque = true;
 179 }
 180
 181 bool ovl_redirect_dir(struct super_block *sb)
 182 {
 183         struct ovl_fs *ofs = sb->s_fs_info;
 184
 185         return ofs->config.redirect_dir;
 186 }
 187
 188 void ovl_clear_redirect_dir(struct super_block *sb)
 189 {
 190         struct ovl_fs *ofs = sb->s_fs_info;
 191
 192         ofs->config.redirect_dir = false;
 193 }
 194
 195 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 196 {
 197         struct ovl_entry *oe = dentry->d_fsdata;
 198
 199         return oe->redirect;
 200 }
 201
 202 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 203 {
 204         struct ovl_entry *oe = dentry->d_fsdata;
 205
 206         kfree(oe->redirect);
 207         oe->redirect = redirect;
 208 }
 209
 210 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 211 {
 212         struct ovl_entry *oe = dentry->d_fsdata;
 213
 214         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
 215         WARN_ON(oe->__upperdentry);
 216         /*
 217          * Make sure upperdentry is consistent before making it visible to
 218          * ovl_upperdentry_dereference().
 219          */
 220         smp_wmb();
 221         oe->__upperdentry = upperdentry;
 222 }
 223
 224 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
 225 {
 226         WRITE_ONCE(inode->i_private, (unsigned long) realinode |
 227                    (is_upper ? OVL_ISUPPER_MASK : 0));
 228 }
 229
 230 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
 231 {
 232         WARN_ON(!upperinode);
 233         WARN_ON(!inode_unhashed(inode));
 234         WRITE_ONCE(inode->i_private,
 235                    (unsigned long) upperinode | OVL_ISUPPER_MASK);
 236         if (!S_ISDIR(upperinode->i_mode))
 237                 __insert_inode_hash(inode, (unsigned long) upperinode);
 238 }
 239
 240 void ovl_dentry_version_inc(struct dentry *dentry)
 241 {
 242         struct ovl_entry *oe = dentry->d_fsdata;
 243
 244         WARN_ON(!inode_is_locked(dentry->d_inode));
 245         oe->version++;
 246 }
 247
 248 u64 ovl_dentry_version_get(struct dentry *dentry)
 249 {
 250         struct ovl_entry *oe = dentry->d_fsdata;
 251
 252         WARN_ON(!inode_is_locked(dentry->d_inode));
 253         return oe->version;
 254 }
 255
 256 bool ovl_is_whiteout(struct dentry *dentry)
 257 {
 258         struct inode *inode = dentry->d_inode;
 259
 260         return inode && IS_WHITEOUT(inode);
 261 }
 262
 263 struct file *ovl_path_open(struct path *path, int flags)
 264 {
 265         return dentry_open(path, flags | O_NOATIME, current_cred());
 266 }
 267
 268 int ovl_copy_up_start(struct dentry *dentry)
 269 {
 270         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 271         struct ovl_entry *oe = dentry->d_fsdata;
 272         int err;
 273
 274         spin_lock(&ofs->copyup_wq.lock);
 275         err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
 276         if (!err) {
 277                 if (oe->__upperdentry)
 278                         err = 1; /* Already copied up */
 279                 else
 280                         oe->copying = true;
 281         }
 282         spin_unlock(&ofs->copyup_wq.lock);
 283
 284         return err;
 285 }
 286
 287 void ovl_copy_up_end(struct dentry *dentry)
 288 {
 289         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 290         struct ovl_entry *oe = dentry->d_fsdata;
 291
 292         spin_lock(&ofs->copyup_wq.lock);
 293         oe->copying = false;
 294         wake_up_locked(&ofs->copyup_wq);
 295         spin_unlock(&ofs->copyup_wq.lock);
 296 }