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 <linux/sched/signal.h>
  16 #include "overlayfs.h"
  17 #include "ovl_entry.h"
  18
  19 int ovl_want_write(struct dentry *dentry)
  20 {
  21         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  22         return mnt_want_write(ofs->upper_mnt);
  23 }
  24
  25 void ovl_drop_write(struct dentry *dentry)
  26 {
  27         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  28         mnt_drop_write(ofs->upper_mnt);
  29 }
  30
  31 struct dentry *ovl_workdir(struct dentry *dentry)
  32 {
  33         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
  34         return ofs->workdir;
  35 }
  36
  37 const struct cred *ovl_override_creds(struct super_block *sb)
  38 {
  39         struct ovl_fs *ofs = sb->s_fs_info;
  40
  41         return override_creds(ofs->creator_cred);
  42 }
  43
  44 struct super_block *ovl_same_sb(struct super_block *sb)
  45 {
  46         struct ovl_fs *ofs = sb->s_fs_info;
  47
  48         return ofs->same_sb;
  49 }
  50
  51 struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
  52 {
  53         size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
  54         struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
  55
  56         if (oe)
  57                 oe->numlower = numlower;
  58
  59         return oe;
  60 }
  61
  62 bool ovl_dentry_remote(struct dentry *dentry)
  63 {
  64         return dentry->d_flags &
  65                 (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
  66                  DCACHE_OP_REAL);
  67 }
  68
  69 bool ovl_dentry_weird(struct dentry *dentry)
  70 {
  71         return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
  72                                   DCACHE_MANAGE_TRANSIT |
  73                                   DCACHE_OP_HASH |
  74                                   DCACHE_OP_COMPARE);
  75 }
  76
  77 enum ovl_path_type ovl_path_type(struct dentry *dentry)
  78 {
  79         struct ovl_entry *oe = dentry->d_fsdata;
  80         enum ovl_path_type type = 0;
  81
  82         if (oe->__upperdentry) {
  83                 type = __OVL_PATH_UPPER;
  84
  85                 /*
  86                  * Non-dir dentry can hold lower dentry of its copy up origin.
  87                  */
  88                 if (oe->numlower) {
  89                         type |= __OVL_PATH_ORIGIN;
  90                         if (d_is_dir(dentry))
  91                                 type |= __OVL_PATH_MERGE;
  92                 }
  93         } else {
  94                 if (oe->numlower > 1)
  95                         type |= __OVL_PATH_MERGE;
  96         }
  97         return type;
  98 }
  99
 100 void ovl_path_upper(struct dentry *dentry, struct path *path)
 101 {
 102         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 103         struct ovl_entry *oe = dentry->d_fsdata;
 104
 105         path->mnt = ofs->upper_mnt;
 106         path->dentry = ovl_upperdentry_dereference(oe);
 107 }
 108
 109 void ovl_path_lower(struct dentry *dentry, struct path *path)
 110 {
 111         struct ovl_entry *oe = dentry->d_fsdata;
 112
 113         *path = oe->numlower ? oe->lowerstack[0] : (struct path) { };
 114 }
 115
 116 enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
 117 {
 118         enum ovl_path_type type = ovl_path_type(dentry);
 119
 120         if (!OVL_TYPE_UPPER(type))
 121                 ovl_path_lower(dentry, path);
 122         else
 123                 ovl_path_upper(dentry, path);
 124
 125         return type;
 126 }
 127
 128 struct dentry *ovl_dentry_upper(struct dentry *dentry)
 129 {
 130         struct ovl_entry *oe = dentry->d_fsdata;
 131
 132         return ovl_upperdentry_dereference(oe);
 133 }
 134
 135 static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
 136 {
 137         return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 138 }
 139
 140 struct dentry *ovl_dentry_lower(struct dentry *dentry)
 141 {
 142         struct ovl_entry *oe = dentry->d_fsdata;
 143
 144         return __ovl_dentry_lower(oe);
 145 }
 146
 147 struct dentry *ovl_dentry_real(struct dentry *dentry)
 148 {
 149         struct ovl_entry *oe = dentry->d_fsdata;
 150         struct dentry *realdentry;
 151
 152         realdentry = ovl_upperdentry_dereference(oe);
 153         if (!realdentry)
 154                 realdentry = __ovl_dentry_lower(oe);
 155
 156         return realdentry;
 157 }
 158
 159 struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
 160 {
 161         struct ovl_entry *oe = dentry->d_fsdata;
 162
 163         return oe->cache;
 164 }
 165
 166 void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
 167 {
 168         struct ovl_entry *oe = dentry->d_fsdata;
 169
 170         oe->cache = cache;
 171 }
 172
 173 bool ovl_dentry_is_opaque(struct dentry *dentry)
 174 {
 175         struct ovl_entry *oe = dentry->d_fsdata;
 176         return oe->opaque;
 177 }
 178
 179 bool ovl_dentry_is_whiteout(struct dentry *dentry)
 180 {
 181         return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
 182 }
 183
 184 void ovl_dentry_set_opaque(struct dentry *dentry)
 185 {
 186         struct ovl_entry *oe = dentry->d_fsdata;
 187
 188         oe->opaque = true;
 189 }
 190
 191 bool ovl_redirect_dir(struct super_block *sb)
 192 {
 193         struct ovl_fs *ofs = sb->s_fs_info;
 194
 195         return ofs->config.redirect_dir;
 196 }
 197
 198 void ovl_clear_redirect_dir(struct super_block *sb)
 199 {
 200         struct ovl_fs *ofs = sb->s_fs_info;
 201
 202         ofs->config.redirect_dir = false;
 203 }
 204
 205 const char *ovl_dentry_get_redirect(struct dentry *dentry)
 206 {
 207         struct ovl_entry *oe = dentry->d_fsdata;
 208
 209         return oe->redirect;
 210 }
 211
 212 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 213 {
 214         struct ovl_entry *oe = dentry->d_fsdata;
 215
 216         kfree(oe->redirect);
 217         oe->redirect = redirect;
 218 }
 219
 220 void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
 221 {
 222         struct ovl_entry *oe = dentry->d_fsdata;
 223
 224         WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
 225         WARN_ON(oe->__upperdentry);
 226         /*
 227          * Make sure upperdentry is consistent before making it visible to
 228          * ovl_upperdentry_dereference().
 229          */
 230         smp_wmb();
 231         oe->__upperdentry = upperdentry;
 232 }
 233
 234 void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
 235 {
 236         WRITE_ONCE(inode->i_private, (unsigned long) realinode |
 237                    (is_upper ? OVL_ISUPPER_MASK : 0));
 238 }
 239
 240 void ovl_inode_update(struct inode *inode, struct inode *upperinode)
 241 {
 242         WARN_ON(!upperinode);
 243         WARN_ON(!inode_unhashed(inode));
 244         WRITE_ONCE(inode->i_private,
 245                    (unsigned long) upperinode | OVL_ISUPPER_MASK);
 246         if (!S_ISDIR(upperinode->i_mode))
 247                 __insert_inode_hash(inode, (unsigned long) upperinode);
 248 }
 249
 250 void ovl_dentry_version_inc(struct dentry *dentry)
 251 {
 252         struct ovl_entry *oe = dentry->d_fsdata;
 253
 254         WARN_ON(!inode_is_locked(dentry->d_inode));
 255         oe->version++;
 256 }
 257
 258 u64 ovl_dentry_version_get(struct dentry *dentry)
 259 {
 260         struct ovl_entry *oe = dentry->d_fsdata;
 261
 262         WARN_ON(!inode_is_locked(dentry->d_inode));
 263         return oe->version;
 264 }
 265
 266 bool ovl_is_whiteout(struct dentry *dentry)
 267 {
 268         struct inode *inode = dentry->d_inode;
 269
 270         return inode && IS_WHITEOUT(inode);
 271 }
 272
 273 struct file *ovl_path_open(struct path *path, int flags)
 274 {
 275         return dentry_open(path, flags | O_NOATIME, current_cred());
 276 }
 277
 278 int ovl_copy_up_start(struct dentry *dentry)
 279 {
 280         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 281         struct ovl_entry *oe = dentry->d_fsdata;
 282         int err;
 283
 284         spin_lock(&ofs->copyup_wq.lock);
 285         err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
 286         if (!err) {
 287                 if (oe->__upperdentry)
 288                         err = 1; /* Already copied up */
 289                 else
 290                         oe->copying = true;
 291         }
 292         spin_unlock(&ofs->copyup_wq.lock);
 293
 294         return err;
 295 }
 296
 297 void ovl_copy_up_end(struct dentry *dentry)
 298 {
 299         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 300         struct ovl_entry *oe = dentry->d_fsdata;
 301
 302         spin_lock(&ofs->copyup_wq.lock);
 303         oe->copying = false;
 304         wake_up_locked(&ofs->copyup_wq);
 305         spin_unlock(&ofs->copyup_wq.lock);
 306 }