fs/cachefiles/xattr.c

   1 /* CacheFiles extended attribute management
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/file.h>
  15 #include <linux/fs.h>
  16 #include <linux/fsnotify.h>
  17 #include <linux/quotaops.h>
  18 #include <linux/xattr.h>
  19 #include <linux/slab.h>
  20 #include "internal.h"
  21
  22 static const char cachefiles_xattr_cache[] =
  23         XATTR_USER_PREFIX "CacheFiles.cache";
  24
  25 /*
  26  * check the type label on an object
  27  * - done using xattrs
  28  */
  29 int cachefiles_check_object_type(struct cachefiles_object *object)
  30 {
  31         struct dentry *dentry = object->dentry;
  32         char type[3], xtype[3];
  33         int ret;
  34
  35         ASSERT(dentry);
  36         ASSERT(d_backing_inode(dentry));
  37
  38         if (!object->fscache.cookie)
  39                 strcpy(type, "C3");
  40         else
  41                 snprintf(type, 3, "%02x", object->fscache.cookie->def->type);
  42
  43         _enter("%p{%s}", object, type);
  44
  45         /* attempt to install a type label directly */
  46         ret = vfs_setxattr(dentry, cachefiles_xattr_cache, type, 2,
  47                            XATTR_CREATE);
  48         if (ret == 0) {
  49                 _debug("SET"); /* we succeeded */
  50                 goto error;
  51         }
  52
  53         if (ret != -EEXIST) {
  54                 pr_err("Can't set xattr on %pd [%lu] (err %d)\n",
  55                        dentry, d_backing_inode(dentry)->i_ino,
  56                        -ret);
  57                 goto error;
  58         }
  59
  60         /* read the current type label */
  61         ret = vfs_getxattr(dentry, cachefiles_xattr_cache, xtype, 3);
  62         if (ret < 0) {
  63                 if (ret == -ERANGE)
  64                         goto bad_type_length;
  65
  66                 pr_err("Can't read xattr on %pd [%lu] (err %d)\n",
  67                        dentry, d_backing_inode(dentry)->i_ino,
  68                        -ret);
  69                 goto error;
  70         }
  71
  72         /* check the type is what we're expecting */
  73         if (ret != 2)
  74                 goto bad_type_length;
  75
  76         if (xtype[0] != type[0] || xtype[1] != type[1])
  77                 goto bad_type;
  78
  79         ret = 0;
  80
  81 error:
  82         _leave(" = %d", ret);
  83         return ret;
  84
  85 bad_type_length:
  86         pr_err("Cache object %lu type xattr length incorrect\n",
  87                d_backing_inode(dentry)->i_ino);
  88         ret = -EIO;
  89         goto error;
  90
  91 bad_type:
  92         xtype[2] = 0;
  93         pr_err("Cache object %pd [%lu] type %s not %s\n",
  94                dentry, d_backing_inode(dentry)->i_ino,
  95                xtype, type);
  96         ret = -EIO;
  97         goto error;
  98 }
  99
 100 /*
 101  * set the state xattr on a cache file
 102  */
 103 int cachefiles_set_object_xattr(struct cachefiles_object *object,
 104                                 struct cachefiles_xattr *auxdata)
 105 {
 106         struct dentry *dentry = object->dentry;
 107         int ret;
 108
 109         ASSERT(dentry);
 110
 111         _enter("%p,#%d", object, auxdata->len);
 112
 113         /* attempt to install the cache metadata directly */
 114         _debug("SET #%u", auxdata->len);
 115
 116         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 117                            &auxdata->type, auxdata->len,
 118                            XATTR_CREATE);
 119         if (ret < 0 && ret != -ENOMEM)
 120                 cachefiles_io_error_obj(
 121                         object,
 122                         "Failed to set xattr with error %d", ret);
 123
 124         _leave(" = %d", ret);
 125         return ret;
 126 }
 127
 128 /*
 129  * update the state xattr on a cache file
 130  */
 131 int cachefiles_update_object_xattr(struct cachefiles_object *object,
 132                                    struct cachefiles_xattr *auxdata)
 133 {
 134         struct dentry *dentry = object->dentry;
 135         int ret;
 136
 137         if (!dentry)
 138                 return -ESTALE;
 139
 140         _enter("%p,#%d", object, auxdata->len);
 141
 142         /* attempt to install the cache metadata directly */
 143         _debug("SET #%u", auxdata->len);
 144
 145         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 146                            &auxdata->type, auxdata->len,
 147                            XATTR_REPLACE);
 148         if (ret < 0 && ret != -ENOMEM)
 149                 cachefiles_io_error_obj(
 150                         object,
 151                         "Failed to update xattr with error %d", ret);
 152
 153         _leave(" = %d", ret);
 154         return ret;
 155 }
 156
 157 /*
 158  * check the consistency between the backing cache and the FS-Cache cookie
 159  */
 160 int cachefiles_check_auxdata(struct cachefiles_object *object)
 161 {
 162         struct cachefiles_xattr *auxbuf;
 163         enum fscache_checkaux validity;
 164         struct dentry *dentry = object->dentry;
 165         ssize_t xlen;
 166         int ret;
 167
 168         ASSERT(dentry);
 169         ASSERT(d_backing_inode(dentry));
 170         ASSERT(object->fscache.cookie->def->check_aux);
 171
 172         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
 173         if (!auxbuf)
 174                 return -ENOMEM;
 175
 176         xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
 177                             &auxbuf->type, 512 + 1);
 178         ret = -ESTALE;
 179         if (xlen < 1 ||
 180             auxbuf->type != object->fscache.cookie->def->type)
 181                 goto error;
 182
 183         xlen--;
 184         validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen);
 185         if (validity != FSCACHE_CHECKAUX_OKAY)
 186                 goto error;
 187
 188         ret = 0;
 189 error:
 190         kfree(auxbuf);
 191         return ret;
 192 }
 193
 194 /*
 195  * check the state xattr on a cache file
 196  * - return -ESTALE if the object should be deleted
 197  */
 198 int cachefiles_check_object_xattr(struct cachefiles_object *object,
 199                                   struct cachefiles_xattr *auxdata)
 200 {
 201         struct cachefiles_xattr *auxbuf;
 202         struct dentry *dentry = object->dentry;
 203         int ret;
 204
 205         _enter("%p,#%d", object, auxdata->len);
 206
 207         ASSERT(dentry);
 208         ASSERT(d_backing_inode(dentry));
 209
 210         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
 211         if (!auxbuf) {
 212                 _leave(" = -ENOMEM");
 213                 return -ENOMEM;
 214         }
 215
 216         /* read the current type label */
 217         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
 218                            &auxbuf->type, 512 + 1);
 219         if (ret < 0) {
 220                 if (ret == -ENODATA)
 221                         goto stale; /* no attribute - power went off
 222                                      * mid-cull? */
 223
 224                 if (ret == -ERANGE)
 225                         goto bad_type_length;
 226
 227                 cachefiles_io_error_obj(object,
 228                                         "Can't read xattr on %lu (err %d)",
 229                                         d_backing_inode(dentry)->i_ino, -ret);
 230                 goto error;
 231         }
 232
 233         /* check the on-disk object */
 234         if (ret < 1)
 235                 goto bad_type_length;
 236
 237         if (auxbuf->type != auxdata->type)
 238                 goto stale;
 239
 240         auxbuf->len = ret;
 241
 242         /* consult the netfs */
 243         if (object->fscache.cookie->def->check_aux) {
 244                 enum fscache_checkaux result;
 245                 unsigned int dlen;
 246
 247                 dlen = auxbuf->len - 1;
 248
 249                 _debug("checkaux %s #%u",
 250                        object->fscache.cookie->def->name, dlen);
 251
 252                 result = fscache_check_aux(&object->fscache,
 253                                            &auxbuf->data, dlen);
 254
 255                 switch (result) {
 256                         /* entry okay as is */
 257                 case FSCACHE_CHECKAUX_OKAY:
 258                         goto okay;
 259
 260                         /* entry requires update */
 261                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 262                         break;
 263
 264                         /* entry requires deletion */
 265                 case FSCACHE_CHECKAUX_OBSOLETE:
 266                         goto stale;
 267
 268                 default:
 269                         BUG();
 270                 }
 271
 272                 /* update the current label */
 273                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 274                                    &auxdata->type, auxdata->len,
 275                                    XATTR_REPLACE);
 276                 if (ret < 0) {
 277                         cachefiles_io_error_obj(object,
 278                                                 "Can't update xattr on %lu"
 279                                                 " (error %d)",
 280                                                 d_backing_inode(dentry)->i_ino, -ret);
 281                         goto error;
 282                 }
 283         }
 284
 285 okay:
 286         ret = 0;
 287
 288 error:
 289         kfree(auxbuf);
 290         _leave(" = %d", ret);
 291         return ret;
 292
 293 bad_type_length:
 294         pr_err("Cache object %lu xattr length incorrect\n",
 295                d_backing_inode(dentry)->i_ino);
 296         ret = -EIO;
 297         goto error;
 298
 299 stale:
 300         ret = -ESTALE;
 301         goto error;
 302 }
 303
 304 /*
 305  * remove the object's xattr to mark it stale
 306  */
 307 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 308                                    struct dentry *dentry)
 309 {
 310         int ret;
 311
 312         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 313         if (ret < 0) {
 314                 if (ret == -ENOENT || ret == -ENODATA)
 315                         ret = 0;
 316                 else if (ret != -ENOMEM)
 317                         cachefiles_io_error(cache,
 318                                             "Can't remove xattr from %lu"
 319                                             " (error %d)",
 320                                             d_backing_inode(dentry)->i_ino, -ret);
 321         }
 322
 323         _leave(" = %d", ret);
 324         return ret;
 325 }