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         clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
 117         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 118                            &auxdata->type, auxdata->len,
 119                            XATTR_CREATE);
 120         if (ret < 0 && ret != -ENOMEM)
 121                 cachefiles_io_error_obj(
 122                         object,
 123                         "Failed to set xattr with error %d", ret);
 124
 125         _leave(" = %d", ret);
 126         return ret;
 127 }
 128
 129 /*
 130  * update the state xattr on a cache file
 131  */
 132 int cachefiles_update_object_xattr(struct cachefiles_object *object,
 133                                    struct cachefiles_xattr *auxdata)
 134 {
 135         struct dentry *dentry = object->dentry;
 136         int ret;
 137
 138         ASSERT(dentry);
 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         clear_bit(FSCACHE_COOKIE_AUX_UPDATED, &object->fscache.cookie->flags);
 146         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 147                            &auxdata->type, auxdata->len,
 148                            XATTR_REPLACE);
 149         if (ret < 0 && ret != -ENOMEM)
 150                 cachefiles_io_error_obj(
 151                         object,
 152                         "Failed to update xattr with error %d", ret);
 153
 154         _leave(" = %d", ret);
 155         return ret;
 156 }
 157
 158 /*
 159  * check the consistency between the backing cache and the FS-Cache cookie
 160  */
 161 int cachefiles_check_auxdata(struct cachefiles_object *object)
 162 {
 163         struct cachefiles_xattr *auxbuf;
 164         enum fscache_checkaux validity;
 165         struct dentry *dentry = object->dentry;
 166         ssize_t xlen;
 167         int ret;
 168
 169         ASSERT(dentry);
 170         ASSERT(d_backing_inode(dentry));
 171         ASSERT(object->fscache.cookie->def->check_aux);
 172
 173         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
 174         if (!auxbuf)
 175                 return -ENOMEM;
 176
 177         xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
 178                             &auxbuf->type, 512 + 1);
 179         ret = -ESTALE;
 180         if (xlen < 1 ||
 181             auxbuf->type != object->fscache.cookie->def->type)
 182                 goto error;
 183
 184         xlen--;
 185         validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen,
 186                                      i_size_read(d_backing_inode(dentry)));
 187         if (validity != FSCACHE_CHECKAUX_OKAY)
 188                 goto error;
 189
 190         ret = 0;
 191 error:
 192         kfree(auxbuf);
 193         return ret;
 194 }
 195
 196 /*
 197  * check the state xattr on a cache file
 198  * - return -ESTALE if the object should be deleted
 199  */
 200 int cachefiles_check_object_xattr(struct cachefiles_object *object,
 201                                   struct cachefiles_xattr *auxdata)
 202 {
 203         struct cachefiles_xattr *auxbuf;
 204         struct dentry *dentry = object->dentry;
 205         int ret;
 206
 207         _enter("%p,#%d", object, auxdata->len);
 208
 209         ASSERT(dentry);
 210         ASSERT(d_backing_inode(dentry));
 211
 212         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
 213         if (!auxbuf) {
 214                 _leave(" = -ENOMEM");
 215                 return -ENOMEM;
 216         }
 217
 218         /* read the current type label */
 219         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
 220                            &auxbuf->type, 512 + 1);
 221         if (ret < 0) {
 222                 if (ret == -ENODATA)
 223                         goto stale; /* no attribute - power went off
 224                                      * mid-cull? */
 225
 226                 if (ret == -ERANGE)
 227                         goto bad_type_length;
 228
 229                 cachefiles_io_error_obj(object,
 230                                         "Can't read xattr on %lu (err %d)",
 231                                         d_backing_inode(dentry)->i_ino, -ret);
 232                 goto error;
 233         }
 234
 235         /* check the on-disk object */
 236         if (ret < 1)
 237                 goto bad_type_length;
 238
 239         if (auxbuf->type != auxdata->type)
 240                 goto stale;
 241
 242         auxbuf->len = ret;
 243
 244         /* consult the netfs */
 245         if (object->fscache.cookie->def->check_aux) {
 246                 enum fscache_checkaux result;
 247                 unsigned int dlen;
 248
 249                 dlen = auxbuf->len - 1;
 250
 251                 _debug("checkaux %s #%u",
 252                        object->fscache.cookie->def->name, dlen);
 253
 254                 result = fscache_check_aux(&object->fscache,
 255                                            &auxbuf->data, dlen,
 256                                            i_size_read(d_backing_inode(dentry)));
 257
 258                 switch (result) {
 259                         /* entry okay as is */
 260                 case FSCACHE_CHECKAUX_OKAY:
 261                         goto okay;
 262
 263                         /* entry requires update */
 264                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 265                         break;
 266
 267                         /* entry requires deletion */
 268                 case FSCACHE_CHECKAUX_OBSOLETE:
 269                         goto stale;
 270
 271                 default:
 272                         BUG();
 273                 }
 274
 275                 /* update the current label */
 276                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 277                                    &auxdata->type, auxdata->len,
 278                                    XATTR_REPLACE);
 279                 if (ret < 0) {
 280                         cachefiles_io_error_obj(object,
 281                                                 "Can't update xattr on %lu"
 282                                                 " (error %d)",
 283                                                 d_backing_inode(dentry)->i_ino, -ret);
 284                         goto error;
 285                 }
 286         }
 287
 288 okay:
 289         ret = 0;
 290
 291 error:
 292         kfree(auxbuf);
 293         _leave(" = %d", ret);
 294         return ret;
 295
 296 bad_type_length:
 297         pr_err("Cache object %lu xattr length incorrect\n",
 298                d_backing_inode(dentry)->i_ino);
 299         ret = -EIO;
 300         goto error;
 301
 302 stale:
 303         ret = -ESTALE;
 304         goto error;
 305 }
 306
 307 /*
 308  * remove the object's xattr to mark it stale
 309  */
 310 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 311                                    struct dentry *dentry)
 312 {
 313         int ret;
 314
 315         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 316         if (ret < 0) {
 317                 if (ret == -ENOENT || ret == -ENODATA)
 318                         ret = 0;
 319                 else if (ret != -ENOMEM)
 320                         cachefiles_io_error(cache,
 321                                             "Can't remove xattr from %lu"
 322                                             " (error %d)",
 323                                             d_backing_inode(dentry)->i_ino, -ret);
 324         }
 325
 326         _leave(" = %d", ret);
 327         return ret;
 328 }