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(dentry->d_inode);
  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                 kerror("Can't set xattr on %*.*s [%lu] (err %d)",
  55                        dentry->d_name.len, dentry->d_name.len,
  56                        dentry->d_name.name, dentry->d_inode->i_ino,
  57                        -ret);
  58                 goto error;
  59         }
  60
  61         /* read the current type label */
  62         ret = vfs_getxattr(dentry, cachefiles_xattr_cache, xtype, 3);
  63         if (ret < 0) {
  64                 if (ret == -ERANGE)
  65                         goto bad_type_length;
  66
  67                 kerror("Can't read xattr on %*.*s [%lu] (err %d)",
  68                        dentry->d_name.len, dentry->d_name.len,
  69                        dentry->d_name.name, dentry->d_inode->i_ino,
  70                        -ret);
  71                 goto error;
  72         }
  73
  74         /* check the type is what we're expecting */
  75         if (ret != 2)
  76                 goto bad_type_length;
  77
  78         if (xtype[0] != type[0] || xtype[1] != type[1])
  79                 goto bad_type;
  80
  81         ret = 0;
  82
  83 error:
  84         _leave(" = %d", ret);
  85         return ret;
  86
  87 bad_type_length:
  88         kerror("Cache object %lu type xattr length incorrect",
  89                dentry->d_inode->i_ino);
  90         ret = -EIO;
  91         goto error;
  92
  93 bad_type:
  94         xtype[2] = 0;
  95         kerror("Cache object %*.*s [%lu] type %s not %s",
  96                dentry->d_name.len, dentry->d_name.len,
  97                dentry->d_name.name, dentry->d_inode->i_ino,
  98                xtype, type);
  99         ret = -EIO;
 100         goto error;
 101 }
 102
 103 /*
 104  * set the state xattr on a cache file
 105  */
 106 int cachefiles_set_object_xattr(struct cachefiles_object *object,
 107                                 struct cachefiles_xattr *auxdata)
 108 {
 109         struct dentry *dentry = object->dentry;
 110         int ret;
 111
 112         ASSERT(dentry);
 113
 114         _enter("%p,#%d", object, auxdata->len);
 115
 116         /* attempt to install the cache metadata directly */
 117         _debug("SET #%u", auxdata->len);
 118
 119         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 120                            &auxdata->type, auxdata->len,
 121                            XATTR_CREATE);
 122         if (ret < 0 && ret != -ENOMEM)
 123                 cachefiles_io_error_obj(
 124                         object,
 125                         "Failed to set xattr with error %d", ret);
 126
 127         _leave(" = %d", ret);
 128         return ret;
 129 }
 130
 131 /*
 132  * update the state xattr on a cache file
 133  */
 134 int cachefiles_update_object_xattr(struct cachefiles_object *object,
 135                                    struct cachefiles_xattr *auxdata)
 136 {
 137         struct dentry *dentry = object->dentry;
 138         int ret;
 139
 140         ASSERT(dentry);
 141
 142         _enter("%p,#%d", object, auxdata->len);
 143
 144         /* attempt to install the cache metadata directly */
 145         _debug("SET #%u", auxdata->len);
 146
 147         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 148                            &auxdata->type, auxdata->len,
 149                            XATTR_REPLACE);
 150         if (ret < 0 && ret != -ENOMEM)
 151                 cachefiles_io_error_obj(
 152                         object,
 153                         "Failed to update xattr with error %d", ret);
 154
 155         _leave(" = %d", ret);
 156         return ret;
 157 }
 158
 159 /*
 160  * check the consistency between the backing cache and the FS-Cache cookie
 161  */
 162 int cachefiles_check_auxdata(struct cachefiles_object *object)
 163 {
 164         struct cachefiles_xattr *auxbuf;
 165         enum fscache_checkaux validity;
 166         struct dentry *dentry = object->dentry;
 167         ssize_t xlen;
 168         int ret;
 169
 170         ASSERT(dentry);
 171         ASSERT(dentry->d_inode);
 172         ASSERT(object->fscache.cookie->def->check_aux);
 173
 174         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
 175         if (!auxbuf)
 176                 return -ENOMEM;
 177
 178         xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
 179                             &auxbuf->type, 512 + 1);
 180         ret = -ESTALE;
 181         if (xlen < 1 ||
 182             auxbuf->type != object->fscache.cookie->def->type)
 183                 goto error;
 184
 185         xlen--;
 186         validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen);
 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(dentry->d_inode);
 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                                         dentry->d_inode->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
 257                 switch (result) {
 258                         /* entry okay as is */
 259                 case FSCACHE_CHECKAUX_OKAY:
 260                         goto okay;
 261
 262                         /* entry requires update */
 263                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 264                         break;
 265
 266                         /* entry requires deletion */
 267                 case FSCACHE_CHECKAUX_OBSOLETE:
 268                         goto stale;
 269
 270                 default:
 271                         BUG();
 272                 }
 273
 274                 /* update the current label */
 275                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 276                                    &auxdata->type, auxdata->len,
 277                                    XATTR_REPLACE);
 278                 if (ret < 0) {
 279                         cachefiles_io_error_obj(object,
 280                                                 "Can't update xattr on %lu"
 281                                                 " (error %d)",
 282                                                 dentry->d_inode->i_ino, -ret);
 283                         goto error;
 284                 }
 285         }
 286
 287 okay:
 288         ret = 0;
 289
 290 error:
 291         kfree(auxbuf);
 292         _leave(" = %d", ret);
 293         return ret;
 294
 295 bad_type_length:
 296         kerror("Cache object %lu xattr length incorrect",
 297                dentry->d_inode->i_ino);
 298         ret = -EIO;
 299         goto error;
 300
 301 stale:
 302         ret = -ESTALE;
 303         goto error;
 304 }
 305
 306 /*
 307  * remove the object's xattr to mark it stale
 308  */
 309 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 310                                    struct dentry *dentry)
 311 {
 312         int ret;
 313
 314         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 315         if (ret < 0) {
 316                 if (ret == -ENOENT || ret == -ENODATA)
 317                         ret = 0;
 318                 else if (ret != -ENOMEM)
 319                         cachefiles_io_error(cache,
 320                                             "Can't remove xattr from %lu"
 321                                             " (error %d)",
 322                                             dentry->d_inode->i_ino, -ret);
 323         }
 324
 325         _leave(" = %d", ret);
 326         return ret;
 327 }