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 state xattr on a cache file
 161  * - return -ESTALE if the object should be deleted
 162  */
 163 int cachefiles_check_object_xattr(struct cachefiles_object *object,
 164                                   struct cachefiles_xattr *auxdata)
 165 {
 166         struct cachefiles_xattr *auxbuf;
 167         struct dentry *dentry = object->dentry;
 168         int ret;
 169
 170         _enter("%p,#%d", object, auxdata->len);
 171
 172         ASSERT(dentry);
 173         ASSERT(dentry->d_inode);
 174
 175         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
 176         if (!auxbuf) {
 177                 _leave(" = -ENOMEM");
 178                 return -ENOMEM;
 179         }
 180
 181         /* read the current type label */
 182         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
 183                            &auxbuf->type, 512 + 1);
 184         if (ret < 0) {
 185                 if (ret == -ENODATA)
 186                         goto stale; /* no attribute - power went off
 187                                      * mid-cull? */
 188
 189                 if (ret == -ERANGE)
 190                         goto bad_type_length;
 191
 192                 cachefiles_io_error_obj(object,
 193                                         "Can't read xattr on %lu (err %d)",
 194                                         dentry->d_inode->i_ino, -ret);
 195                 goto error;
 196         }
 197
 198         /* check the on-disk object */
 199         if (ret < 1)
 200                 goto bad_type_length;
 201
 202         if (auxbuf->type != auxdata->type)
 203                 goto stale;
 204
 205         auxbuf->len = ret;
 206
 207         /* consult the netfs */
 208         if (object->fscache.cookie->def->check_aux) {
 209                 enum fscache_checkaux result;
 210                 unsigned int dlen;
 211
 212                 dlen = auxbuf->len - 1;
 213
 214                 _debug("checkaux %s #%u",
 215                        object->fscache.cookie->def->name, dlen);
 216
 217                 result = fscache_check_aux(&object->fscache,
 218                                            &auxbuf->data, dlen);
 219
 220                 switch (result) {
 221                         /* entry okay as is */
 222                 case FSCACHE_CHECKAUX_OKAY:
 223                         goto okay;
 224
 225                         /* entry requires update */
 226                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 227                         break;
 228
 229                         /* entry requires deletion */
 230                 case FSCACHE_CHECKAUX_OBSOLETE:
 231                         goto stale;
 232
 233                 default:
 234                         BUG();
 235                 }
 236
 237                 /* update the current label */
 238                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 239                                    &auxdata->type, auxdata->len,
 240                                    XATTR_REPLACE);
 241                 if (ret < 0) {
 242                         cachefiles_io_error_obj(object,
 243                                                 "Can't update xattr on %lu"
 244                                                 " (error %d)",
 245                                                 dentry->d_inode->i_ino, -ret);
 246                         goto error;
 247                 }
 248         }
 249
 250 okay:
 251         ret = 0;
 252
 253 error:
 254         kfree(auxbuf);
 255         _leave(" = %d", ret);
 256         return ret;
 257
 258 bad_type_length:
 259         kerror("Cache object %lu xattr length incorrect",
 260                dentry->d_inode->i_ino);
 261         ret = -EIO;
 262         goto error;
 263
 264 stale:
 265         ret = -ESTALE;
 266         goto error;
 267 }
 268
 269 /*
 270  * remove the object's xattr to mark it stale
 271  */
 272 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 273                                    struct dentry *dentry)
 274 {
 275         int ret;
 276
 277         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 278         if (ret < 0) {
 279                 if (ret == -ENOENT || ret == -ENODATA)
 280                         ret = 0;
 281                 else if (ret != -ENOMEM)
 282                         cachefiles_io_error(cache,
 283                                             "Can't remove xattr from %lu"
 284                                             " (error %d)",
 285                                             dentry->d_inode->i_ino, -ret);
 286         }
 287
 288         _leave(" = %d", ret);
 289         return ret;
 290 }