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/quotaops.h>
  17 #include <linux/xattr.h>
  18 #include <linux/slab.h>
  19 #include "internal.h"
  20
  21 static const char cachefiles_xattr_cache[] =
  22         XATTR_USER_PREFIX "CacheFiles.cache";
  23
  24 /*
  25  * check the type label on an object
  26  * - done using xattrs
  27  */
  28 int cachefiles_check_object_type(struct cachefiles_object *object)
  29 {
  30         struct dentry *dentry = object->dentry;
  31         char type[3], xtype[3];
  32         int ret;
  33
  34         ASSERT(dentry);
  35         ASSERT(dentry->d_inode);
  36
  37         if (!object->fscache.cookie)
  38                 strcpy(type, "C3");
  39         else
  40                 snprintf(type, 3, "%02x", object->fscache.cookie->def->type);
  41
  42         _enter("%p{%s}", object, type);
  43
  44         /* attempt to install a type label directly */
  45         ret = vfs_setxattr(dentry, cachefiles_xattr_cache, type, 2,
  46                            XATTR_CREATE);
  47         if (ret == 0) {
  48                 _debug("SET"); /* we succeeded */
  49                 goto error;
  50         }
  51
  52         if (ret != -EEXIST) {
  53                 kerror("Can't set xattr on %*.*s [%lu] (err %d)",
  54                        dentry->d_name.len, dentry->d_name.len,
  55                        dentry->d_name.name, dentry->d_inode->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                 kerror("Can't read xattr on %*.*s [%lu] (err %d)",
  67                        dentry->d_name.len, dentry->d_name.len,
  68                        dentry->d_name.name, dentry->d_inode->i_ino,
  69                        -ret);
  70                 goto error;
  71         }
  72
  73         /* check the type is what we're expecting */
  74         if (ret != 2)
  75                 goto bad_type_length;
  76
  77         if (xtype[0] != type[0] || xtype[1] != type[1])
  78                 goto bad_type;
  79
  80         ret = 0;
  81
  82 error:
  83         _leave(" = %d", ret);
  84         return ret;
  85
  86 bad_type_length:
  87         kerror("Cache object %lu type xattr length incorrect",
  88                dentry->d_inode->i_ino);
  89         ret = -EIO;
  90         goto error;
  91
  92 bad_type:
  93         xtype[2] = 0;
  94         kerror("Cache object %*.*s [%lu] type %s not %s",
  95                dentry->d_name.len, dentry->d_name.len,
  96                dentry->d_name.name, dentry->d_inode->i_ino,
  97                xtype, type);
  98         ret = -EIO;
  99         goto error;
 100 }
 101
 102 /*
 103  * set the state xattr on a cache file
 104  */
 105 int cachefiles_set_object_xattr(struct cachefiles_object *object,
 106                                 struct cachefiles_xattr *auxdata)
 107 {
 108         struct dentry *dentry = object->dentry;
 109         int ret;
 110
 111         ASSERT(object->fscache.cookie);
 112         ASSERT(dentry);
 113
 114         _enter("%p,#%d", object, auxdata->len);
 115
 116         /* attempt to install the cache metadata directly */
 117         _debug("SET %s #%u", object->fscache.cookie->def->name, 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(object->fscache.cookie);
 141         ASSERT(dentry);
 142
 143         _enter("%p,#%d", object, auxdata->len);
 144
 145         /* attempt to install the cache metadata directly */
 146         _debug("SET %s #%u", object->fscache.cookie->def->name, auxdata->len);
 147
 148         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 149                            &auxdata->type, auxdata->len,
 150                            XATTR_REPLACE);
 151         if (ret < 0 && ret != -ENOMEM)
 152                 cachefiles_io_error_obj(
 153                         object,
 154                         "Failed to update xattr with error %d", ret);
 155
 156         _leave(" = %d", ret);
 157         return ret;
 158 }
 159
 160 /*
 161  * check the state xattr on a cache file
 162  * - return -ESTALE if the object should be deleted
 163  */
 164 int cachefiles_check_object_xattr(struct cachefiles_object *object,
 165                                   struct cachefiles_xattr *auxdata)
 166 {
 167         struct cachefiles_xattr *auxbuf;
 168         struct dentry *dentry = object->dentry;
 169         int ret;
 170
 171         _enter("%p,#%d", object, auxdata->len);
 172
 173         ASSERT(dentry);
 174         ASSERT(dentry->d_inode);
 175
 176         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
 177         if (!auxbuf) {
 178                 _leave(" = -ENOMEM");
 179                 return -ENOMEM;
 180         }
 181
 182         /* read the current type label */
 183         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
 184                            &auxbuf->type, 512 + 1);
 185         if (ret < 0) {
 186                 if (ret == -ENODATA)
 187                         goto stale; /* no attribute - power went off
 188                                      * mid-cull? */
 189
 190                 if (ret == -ERANGE)
 191                         goto bad_type_length;
 192
 193                 cachefiles_io_error_obj(object,
 194                                         "Can't read xattr on %lu (err %d)",
 195                                         dentry->d_inode->i_ino, -ret);
 196                 goto error;
 197         }
 198
 199         /* check the on-disk object */
 200         if (ret < 1)
 201                 goto bad_type_length;
 202
 203         if (auxbuf->type != auxdata->type)
 204                 goto stale;
 205
 206         auxbuf->len = ret;
 207
 208         /* consult the netfs */
 209         if (object->fscache.cookie->def->check_aux) {
 210                 enum fscache_checkaux result;
 211                 unsigned int dlen;
 212
 213                 dlen = auxbuf->len - 1;
 214
 215                 _debug("checkaux %s #%u",
 216                        object->fscache.cookie->def->name, dlen);
 217
 218                 result = fscache_check_aux(&object->fscache,
 219                                            &auxbuf->data, dlen);
 220
 221                 switch (result) {
 222                         /* entry okay as is */
 223                 case FSCACHE_CHECKAUX_OKAY:
 224                         goto okay;
 225
 226                         /* entry requires update */
 227                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 228                         break;
 229
 230                         /* entry requires deletion */
 231                 case FSCACHE_CHECKAUX_OBSOLETE:
 232                         goto stale;
 233
 234                 default:
 235                         BUG();
 236                 }
 237
 238                 /* update the current label */
 239                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 240                                    &auxdata->type, auxdata->len,
 241                                    XATTR_REPLACE);
 242                 if (ret < 0) {
 243                         cachefiles_io_error_obj(object,
 244                                                 "Can't update xattr on %lu"
 245                                                 " (error %d)",
 246                                                 dentry->d_inode->i_ino, -ret);
 247                         goto error;
 248                 }
 249         }
 250
 251 okay:
 252         ret = 0;
 253
 254 error:
 255         kfree(auxbuf);
 256         _leave(" = %d", ret);
 257         return ret;
 258
 259 bad_type_length:
 260         kerror("Cache object %lu xattr length incorrect",
 261                dentry->d_inode->i_ino);
 262         ret = -EIO;
 263         goto error;
 264
 265 stale:
 266         ret = -ESTALE;
 267         goto error;
 268 }
 269
 270 /*
 271  * remove the object's xattr to mark it stale
 272  */
 273 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 274                                    struct dentry *dentry)
 275 {
 276         int ret;
 277
 278         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 279         if (ret < 0) {
 280                 if (ret == -ENOENT || ret == -ENODATA)
 281                         ret = 0;
 282                 else if (ret != -ENOMEM)
 283                         cachefiles_io_error(cache,
 284                                             "Can't remove xattr from %lu"
 285                                             " (error %d)",
 286                                             dentry->d_inode->i_ino, -ret);
 287         }
 288
 289         _leave(" = %d", ret);
 290         return ret;
 291 }