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(object->fscache.cookie);
 113         ASSERT(dentry);
 114
 115         _enter("%p,#%d", object, auxdata->len);
 116
 117         /* attempt to install the cache metadata directly */
 118         _debug("SET %s #%u", object->fscache.cookie->def->name, auxdata->len);
 119
 120         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 121                            &auxdata->type, auxdata->len,
 122                            XATTR_CREATE);
 123         if (ret < 0 && ret != -ENOMEM)
 124                 cachefiles_io_error_obj(
 125                         object,
 126                         "Failed to set xattr with error %d", ret);
 127
 128         _leave(" = %d", ret);
 129         return ret;
 130 }
 131
 132 /*
 133  * update the state xattr on a cache file
 134  */
 135 int cachefiles_update_object_xattr(struct cachefiles_object *object,
 136                                    struct cachefiles_xattr *auxdata)
 137 {
 138         struct dentry *dentry = object->dentry;
 139         int ret;
 140
 141         ASSERT(object->fscache.cookie);
 142         ASSERT(dentry);
 143
 144         _enter("%p,#%d", object, auxdata->len);
 145
 146         /* attempt to install the cache metadata directly */
 147         _debug("SET %s #%u", object->fscache.cookie->def->name, auxdata->len);
 148
 149         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 150                            &auxdata->type, auxdata->len,
 151                            XATTR_REPLACE);
 152         if (ret < 0 && ret != -ENOMEM)
 153                 cachefiles_io_error_obj(
 154                         object,
 155                         "Failed to update xattr with error %d", ret);
 156
 157         _leave(" = %d", ret);
 158         return ret;
 159 }
 160
 161 /*
 162  * check the state xattr on a cache file
 163  * - return -ESTALE if the object should be deleted
 164  */
 165 int cachefiles_check_object_xattr(struct cachefiles_object *object,
 166                                   struct cachefiles_xattr *auxdata)
 167 {
 168         struct cachefiles_xattr *auxbuf;
 169         struct dentry *dentry = object->dentry;
 170         int ret;
 171
 172         _enter("%p,#%d", object, auxdata->len);
 173
 174         ASSERT(dentry);
 175         ASSERT(dentry->d_inode);
 176
 177         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
 178         if (!auxbuf) {
 179                 _leave(" = -ENOMEM");
 180                 return -ENOMEM;
 181         }
 182
 183         /* read the current type label */
 184         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
 185                            &auxbuf->type, 512 + 1);
 186         if (ret < 0) {
 187                 if (ret == -ENODATA)
 188                         goto stale; /* no attribute - power went off
 189                                      * mid-cull? */
 190
 191                 if (ret == -ERANGE)
 192                         goto bad_type_length;
 193
 194                 cachefiles_io_error_obj(object,
 195                                         "Can't read xattr on %lu (err %d)",
 196                                         dentry->d_inode->i_ino, -ret);
 197                 goto error;
 198         }
 199
 200         /* check the on-disk object */
 201         if (ret < 1)
 202                 goto bad_type_length;
 203
 204         if (auxbuf->type != auxdata->type)
 205                 goto stale;
 206
 207         auxbuf->len = ret;
 208
 209         /* consult the netfs */
 210         if (object->fscache.cookie->def->check_aux) {
 211                 enum fscache_checkaux result;
 212                 unsigned int dlen;
 213
 214                 dlen = auxbuf->len - 1;
 215
 216                 _debug("checkaux %s #%u",
 217                        object->fscache.cookie->def->name, dlen);
 218
 219                 result = fscache_check_aux(&object->fscache,
 220                                            &auxbuf->data, dlen);
 221
 222                 switch (result) {
 223                         /* entry okay as is */
 224                 case FSCACHE_CHECKAUX_OKAY:
 225                         goto okay;
 226
 227                         /* entry requires update */
 228                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
 229                         break;
 230
 231                         /* entry requires deletion */
 232                 case FSCACHE_CHECKAUX_OBSOLETE:
 233                         goto stale;
 234
 235                 default:
 236                         BUG();
 237                 }
 238
 239                 /* update the current label */
 240                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 241                                    &auxdata->type, auxdata->len,
 242                                    XATTR_REPLACE);
 243                 if (ret < 0) {
 244                         cachefiles_io_error_obj(object,
 245                                                 "Can't update xattr on %lu"
 246                                                 " (error %d)",
 247                                                 dentry->d_inode->i_ino, -ret);
 248                         goto error;
 249                 }
 250         }
 251
 252 okay:
 253         ret = 0;
 254
 255 error:
 256         kfree(auxbuf);
 257         _leave(" = %d", ret);
 258         return ret;
 259
 260 bad_type_length:
 261         kerror("Cache object %lu xattr length incorrect",
 262                dentry->d_inode->i_ino);
 263         ret = -EIO;
 264         goto error;
 265
 266 stale:
 267         ret = -ESTALE;
 268         goto error;
 269 }
 270
 271 /*
 272  * remove the object's xattr to mark it stale
 273  */
 274 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 275                                    struct dentry *dentry)
 276 {
 277         int ret;
 278
 279         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
 280         if (ret < 0) {
 281                 if (ret == -ENOENT || ret == -ENODATA)
 282                         ret = 0;
 283                 else if (ret != -ENOMEM)
 284                         cachefiles_io_error(cache,
 285                                             "Can't remove xattr from %lu"
 286                                             " (error %d)",
 287                                             dentry->d_inode->i_ino, -ret);
 288         }
 289
 290         _leave(" = %d", ret);
 291         return ret;
 292 }