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Linux/fs/cachefiles/xattr.c

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  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, cachefiles_gfp);
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 }
293 

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