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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(d_backing_inode(dentry));
 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                 pr_err("Can't set xattr on %pd [%lu] (err %d)\n",
 55                        dentry, d_backing_inode(dentry)->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                 pr_err("Can't read xattr on %pd [%lu] (err %d)\n",
 67                        dentry, d_backing_inode(dentry)->i_ino,
 68                        -ret);
 69                 goto error;
 70         }
 71 
 72         /* check the type is what we're expecting */
 73         if (ret != 2)
 74                 goto bad_type_length;
 75 
 76         if (xtype[0] != type[0] || xtype[1] != type[1])
 77                 goto bad_type;
 78 
 79         ret = 0;
 80 
 81 error:
 82         _leave(" = %d", ret);
 83         return ret;
 84 
 85 bad_type_length:
 86         pr_err("Cache object %lu type xattr length incorrect\n",
 87                d_backing_inode(dentry)->i_ino);
 88         ret = -EIO;
 89         goto error;
 90 
 91 bad_type:
 92         xtype[2] = 0;
 93         pr_err("Cache object %pd [%lu] type %s not %s\n",
 94                dentry, d_backing_inode(dentry)->i_ino,
 95                xtype, type);
 96         ret = -EIO;
 97         goto error;
 98 }
 99 
100 /*
101  * set the state xattr on a cache file
102  */
103 int cachefiles_set_object_xattr(struct cachefiles_object *object,
104                                 struct cachefiles_xattr *auxdata)
105 {
106         struct dentry *dentry = object->dentry;
107         int ret;
108 
109         ASSERT(dentry);
110 
111         _enter("%p,#%d", object, auxdata->len);
112 
113         /* attempt to install the cache metadata directly */
114         _debug("SET #%u", auxdata->len);
115 
116         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
117                            &auxdata->type, auxdata->len,
118                            XATTR_CREATE);
119         if (ret < 0 && ret != -ENOMEM)
120                 cachefiles_io_error_obj(
121                         object,
122                         "Failed to set xattr with error %d", ret);
123 
124         _leave(" = %d", ret);
125         return ret;
126 }
127 
128 /*
129  * update the state xattr on a cache file
130  */
131 int cachefiles_update_object_xattr(struct cachefiles_object *object,
132                                    struct cachefiles_xattr *auxdata)
133 {
134         struct dentry *dentry = object->dentry;
135         int ret;
136 
137         ASSERT(dentry);
138 
139         _enter("%p,#%d", object, auxdata->len);
140 
141         /* attempt to install the cache metadata directly */
142         _debug("SET #%u", auxdata->len);
143 
144         ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
145                            &auxdata->type, auxdata->len,
146                            XATTR_REPLACE);
147         if (ret < 0 && ret != -ENOMEM)
148                 cachefiles_io_error_obj(
149                         object,
150                         "Failed to update xattr with error %d", ret);
151 
152         _leave(" = %d", ret);
153         return ret;
154 }
155 
156 /*
157  * check the consistency between the backing cache and the FS-Cache cookie
158  */
159 int cachefiles_check_auxdata(struct cachefiles_object *object)
160 {
161         struct cachefiles_xattr *auxbuf;
162         enum fscache_checkaux validity;
163         struct dentry *dentry = object->dentry;
164         ssize_t xlen;
165         int ret;
166 
167         ASSERT(dentry);
168         ASSERT(d_backing_inode(dentry));
169         ASSERT(object->fscache.cookie->def->check_aux);
170 
171         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
172         if (!auxbuf)
173                 return -ENOMEM;
174 
175         xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
176                             &auxbuf->type, 512 + 1);
177         ret = -ESTALE;
178         if (xlen < 1 ||
179             auxbuf->type != object->fscache.cookie->def->type)
180                 goto error;
181 
182         xlen--;
183         validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen);
184         if (validity != FSCACHE_CHECKAUX_OKAY)
185                 goto error;
186 
187         ret = 0;
188 error:
189         kfree(auxbuf);
190         return ret;
191 }
192 
193 /*
194  * check the state xattr on a cache file
195  * - return -ESTALE if the object should be deleted
196  */
197 int cachefiles_check_object_xattr(struct cachefiles_object *object,
198                                   struct cachefiles_xattr *auxdata)
199 {
200         struct cachefiles_xattr *auxbuf;
201         struct dentry *dentry = object->dentry;
202         int ret;
203 
204         _enter("%p,#%d", object, auxdata->len);
205 
206         ASSERT(dentry);
207         ASSERT(d_backing_inode(dentry));
208 
209         auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
210         if (!auxbuf) {
211                 _leave(" = -ENOMEM");
212                 return -ENOMEM;
213         }
214 
215         /* read the current type label */
216         ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
217                            &auxbuf->type, 512 + 1);
218         if (ret < 0) {
219                 if (ret == -ENODATA)
220                         goto stale; /* no attribute - power went off
221                                      * mid-cull? */
222 
223                 if (ret == -ERANGE)
224                         goto bad_type_length;
225 
226                 cachefiles_io_error_obj(object,
227                                         "Can't read xattr on %lu (err %d)",
228                                         d_backing_inode(dentry)->i_ino, -ret);
229                 goto error;
230         }
231 
232         /* check the on-disk object */
233         if (ret < 1)
234                 goto bad_type_length;
235 
236         if (auxbuf->type != auxdata->type)
237                 goto stale;
238 
239         auxbuf->len = ret;
240 
241         /* consult the netfs */
242         if (object->fscache.cookie->def->check_aux) {
243                 enum fscache_checkaux result;
244                 unsigned int dlen;
245 
246                 dlen = auxbuf->len - 1;
247 
248                 _debug("checkaux %s #%u",
249                        object->fscache.cookie->def->name, dlen);
250 
251                 result = fscache_check_aux(&object->fscache,
252                                            &auxbuf->data, dlen);
253 
254                 switch (result) {
255                         /* entry okay as is */
256                 case FSCACHE_CHECKAUX_OKAY:
257                         goto okay;
258 
259                         /* entry requires update */
260                 case FSCACHE_CHECKAUX_NEEDS_UPDATE:
261                         break;
262 
263                         /* entry requires deletion */
264                 case FSCACHE_CHECKAUX_OBSOLETE:
265                         goto stale;
266 
267                 default:
268                         BUG();
269                 }
270 
271                 /* update the current label */
272                 ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
273                                    &auxdata->type, auxdata->len,
274                                    XATTR_REPLACE);
275                 if (ret < 0) {
276                         cachefiles_io_error_obj(object,
277                                                 "Can't update xattr on %lu"
278                                                 " (error %d)",
279                                                 d_backing_inode(dentry)->i_ino, -ret);
280                         goto error;
281                 }
282         }
283 
284 okay:
285         ret = 0;
286 
287 error:
288         kfree(auxbuf);
289         _leave(" = %d", ret);
290         return ret;
291 
292 bad_type_length:
293         pr_err("Cache object %lu xattr length incorrect\n",
294                d_backing_inode(dentry)->i_ino);
295         ret = -EIO;
296         goto error;
297 
298 stale:
299         ret = -ESTALE;
300         goto error;
301 }
302 
303 /*
304  * remove the object's xattr to mark it stale
305  */
306 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
307                                    struct dentry *dentry)
308 {
309         int ret;
310 
311         ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
312         if (ret < 0) {
313                 if (ret == -ENOENT || ret == -ENODATA)
314                         ret = 0;
315                 else if (ret != -ENOMEM)
316                         cachefiles_io_error(cache,
317                                             "Can't remove xattr from %lu"
318                                             " (error %d)",
319                                             d_backing_inode(dentry)->i_ino, -ret);
320         }
321 
322         _leave(" = %d", ret);
323         return ret;
324 }
325 

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