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  */
cachefiles_check_object_type(struct cachefiles_object * object)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  */
cachefiles_set_object_xattr(struct cachefiles_object * object,struct cachefiles_xattr * auxdata)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  */
cachefiles_update_object_xattr(struct cachefiles_object * object,struct cachefiles_xattr * auxdata)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  */
cachefiles_check_object_xattr(struct cachefiles_object * object,struct cachefiles_xattr * auxdata)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  */
cachefiles_remove_object_xattr(struct cachefiles_cache * cache,struct dentry * dentry)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