1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* CacheFiles extended attribute management
3 *
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/module.h>
9 #include <linux/sched.h>
10 #include <linux/file.h>
11 #include <linux/fs.h>
12 #include <linux/fsnotify.h>
13 #include <linux/quotaops.h>
14 #include <linux/xattr.h>
15 #include <linux/slab.h>
16 #include "internal.h"
17
18 #define CACHEFILES_COOKIE_TYPE_DATA 1
19
20 struct cachefiles_xattr {
21 __be64 object_size; /* Actual size of the object */
22 __be64 zero_point; /* Size after which server has no data not written by us */
23 __u8 type; /* Type of object */
24 __u8 content; /* Content presence (enum cachefiles_content) */
25 __u8 data[]; /* netfs coherency data */
26 } __packed;
27
28 static const char cachefiles_xattr_cache[] =
29 XATTR_USER_PREFIX "CacheFiles.cache";
30
31 struct cachefiles_vol_xattr {
32 __be32 reserved; /* Reserved, should be 0 */
33 __u8 data[]; /* netfs volume coherency data */
34 } __packed;
35
36 /*
37 * set the state xattr on a cache file
38 */
39 int cachefiles_set_object_xattr(struct cachefiles_object *object)
40 {
41 struct cachefiles_xattr *buf;
42 struct dentry *dentry;
43 struct file *file = object->file;
44 unsigned int len = object->cookie->aux_len;
45 int ret;
46
47 if (!file)
48 return -ESTALE;
49 dentry = file->f_path.dentry;
50
51 _enter("%x,#%d", object->debug_id, len);
52
53 buf = kmalloc(sizeof(struct cachefiles_xattr) + len, GFP_KERNEL);
54 if (!buf)
55 return -ENOMEM;
56
57 buf->object_size = cpu_to_be64(object->cookie->object_size);
58 buf->zero_point = 0;
59 buf->type = CACHEFILES_COOKIE_TYPE_DATA;
60 buf->content = object->content_info;
61 if (test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
62 buf->content = CACHEFILES_CONTENT_DIRTY;
63 if (len > 0)
64 memcpy(buf->data, fscache_get_aux(object->cookie), len);
65
66 ret = cachefiles_inject_write_error();
67 if (ret == 0) {
68 ret = mnt_want_write_file(file);
69 if (ret == 0) {
70 ret = vfs_setxattr(&nop_mnt_idmap, dentry,
71 cachefiles_xattr_cache, buf,
72 sizeof(struct cachefiles_xattr) + len, 0);
73 mnt_drop_write_file(file);
74 }
75 }
76 if (ret < 0) {
77 trace_cachefiles_vfs_error(object, file_inode(file), ret,
78 cachefiles_trace_setxattr_error);
79 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
80 buf->content,
81 cachefiles_coherency_set_fail);
82 if (ret != -ENOMEM)
83 cachefiles_io_error_obj(
84 object,
85 "Failed to set xattr with error %d", ret);
86 } else {
87 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
88 buf->content,
89 cachefiles_coherency_set_ok);
90 }
91
92 kfree(buf);
93 _leave(" = %d", ret);
94 return ret;
95 }
96
97 /*
98 * check the consistency between the backing cache and the FS-Cache cookie
99 */
100 int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file)
101 {
102 struct cachefiles_xattr *buf;
103 struct dentry *dentry = file->f_path.dentry;
104 unsigned int len = object->cookie->aux_len, tlen;
105 const void *p = fscache_get_aux(object->cookie);
106 enum cachefiles_coherency_trace why;
107 ssize_t xlen;
108 int ret = -ESTALE;
109
110 tlen = sizeof(struct cachefiles_xattr) + len;
111 buf = kmalloc(tlen, GFP_KERNEL);
112 if (!buf)
113 return -ENOMEM;
114
115 xlen = cachefiles_inject_read_error();
116 if (xlen == 0)
117 xlen = vfs_getxattr(&nop_mnt_idmap, dentry, cachefiles_xattr_cache, buf, tlen);
118 if (xlen != tlen) {
119 if (xlen < 0) {
120 ret = xlen;
121 trace_cachefiles_vfs_error(object, file_inode(file), xlen,
122 cachefiles_trace_getxattr_error);
123 }
124 if (xlen == -EIO)
125 cachefiles_io_error_obj(
126 object,
127 "Failed to read aux with error %zd", xlen);
128 why = cachefiles_coherency_check_xattr;
129 } else if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
130 why = cachefiles_coherency_check_type;
131 } else if (memcmp(buf->data, p, len) != 0) {
132 why = cachefiles_coherency_check_aux;
133 } else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) {
134 why = cachefiles_coherency_check_objsize;
135 } else if (buf->content == CACHEFILES_CONTENT_DIRTY) {
136 // TODO: Begin conflict resolution
137 pr_warn("Dirty object in cache\n");
138 why = cachefiles_coherency_check_dirty;
139 } else {
140 why = cachefiles_coherency_check_ok;
141 ret = 0;
142 }
143
144 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
145 buf->content, why);
146 kfree(buf);
147 return ret;
148 }
149
150 /*
151 * remove the object's xattr to mark it stale
152 */
153 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
154 struct cachefiles_object *object,
155 struct dentry *dentry)
156 {
157 int ret;
158
159 ret = cachefiles_inject_remove_error();
160 if (ret == 0) {
161 ret = mnt_want_write(cache->mnt);
162 if (ret == 0) {
163 ret = vfs_removexattr(&nop_mnt_idmap, dentry,
164 cachefiles_xattr_cache);
165 mnt_drop_write(cache->mnt);
166 }
167 }
168 if (ret < 0) {
169 trace_cachefiles_vfs_error(object, d_inode(dentry), ret,
170 cachefiles_trace_remxattr_error);
171 if (ret == -ENOENT || ret == -ENODATA)
172 ret = 0;
173 else if (ret != -ENOMEM)
174 cachefiles_io_error(cache,
175 "Can't remove xattr from %lu"
176 " (error %d)",
177 d_backing_inode(dentry)->i_ino, -ret);
178 }
179
180 _leave(" = %d", ret);
181 return ret;
182 }
183
184 /*
185 * Stick a marker on the cache object to indicate that it's dirty.
186 */
187 void cachefiles_prepare_to_write(struct fscache_cookie *cookie)
188 {
189 const struct cred *saved_cred;
190 struct cachefiles_object *object = cookie->cache_priv;
191 struct cachefiles_cache *cache = object->volume->cache;
192
193 _enter("c=%08x", object->cookie->debug_id);
194
195 if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
196 cachefiles_begin_secure(cache, &saved_cred);
197 cachefiles_set_object_xattr(object);
198 cachefiles_end_secure(cache, saved_cred);
199 }
200 }
201
202 /*
203 * Set the state xattr on a volume directory.
204 */
205 bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
206 {
207 struct cachefiles_vol_xattr *buf;
208 unsigned int len = volume->vcookie->coherency_len;
209 const void *p = volume->vcookie->coherency;
210 struct dentry *dentry = volume->dentry;
211 int ret;
212
213 _enter("%x,#%d", volume->vcookie->debug_id, len);
214
215 len += sizeof(*buf);
216 buf = kmalloc(len, GFP_KERNEL);
217 if (!buf)
218 return false;
219 buf->reserved = cpu_to_be32(0);
220 memcpy(buf->data, p, volume->vcookie->coherency_len);
221
222 ret = cachefiles_inject_write_error();
223 if (ret == 0) {
224 ret = mnt_want_write(volume->cache->mnt);
225 if (ret == 0) {
226 ret = vfs_setxattr(&nop_mnt_idmap, dentry,
227 cachefiles_xattr_cache,
228 buf, len, 0);
229 mnt_drop_write(volume->cache->mnt);
230 }
231 }
232 if (ret < 0) {
233 trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,
234 cachefiles_trace_setxattr_error);
235 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
236 cachefiles_coherency_vol_set_fail);
237 if (ret != -ENOMEM)
238 cachefiles_io_error(
239 volume->cache, "Failed to set xattr with error %d", ret);
240 } else {
241 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
242 cachefiles_coherency_vol_set_ok);
243 }
244
245 kfree(buf);
246 _leave(" = %d", ret);
247 return ret == 0;
248 }
249
250 /*
251 * Check the consistency between the backing cache and the volume cookie.
252 */
253 int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
254 {
255 struct cachefiles_vol_xattr *buf;
256 struct dentry *dentry = volume->dentry;
257 unsigned int len = volume->vcookie->coherency_len;
258 const void *p = volume->vcookie->coherency;
259 enum cachefiles_coherency_trace why;
260 ssize_t xlen;
261 int ret = -ESTALE;
262
263 _enter("");
264
265 len += sizeof(*buf);
266 buf = kmalloc(len, GFP_KERNEL);
267 if (!buf)
268 return -ENOMEM;
269
270 xlen = cachefiles_inject_read_error();
271 if (xlen == 0)
272 xlen = vfs_getxattr(&nop_mnt_idmap, dentry, cachefiles_xattr_cache, buf, len);
273 if (xlen != len) {
274 if (xlen < 0) {
275 ret = xlen;
276 trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,
277 cachefiles_trace_getxattr_error);
278 if (xlen == -EIO)
279 cachefiles_io_error(
280 volume->cache,
281 "Failed to read xattr with error %zd", xlen);
282 }
283 why = cachefiles_coherency_vol_check_xattr;
284 } else if (buf->reserved != cpu_to_be32(0)) {
285 why = cachefiles_coherency_vol_check_resv;
286 } else if (memcmp(buf->data, p, len - sizeof(*buf)) != 0) {
287 why = cachefiles_coherency_vol_check_cmp;
288 } else {
289 why = cachefiles_coherency_vol_check_ok;
290 ret = 0;
291 }
292
293 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino, why);
294 kfree(buf);
295 _leave(" = %d", ret);
296 return ret;
297 }
298
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