1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * V9FS FID Management
4 *
5 * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
6 * Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
7 */
8
9 #include <linux/module.h>
10 #include <linux/errno.h>
11 #include <linux/fs.h>
12 #include <linux/slab.h>
13 #include <linux/sched.h>
14 #include <net/9p/9p.h>
15 #include <net/9p/client.h>
16
17 #include "v9fs.h"
18 #include "v9fs_vfs.h"
19 #include "fid.h"
20
__add_fid(struct dentry * dentry,struct p9_fid * fid)21 static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
22 {
23 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
24 }
25
26
27 /**
28 * v9fs_fid_add - add a fid to a dentry
29 * @dentry: dentry that the fid is being added to
30 * @pfid: fid to add, NULLed out
31 *
32 */
v9fs_fid_add(struct dentry * dentry,struct p9_fid ** pfid)33 void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
34 {
35 struct p9_fid *fid = *pfid;
36
37 spin_lock(&dentry->d_lock);
38 __add_fid(dentry, fid);
39 spin_unlock(&dentry->d_lock);
40
41 *pfid = NULL;
42 }
43
44 /**
45 * v9fs_fid_find_inode - search for an open fid off of the inode list
46 * @inode: return a fid pointing to a specific inode
47 * @uid: return a fid belonging to the specified user
48 *
49 */
50
v9fs_fid_find_inode(struct inode * inode,kuid_t uid)51 static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid)
52 {
53 struct hlist_head *h;
54 struct p9_fid *fid, *ret = NULL;
55
56 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
57
58 spin_lock(&inode->i_lock);
59 h = (struct hlist_head *)&inode->i_private;
60 hlist_for_each_entry(fid, h, ilist) {
61 if (uid_eq(fid->uid, uid)) {
62 p9_fid_get(fid);
63 ret = fid;
64 break;
65 }
66 }
67 spin_unlock(&inode->i_lock);
68 return ret;
69 }
70
71 /**
72 * v9fs_open_fid_add - add an open fid to an inode
73 * @inode: inode that the fid is being added to
74 * @pfid: fid to add, NULLed out
75 *
76 */
77
v9fs_open_fid_add(struct inode * inode,struct p9_fid ** pfid)78 void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
79 {
80 struct p9_fid *fid = *pfid;
81
82 spin_lock(&inode->i_lock);
83 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
84 spin_unlock(&inode->i_lock);
85
86 *pfid = NULL;
87 }
88
89
90 /**
91 * v9fs_fid_find - retrieve a fid that belongs to the specified uid
92 * @dentry: dentry to look for fid in
93 * @uid: return fid that belongs to the specified user
94 * @any: if non-zero, return any fid associated with the dentry
95 *
96 */
97
v9fs_fid_find(struct dentry * dentry,kuid_t uid,int any)98 static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
99 {
100 struct p9_fid *fid, *ret;
101
102 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
103 dentry, dentry, from_kuid(&init_user_ns, uid),
104 any);
105 ret = NULL;
106 /* we'll recheck under lock if there's anything to look in */
107 if (dentry->d_fsdata) {
108 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
109
110 spin_lock(&dentry->d_lock);
111 hlist_for_each_entry(fid, h, dlist) {
112 if (any || uid_eq(fid->uid, uid)) {
113 ret = fid;
114 p9_fid_get(ret);
115 break;
116 }
117 }
118 spin_unlock(&dentry->d_lock);
119 } else {
120 if (dentry->d_inode)
121 ret = v9fs_fid_find_inode(dentry->d_inode, uid);
122 }
123
124 return ret;
125 }
126
127 /*
128 * We need to hold v9ses->rename_sem as long as we hold references
129 * to returned path array. Array element contain pointers to
130 * dentry names.
131 */
build_path_from_dentry(struct v9fs_session_info * v9ses,struct dentry * dentry,const unsigned char *** names)132 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
133 struct dentry *dentry, const unsigned char ***names)
134 {
135 int n = 0, i;
136 const unsigned char **wnames;
137 struct dentry *ds;
138
139 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
140 n++;
141
142 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
143 if (!wnames)
144 goto err_out;
145
146 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
147 wnames[i] = ds->d_name.name;
148
149 *names = wnames;
150 return n;
151 err_out:
152 return -ENOMEM;
153 }
154
v9fs_fid_lookup_with_uid(struct dentry * dentry,kuid_t uid,int any)155 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
156 kuid_t uid, int any)
157 {
158 struct dentry *ds;
159 const unsigned char **wnames, *uname;
160 int i, n, l, access;
161 struct v9fs_session_info *v9ses;
162 struct p9_fid *fid, *root_fid, *old_fid;
163
164 v9ses = v9fs_dentry2v9ses(dentry);
165 access = v9ses->flags & V9FS_ACCESS_MASK;
166 fid = v9fs_fid_find(dentry, uid, any);
167 if (fid)
168 return fid;
169 /*
170 * we don't have a matching fid. To do a TWALK we need
171 * parent fid. We need to prevent rename when we want to
172 * look at the parent.
173 */
174 down_read(&v9ses->rename_sem);
175 ds = dentry->d_parent;
176 fid = v9fs_fid_find(ds, uid, any);
177 if (fid) {
178 /* Found the parent fid do a lookup with that */
179 old_fid = fid;
180
181 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);
182 p9_fid_put(old_fid);
183 goto fid_out;
184 }
185 up_read(&v9ses->rename_sem);
186
187 /* start from the root and try to do a lookup */
188 root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
189 if (!root_fid) {
190 /* the user is not attached to the fs yet */
191 if (access == V9FS_ACCESS_SINGLE)
192 return ERR_PTR(-EPERM);
193
194 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
195 uname = NULL;
196 else
197 uname = v9ses->uname;
198
199 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
200 v9ses->aname);
201 if (IS_ERR(fid))
202 return fid;
203
204 root_fid = p9_fid_get(fid);
205 v9fs_fid_add(dentry->d_sb->s_root, &fid);
206 }
207 /* If we are root ourself just return that */
208 if (dentry->d_sb->s_root == dentry)
209 return root_fid;
210
211 /*
212 * Do a multipath walk with attached root.
213 * When walking parent we need to make sure we
214 * don't have a parallel rename happening
215 */
216 down_read(&v9ses->rename_sem);
217 n = build_path_from_dentry(v9ses, dentry, &wnames);
218 if (n < 0) {
219 fid = ERR_PTR(n);
220 goto err_out;
221 }
222 fid = root_fid;
223 old_fid = root_fid;
224 i = 0;
225 while (i < n) {
226 l = min(n - i, P9_MAXWELEM);
227 /*
228 * We need to hold rename lock when doing a multipath
229 * walk to ensure none of the path components change
230 */
231 fid = p9_client_walk(old_fid, l, &wnames[i],
232 old_fid == root_fid /* clone */);
233 /* non-cloning walk will return the same fid */
234 if (fid != old_fid) {
235 p9_fid_put(old_fid);
236 old_fid = fid;
237 }
238 if (IS_ERR(fid)) {
239 kfree(wnames);
240 goto err_out;
241 }
242 i += l;
243 }
244 kfree(wnames);
245 fid_out:
246 if (!IS_ERR(fid)) {
247 spin_lock(&dentry->d_lock);
248 if (d_unhashed(dentry)) {
249 spin_unlock(&dentry->d_lock);
250 p9_fid_put(fid);
251 fid = ERR_PTR(-ENOENT);
252 } else {
253 __add_fid(dentry, fid);
254 p9_fid_get(fid);
255 spin_unlock(&dentry->d_lock);
256 }
257 }
258 err_out:
259 up_read(&v9ses->rename_sem);
260 return fid;
261 }
262
263 /**
264 * v9fs_fid_lookup - lookup for a fid, try to walk if not found
265 * @dentry: dentry to look for fid in
266 *
267 * Look for a fid in the specified dentry for the current user.
268 * If no fid is found, try to create one walking from a fid from the parent
269 * dentry (if it has one), or the root dentry. If the user haven't accessed
270 * the fs yet, attach now and walk from the root.
271 */
272
v9fs_fid_lookup(struct dentry * dentry)273 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
274 {
275 kuid_t uid;
276 int any, access;
277 struct v9fs_session_info *v9ses;
278
279 v9ses = v9fs_dentry2v9ses(dentry);
280 access = v9ses->flags & V9FS_ACCESS_MASK;
281 switch (access) {
282 case V9FS_ACCESS_SINGLE:
283 case V9FS_ACCESS_USER:
284 case V9FS_ACCESS_CLIENT:
285 uid = current_fsuid();
286 any = 0;
287 break;
288
289 case V9FS_ACCESS_ANY:
290 uid = v9ses->uid;
291 any = 1;
292 break;
293
294 default:
295 uid = INVALID_UID;
296 any = 0;
297 break;
298 }
299 return v9fs_fid_lookup_with_uid(dentry, uid, any);
300 }
301
v9fs_writeback_fid(struct dentry * dentry)302 struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
303 {
304 int err;
305 struct p9_fid *fid, *ofid;
306
307 ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0);
308 fid = clone_fid(ofid);
309 if (IS_ERR(fid))
310 goto error_out;
311 p9_fid_put(ofid);
312 /*
313 * writeback fid will only be used to write back the
314 * dirty pages. We always request for the open fid in read-write
315 * mode so that a partial page write which result in page
316 * read can work.
317 */
318 err = p9_client_open(fid, O_RDWR);
319 if (err < 0) {
320 p9_fid_put(fid);
321 fid = ERR_PTR(err);
322 goto error_out;
323 }
324 error_out:
325 return fid;
326 }
327