1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* AFS silly rename handling
3 *
4 * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 * - Derived from NFS's sillyrename.
7 */
8
9 #include <linux/kernel.h>
10 #include <linux/fs.h>
11 #include <linux/namei.h>
12 #include <linux/fsnotify.h>
13 #include "internal.h"
14
15 /*
16 * Actually perform the silly rename step.
17 */
afs_do_silly_rename(struct afs_vnode * dvnode,struct afs_vnode * vnode,struct dentry * old,struct dentry * new,struct key * key)18 static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
19 struct dentry *old, struct dentry *new,
20 struct key *key)
21 {
22 struct afs_fs_cursor fc;
23 struct afs_status_cb *scb;
24 afs_dataversion_t dir_data_version;
25 int ret = -ERESTARTSYS;
26
27 _enter("%pd,%pd", old, new);
28
29 scb = kzalloc(sizeof(struct afs_status_cb), GFP_KERNEL);
30 if (!scb)
31 return -ENOMEM;
32
33 trace_afs_silly_rename(vnode, false);
34 if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {
35 dir_data_version = dvnode->status.data_version + 1;
36
37 while (afs_select_fileserver(&fc)) {
38 fc.cb_break = afs_calc_vnode_cb_break(dvnode);
39 afs_fs_rename(&fc, old->d_name.name,
40 dvnode, new->d_name.name,
41 scb, scb);
42 }
43
44 afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
45 &dir_data_version, scb);
46 ret = afs_end_vnode_operation(&fc);
47 }
48
49 if (ret == 0) {
50 spin_lock(&old->d_lock);
51 old->d_flags |= DCACHE_NFSFS_RENAMED;
52 spin_unlock(&old->d_lock);
53 if (dvnode->silly_key != key) {
54 key_put(dvnode->silly_key);
55 dvnode->silly_key = key_get(key);
56 }
57
58 down_write(&dvnode->validate_lock);
59 if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
60 dvnode->status.data_version == dir_data_version) {
61 afs_edit_dir_remove(dvnode, &old->d_name,
62 afs_edit_dir_for_silly_0);
63 afs_edit_dir_add(dvnode, &new->d_name,
64 &vnode->fid, afs_edit_dir_for_silly_1);
65 }
66 up_write(&dvnode->validate_lock);
67 }
68
69 kfree(scb);
70 _leave(" = %d", ret);
71 return ret;
72 }
73
74 /**
75 * afs_sillyrename - Perform a silly-rename of a dentry
76 *
77 * AFS is stateless and the server doesn't know when the client is holding a
78 * file open. To prevent application problems when a file is unlinked while
79 * it's still open, the client performs a "silly-rename". That is, it renames
80 * the file to a hidden file in the same directory, and only performs the
81 * unlink once the last reference to it is put.
82 *
83 * The final cleanup is done during dentry_iput.
84 */
afs_sillyrename(struct afs_vnode * dvnode,struct afs_vnode * vnode,struct dentry * dentry,struct key * key)85 int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
86 struct dentry *dentry, struct key *key)
87 {
88 static unsigned int sillycounter;
89 struct dentry *sdentry = NULL;
90 unsigned char silly[16];
91 int ret = -EBUSY;
92
93 _enter("");
94
95 /* We don't allow a dentry to be silly-renamed twice. */
96 if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
97 return -EBUSY;
98
99 sdentry = NULL;
100 do {
101 int slen;
102
103 dput(sdentry);
104 sillycounter++;
105
106 /* Create a silly name. Note that the ".__afs" prefix is
107 * understood by the salvager and must not be changed.
108 */
109 slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
110 sdentry = lookup_one_len(silly, dentry->d_parent, slen);
111
112 /* N.B. Better to return EBUSY here ... it could be dangerous
113 * to delete the file while it's in use.
114 */
115 if (IS_ERR(sdentry))
116 goto out;
117 } while (!d_is_negative(sdentry));
118
119 ihold(&vnode->vfs_inode);
120
121 ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
122 switch (ret) {
123 case 0:
124 /* The rename succeeded. */
125 d_move(dentry, sdentry);
126 break;
127 case -ERESTARTSYS:
128 /* The result of the rename is unknown. Play it safe by forcing
129 * a new lookup.
130 */
131 d_drop(dentry);
132 d_drop(sdentry);
133 }
134
135 iput(&vnode->vfs_inode);
136 dput(sdentry);
137 out:
138 _leave(" = %d", ret);
139 return ret;
140 }
141
142 /*
143 * Tell the server to remove a sillyrename file.
144 */
afs_do_silly_unlink(struct afs_vnode * dvnode,struct afs_vnode * vnode,struct dentry * dentry,struct key * key)145 static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
146 struct dentry *dentry, struct key *key)
147 {
148 struct afs_fs_cursor fc;
149 struct afs_status_cb *scb;
150 int ret = -ERESTARTSYS;
151
152 _enter("");
153
154 scb = kcalloc(2, sizeof(struct afs_status_cb), GFP_KERNEL);
155 if (!scb)
156 return -ENOMEM;
157
158 trace_afs_silly_rename(vnode, true);
159 if (afs_begin_vnode_operation(&fc, dvnode, key, false)) {
160 afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;
161
162 while (afs_select_fileserver(&fc)) {
163 fc.cb_break = afs_calc_vnode_cb_break(dvnode);
164
165 if (test_bit(AFS_SERVER_FL_IS_YFS, &fc.cbi->server->flags) &&
166 !test_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags)) {
167 yfs_fs_remove_file2(&fc, vnode, dentry->d_name.name,
168 &scb[0], &scb[1]);
169 if (fc.ac.error != -ECONNABORTED ||
170 fc.ac.abort_code != RXGEN_OPCODE)
171 continue;
172 set_bit(AFS_SERVER_FL_NO_RM2, &fc.cbi->server->flags);
173 }
174
175 afs_fs_remove(&fc, vnode, dentry->d_name.name, false, &scb[0]);
176 }
177
178 afs_vnode_commit_status(&fc, dvnode, fc.cb_break,
179 &dir_data_version, &scb[0]);
180 ret = afs_end_vnode_operation(&fc);
181 if (ret == 0) {
182 drop_nlink(&vnode->vfs_inode);
183 if (vnode->vfs_inode.i_nlink == 0) {
184 set_bit(AFS_VNODE_DELETED, &vnode->flags);
185 clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
186 }
187 }
188 if (ret == 0) {
189 down_write(&dvnode->validate_lock);
190 if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
191 dvnode->status.data_version == dir_data_version)
192 afs_edit_dir_remove(dvnode, &dentry->d_name,
193 afs_edit_dir_for_unlink);
194 up_write(&dvnode->validate_lock);
195 }
196 }
197
198 kfree(scb);
199 _leave(" = %d", ret);
200 return ret;
201 }
202
203 /*
204 * Remove sillyrename file on iput.
205 */
afs_silly_iput(struct dentry * dentry,struct inode * inode)206 int afs_silly_iput(struct dentry *dentry, struct inode *inode)
207 {
208 struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
209 struct afs_vnode *vnode = AFS_FS_I(inode);
210 struct dentry *alias;
211 int ret;
212
213 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
214
215 _enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);
216
217 down_read(&dvnode->rmdir_lock);
218
219 alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
220 if (IS_ERR(alias)) {
221 up_read(&dvnode->rmdir_lock);
222 return 0;
223 }
224
225 if (!d_in_lookup(alias)) {
226 /* We raced with lookup... See if we need to transfer the
227 * sillyrename information to the aliased dentry.
228 */
229 ret = 0;
230 spin_lock(&alias->d_lock);
231 if (d_really_is_positive(alias) &&
232 !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
233 alias->d_flags |= DCACHE_NFSFS_RENAMED;
234 ret = 1;
235 }
236 spin_unlock(&alias->d_lock);
237 up_read(&dvnode->rmdir_lock);
238 dput(alias);
239 return ret;
240 }
241
242 /* Stop lock-release from complaining. */
243 spin_lock(&vnode->lock);
244 vnode->lock_state = AFS_VNODE_LOCK_DELETED;
245 trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
246 spin_unlock(&vnode->lock);
247
248 afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
249 up_read(&dvnode->rmdir_lock);
250 d_lookup_done(alias);
251 dput(alias);
252 return 1;
253 }
254