1 /*
2  * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
3  *
4  * This software may be freely redistributed under the terms of the
5  * GNU General Public License.
6  *
7  * You should have received a copy of the GNU General Public License
8  * along with this program; if not, write to the Free Software
9  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
10  *
11  * Authors: David Woodhouse <dwmw2@infradead.org>
12  *          David Howells <dhowells@redhat.com>
13  *
14  */
15 
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/init.h>
19 #include <linux/circ_buf.h>
20 #include <linux/sched.h>
21 #include "internal.h"
22 
23 /*
24  * Handle invalidation of an mmap'd file.  We invalidate all the PTEs referring
25  * to the pages in this file's pagecache, forcing the kernel to go through
26  * ->fault() or ->page_mkwrite() - at which point we can handle invalidation
27  * more fully.
28  */
afs_invalidate_mmap_work(struct work_struct * work)29 void afs_invalidate_mmap_work(struct work_struct *work)
30 {
31 	struct afs_vnode *vnode = container_of(work, struct afs_vnode, cb_work);
32 
33 	unmap_mapping_pages(vnode->netfs.inode.i_mapping, 0, 0, false);
34 }
35 
afs_volume_init_callback(struct afs_volume * volume)36 static void afs_volume_init_callback(struct afs_volume *volume)
37 {
38 	struct afs_vnode *vnode;
39 
40 	down_read(&volume->open_mmaps_lock);
41 
42 	list_for_each_entry(vnode, &volume->open_mmaps, cb_mmap_link) {
43 		if (vnode->cb_v_check != atomic_read(&volume->cb_v_break)) {
44 			atomic64_set(&vnode->cb_expires_at, AFS_NO_CB_PROMISE);
45 			queue_work(system_unbound_wq, &vnode->cb_work);
46 		}
47 	}
48 
49 	up_read(&volume->open_mmaps_lock);
50 }
51 
52 /*
53  * Allow the fileserver to request callback state (re-)initialisation.
54  * Unfortunately, UUIDs are not guaranteed unique.
55  */
afs_init_callback_state(struct afs_server * server)56 void afs_init_callback_state(struct afs_server *server)
57 {
58 	struct afs_server_entry *se;
59 
60 	down_read(&server->cell->vs_lock);
61 
62 	list_for_each_entry(se, &server->volumes, slink) {
63 		se->cb_expires_at = AFS_NO_CB_PROMISE;
64 		se->volume->cb_expires_at = AFS_NO_CB_PROMISE;
65 		trace_afs_cb_v_break(se->volume->vid, atomic_read(&se->volume->cb_v_break),
66 				     afs_cb_break_for_s_reinit);
67 		if (!list_empty(&se->volume->open_mmaps))
68 			afs_volume_init_callback(se->volume);
69 	}
70 
71 	up_read(&server->cell->vs_lock);
72 }
73 
74 /*
75  * actually break a callback
76  */
__afs_break_callback(struct afs_vnode * vnode,enum afs_cb_break_reason reason)77 void __afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
78 {
79 	_enter("");
80 
81 	clear_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
82 	if (atomic64_xchg(&vnode->cb_expires_at, AFS_NO_CB_PROMISE) != AFS_NO_CB_PROMISE) {
83 		vnode->cb_break++;
84 		vnode->cb_v_check = atomic_read(&vnode->volume->cb_v_break);
85 		afs_clear_permits(vnode);
86 
87 		if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
88 			afs_lock_may_be_available(vnode);
89 
90 		if (reason != afs_cb_break_for_deleted &&
91 		    vnode->status.type == AFS_FTYPE_FILE &&
92 		    atomic_read(&vnode->cb_nr_mmap))
93 			queue_work(system_unbound_wq, &vnode->cb_work);
94 
95 		trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, true);
96 	} else {
97 		trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, false);
98 	}
99 }
100 
afs_break_callback(struct afs_vnode * vnode,enum afs_cb_break_reason reason)101 void afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
102 {
103 	write_seqlock(&vnode->cb_lock);
104 	__afs_break_callback(vnode, reason);
105 	write_sequnlock(&vnode->cb_lock);
106 }
107 
108 /*
109  * Look up a volume by volume ID under RCU conditions.
110  */
afs_lookup_volume_rcu(struct afs_cell * cell,afs_volid_t vid)111 static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
112 						afs_volid_t vid)
113 {
114 	struct afs_volume *volume = NULL;
115 	struct rb_node *p;
116 	int seq = 1;
117 
118 	for (;;) {
119 		/* Unfortunately, rbtree walking doesn't give reliable results
120 		 * under just the RCU read lock, so we have to check for
121 		 * changes.
122 		 */
123 		seq++; /* 2 on the 1st/lockless path, otherwise odd */
124 		read_seqbegin_or_lock(&cell->volume_lock, &seq);
125 
126 		p = rcu_dereference_raw(cell->volumes.rb_node);
127 		while (p) {
128 			volume = rb_entry(p, struct afs_volume, cell_node);
129 
130 			if (volume->vid < vid)
131 				p = rcu_dereference_raw(p->rb_left);
132 			else if (volume->vid > vid)
133 				p = rcu_dereference_raw(p->rb_right);
134 			else
135 				break;
136 			volume = NULL;
137 		}
138 
139 		if (volume && afs_try_get_volume(volume, afs_volume_trace_get_callback))
140 			break;
141 		if (!need_seqretry(&cell->volume_lock, seq))
142 			break;
143 		seq |= 1; /* Want a lock next time */
144 	}
145 
146 	done_seqretry(&cell->volume_lock, seq);
147 	return volume;
148 }
149 
150 /*
151  * Allow the fileserver to break callbacks at the volume-level.  This is
152  * typically done when, for example, a R/W volume is snapshotted to a R/O
153  * volume (the only way to change an R/O volume).  It may also, however, happen
154  * when a volserver takes control of a volume (offlining it, moving it, etc.).
155  *
156  * Every file in that volume will need to be reevaluated.
157  */
afs_break_volume_callback(struct afs_server * server,struct afs_volume * volume)158 static void afs_break_volume_callback(struct afs_server *server,
159 				      struct afs_volume *volume)
160 	__releases(RCU)
161 {
162 	struct afs_server_list *slist = rcu_dereference(volume->servers);
163 	unsigned int i, cb_v_break;
164 
165 	write_lock(&volume->cb_v_break_lock);
166 
167 	for (i = 0; i < slist->nr_servers; i++)
168 		if (slist->servers[i].server == server)
169 			slist->servers[i].cb_expires_at = AFS_NO_CB_PROMISE;
170 	volume->cb_expires_at = AFS_NO_CB_PROMISE;
171 
172 	cb_v_break = atomic_inc_return_release(&volume->cb_v_break);
173 	trace_afs_cb_v_break(volume->vid, cb_v_break, afs_cb_break_for_volume_callback);
174 
175 	write_unlock(&volume->cb_v_break_lock);
176 	rcu_read_unlock();
177 
178 	if (!list_empty(&volume->open_mmaps))
179 		afs_volume_init_callback(volume);
180 }
181 
182 /*
183  * allow the fileserver to explicitly break one callback
184  * - happens when
185  *   - the backing file is changed
186  *   - a lock is released
187  */
afs_break_one_callback(struct afs_server * server,struct afs_volume * volume,struct afs_fid * fid)188 static void afs_break_one_callback(struct afs_server *server,
189 				   struct afs_volume *volume,
190 				   struct afs_fid *fid)
191 {
192 	struct super_block *sb;
193 	struct afs_vnode *vnode;
194 	struct inode *inode;
195 
196 	/* See if we can find a matching inode - even an I_NEW inode needs to
197 	 * be marked as it can have its callback broken before we finish
198 	 * setting up the local inode.
199 	 */
200 	sb = rcu_dereference(volume->sb);
201 	if (!sb)
202 		return;
203 
204 	inode = find_inode_rcu(sb, fid->vnode, afs_ilookup5_test_by_fid, fid);
205 	if (inode) {
206 		vnode = AFS_FS_I(inode);
207 		afs_break_callback(vnode, afs_cb_break_for_callback);
208 	} else {
209 		trace_afs_cb_miss(fid, afs_cb_break_for_callback);
210 	}
211 }
212 
afs_break_some_callbacks(struct afs_server * server,struct afs_callback_break * cbb,size_t * _count)213 static void afs_break_some_callbacks(struct afs_server *server,
214 				     struct afs_callback_break *cbb,
215 				     size_t *_count)
216 {
217 	struct afs_callback_break *residue = cbb;
218 	struct afs_volume *volume;
219 	afs_volid_t vid = cbb->fid.vid;
220 	size_t i;
221 
222 	rcu_read_lock();
223 	volume = afs_lookup_volume_rcu(server->cell, vid);
224 	if (cbb->fid.vnode == 0 && cbb->fid.unique == 0) {
225 		afs_break_volume_callback(server, volume);
226 		*_count -= 1;
227 		if (*_count)
228 			memmove(cbb, cbb + 1, sizeof(*cbb) * *_count);
229 	} else {
230 		/* TODO: Find all matching volumes if we couldn't match the server and
231 		 * break them anyway.
232 		 */
233 
234 		for (i = *_count; i > 0; cbb++, i--) {
235 			if (cbb->fid.vid == vid) {
236 				_debug("- Fid { vl=%08llx n=%llu u=%u }",
237 				       cbb->fid.vid,
238 				       cbb->fid.vnode,
239 				       cbb->fid.unique);
240 				--*_count;
241 				if (volume)
242 					afs_break_one_callback(server, volume, &cbb->fid);
243 			} else {
244 				*residue++ = *cbb;
245 			}
246 		}
247 		rcu_read_unlock();
248 	}
249 
250 	afs_put_volume(volume, afs_volume_trace_put_callback);
251 }
252 
253 /*
254  * allow the fileserver to break callback promises
255  */
afs_break_callbacks(struct afs_server * server,size_t count,struct afs_callback_break * callbacks)256 void afs_break_callbacks(struct afs_server *server, size_t count,
257 			 struct afs_callback_break *callbacks)
258 {
259 	_enter("%p,%zu,", server, count);
260 
261 	ASSERT(server != NULL);
262 
263 	while (count > 0)
264 		afs_break_some_callbacks(server, callbacks, &count);
265 }
266