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authorIan Kent <raven@themaw.net>2006-05-15 12:43:51 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-15 14:20:54 -0400
commita5370553952a9a414860d878b67c49eff11313bd (patch)
tree8a893bd5e6519fbb7e1b46506096607be7093a50 /fs/autofs4/waitq.c
parent6aff5cb8ec270db569800b1bb59bd20003a76f07 (diff)
[PATCH] autofs4: NFY_NONE wait race fix
This patch fixes two problems. First, the comparison of entries in the waitq.c was incorrect. Second, the NFY_NONE check was incorrect. The test of whether the dentry is mounted if ineffective, for example, if an expire fails then we could wait forever on a non existant expire. The bug was identified by Jeff Moyer. The patch changes autofs4 to wait on expires only as this is all that's needed. If there is no existing wait when autofs4_wait is call with a type of NFY_NONE it delays until either a wait appears or the the expire flag is cleared. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/autofs4/waitq.c')
-rw-r--r--fs/autofs4/waitq.c77
1 files changed, 53 insertions, 24 deletions
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index 142ab6aa2aa1..ce103e7b0bc3 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -189,14 +189,30 @@ static int autofs4_getpath(struct autofs_sb_info *sbi,
189 return len; 189 return len;
190} 190}
191 191
192static struct autofs_wait_queue *
193autofs4_find_wait(struct autofs_sb_info *sbi,
194 char *name, unsigned int hash, unsigned int len)
195{
196 struct autofs_wait_queue *wq;
197
198 for (wq = sbi->queues; wq; wq = wq->next) {
199 if (wq->hash == hash &&
200 wq->len == len &&
201 wq->name && !memcmp(wq->name, name, len))
202 break;
203 }
204 return wq;
205}
206
192int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry, 207int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
193 enum autofs_notify notify) 208 enum autofs_notify notify)
194{ 209{
210 struct autofs_info *ino;
195 struct autofs_wait_queue *wq; 211 struct autofs_wait_queue *wq;
196 char *name; 212 char *name;
197 unsigned int len = 0; 213 unsigned int len = 0;
198 unsigned int hash = 0; 214 unsigned int hash = 0;
199 int status; 215 int status, type;
200 216
201 /* In catatonic mode, we don't wait for nobody */ 217 /* In catatonic mode, we don't wait for nobody */
202 if (sbi->catatonic) 218 if (sbi->catatonic)
@@ -223,21 +239,41 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
223 return -EINTR; 239 return -EINTR;
224 } 240 }
225 241
226 for (wq = sbi->queues ; wq ; wq = wq->next) { 242 wq = autofs4_find_wait(sbi, name, hash, len);
227 if (wq->hash == dentry->d_name.hash && 243 ino = autofs4_dentry_ino(dentry);
228 wq->len == len && 244 if (!wq && ino && notify == NFY_NONE) {
229 wq->name && !memcmp(wq->name, name, len)) 245 /*
230 break; 246 * Either we've betean the pending expire to post it's
231 } 247 * wait or it finished while we waited on the mutex.
248 * So we need to wait till either, the wait appears
249 * or the expire finishes.
250 */
251
252 while (ino->flags & AUTOFS_INF_EXPIRING) {
253 mutex_unlock(&sbi->wq_mutex);
254 schedule_timeout_interruptible(HZ/10);
255 if (mutex_lock_interruptible(&sbi->wq_mutex)) {
256 kfree(name);
257 return -EINTR;
258 }
259 wq = autofs4_find_wait(sbi, name, hash, len);
260 if (wq)
261 break;
262 }
232 263
233 if (!wq) { 264 /*
234 /* Can't wait for an expire if there's no mount */ 265 * Not ideal but the status has already gone. Of the two
235 if (notify == NFY_NONE && !d_mountpoint(dentry)) { 266 * cases where we wait on NFY_NONE neither depend on the
267 * return status of the wait.
268 */
269 if (!wq) {
236 kfree(name); 270 kfree(name);
237 mutex_unlock(&sbi->wq_mutex); 271 mutex_unlock(&sbi->wq_mutex);
238 return -ENOENT; 272 return 0;
239 } 273 }
274 }
240 275
276 if (!wq) {
241 /* Create a new wait queue */ 277 /* Create a new wait queue */
242 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL); 278 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
243 if (!wq) { 279 if (!wq) {
@@ -263,20 +299,7 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
263 wq->tgid = current->tgid; 299 wq->tgid = current->tgid;
264 wq->status = -EINTR; /* Status return if interrupted */ 300 wq->status = -EINTR; /* Status return if interrupted */
265 atomic_set(&wq->wait_ctr, 2); 301 atomic_set(&wq->wait_ctr, 2);
266 atomic_set(&wq->notify, 1);
267 mutex_unlock(&sbi->wq_mutex);
268 } else {
269 atomic_inc(&wq->wait_ctr);
270 mutex_unlock(&sbi->wq_mutex); 302 mutex_unlock(&sbi->wq_mutex);
271 kfree(name);
272 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
273 (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
274 }
275
276 if (notify != NFY_NONE && atomic_read(&wq->notify)) {
277 int type;
278
279 atomic_dec(&wq->notify);
280 303
281 if (sbi->version < 5) { 304 if (sbi->version < 5) {
282 if (notify == NFY_MOUNT) 305 if (notify == NFY_MOUNT)
@@ -299,6 +322,12 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
299 322
300 /* autofs4_notify_daemon() may block */ 323 /* autofs4_notify_daemon() may block */
301 autofs4_notify_daemon(sbi, wq, type); 324 autofs4_notify_daemon(sbi, wq, type);
325 } else {
326 atomic_inc(&wq->wait_ctr);
327 mutex_unlock(&sbi->wq_mutex);
328 kfree(name);
329 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
330 (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
302 } 331 }
303 332
304 /* wq->name is NULL if and only if the lock is already released */ 333 /* wq->name is NULL if and only if the lock is already released */