1 /* -*- linux-c -*- --------------------------------------------------------- *
2 *
3 * linux/fs/autofs/waitq.c
4 *
5 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
6 *
7 * This file is part of the Linux kernel and is made available under
8 * the terms of the GNU General Public License, version 2, or at your
9 * option, any later version, incorporated herein by reference.
10 *
11 * ------------------------------------------------------------------------- */
12
13 #include <linux/slab.h>
14 #include <linux/time.h>
15 #include <linux/signal.h>
16 #include <linux/file.h>
17 #include "autofs_i.h"
18
19 /* We make this a static variable rather than a part of the superblock; it
20 is better if we don't reassign numbers easily even across filesystems */
21 static autofs_wqt_t autofs_next_wait_queue = 1;
22
23 /* These are the signals we allow interrupting a pending mount */
24 #define SHUTDOWN_SIGS (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
25
26 void autofs_catatonic_mode(struct autofs_sb_info *sbi)
27 {
28 struct autofs_wait_queue *wq, *nwq;
29
30 DPRINTK(("autofs: entering catatonic mode\n"));
31
32 sbi->catatonic = 1;
33 wq = sbi->queues;
34 sbi->queues = NULL; /* Erase all wait queues */
35 while ( wq ) {
36 nwq = wq->next;
37 wq->status = -ENOENT; /* Magic is gone - report failure */
38 kfree(wq->name);
39 wq->name = NULL;
40 wake_up(&wq->queue);
41 wq = nwq;
42 }
43 fput(sbi->pipe); /* Close the pipe */
44 autofs_hash_dputall(&sbi->dirhash); /* Remove all dentry pointers */
45 }
46
47 static int autofs_write(struct file *file, const void *addr, int bytes)
48 {
49 unsigned long sigpipe, flags;
50 mm_segment_t fs;
51 const char *data = (const char *)addr;
52 ssize_t wr = 0;
53
54 /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
55
56 sigpipe = sigismember(¤t->pending.signal, SIGPIPE);
57
58 /* Save pointer to user space and point back to kernel space */
59 fs = get_fs();
60 set_fs(KERNEL_DS);
61
62 while (bytes &&
63 (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
64 data += wr;
65 bytes -= wr;
66 }
67
68 set_fs(fs);
69
70 /* Keep the currently executing process from receiving a
71 SIGPIPE unless it was already supposed to get one */
72 if (wr == -EPIPE && !sigpipe) {
73 spin_lock_irqsave(¤t->sighand->siglock, flags);
74 sigdelset(¤t->pending.signal, SIGPIPE);
75 recalc_sigpending();
76 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
77 }
78
79 return (bytes > 0);
80 }
81
82 static void autofs_notify_daemon(struct autofs_sb_info *sbi, struct autofs_wait_queue *wq)
83 {
84 struct autofs_packet_missing pkt;
85
86 DPRINTK(("autofs_wait: wait id = 0x%08lx, name = ", wq->wait_queue_token));
87 autofs_say(wq->name,wq->len);
88
89 memset(&pkt,0,sizeof pkt); /* For security reasons */
90
91 pkt.hdr.proto_version = AUTOFS_PROTO_VERSION;
92 pkt.hdr.type = autofs_ptype_missing;
93 pkt.wait_queue_token = wq->wait_queue_token;
94 pkt.len = wq->len;
95 memcpy(pkt.name, wq->name, pkt.len);
96 pkt.name[pkt.len] = '\0';
97
98 if ( autofs_write(sbi->pipe,&pkt,sizeof(struct autofs_packet_missing)) )
99 autofs_catatonic_mode(sbi);
100 }
101
102 int autofs_wait(struct autofs_sb_info *sbi, struct qstr *name)
103 {
104 struct autofs_wait_queue *wq;
105 int status;
106
107 /* In catatonic mode, we don't wait for nobody */
108 if ( sbi->catatonic )
109 return -ENOENT;
110
111 /* We shouldn't be able to get here, but just in case */
112 if ( name->len > NAME_MAX )
113 return -ENOENT;
114
115 for ( wq = sbi->queues ; wq ; wq = wq->next ) {
116 if ( wq->hash == name->hash &&
117 wq->len == name->len &&
118 wq->name && !memcmp(wq->name,name->name,name->len) )
119 break;
120 }
121
122 if ( !wq ) {
123 /* Create a new wait queue */
124 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
125 if ( !wq )
126 return -ENOMEM;
127
128 wq->name = kmalloc(name->len,GFP_KERNEL);
129 if ( !wq->name ) {
130 kfree(wq);
131 return -ENOMEM;
132 }
133 wq->wait_queue_token = autofs_next_wait_queue++;
134 init_waitqueue_head(&wq->queue);
135 wq->hash = name->hash;
136 wq->len = name->len;
137 wq->status = -EINTR; /* Status return if interrupted */
138 memcpy(wq->name, name->name, name->len);
139 wq->next = sbi->queues;
140 sbi->queues = wq;
141
142 /* autofs_notify_daemon() may block */
143 wq->wait_ctr = 2;
144 autofs_notify_daemon(sbi,wq);
145 } else
146 wq->wait_ctr++;
147
148 /* wq->name is NULL if and only if the lock is already released */
149
150 if ( sbi->catatonic ) {
151 /* We might have slept, so check again for catatonic mode */
152 wq->status = -ENOENT;
153 if ( wq->name ) {
154 kfree(wq->name);
155 wq->name = NULL;
156 }
157 }
158
159 if ( wq->name ) {
160 /* Block all but "shutdown" signals while waiting */
161 sigset_t sigmask;
162
163 siginitsetinv(&sigmask, SHUTDOWN_SIGS);
164 sigprocmask(SIG_BLOCK, &sigmask, &sigmask);
165
166 interruptible_sleep_on(&wq->queue);
167
168 sigprocmask(SIG_SETMASK, &sigmask, NULL);
169 } else {
170 DPRINTK(("autofs_wait: skipped sleeping\n"));
171 }
172
173 status = wq->status;
174
175 if ( ! --wq->wait_ctr ) /* Are we the last process to need status? */
176 kfree(wq);
177
178 return status;
179 }
180
181
182 int autofs_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
183 {
184 struct autofs_wait_queue *wq, **wql;
185
186 for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
187 if ( wq->wait_queue_token == wait_queue_token )
188 break;
189 }
190 if ( !wq )
191 return -EINVAL;
192
193 *wql = wq->next; /* Unlink from chain */
194 kfree(wq->name);
195 wq->name = NULL; /* Do not wait on this queue */
196
197 wq->status = status;
198
199 if ( ! --wq->wait_ctr ) /* Is anyone still waiting for this guy? */
200 kfree(wq);
201 else
202 wake_up(&wq->queue);
203
204 return 0;
205 }
206
207
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