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 */
21static 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
26void 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	sbi->pipe = NULL;
45	autofs_hash_dputall(&sbi->dirhash); /* Remove all dentry pointers */
46}
47
48static int autofs_write(struct file *file, const void *addr, int bytes)
49{
50	unsigned long sigpipe, flags;
51	mm_segment_t fs;
52	const char *data = (const char *)addr;
53	ssize_t wr = 0;
54
55	/** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
56
57	sigpipe = sigismember(&current->pending.signal, SIGPIPE);
58
59	/* Save pointer to user space and point back to kernel space */
60	fs = get_fs();
61	set_fs(KERNEL_DS);
62
63	while (bytes &&
64	       (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
65		data += wr;
66		bytes -= wr;
67	}
68
69	set_fs(fs);
70
71	/* Keep the currently executing process from receiving a
72	   SIGPIPE unless it was already supposed to get one */
73	if (wr == -EPIPE && !sigpipe) {
74		spin_lock_irqsave(&current->sighand->siglock, flags);
75		sigdelset(&current->pending.signal, SIGPIPE);
76		recalc_sigpending();
77		spin_unlock_irqrestore(&current->sighand->siglock, flags);
78	}
79
80	return (bytes > 0);
81}
82
83static void autofs_notify_daemon(struct autofs_sb_info *sbi, struct autofs_wait_queue *wq)
84{
85	struct autofs_packet_missing pkt;
86
87	DPRINTK(("autofs_wait: wait id = 0x%08lx, name = ", wq->wait_queue_token));
88	autofs_say(wq->name,wq->len);
89
90	memset(&pkt,0,sizeof pkt); /* For security reasons */
91
92	pkt.hdr.proto_version = AUTOFS_PROTO_VERSION;
93	pkt.hdr.type = autofs_ptype_missing;
94	pkt.wait_queue_token = wq->wait_queue_token;
95	pkt.len = wq->len;
96        memcpy(pkt.name, wq->name, pkt.len);
97	pkt.name[pkt.len] = '\0';
98
99	if ( autofs_write(sbi->pipe,&pkt,sizeof(struct autofs_packet_missing)) )
100		autofs_catatonic_mode(sbi);
101}
102
103int autofs_wait(struct autofs_sb_info *sbi, struct qstr *name)
104{
105	struct autofs_wait_queue *wq;
106	int status;
107
108	/* In catatonic mode, we don't wait for nobody */
109	if ( sbi->catatonic )
110		return -ENOENT;
111
112	/* We shouldn't be able to get here, but just in case */
113	if ( name->len > NAME_MAX )
114		return -ENOENT;
115
116	for ( wq = sbi->queues ; wq ; wq = wq->next ) {
117		if ( wq->hash == name->hash &&
118		     wq->len == name->len &&
119		     wq->name && !memcmp(wq->name,name->name,name->len) )
120			break;
121	}
122
123	if ( !wq ) {
124		/* Create a new wait queue */
125		wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
126		if ( !wq )
127			return -ENOMEM;
128
129		wq->name = kmalloc(name->len,GFP_KERNEL);
130		if ( !wq->name ) {
131			kfree(wq);
132			return -ENOMEM;
133		}
134		wq->wait_queue_token = autofs_next_wait_queue++;
135		init_waitqueue_head(&wq->queue);
136		wq->hash = name->hash;
137		wq->len = name->len;
138		wq->status = -EINTR; /* Status return if interrupted */
139		memcpy(wq->name, name->name, name->len);
140		wq->next = sbi->queues;
141		sbi->queues = wq;
142
143		/* autofs_notify_daemon() may block */
144		wq->wait_ctr = 2;
145		autofs_notify_daemon(sbi,wq);
146	} else
147		wq->wait_ctr++;
148
149	/* wq->name is NULL if and only if the lock is already released */
150
151	if ( sbi->catatonic ) {
152		/* We might have slept, so check again for catatonic mode */
153		wq->status = -ENOENT;
154		kfree(wq->name);
155		wq->name = NULL;
156	}
157
158	if ( wq->name ) {
159		/* Block all but "shutdown" signals while waiting */
160		sigset_t sigmask;
161
162		siginitsetinv(&sigmask, SHUTDOWN_SIGS);
163		sigprocmask(SIG_BLOCK, &sigmask, &sigmask);
164
165		interruptible_sleep_on(&wq->queue);
166
167		sigprocmask(SIG_SETMASK, &sigmask, NULL);
168	} else {
169		DPRINTK(("autofs_wait: skipped sleeping\n"));
170	}
171
172	status = wq->status;
173
174	if ( ! --wq->wait_ctr )	/* Are we the last process to need status? */
175		kfree(wq);
176
177	return status;
178}
179
180
181int autofs_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
182{
183	struct autofs_wait_queue *wq, **wql;
184
185	for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
186		if ( wq->wait_queue_token == wait_queue_token )
187			break;
188	}
189	if ( !wq )
190		return -EINVAL;
191
192	*wql = wq->next;	/* Unlink from chain */
193	kfree(wq->name);
194	wq->name = NULL;	/* Do not wait on this queue */
195
196	wq->status = status;
197
198	if ( ! --wq->wait_ctr )	/* Is anyone still waiting for this guy? */
199		kfree(wq);
200	else
201		wake_up(&wq->queue);
202
203	return 0;
204}
205