Root/fs/autofs/waitq.c

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) != NULL; 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
206

Archive Download this file



interactive