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 */
  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(&current->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(&current->sighand->siglock, flags);
  74                 sigdelset(&current->pending.signal, SIGPIPE);
  75                 recalc_sigpending();
  76                 spin_unlock_irqrestore(&current->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