fs/autofs4/waitq.c

   1 /* -*- 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/sched.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 autofs4_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 autofs4_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         if (sbi->pipe) {
  44                 fput(sbi->pipe);        /* Close the pipe */
  45                 sbi->pipe = NULL;
  46         }
  47
  48         shrink_dcache_sb(sbi->sb);
  49 }
  50
  51 static int autofs4_write(struct file *file, const void *addr, int bytes)
  52 {
  53         unsigned long sigpipe, flags;
  54         mm_segment_t fs;
  55         const char *data = (const char *)addr;
  56         ssize_t wr = 0;
  57
  58         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  59
  60         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  61
  62         /* Save pointer to user space and point back to kernel space */
  63         fs = get_fs();
  64         set_fs(KERNEL_DS);
  65
  66         while (bytes &&
  67                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  68                 data += wr;
  69                 bytes -= wr;
  70         }
  71
  72         set_fs(fs);
  73
  74         /* Keep the currently executing process from receiving a
  75            SIGPIPE unless it was already supposed to get one */
  76         if (wr == -EPIPE && !sigpipe) {
  77                 spin_lock_irqsave(&current->sigmask_lock, flags);
  78                 sigdelset(&current->pending.signal, SIGPIPE);
  79                 recalc_sigpending(current);
  80                 spin_unlock_irqrestore(&current->sigmask_lock, flags);
  81         }
  82
  83         return (bytes > 0);
  84 }
  85
  86 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  87                                  struct autofs_wait_queue *wq,
  88                                  int type)
  89 {
  90         union autofs_packet_union pkt;
  91         size_t pktsz;
  92
  93         DPRINTK(("autofs_notify: wait id = 0x%08lx, name = %.*s, type=%d\n",
  94                  wq->wait_queue_token, wq->len, wq->name, type));
  95
  96         memset(&pkt,0,sizeof pkt); /* For security reasons */
  97
  98         pkt.hdr.proto_version = sbi->version;
  99         pkt.hdr.type = type;
 100         if (type == autofs_ptype_missing) {
 101                 struct autofs_packet_missing *mp = &pkt.missing;
 102
 103                 pktsz = sizeof(*mp);
 104
 105                 mp->wait_queue_token = wq->wait_queue_token;
 106                 mp->len = wq->len;
 107                 memcpy(mp->name, wq->name, wq->len);
 108                 mp->name[wq->len] = '\0';
 109         } else if (type == autofs_ptype_expire_multi) {
 110                 struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
 111
 112                 pktsz = sizeof(*ep);
 113
 114                 ep->wait_queue_token = wq->wait_queue_token;
 115                 ep->len = wq->len;
 116                 memcpy(ep->name, wq->name, wq->len);
 117                 ep->name[wq->len] = '\0';
 118         } else {
 119                 printk("autofs_notify_daemon: bad type %d!\n", type);
 120                 return;
 121         }
 122
 123         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 124                 autofs4_catatonic_mode(sbi);
 125 }
 126
 127 int autofs4_wait(struct autofs_sb_info *sbi, struct qstr *name,
 128                 enum autofs_notify notify)
 129 {
 130         struct autofs_wait_queue *wq;
 131         int status;
 132
 133         /* In catatonic mode, we don't wait for nobody */
 134         if ( sbi->catatonic )
 135                 return -ENOENT;
 136
 137         /* We shouldn't be able to get here, but just in case */
 138         if ( name->len > NAME_MAX )
 139                 return -ENOENT;
 140
 141         for ( wq = sbi->queues ; wq ; wq = wq->next ) {
 142                 if ( wq->hash == name->hash &&
 143                      wq->len == name->len &&
 144                      wq->name && !memcmp(wq->name,name->name,name->len) )
 145                         break;
 146         }
 147
 148         if ( !wq ) {
 149                 /* Create a new wait queue */
 150                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 151                 if ( !wq )
 152                         return -ENOMEM;
 153
 154                 wq->name = kmalloc(name->len,GFP_KERNEL);
 155                 if ( !wq->name ) {
 156                         kfree(wq);
 157                         return -ENOMEM;
 158                 }
 159                 wq->wait_queue_token = autofs4_next_wait_queue;
 160                 if (++autofs4_next_wait_queue == 0)
 161                         autofs4_next_wait_queue = 1;
 162                 init_waitqueue_head(&wq->queue);
 163                 wq->hash = name->hash;
 164                 wq->len = name->len;
 165                 wq->status = -EINTR; /* Status return if interrupted */
 166                 memcpy(wq->name, name->name, name->len);
 167                 wq->next = sbi->queues;
 168                 sbi->queues = wq;
 169
 170                 DPRINTK(("autofs_wait: new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 171                          wq->wait_queue_token, wq->len, wq->name, notify));
 172                 /* autofs4_notify_daemon() may block */
 173                 wq->wait_ctr = 2;
 174                 if (notify != NFY_NONE) {
 175                         autofs4_notify_daemon(sbi,wq,
 176                                               notify == NFY_MOUNT ? autofs_ptype_missing :
 177                                                                     autofs_ptype_expire_multi);
 178                 }
 179         } else {
 180                 wq->wait_ctr++;
 181                 DPRINTK(("autofs_wait: existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 182                          wq->wait_queue_token, wq->len, wq->name, notify));
 183         }
 184
 185         /* wq->name is NULL if and only if the lock is already released */
 186
 187         if ( sbi->catatonic ) {
 188                 /* We might have slept, so check again for catatonic mode */
 189                 wq->status = -ENOENT;
 190                 if ( wq->name ) {
 191                         kfree(wq->name);
 192                         wq->name = NULL;
 193                 }
 194         }
 195
 196         if ( wq->name ) {
 197                 /* Block all but "shutdown" signals while waiting */
 198                 sigset_t oldset;
 199                 unsigned long irqflags;
 200
 201                 spin_lock_irqsave(&current->sigmask_lock, irqflags);
 202                 oldset = current->blocked;
 203                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 204                 recalc_sigpending(current);
 205                 spin_unlock_irqrestore(&current->sigmask_lock, irqflags);
 206
 207                 interruptible_sleep_on(&wq->queue);
 208
 209                 spin_lock_irqsave(&current->sigmask_lock, irqflags);
 210                 current->blocked = oldset;
 211                 recalc_sigpending(current);
 212                 spin_unlock_irqrestore(&current->sigmask_lock, irqflags);
 213         } else {
 214                 DPRINTK(("autofs_wait: skipped sleeping\n"));
 215         }
 216
 217         status = wq->status;
 218
 219         if (--wq->wait_ctr == 0)        /* Are we the last process to need status? */
 220                 kfree(wq);
 221
 222         return status;
 223 }
 224
 225
 226 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 227 {
 228         struct autofs_wait_queue *wq, **wql;
 229
 230         for ( wql = &sbi->queues ; (wq = *wql) ; wql = &wq->next ) {
 231                 if ( wq->wait_queue_token == wait_queue_token )
 232                         break;
 233         }
 234         if ( !wq )
 235                 return -EINVAL;
 236
 237         *wql = wq->next;        /* Unlink from chain */
 238         kfree(wq->name);
 239         wq->name = NULL;        /* Do not wait on this queue */
 240
 241         wq->status = status;
 242
 243         if (--wq->wait_ctr == 0)        /* Is anyone still waiting for this guy? */
 244                 kfree(wq);
 245         else
 246                 wake_up(&wq->queue);
 247
 248         return 0;
 249 }
 250