fs/autofs4/waitq.c

   1 /* -*- c -*- --------------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/waitq.c
   4  *
   5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   6  *  Copyright 2001-2003 Ian Kent <raven@themaw.net>
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * ------------------------------------------------------------------------- */
  13
  14 #include <linux/slab.h>
  15 #include <linux/time.h>
  16 #include <linux/signal.h>
  17 #include <linux/file.h>
  18 #include "autofs_i.h"
  19
  20 /* We make this a static variable rather than a part of the superblock; it
  21    is better if we don't reassign numbers easily even across filesystems */
  22 static autofs_wqt_t autofs4_next_wait_queue = 1;
  23
  24 /* These are the signals we allow interrupting a pending mount */
  25 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  26
  27 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  28 {
  29         struct autofs_wait_queue *wq, *nwq;
  30
  31         DPRINTK("entering catatonic mode");
  32
  33         sbi->catatonic = 1;
  34         wq = sbi->queues;
  35         sbi->queues = NULL;     /* Erase all wait queues */
  36         while ( wq ) {
  37                 nwq = wq->next;
  38                 wq->status = -ENOENT; /* Magic is gone - report failure */
  39                 kfree(wq->name);
  40                 wq->name = NULL;
  41                 wake_up_interruptible(&wq->queue);
  42                 wq = nwq;
  43         }
  44         if (sbi->pipe) {
  45                 fput(sbi->pipe);        /* Close the pipe */
  46                 sbi->pipe = NULL;
  47         }
  48
  49         shrink_dcache_sb(sbi->sb);
  50 }
  51
  52 static int autofs4_write(struct file *file, const void *addr, int bytes)
  53 {
  54         unsigned long sigpipe, flags;
  55         mm_segment_t fs;
  56         const char *data = (const char *)addr;
  57         ssize_t wr = 0;
  58
  59         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  60
  61         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  62
  63         /* Save pointer to user space and point back to kernel space */
  64         fs = get_fs();
  65         set_fs(KERNEL_DS);
  66
  67         while (bytes &&
  68                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  69                 data += wr;
  70                 bytes -= wr;
  71         }
  72
  73         set_fs(fs);
  74
  75         /* Keep the currently executing process from receiving a
  76            SIGPIPE unless it was already supposed to get one */
  77         if (wr == -EPIPE && !sigpipe) {
  78                 spin_lock_irqsave(&current->sighand->siglock, flags);
  79                 sigdelset(&current->pending.signal, SIGPIPE);
  80                 recalc_sigpending();
  81                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  82         }
  83
  84         return (bytes > 0);
  85 }
  86
  87 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  88                                  struct autofs_wait_queue *wq,
  89                                  int type)
  90 {
  91         union autofs_packet_union pkt;
  92         size_t pktsz;
  93
  94         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  95                 wq->wait_queue_token, wq->len, wq->name, type);
  96
  97         memset(&pkt,0,sizeof pkt); /* For security reasons */
  98
  99         pkt.hdr.proto_version = sbi->version;
 100         pkt.hdr.type = type;
 101         if (type == autofs_ptype_missing) {
 102                 struct autofs_packet_missing *mp = &pkt.missing;
 103
 104                 pktsz = sizeof(*mp);
 105
 106                 mp->wait_queue_token = wq->wait_queue_token;
 107                 mp->len = wq->len;
 108                 memcpy(mp->name, wq->name, wq->len);
 109                 mp->name[wq->len] = '\0';
 110         } else if (type == autofs_ptype_expire_multi) {
 111                 struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
 112
 113                 pktsz = sizeof(*ep);
 114
 115                 ep->wait_queue_token = wq->wait_queue_token;
 116                 ep->len = wq->len;
 117                 memcpy(ep->name, wq->name, wq->len);
 118                 ep->name[wq->len] = '\0';
 119         } else {
 120                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 121                 return;
 122         }
 123
 124         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 125                 autofs4_catatonic_mode(sbi);
 126 }
 127
 128 static int autofs4_getpath(struct autofs_sb_info *sbi,
 129                            struct dentry *dentry, char **name)
 130 {
 131         struct dentry *root = sbi->sb->s_root;
 132         struct dentry *tmp;
 133         char *buf = *name;
 134         char *p;
 135         int len = 0;
 136
 137         spin_lock(&dcache_lock);
 138         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 139                 len += tmp->d_name.len + 1;
 140
 141         if (--len > NAME_MAX) {
 142                 spin_unlock(&dcache_lock);
 143                 return 0;
 144         }
 145
 146         *(buf + len) = '\0';
 147         p = buf + len - dentry->d_name.len;
 148         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 149
 150         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 151                 *(--p) = '/';
 152                 p -= tmp->d_name.len;
 153                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 154         }
 155         spin_unlock(&dcache_lock);
 156
 157         return len;
 158 }
 159
 160 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 161                 enum autofs_notify notify)
 162 {
 163         struct autofs_wait_queue *wq;
 164         char *name;
 165         int len, status;
 166
 167         /* In catatonic mode, we don't wait for nobody */
 168         if ( sbi->catatonic )
 169                 return -ENOENT;
 170
 171         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 172         if (!name)
 173                 return -ENOMEM;
 174
 175         len = autofs4_getpath(sbi, dentry, &name);
 176         if (!len) {
 177                 kfree(name);
 178                 return -ENOENT;
 179         }
 180
 181         if (down_interruptible(&sbi->wq_sem)) {
 182                 kfree(name);
 183                 return -EINTR;
 184         }
 185
 186         for (wq = sbi->queues ; wq ; wq = wq->next) {
 187                 if (wq->hash == dentry->d_name.hash &&
 188                     wq->len == len &&
 189                     wq->name && !memcmp(wq->name, name, len))
 190                         break;
 191         }
 192
 193         if ( !wq ) {
 194                 /* Can't wait for an expire if there's no mount */
 195                 if (notify == NFY_NONE && !d_mountpoint(dentry)) {
 196                         kfree(name);
 197                         up(&sbi->wq_sem);
 198                         return -ENOENT;
 199                 }
 200
 201                 /* Create a new wait queue */
 202                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 203                 if ( !wq ) {
 204                         kfree(name);
 205                         up(&sbi->wq_sem);
 206                         return -ENOMEM;
 207                 }
 208
 209                 wq->wait_queue_token = autofs4_next_wait_queue;
 210                 if (++autofs4_next_wait_queue == 0)
 211                         autofs4_next_wait_queue = 1;
 212                 wq->next = sbi->queues;
 213                 sbi->queues = wq;
 214                 init_waitqueue_head(&wq->queue);
 215                 wq->hash = dentry->d_name.hash;
 216                 wq->name = name;
 217                 wq->len = len;
 218                 wq->status = -EINTR; /* Status return if interrupted */
 219                 atomic_set(&wq->wait_ctr, 2);
 220                 atomic_set(&wq->notified, 1);
 221                 up(&sbi->wq_sem);
 222         } else {
 223                 atomic_inc(&wq->wait_ctr);
 224                 up(&sbi->wq_sem);
 225                 kfree(name);
 226                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 227                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 228         }
 229
 230         if (notify != NFY_NONE && atomic_dec_and_test(&wq->notified)) {
 231                 int type = (notify == NFY_MOUNT ?
 232                         autofs_ptype_missing : autofs_ptype_expire_multi);
 233
 234                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 235                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 236
 237                 /* autofs4_notify_daemon() may block */
 238                 autofs4_notify_daemon(sbi, wq, type);
 239         }
 240
 241         /* wq->name is NULL if and only if the lock is already released */
 242
 243         if ( sbi->catatonic ) {
 244                 /* We might have slept, so check again for catatonic mode */
 245                 wq->status = -ENOENT;
 246                 kfree(wq->name);
 247                 wq->name = NULL;
 248         }
 249
 250         if ( wq->name ) {
 251                 /* Block all but "shutdown" signals while waiting */
 252                 sigset_t oldset;
 253                 unsigned long irqflags;
 254
 255                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 256                 oldset = current->blocked;
 257                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 258                 recalc_sigpending();
 259                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 260
 261                 wait_event_interruptible(wq->queue, wq->name == NULL);
 262
 263                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 264                 current->blocked = oldset;
 265                 recalc_sigpending();
 266                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 267         } else {
 268                 DPRINTK("skipped sleeping");
 269         }
 270
 271         status = wq->status;
 272
 273         /* Are we the last process to need status? */
 274         if (atomic_dec_and_test(&wq->wait_ctr))
 275                 kfree(wq);
 276
 277         return status;
 278 }
 279
 280
 281 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 282 {
 283         struct autofs_wait_queue *wq, **wql;
 284
 285         down(&sbi->wq_sem);
 286         for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
 287                 if ( wq->wait_queue_token == wait_queue_token )
 288                         break;
 289         }
 290
 291         if ( !wq ) {
 292                 up(&sbi->wq_sem);
 293                 return -EINVAL;
 294         }
 295
 296         *wql = wq->next;        /* Unlink from chain */
 297         up(&sbi->wq_sem);
 298         kfree(wq->name);
 299         wq->name = NULL;        /* Do not wait on this queue */
 300
 301         wq->status = status;
 302
 303         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 304                 kfree(wq);
 305         else
 306                 wake_up_interruptible(&wq->queue);
 307
 308         return 0;
 309 }
 310