fs/autofs/waitq.c

   1 /* -*- linux-c -*- --------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/waitq.c
   4  *
   5  *  Copyright 1997 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/malloc.h>
  14 #include <linux/sched.h>
  15 #include <linux/signal.h>
  16 #include <linux/file.h>
  17 #include "autofs_i.h"
  18
  19 #ifdef DEBUG_WAITLIST
  20 #ifndef i386
  21 #error Only i386 implemented
  22 #endif
  23
  24 static inline int sane_pointer(void *p)
  25 {
  26         return (p == NULL) || ((unsigned) p > 0xc0000000);
  27 }
  28
  29 void autofs_check_waitlist_integrity(struct autofs_sb_info *sbi, char *op)
  30 {
  31         struct autofs_wait_queue **wqp, *wq;
  32
  33         if ( sbi->magic != AUTOFS_SBI_MAGIC ) {
  34                 printk("autofs: CHECK_WAITLIST with bogus sbi pointer: %p\n",
  35                        sbi);
  36                 return;
  37         }
  38
  39         wqp = &(sbi->queues);
  40         while ( (wq = *wqp) ) {
  41                 if ( !sane_pointer(wq) ) {
  42                         printk("autofs(%s): wait queue pointer corrupt: ", op);
  43                         wqp = &(sbi->queues);
  44                         do {
  45                                 wq = *wqp;
  46                                 printk(" %p", wq);
  47                                 wqp = &(wq->next);
  48                         } while ( sane_pointer(*wqp) );
  49                         printk("\n");
  50                         *wqp = NULL;
  51                         break;
  52                 } else {
  53                         wqp = &(wq->next);
  54                 }
  55         }
  56 }
  57 #endif
  58
  59 /* We make this a static variable rather than a part of the superblock; it
  60    is better if we don't reassign numbers easily even across filesystems */
  61 static int autofs_next_wait_queue = 1;
  62
  63 void autofs_catatonic_mode(struct autofs_sb_info *sbi)
  64 {
  65         struct autofs_wait_queue *wq, *nwq;
  66
  67         DPRINTK(("autofs: entering catatonic mode\n"));
  68
  69         sbi->catatonic = 1;
  70         wq = sbi->queues;
  71         sbi->queues = NULL;     /* Erase all wait queues */
  72         while ( wq ) {
  73                 nwq = wq->next;
  74                 wq->status = -ENOENT; /* Magic is gone - report failure */
  75                 kfree(wq->name);
  76                 wq->name = NULL;
  77                 wake_up(&wq->queue);
  78                 wq = nwq;
  79         }
  80         fput(sbi->pipe, sbi->pipe->f_inode);    /* Close the pipe */
  81 }
  82
  83 static int autofs_write(struct file *file, const void *addr, int bytes)
  84 {
  85         unsigned short fs;
  86         unsigned long old_signal;
  87         const char *data = (const char *)addr;
  88         int written = 0;
  89
  90         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  91
  92         /* Save pointer to user space and point back to kernel space */
  93         fs = get_fs();
  94         set_fs(KERNEL_DS);
  95
  96         old_signal = current->signal;
  97
  98         while ( bytes && (written = file->f_op->write(file->f_inode,file,data,bytes)) > 0 ) {
  99                 data += written;
 100                 bytes -= written;
 101         }
 102
 103         if ( written == -EPIPE && !(old_signal & (1 << (SIGPIPE-1))) ) {
 104                 /* Keep the currently executing process from receiving a
 105                    SIGPIPE unless it was already supposed to get one */
 106                 current->signal &= ~(1 << (SIGPIPE-1));
 107         }
 108         set_fs(fs);
 109
 110         return (bytes > 0);
 111 }
 112
 113 static void autofs_notify_daemon(struct autofs_sb_info *sbi, struct autofs_wait_queue *wq)
 114 {
 115         struct autofs_packet_missing pkt;
 116
 117         DPRINTK(("autofs_wait: wait id = 0x%08lx, name = ", wq->wait_queue_token));
 118         autofs_say(wq->name,wq->len);
 119
 120         memset(&pkt,0,sizeof pkt); /* For security reasons */
 121
 122         pkt.hdr.proto_version = AUTOFS_PROTO_VERSION;
 123         pkt.hdr.type = autofs_ptype_missing;
 124         pkt.wait_queue_token = wq->wait_queue_token;
 125         pkt.len = wq->len;
 126         memcpy(pkt.name, wq->name, pkt.len);
 127         pkt.name[pkt.len] = '\0';
 128
 129         if ( autofs_write(sbi->pipe,&pkt,sizeof(struct autofs_packet_missing)) )
 130                 autofs_catatonic_mode(sbi);
 131 }
 132
 133 int autofs_wait(struct autofs_sb_info *sbi, autofs_hash_t hash, const char *name, int len)
 134 {
 135         struct autofs_wait_queue *wq;
 136         int status;
 137
 138         CHECK_WAITLIST(sbi,"wait");
 139
 140         for ( wq = sbi->queues ; wq ; wq = wq->next ) {
 141                 if ( wq->hash == hash &&
 142                      wq->len == len &&
 143                      wq->name && !memcmp(wq->name,name,len) )
 144                         break;
 145         }
 146
 147         if ( !wq ) {
 148                 /* Create a new wait queue */
 149                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 150                 if ( !wq )
 151                         return -ENOMEM;
 152
 153                 wq->name = kmalloc(len,GFP_KERNEL);
 154                 if ( !wq->name ) {
 155                         kfree(wq);
 156                         return -ENOMEM;
 157                 }
 158                 wq->wait_queue_token = autofs_next_wait_queue++;
 159                 init_waitqueue(&wq->queue);
 160                 wq->hash = hash;
 161                 wq->len = len;
 162                 wq->status = -EINTR; /* Status return if interrupted */
 163                 memcpy(wq->name, name, len);
 164                 wq->next = sbi->queues;
 165                 sbi->queues = wq;
 166
 167                 /* autofs_notify_daemon() may block */
 168                 wq->wait_ctr = 1;
 169                 autofs_notify_daemon(sbi,wq);
 170         } else
 171                 wq->wait_ctr++;
 172
 173         if ( wq->name ) {
 174                 /* wq->name is NULL if and only if the lock is released */
 175                 interruptible_sleep_on(&wq->queue);
 176         } else {
 177                 DPRINTK(("autofs_wait: skipped sleeping\n"));
 178         }
 179
 180         status = wq->status;
 181
 182         if ( ! --wq->wait_ctr ) /* Are we the last process to need status? */
 183                 kfree(wq);
 184
 185         return status;
 186 }
 187
 188
 189 int autofs_wait_release(struct autofs_sb_info *sbi, unsigned long wait_queue_token, int status)
 190 {
 191         struct autofs_wait_queue *wq, **wql;
 192
 193         CHECK_WAITLIST(sbi,"release");
 194
 195         for ( wql = &sbi->queues ; (wq = *wql) ; wql = &wq->next ) {
 196                 if ( wq->wait_queue_token == wait_queue_token )
 197                         break;
 198         }
 199         if ( !wq )
 200                 return -EINVAL;
 201
 202         *wql = wq->next;        /* Unlink from chain */
 203         kfree(wq->name);
 204         wq->name = NULL;        /* Do not wait on this queue */
 205
 206         wq->status = status;
 207
 208         wake_up(&wq->queue);
 209
 210         return 0;
 211 }
 212