fs/fifo.c

/* */
This source file includes following definitions.
fifo_open
init_fifo
   1 /*
   2  *  linux/fs/fifo.c
   3  *
   4  *  written by Paul H. Hargrove
   5  */
   6 
   7 #include <linux/sched.h>
   8 #include <linux/kernel.h>
   9 #include <linux/errno.h>
  10 #include <linux/fcntl.h>
  11 #include <linux/mm.h>
  12 
  13 static int fifo_open(struct inode * inode,struct file * filp)
     /*  */
  14 {
  15         int retval = 0;
  16         unsigned long page;
  17 
  18         switch( filp->f_mode ) {
  19 
  20         case 1:
  21         /*
  22          *  O_RDONLY
  23          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
  24          *  opened, even when there is no process writing the FIFO.
  25          */
  26                 filp->f_op = &connecting_fifo_fops;
  27                 if (!PIPE_READERS(*inode)++)
  28                         wake_up_interruptible(&PIPE_WAIT(*inode));
  29                 if (!(filp->f_flags & O_NONBLOCK) && !PIPE_WRITERS(*inode)) {
  30                         PIPE_RD_OPENERS(*inode)++;
  31                         while (!PIPE_WRITERS(*inode)) {
  32                                 if (current->signal & ~current->blocked) {
  33                                         retval = -ERESTARTSYS;
  34                                         break;
  35                                 }
  36                                 interruptible_sleep_on(&PIPE_WAIT(*inode));
  37                         }
  38                         if (!--PIPE_RD_OPENERS(*inode))
  39                                 wake_up_interruptible(&PIPE_WAIT(*inode));
  40                 }
  41                 while (PIPE_WR_OPENERS(*inode))
  42                         interruptible_sleep_on(&PIPE_WAIT(*inode));
  43                 if (PIPE_WRITERS(*inode))
  44                         filp->f_op = &read_fifo_fops;
  45                 if (retval && !--PIPE_READERS(*inode))
  46                         wake_up_interruptible(&PIPE_WAIT(*inode));
  47                 break;
  48         
  49         case 2:
  50         /*
  51          *  O_WRONLY
  52          *  POSIX.1 says that O_NONBLOCK means return -1 with
  53          *  errno=ENXIO when there is no process reading the FIFO.
  54          */
  55                 if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode)) {
  56                         retval = -ENXIO;
  57                         break;
  58                 }
  59                 filp->f_op = &write_fifo_fops;
  60                 if (!PIPE_WRITERS(*inode)++)
  61                         wake_up_interruptible(&PIPE_WAIT(*inode));
  62                 if (!PIPE_READERS(*inode)) {
  63                         PIPE_WR_OPENERS(*inode)++;
  64                         while (!PIPE_READERS(*inode)) {
  65                                 if (current->signal & ~current->blocked) {
  66                                         retval = -ERESTARTSYS;
  67                                         break;
  68                                 }
  69                                 interruptible_sleep_on(&PIPE_WAIT(*inode));
  70                         }
  71                         if (!--PIPE_WR_OPENERS(*inode))
  72                                 wake_up_interruptible(&PIPE_WAIT(*inode));
  73                 }
  74                 while (PIPE_RD_OPENERS(*inode))
  75                         interruptible_sleep_on(&PIPE_WAIT(*inode));
  76                 if (retval && !--PIPE_WRITERS(*inode))
  77                         wake_up_interruptible(&PIPE_WAIT(*inode));
  78                 break;
  79         
  80         case 3:
  81         /*
  82          *  O_RDWR
  83          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
  84          *  This implementation will NEVER block on a O_RDWR open, since
  85          *  the process can at least talk to itself.
  86          */
  87                 filp->f_op = &rdwr_fifo_fops;
  88                 if (!PIPE_READERS(*inode)++)
  89                         wake_up_interruptible(&PIPE_WAIT(*inode));
  90                 while (PIPE_WR_OPENERS(*inode))
  91                         interruptible_sleep_on(&PIPE_WAIT(*inode));
  92                 if (!PIPE_WRITERS(*inode)++)
  93                         wake_up_interruptible(&PIPE_WAIT(*inode));
  94                 while (PIPE_RD_OPENERS(*inode))
  95                         interruptible_sleep_on(&PIPE_WAIT(*inode));
  96                 break;
  97 
  98         default:
  99                 retval = -EINVAL;
 100         }
 101         if (retval || PIPE_BASE(*inode))
 102                 return retval;
 103         page = __get_free_page(GFP_KERNEL);
 104         if (PIPE_BASE(*inode)) {
 105                 free_page(page);
 106                 return 0;
 107         }
 108         if (!page)
 109                 return -ENOMEM;
 110         PIPE_LOCK(*inode) = 0;
 111         PIPE_START(*inode) = PIPE_LEN(*inode) = 0;
 112         PIPE_BASE(*inode) = (char *) page;
 113         return 0;
 114 }
 115 
 116 /*
 117  * Dummy default file-operations: the only thing this does
 118  * is contain the open that then fills in the correct operations
 119  * depending on the access mode of the file...
 120  */
 121 static struct file_operations def_fifo_fops = {
 122         NULL,
 123         NULL,
 124         NULL,
 125         NULL,
 126         NULL,
 127         NULL,
 128         NULL,
 129         fifo_open,              /* will set read or write pipe_fops */
 130         NULL,
 131         NULL
 132 };
 133 
 134 static struct inode_operations fifo_inode_operations = {
 135         &def_fifo_fops,         /* default file operations */
 136         NULL,                   /* create */
 137         NULL,                   /* lookup */
 138         NULL,                   /* link */
 139         NULL,                   /* unlink */
 140         NULL,                   /* symlink */
 141         NULL,                   /* mkdir */
 142         NULL,                   /* rmdir */
 143         NULL,                   /* mknod */
 144         NULL,                   /* rename */
 145         NULL,                   /* readlink */
 146         NULL,                   /* follow_link */
 147         NULL,                   /* bmap */
 148         NULL,                   /* truncate */
 149         NULL                    /* permission */
 150 };
 151 
 152 void init_fifo(struct inode * inode)
     /*  */
 153 {
 154         inode->i_op = &fifo_inode_operations;
 155         inode->i_pipe = 1;
 156         PIPE_LOCK(*inode) = 0;
 157         PIPE_BASE(*inode) = NULL;
 158         PIPE_START(*inode) = PIPE_LEN(*inode) = 0;
 159         PIPE_RD_OPENERS(*inode) = PIPE_WR_OPENERS(*inode) = 0;
 160         PIPE_WAIT(*inode) = NULL;
 161         PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0;
 162 }
/* */
root/fs/fifo.c

DEFINITIONS
