9p: Make use of iounit for read/write
[linux-2.6.git] / fs / fifo.c
1 /*
2  *  linux/fs/fifo.c
3  *
4  *  written by Paul H. Hargrove
5  *
6  *  Fixes:
7  *      10-06-1999, AV: fixed OOM handling in fifo_open(), moved
8  *                      initialization there, switched to external
9  *                      allocation of pipe_inode_info.
10  */
11
12 #include <linux/mm.h>
13 #include <linux/fs.h>
14 #include <linux/sched.h>
15 #include <linux/pipe_fs_i.h>
16
17 static void wait_for_partner(struct inode* inode, unsigned int *cnt)
18 {
19         int cur = *cnt; 
20
21         while (cur == *cnt) {
22                 pipe_wait(inode->i_pipe);
23                 if (signal_pending(current))
24                         break;
25         }
26 }
27
28 static void wake_up_partner(struct inode* inode)
29 {
30         wake_up_interruptible(&inode->i_pipe->wait);
31 }
32
33 static int fifo_open(struct inode *inode, struct file *filp)
34 {
35         struct pipe_inode_info *pipe;
36         int ret;
37
38         mutex_lock(&inode->i_mutex);
39         pipe = inode->i_pipe;
40         if (!pipe) {
41                 ret = -ENOMEM;
42                 pipe = alloc_pipe_info(inode);
43                 if (!pipe)
44                         goto err_nocleanup;
45                 inode->i_pipe = pipe;
46         }
47         filp->f_version = 0;
48
49         /* We can only do regular read/write on fifos */
50         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
51
52         switch (filp->f_mode) {
53         case FMODE_READ:
54         /*
55          *  O_RDONLY
56          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
57          *  opened, even when there is no process writing the FIFO.
58          */
59                 filp->f_op = &read_pipefifo_fops;
60                 pipe->r_counter++;
61                 if (pipe->readers++ == 0)
62                         wake_up_partner(inode);
63
64                 if (!pipe->writers) {
65                         if ((filp->f_flags & O_NONBLOCK)) {
66                                 /* suppress POLLHUP until we have
67                                  * seen a writer */
68                                 filp->f_version = pipe->w_counter;
69                         } else 
70                         {
71                                 wait_for_partner(inode, &pipe->w_counter);
72                                 if(signal_pending(current))
73                                         goto err_rd;
74                         }
75                 }
76                 break;
77         
78         case FMODE_WRITE:
79         /*
80          *  O_WRONLY
81          *  POSIX.1 says that O_NONBLOCK means return -1 with
82          *  errno=ENXIO when there is no process reading the FIFO.
83          */
84                 ret = -ENXIO;
85                 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
86                         goto err;
87
88                 filp->f_op = &write_pipefifo_fops;
89                 pipe->w_counter++;
90                 if (!pipe->writers++)
91                         wake_up_partner(inode);
92
93                 if (!pipe->readers) {
94                         wait_for_partner(inode, &pipe->r_counter);
95                         if (signal_pending(current))
96                                 goto err_wr;
97                 }
98                 break;
99         
100         case FMODE_READ | FMODE_WRITE:
101         /*
102          *  O_RDWR
103          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
104          *  This implementation will NEVER block on a O_RDWR open, since
105          *  the process can at least talk to itself.
106          */
107                 filp->f_op = &rdwr_pipefifo_fops;
108
109                 pipe->readers++;
110                 pipe->writers++;
111                 pipe->r_counter++;
112                 pipe->w_counter++;
113                 if (pipe->readers == 1 || pipe->writers == 1)
114                         wake_up_partner(inode);
115                 break;
116
117         default:
118                 ret = -EINVAL;
119                 goto err;
120         }
121
122         /* Ok! */
123         mutex_unlock(&inode->i_mutex);
124         return 0;
125
126 err_rd:
127         if (!--pipe->readers)
128                 wake_up_interruptible(&pipe->wait);
129         ret = -ERESTARTSYS;
130         goto err;
131
132 err_wr:
133         if (!--pipe->writers)
134                 wake_up_interruptible(&pipe->wait);
135         ret = -ERESTARTSYS;
136         goto err;
137
138 err:
139         if (!pipe->readers && !pipe->writers)
140                 free_pipe_info(inode);
141
142 err_nocleanup:
143         mutex_unlock(&inode->i_mutex);
144         return ret;
145 }
146
147 /*
148  * Dummy default file-operations: the only thing this does
149  * is contain the open that then fills in the correct operations
150  * depending on the access mode of the file...
151  */
152 const struct file_operations def_fifo_fops = {
153         .open           = fifo_open,    /* will set read_ or write_pipefifo_fops */
154 };