Merge branch 'master'
[linux-2.6] / 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/slab.h>
14 #include <linux/smp_lock.h>
15 #include <linux/fs.h>
16 #include <linux/pipe_fs_i.h>
17
18 static void wait_for_partner(struct inode* inode, unsigned int* cnt)
19 {
20         int cur = *cnt; 
21         while(cur == *cnt) {
22                 pipe_wait(inode);
23                 if(signal_pending(current))
24                         break;
25         }
26 }
27
28 static void wake_up_partner(struct inode* inode)
29 {
30         wake_up_interruptible(PIPE_WAIT(*inode));
31 }
32
33 static int fifo_open(struct inode *inode, struct file *filp)
34 {
35         int ret;
36
37         mutex_lock(PIPE_MUTEX(*inode));
38         if (!inode->i_pipe) {
39                 ret = -ENOMEM;
40                 if(!pipe_new(inode))
41                         goto err_nocleanup;
42         }
43         filp->f_version = 0;
44
45         /* We can only do regular read/write on fifos */
46         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
47
48         switch (filp->f_mode) {
49         case 1:
50         /*
51          *  O_RDONLY
52          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
53          *  opened, even when there is no process writing the FIFO.
54          */
55                 filp->f_op = &read_fifo_fops;
56                 PIPE_RCOUNTER(*inode)++;
57                 if (PIPE_READERS(*inode)++ == 0)
58                         wake_up_partner(inode);
59
60                 if (!PIPE_WRITERS(*inode)) {
61                         if ((filp->f_flags & O_NONBLOCK)) {
62                                 /* suppress POLLHUP until we have
63                                  * seen a writer */
64                                 filp->f_version = PIPE_WCOUNTER(*inode);
65                         } else 
66                         {
67                                 wait_for_partner(inode, &PIPE_WCOUNTER(*inode));
68                                 if(signal_pending(current))
69                                         goto err_rd;
70                         }
71                 }
72                 break;
73         
74         case 2:
75         /*
76          *  O_WRONLY
77          *  POSIX.1 says that O_NONBLOCK means return -1 with
78          *  errno=ENXIO when there is no process reading the FIFO.
79          */
80                 ret = -ENXIO;
81                 if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode))
82                         goto err;
83
84                 filp->f_op = &write_fifo_fops;
85                 PIPE_WCOUNTER(*inode)++;
86                 if (!PIPE_WRITERS(*inode)++)
87                         wake_up_partner(inode);
88
89                 if (!PIPE_READERS(*inode)) {
90                         wait_for_partner(inode, &PIPE_RCOUNTER(*inode));
91                         if (signal_pending(current))
92                                 goto err_wr;
93                 }
94                 break;
95         
96         case 3:
97         /*
98          *  O_RDWR
99          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
100          *  This implementation will NEVER block on a O_RDWR open, since
101          *  the process can at least talk to itself.
102          */
103                 filp->f_op = &rdwr_fifo_fops;
104
105                 PIPE_READERS(*inode)++;
106                 PIPE_WRITERS(*inode)++;
107                 PIPE_RCOUNTER(*inode)++;
108                 PIPE_WCOUNTER(*inode)++;
109                 if (PIPE_READERS(*inode) == 1 || PIPE_WRITERS(*inode) == 1)
110                         wake_up_partner(inode);
111                 break;
112
113         default:
114                 ret = -EINVAL;
115                 goto err;
116         }
117
118         /* Ok! */
119         mutex_unlock(PIPE_MUTEX(*inode));
120         return 0;
121
122 err_rd:
123         if (!--PIPE_READERS(*inode))
124                 wake_up_interruptible(PIPE_WAIT(*inode));
125         ret = -ERESTARTSYS;
126         goto err;
127
128 err_wr:
129         if (!--PIPE_WRITERS(*inode))
130                 wake_up_interruptible(PIPE_WAIT(*inode));
131         ret = -ERESTARTSYS;
132         goto err;
133
134 err:
135         if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode))
136                 free_pipe_info(inode);
137
138 err_nocleanup:
139         mutex_unlock(PIPE_MUTEX(*inode));
140         return ret;
141 }
142
143 /*
144  * Dummy default file-operations: the only thing this does
145  * is contain the open that then fills in the correct operations
146  * depending on the access mode of the file...
147  */
148 struct file_operations def_fifo_fops = {
149         .open           = fifo_open,    /* will set read or write pipe_fops */
150 };