[PATCH] introduce fmode_t, do annotations
[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/slab.h>
14 #include <linux/fs.h>
15 #include <linux/sched.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
22         while (cur == *cnt) {
23                 pipe_wait(inode->i_pipe);
24                 if (signal_pending(current))
25                         break;
26         }
27 }
28
29 static void wake_up_partner(struct inode* inode)
30 {
31         wake_up_interruptible(&inode->i_pipe->wait);
32 }
33
34 static int fifo_open(struct inode *inode, struct file *filp)
35 {
36         struct pipe_inode_info *pipe;
37         int ret;
38
39         mutex_lock(&inode->i_mutex);
40         pipe = inode->i_pipe;
41         if (!pipe) {
42                 ret = -ENOMEM;
43                 pipe = alloc_pipe_info(inode);
44                 if (!pipe)
45                         goto err_nocleanup;
46                 inode->i_pipe = pipe;
47         }
48         filp->f_version = 0;
49
50         /* We can only do regular read/write on fifos */
51         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
52
53         switch (filp->f_mode) {
54         case FMODE_READ:
55         /*
56          *  O_RDONLY
57          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
58          *  opened, even when there is no process writing the FIFO.
59          */
60                 filp->f_op = &read_pipefifo_fops;
61                 pipe->r_counter++;
62                 if (pipe->readers++ == 0)
63                         wake_up_partner(inode);
64
65                 if (!pipe->writers) {
66                         if ((filp->f_flags & O_NONBLOCK)) {
67                                 /* suppress POLLHUP until we have
68                                  * seen a writer */
69                                 filp->f_version = pipe->w_counter;
70                         } else 
71                         {
72                                 wait_for_partner(inode, &pipe->w_counter);
73                                 if(signal_pending(current))
74                                         goto err_rd;
75                         }
76                 }
77                 break;
78         
79         case FMODE_WRITE:
80         /*
81          *  O_WRONLY
82          *  POSIX.1 says that O_NONBLOCK means return -1 with
83          *  errno=ENXIO when there is no process reading the FIFO.
84          */
85                 ret = -ENXIO;
86                 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
87                         goto err;
88
89                 filp->f_op = &write_pipefifo_fops;
90                 pipe->w_counter++;
91                 if (!pipe->writers++)
92                         wake_up_partner(inode);
93
94                 if (!pipe->readers) {
95                         wait_for_partner(inode, &pipe->r_counter);
96                         if (signal_pending(current))
97                                 goto err_wr;
98                 }
99                 break;
100         
101         case FMODE_READ | FMODE_WRITE:
102         /*
103          *  O_RDWR
104          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
105          *  This implementation will NEVER block on a O_RDWR open, since
106          *  the process can at least talk to itself.
107          */
108                 filp->f_op = &rdwr_pipefifo_fops;
109
110                 pipe->readers++;
111                 pipe->writers++;
112                 pipe->r_counter++;
113                 pipe->w_counter++;
114                 if (pipe->readers == 1 || pipe->writers == 1)
115                         wake_up_partner(inode);
116                 break;
117
118         default:
119                 ret = -EINVAL;
120                 goto err;
121         }
122
123         /* Ok! */
124         mutex_unlock(&inode->i_mutex);
125         return 0;
126
127 err_rd:
128         if (!--pipe->readers)
129                 wake_up_interruptible(&pipe->wait);
130         ret = -ERESTARTSYS;
131         goto err;
132
133 err_wr:
134         if (!--pipe->writers)
135                 wake_up_interruptible(&pipe->wait);
136         ret = -ERESTARTSYS;
137         goto err;
138
139 err:
140         if (!pipe->readers && !pipe->writers)
141                 free_pipe_info(inode);
142
143 err_nocleanup:
144         mutex_unlock(&inode->i_mutex);
145         return ret;
146 }
147
148 /*
149  * Dummy default file-operations: the only thing this does
150  * is contain the open that then fills in the correct operations
151  * depending on the access mode of the file...
152  */
153 const struct file_operations def_fifo_fops = {
154         .open           = fifo_open,    /* will set read_ or write_pipefifo_fops */
155 };