[PATCH] mutex subsystem, semaphore to mutex: VFS, ->i_sem
[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/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         ret = -ERESTARTSYS;
38         if (mutex_lock_interruptible(PIPE_MUTEX(*inode)))
39                 goto err_nolock_nocleanup;
40
41         if (!inode->i_pipe) {
42                 ret = -ENOMEM;
43                 if(!pipe_new(inode))
44                         goto err_nocleanup;
45         }
46         filp->f_version = 0;
47
48         /* We can only do regular read/write on fifos */
49         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
50
51         switch (filp->f_mode) {
52         case 1:
53         /*
54          *  O_RDONLY
55          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
56          *  opened, even when there is no process writing the FIFO.
57          */
58                 filp->f_op = &read_fifo_fops;
59                 PIPE_RCOUNTER(*inode)++;
60                 if (PIPE_READERS(*inode)++ == 0)
61                         wake_up_partner(inode);
62
63                 if (!PIPE_WRITERS(*inode)) {
64                         if ((filp->f_flags & O_NONBLOCK)) {
65                                 /* suppress POLLHUP until we have
66                                  * seen a writer */
67                                 filp->f_version = PIPE_WCOUNTER(*inode);
68                         } else 
69                         {
70                                 wait_for_partner(inode, &PIPE_WCOUNTER(*inode));
71                                 if(signal_pending(current))
72                                         goto err_rd;
73                         }
74                 }
75                 break;
76         
77         case 2:
78         /*
79          *  O_WRONLY
80          *  POSIX.1 says that O_NONBLOCK means return -1 with
81          *  errno=ENXIO when there is no process reading the FIFO.
82          */
83                 ret = -ENXIO;
84                 if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode))
85                         goto err;
86
87                 filp->f_op = &write_fifo_fops;
88                 PIPE_WCOUNTER(*inode)++;
89                 if (!PIPE_WRITERS(*inode)++)
90                         wake_up_partner(inode);
91
92                 if (!PIPE_READERS(*inode)) {
93                         wait_for_partner(inode, &PIPE_RCOUNTER(*inode));
94                         if (signal_pending(current))
95                                 goto err_wr;
96                 }
97                 break;
98         
99         case 3:
100         /*
101          *  O_RDWR
102          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
103          *  This implementation will NEVER block on a O_RDWR open, since
104          *  the process can at least talk to itself.
105          */
106                 filp->f_op = &rdwr_fifo_fops;
107
108                 PIPE_READERS(*inode)++;
109                 PIPE_WRITERS(*inode)++;
110                 PIPE_RCOUNTER(*inode)++;
111                 PIPE_WCOUNTER(*inode)++;
112                 if (PIPE_READERS(*inode) == 1 || PIPE_WRITERS(*inode) == 1)
113                         wake_up_partner(inode);
114                 break;
115
116         default:
117                 ret = -EINVAL;
118                 goto err;
119         }
120
121         /* Ok! */
122         mutex_unlock(PIPE_MUTEX(*inode));
123         return 0;
124
125 err_rd:
126         if (!--PIPE_READERS(*inode))
127                 wake_up_interruptible(PIPE_WAIT(*inode));
128         ret = -ERESTARTSYS;
129         goto err;
130
131 err_wr:
132         if (!--PIPE_WRITERS(*inode))
133                 wake_up_interruptible(PIPE_WAIT(*inode));
134         ret = -ERESTARTSYS;
135         goto err;
136
137 err:
138         if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode))
139                 free_pipe_info(inode);
140
141 err_nocleanup:
142         mutex_unlock(PIPE_MUTEX(*inode));
143
144 err_nolock_nocleanup:
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 struct file_operations def_fifo_fops = {
154         .open           = fifo_open,    /* will set read or write pipe_fops */
155 };