cifs: reduce false positives with inode aliasing serverino autodisable
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / fifo.c
blob5d6606ffc2d28de7b94c4dc3bb04367ac6a57f93
1 /*
2 * linux/fs/fifo.c
4 * written by Paul H. Hargrove
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.
12 #include <linux/mm.h>
13 #include <linux/fs.h>
14 #include <linux/sched.h>
15 #include <linux/pipe_fs_i.h>
17 static void wait_for_partner(struct inode* inode, unsigned int *cnt)
19 int cur = *cnt;
21 while (cur == *cnt) {
22 pipe_wait(inode->i_pipe);
23 if (signal_pending(current))
24 break;
28 static void wake_up_partner(struct inode* inode)
30 wake_up_interruptible(&inode->i_pipe->wait);
33 static int fifo_open(struct inode *inode, struct file *filp)
35 struct pipe_inode_info *pipe;
36 int ret;
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;
47 filp->f_version = 0;
49 /* We can only do regular read/write on fifos */
50 filp->f_mode &= (FMODE_READ | FMODE_WRITE);
52 switch (filp->f_mode) {
53 case FMODE_READ:
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.
59 filp->f_op = &read_pipefifo_fops;
60 pipe->r_counter++;
61 if (pipe->readers++ == 0)
62 wake_up_partner(inode);
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
71 wait_for_partner(inode, &pipe->w_counter);
72 if(signal_pending(current))
73 goto err_rd;
76 break;
78 case FMODE_WRITE:
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.
84 ret = -ENXIO;
85 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
86 goto err;
88 filp->f_op = &write_pipefifo_fops;
89 pipe->w_counter++;
90 if (!pipe->writers++)
91 wake_up_partner(inode);
93 if (!pipe->readers) {
94 wait_for_partner(inode, &pipe->r_counter);
95 if (signal_pending(current))
96 goto err_wr;
98 break;
100 case FMODE_READ | FMODE_WRITE:
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.
107 filp->f_op = &rdwr_pipefifo_fops;
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;
117 default:
118 ret = -EINVAL;
119 goto err;
122 /* Ok! */
123 mutex_unlock(&inode->i_mutex);
124 return 0;
126 err_rd:
127 if (!--pipe->readers)
128 wake_up_interruptible(&pipe->wait);
129 ret = -ERESTARTSYS;
130 goto err;
132 err_wr:
133 if (!--pipe->writers)
134 wake_up_interruptible(&pipe->wait);
135 ret = -ERESTARTSYS;
136 goto err;
138 err:
139 if (!pipe->readers && !pipe->writers)
140 free_pipe_info(inode);
142 err_nocleanup:
143 mutex_unlock(&inode->i_mutex);
144 return ret;
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...
152 const struct file_operations def_fifo_fops = {
153 .open = fifo_open, /* will set read_ or write_pipefifo_fops */