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1da177e4
LT
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>
1da177e4 14#include <linux/fs.h>
e8edc6e0 15#include <linux/sched.h>
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16#include <linux/pipe_fs_i.h>
17
3a326a2c 18static void wait_for_partner(struct inode* inode, unsigned int *cnt)
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19{
20 int cur = *cnt;
3a326a2c
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21
22 while (cur == *cnt) {
23 pipe_wait(inode->i_pipe);
24 if (signal_pending(current))
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25 break;
26 }
27}
28
29static void wake_up_partner(struct inode* inode)
30{
9aeedfc4 31 wake_up_interruptible(&inode->i_pipe->wait);
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32}
33
34static int fifo_open(struct inode *inode, struct file *filp)
35{
923f4f23 36 struct pipe_inode_info *pipe;
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37 int ret;
38
9aeedfc4 39 mutex_lock(&inode->i_mutex);
923f4f23
IM
40 pipe = inode->i_pipe;
41 if (!pipe) {
1da177e4 42 ret = -ENOMEM;
923f4f23
IM
43 pipe = alloc_pipe_info(inode);
44 if (!pipe)
1da177e4 45 goto err_nocleanup;
923f4f23 46 inode->i_pipe = pipe;
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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 1:
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 */
d2d9648e 60 filp->f_op = &read_pipefifo_fops;
923f4f23
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61 pipe->r_counter++;
62 if (pipe->readers++ == 0)
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63 wake_up_partner(inode);
64
923f4f23 65 if (!pipe->writers) {
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66 if ((filp->f_flags & O_NONBLOCK)) {
67 /* suppress POLLHUP until we have
68 * seen a writer */
923f4f23 69 filp->f_version = pipe->w_counter;
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70 } else
71 {
923f4f23 72 wait_for_partner(inode, &pipe->w_counter);
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73 if(signal_pending(current))
74 goto err_rd;
75 }
76 }
77 break;
78
79 case 2:
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;
923f4f23 86 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
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87 goto err;
88
d2d9648e 89 filp->f_op = &write_pipefifo_fops;
923f4f23
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90 pipe->w_counter++;
91 if (!pipe->writers++)
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92 wake_up_partner(inode);
93
923f4f23
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94 if (!pipe->readers) {
95 wait_for_partner(inode, &pipe->r_counter);
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96 if (signal_pending(current))
97 goto err_wr;
98 }
99 break;
100
101 case 3:
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 */
d2d9648e 108 filp->f_op = &rdwr_pipefifo_fops;
1da177e4 109
923f4f23
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110 pipe->readers++;
111 pipe->writers++;
112 pipe->r_counter++;
113 pipe->w_counter++;
114 if (pipe->readers == 1 || pipe->writers == 1)
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115 wake_up_partner(inode);
116 break;
117
118 default:
119 ret = -EINVAL;
120 goto err;
121 }
122
123 /* Ok! */
9aeedfc4 124 mutex_unlock(&inode->i_mutex);
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125 return 0;
126
127err_rd:
923f4f23
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128 if (!--pipe->readers)
129 wake_up_interruptible(&pipe->wait);
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130 ret = -ERESTARTSYS;
131 goto err;
132
133err_wr:
923f4f23
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134 if (!--pipe->writers)
135 wake_up_interruptible(&pipe->wait);
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136 ret = -ERESTARTSYS;
137 goto err;
138
139err:
923f4f23 140 if (!pipe->readers && !pipe->writers)
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141 free_pipe_info(inode);
142
143err_nocleanup:
9aeedfc4 144 mutex_unlock(&inode->i_mutex);
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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 */
4b6f5d20 153const struct file_operations def_fifo_fops = {
d2d9648e 154 .open = fifo_open, /* will set read_ or write_pipefifo_fops */
1da177e4 155};