Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
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
18static 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
28static void wake_up_partner(struct inode* inode)
29{
30 wake_up_interruptible(PIPE_WAIT(*inode));
31}
32
33static int fifo_open(struct inode *inode, struct file *filp)
34{
35 int ret;
36
37 ret = -ERESTARTSYS;
38 if (down_interruptible(PIPE_SEM(*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 up(PIPE_SEM(*inode));
123 return 0;
124
125err_rd:
126 if (!--PIPE_READERS(*inode))
127 wake_up_interruptible(PIPE_WAIT(*inode));
128 ret = -ERESTARTSYS;
129 goto err;
130
131err_wr:
132 if (!--PIPE_WRITERS(*inode))
133 wake_up_interruptible(PIPE_WAIT(*inode));
134 ret = -ERESTARTSYS;
135 goto err;
136
137err:
138 if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode))
139 free_pipe_info(inode);
140
141err_nocleanup:
142 up(PIPE_SEM(*inode));
143
144err_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 */
153struct file_operations def_fifo_fops = {
154 .open = fifo_open, /* will set read or write pipe_fops */
155};