blob: 987bf94114957beca2250a221778f3f93c20d6d2 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/fs.h>
Alexey Dobriyane8edc6e2007-05-21 01:22:52 +040015#include <linux/sched.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/pipe_fs_i.h>
17
Ingo Molnar3a326a22006-04-10 15:18:35 +020018static void wait_for_partner(struct inode* inode, unsigned int *cnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -070019{
20 int cur = *cnt;
Ingo Molnar3a326a22006-04-10 15:18:35 +020021
22 while (cur == *cnt) {
23 pipe_wait(inode->i_pipe);
24 if (signal_pending(current))
Linus Torvalds1da177e2005-04-16 15:20:36 -070025 break;
26 }
27}
28
29static void wake_up_partner(struct inode* inode)
30{
Ingo Molnar9aeedfc2006-04-11 13:53:10 +020031 wake_up_interruptible(&inode->i_pipe->wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -070032}
33
34static int fifo_open(struct inode *inode, struct file *filp)
35{
Ingo Molnar923f4f22006-04-11 13:53:33 +020036 struct pipe_inode_info *pipe;
Linus Torvalds1da177e2005-04-16 15:20:36 -070037 int ret;
38
Ingo Molnar9aeedfc2006-04-11 13:53:10 +020039 mutex_lock(&inode->i_mutex);
Ingo Molnar923f4f22006-04-11 13:53:33 +020040 pipe = inode->i_pipe;
41 if (!pipe) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070042 ret = -ENOMEM;
Ingo Molnar923f4f22006-04-11 13:53:33 +020043 pipe = alloc_pipe_info(inode);
44 if (!pipe)
Linus Torvalds1da177e2005-04-16 15:20:36 -070045 goto err_nocleanup;
Ingo Molnar923f4f22006-04-11 13:53:33 +020046 inode->i_pipe = pipe;
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 }
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 */
Denys Vlasenkod2d96482008-07-01 14:16:09 +020060 filp->f_op = &read_pipefifo_fops;
Ingo Molnar923f4f22006-04-11 13:53:33 +020061 pipe->r_counter++;
62 if (pipe->readers++ == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 wake_up_partner(inode);
64
Ingo Molnar923f4f22006-04-11 13:53:33 +020065 if (!pipe->writers) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 if ((filp->f_flags & O_NONBLOCK)) {
67 /* suppress POLLHUP until we have
68 * seen a writer */
Ingo Molnar923f4f22006-04-11 13:53:33 +020069 filp->f_version = pipe->w_counter;
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 } else
71 {
Ingo Molnar923f4f22006-04-11 13:53:33 +020072 wait_for_partner(inode, &pipe->w_counter);
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 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;
Ingo Molnar923f4f22006-04-11 13:53:33 +020086 if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 goto err;
88
Denys Vlasenkod2d96482008-07-01 14:16:09 +020089 filp->f_op = &write_pipefifo_fops;
Ingo Molnar923f4f22006-04-11 13:53:33 +020090 pipe->w_counter++;
91 if (!pipe->writers++)
Linus Torvalds1da177e2005-04-16 15:20:36 -070092 wake_up_partner(inode);
93
Ingo Molnar923f4f22006-04-11 13:53:33 +020094 if (!pipe->readers) {
95 wait_for_partner(inode, &pipe->r_counter);
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 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 */
Denys Vlasenkod2d96482008-07-01 14:16:09 +0200108 filp->f_op = &rdwr_pipefifo_fops;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
Ingo Molnar923f4f22006-04-11 13:53:33 +0200110 pipe->readers++;
111 pipe->writers++;
112 pipe->r_counter++;
113 pipe->w_counter++;
114 if (pipe->readers == 1 || pipe->writers == 1)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 wake_up_partner(inode);
116 break;
117
118 default:
119 ret = -EINVAL;
120 goto err;
121 }
122
123 /* Ok! */
Ingo Molnar9aeedfc2006-04-11 13:53:10 +0200124 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 return 0;
126
127err_rd:
Ingo Molnar923f4f22006-04-11 13:53:33 +0200128 if (!--pipe->readers)
129 wake_up_interruptible(&pipe->wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 ret = -ERESTARTSYS;
131 goto err;
132
133err_wr:
Ingo Molnar923f4f22006-04-11 13:53:33 +0200134 if (!--pipe->writers)
135 wake_up_interruptible(&pipe->wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 ret = -ERESTARTSYS;
137 goto err;
138
139err:
Ingo Molnar923f4f22006-04-11 13:53:33 +0200140 if (!pipe->readers && !pipe->writers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 free_pipe_info(inode);
142
143err_nocleanup:
Ingo Molnar9aeedfc2006-04-11 13:53:10 +0200144 mutex_unlock(&inode->i_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 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 */
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -0800153const struct file_operations def_fifo_fops = {
Denys Vlasenkod2d96482008-07-01 14:16:09 +0200154 .open = fifo_open, /* will set read_ or write_pipefifo_fops */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155};