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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 | /* * linux/fs/fifo.c * * written by Paul H. Hargrove */ #include <linux/sched.h> #include <linux/kernel.h> #include <linux/errno.h> #include <linux/fcntl.h> #include <linux/mm.h> static int fifo_open(struct inode * inode,struct file * filp) { int retval = 0; unsigned long page; switch( filp->f_mode ) { case 1: /* * O_RDONLY * POSIX.1 says that O_NONBLOCK means return with the FIFO * opened, even when there is no process writing the FIFO. */ filp->f_op = &connecting_fifo_fops; if (!PIPE_READERS(*inode)++) wake_up_interruptible(&PIPE_WAIT(*inode)); if (!(filp->f_flags & O_NONBLOCK) && !PIPE_WRITERS(*inode)) { PIPE_RD_OPENERS(*inode)++; while (!PIPE_WRITERS(*inode)) { if (signal_pending(current)) { retval = -ERESTARTSYS; break; } interruptible_sleep_on(&PIPE_WAIT(*inode)); } if (!--PIPE_RD_OPENERS(*inode)) wake_up_interruptible(&PIPE_WAIT(*inode)); } while (PIPE_WR_OPENERS(*inode)) interruptible_sleep_on(&PIPE_WAIT(*inode)); if (PIPE_WRITERS(*inode)) filp->f_op = &read_fifo_fops; if (retval && !--PIPE_READERS(*inode)) wake_up_interruptible(&PIPE_WAIT(*inode)); break; case 2: /* * O_WRONLY * POSIX.1 says that O_NONBLOCK means return -1 with * errno=ENXIO when there is no process reading the FIFO. */ if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode)) { retval = -ENXIO; break; } filp->f_op = &write_fifo_fops; if (!PIPE_WRITERS(*inode)++) wake_up_interruptible(&PIPE_WAIT(*inode)); if (!PIPE_READERS(*inode)) { PIPE_WR_OPENERS(*inode)++; while (!PIPE_READERS(*inode)) { if (signal_pending(current)) { retval = -ERESTARTSYS; break; } interruptible_sleep_on(&PIPE_WAIT(*inode)); } if (!--PIPE_WR_OPENERS(*inode)) wake_up_interruptible(&PIPE_WAIT(*inode)); } while (PIPE_RD_OPENERS(*inode)) interruptible_sleep_on(&PIPE_WAIT(*inode)); if (retval && !--PIPE_WRITERS(*inode)) wake_up_interruptible(&PIPE_WAIT(*inode)); break; case 3: /* * O_RDWR * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set. * This implementation will NEVER block on a O_RDWR open, since * the process can at least talk to itself. */ filp->f_op = &rdwr_fifo_fops; if (!PIPE_READERS(*inode)++) wake_up_interruptible(&PIPE_WAIT(*inode)); while (PIPE_WR_OPENERS(*inode)) interruptible_sleep_on(&PIPE_WAIT(*inode)); if (!PIPE_WRITERS(*inode)++) wake_up_interruptible(&PIPE_WAIT(*inode)); while (PIPE_RD_OPENERS(*inode)) interruptible_sleep_on(&PIPE_WAIT(*inode)); break; default: retval = -EINVAL; } if (retval || PIPE_BASE(*inode)) return retval; page = __get_free_page(GFP_KERNEL); if (PIPE_BASE(*inode)) { free_page(page); return 0; } if (!page) return -ENOMEM; PIPE_LOCK(*inode) = 0; PIPE_START(*inode) = PIPE_LEN(*inode) = 0; PIPE_BASE(*inode) = (char *) page; return 0; } /* * Dummy default file-operations: the only thing this does * is contain the open that then fills in the correct operations * depending on the access mode of the file... */ static struct file_operations def_fifo_fops = { NULL, NULL, NULL, NULL, NULL, NULL, NULL, fifo_open, /* will set read or write pipe_fops */ NULL, NULL, NULL, NULL }; struct inode_operations fifo_inode_operations = { &def_fifo_fops, /* default file operations */ NULL, /* create */ NULL, /* lookup */ NULL, /* link */ NULL, /* unlink */ NULL, /* symlink */ NULL, /* mkdir */ NULL, /* rmdir */ NULL, /* mknod */ NULL, /* rename */ NULL, /* readlink */ NULL, /* readpage */ NULL, /* writepage */ NULL, /* bmap */ NULL, /* truncate */ NULL /* permission */ }; void init_fifo(struct inode * inode) { inode->i_op = &fifo_inode_operations; PIPE_LOCK(*inode) = 0; PIPE_BASE(*inode) = NULL; PIPE_START(*inode) = PIPE_LEN(*inode) = 0; PIPE_RD_OPENERS(*inode) = PIPE_WR_OPENERS(*inode) = 0; PIPE_WAIT(*inode) = NULL; PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0; } |