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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 | /* * linux/fs/fifo.c * * written by Paul H. Hargrove * * Fixes: * 10-06-1999, AV: fixed OOM handling in fifo_open(), moved * initialization there, switched to external * allocation of pipe_inode_info. */ #include <linux/mm.h> #include <linux/malloc.h> static int fifo_open(struct inode *inode, struct file *filp) { int ret; ret = -ERESTARTSYS; if (down_interruptible(PIPE_SEM(*inode))) goto err_nolock_nocleanup; if (! inode->i_pipe) { unsigned long page; struct pipe_inode_info *info; info = kmalloc(sizeof(struct pipe_inode_info),GFP_KERNEL); ret = -ENOMEM; if (!info) goto err_nocleanup; page = __get_free_page(GFP_KERNEL); if (!page) { kfree(info); goto err_nocleanup; } inode->i_pipe = info; init_waitqueue_head(PIPE_WAIT(*inode)); PIPE_BASE(*inode) = (char *) page; PIPE_START(*inode) = PIPE_LEN(*inode) = 0; PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 0; } 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)++ == 0) wake_up_interruptible(PIPE_WAIT(*inode)); if (!(filp->f_flags & O_NONBLOCK)) { while (!PIPE_WRITERS(*inode)) { if (signal_pending(current)) goto err_rd; up(PIPE_SEM(*inode)); interruptible_sleep_on(PIPE_WAIT(*inode)); /* Note that using down_interruptible here and similar places below is pointless, since we have to acquire the lock to clean up properly. */ down(PIPE_SEM(*inode)); } } if (PIPE_WRITERS(*inode)) filp->f_op = &read_fifo_fops; 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. */ ret = -ENXIO; if ((filp->f_flags & O_NONBLOCK) && !PIPE_READERS(*inode)) goto err; filp->f_op = &write_fifo_fops; if (!PIPE_WRITERS(*inode)++) wake_up_interruptible(PIPE_WAIT(*inode)); while (!PIPE_READERS(*inode)) { if (signal_pending(current)) goto err_wr; up(PIPE_SEM(*inode)); interruptible_sleep_on(PIPE_WAIT(*inode)); down(PIPE_SEM(*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; PIPE_READERS(*inode)++; PIPE_WRITERS(*inode)++; if (PIPE_READERS(*inode) == 1 || PIPE_WRITERS(*inode) == 1) wake_up_interruptible(PIPE_WAIT(*inode)); break; default: ret = -EINVAL; goto err; } /* Ok! */ up(PIPE_SEM(*inode)); return 0; err_rd: if (!--PIPE_READERS(*inode)) wake_up_interruptible(PIPE_WAIT(*inode)); ret = -ERESTARTSYS; goto err; err_wr: if (!--PIPE_WRITERS(*inode)) wake_up_interruptible(PIPE_WAIT(*inode)); ret = -ERESTARTSYS; goto err; err: if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) { struct pipe_inode_info *info = inode->i_pipe; inode->i_pipe = NULL; free_page((unsigned long)info->base); kfree(info); } err_nocleanup: up(PIPE_SEM(*inode)); err_nolock_nocleanup: return ret; } /* * 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, /* follow_link */ NULL, /* get_block */ NULL, /* readpage */ NULL, /* writepage */ NULL, /* flushpage */ NULL, /* truncate */ NULL, /* permission */ NULL, /* smap */ NULL /* revalidate */ }; /* Goner. Filesystems do not use it anymore. */ void init_fifo(struct inode * inode) { inode->i_op = &fifo_inode_operations; } |