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[/] [test_project/] [trunk/] [linux_sd_driver/] [fs/] [fifo.c] - Blame information for rev 79

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Line No. Rev Author Line
1 62 marcus.erl 
/*
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 *  linux/fs/fifo.c
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 *
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 *  written by Paul H. Hargrove
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 *
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 *  Fixes:
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 *      10-06-1999, AV: fixed OOM handling in fifo_open(), moved
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 *                      initialization there, switched to external
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 *                      allocation of pipe_inode_info.
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 */
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/pipe_fs_i.h>
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static void wait_for_partner(struct inode* inode, unsigned int *cnt)
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{
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        int cur = *cnt;
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        while (cur == *cnt) {
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                pipe_wait(inode->i_pipe);
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                if (signal_pending(current))
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                        break;
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        }
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}
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static void wake_up_partner(struct inode* inode)
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{
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        wake_up_interruptible(&inode->i_pipe->wait);
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}
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static int fifo_open(struct inode *inode, struct file *filp)
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{
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        struct pipe_inode_info *pipe;
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        int ret;
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        mutex_lock(&inode->i_mutex);
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        pipe = inode->i_pipe;
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        if (!pipe) {
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                ret = -ENOMEM;
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                pipe = alloc_pipe_info(inode);
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                if (!pipe)
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                        goto err_nocleanup;
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                inode->i_pipe = pipe;
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        }
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        filp->f_version = 0;
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        /* We can only do regular read/write on fifos */
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        filp->f_mode &= (FMODE_READ | FMODE_WRITE);
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        switch (filp->f_mode) {
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        case 1:
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        /*
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         *  O_RDONLY
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         *  POSIX.1 says that O_NONBLOCK means return with the FIFO
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         *  opened, even when there is no process writing the FIFO.
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         */
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                filp->f_op = &read_fifo_fops;
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                pipe->r_counter++;
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                if (pipe->readers++ == 0)
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                        wake_up_partner(inode);
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                if (!pipe->writers) {
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                        if ((filp->f_flags & O_NONBLOCK)) {
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                                /* suppress POLLHUP until we have
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                                 * seen a writer */
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                                filp->f_version = pipe->w_counter;
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                        } else
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                        {
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                                wait_for_partner(inode, &pipe->w_counter);
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                                if(signal_pending(current))
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                                        goto err_rd;
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                        }
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                }
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                break;
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        case 2:
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        /*
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         *  O_WRONLY
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         *  POSIX.1 says that O_NONBLOCK means return -1 with
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         *  errno=ENXIO when there is no process reading the FIFO.
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         */
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                ret = -ENXIO;
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                if ((filp->f_flags & O_NONBLOCK) && !pipe->readers)
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                        goto err;
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                filp->f_op = &write_fifo_fops;
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                pipe->w_counter++;
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                if (!pipe->writers++)
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                        wake_up_partner(inode);
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                if (!pipe->readers) {
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                        wait_for_partner(inode, &pipe->r_counter);
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                        if (signal_pending(current))
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                                goto err_wr;
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                }
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                break;
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        case 3:
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        /*
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         *  O_RDWR
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         *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
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         *  This implementation will NEVER block on a O_RDWR open, since
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         *  the process can at least talk to itself.
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         */
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                filp->f_op = &rdwr_fifo_fops;
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                pipe->readers++;
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                pipe->writers++;
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                pipe->r_counter++;
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                pipe->w_counter++;
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                if (pipe->readers == 1 || pipe->writers == 1)
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                        wake_up_partner(inode);
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                break;
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        default:
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                ret = -EINVAL;
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                goto err;
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        }
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        /* Ok! */
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        mutex_unlock(&inode->i_mutex);
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        return 0;
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err_rd:
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        if (!--pipe->readers)
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                wake_up_interruptible(&pipe->wait);
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        ret = -ERESTARTSYS;
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        goto err;
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err_wr:
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        if (!--pipe->writers)
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                wake_up_interruptible(&pipe->wait);
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        ret = -ERESTARTSYS;
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        goto err;
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139 
err:
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        if (!pipe->readers && !pipe->writers)
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                free_pipe_info(inode);
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143 
err_nocleanup:
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        mutex_unlock(&inode->i_mutex);
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        return ret;
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}
147 
 
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/*
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 * Dummy default file-operations: the only thing this does
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 * is contain the open that then fills in the correct operations
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 * depending on the access mode of the file...
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 */
153 
const struct file_operations def_fifo_fops = {
154 
        .open           = fifo_open,    /* will set read or write pipe_fops */
155 
};

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