path: root/fs/pipe.c

/*
 *  linux/fs/pipe.c
 *
 *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
 */

#include <linux/mm.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/pipe_fs_i.h>
#include <linux/uio.h>
#include <linux/highmem.h>

#include <asm/uaccess.h>
#include <asm/ioctls.h>

/*
 * We use a start+len construction, which provides full use of the 
 * allocated memory.
 * -- Florian Coosmann (FGC)
 * 
 * Reads with count = 0 should always return 0.
 * -- Julian Bradfield 1999-06-07.
 *
 * FIFOs and Pipes now generate SIGIO for both readers and writers.
 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
 *
 * pipe_read & write cleanup
 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
 */

/* Drop the inode semaphore and wait for a pipe event, atomically */
void pipe_wait(struct inode * inode)
{
	DEFINE_WAIT(wait);

	/*
	 * Pipes are system-local resources, so sleeping on them
	 * is considered a noninteractive wait:
	 */
	prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE|TASK_NONINTERACTIVE);
	up(PIPE_SEM(*inode));
	schedule();
	finish_wait(PIPE_WAIT(*inode), &wait);
	down(PIPE_SEM(*inode));
}

static inline int
pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
{
	unsigned long copy;

	while (len > 0) {
		while (!iov->iov_len)
			iov++;
		copy = min_t(unsigned long, len, iov->iov_len);

		if (copy_from_user(to, iov->iov_base, copy))
			return -EFAULT;
		to += copy;
		len -= copy;
		iov->iov_base += copy;
		iov->iov_len -= copy;
	}
	return 0;
}

static inline int
pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
{
	unsigned long copy;

	while (len > 0) {
		while (!iov->iov_len)
			iov++;
		copy = min_t(unsigned long, len, iov->iov_len);

		if (copy_to_user(iov->iov_base, from, copy))
			return -EFAULT;
		from += copy;
		len -= copy;
		iov->iov_base += copy;
		iov->iov_len -= copy;
	}
	return 0;
}

static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buffer *buf)
{
	struct page *page = buf->page;

	if (info->tmp_page) {
		__free_page(page);
		return;
	}
	info->tmp_page = page;
}

static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf)
{
	return kmap(buf->page);
}

static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer *buf)
{
	kunmap(buf->page);
}

static struct pipe_buf_operations anon_pipe_buf_ops = {
	.can_merge = 1,
	.map = anon_pipe_buf_map,
	.unmap = anon_pipe_buf_unmap,
	.release = anon_pipe_buf_release,
};

static ssize_t
pipe_readv(struct file *filp, const struct iovec *_iov,
	   unsigned long nr_segs, loff_t *ppos)
{
	struct inode *inode = filp->f_dentry->d_inode;
	struct pipe_inode_info *info;
	int do_wakeup;
	ssize_t ret;
	struct iovec *iov = (struct iovec *)_iov;
	size_t total_len;

	total_len = iov_length(iov, nr_segs);
	/* Null read succeeds. */
	if (unlikely(total_len == 0))
		return 0;

	do_wakeup = 0;
	ret = 0;
	down(PIPE_SEM(*inode));
	info = inode->i_pipe;
	for (;;) {
		int bufs = info->nrbufs;
		if (bufs) {
			int curbuf = info->curbuf;
			struct pipe_buffer *buf = info->bufs + curbuf;
			struct pipe_buf_operations *ops = buf->ops;
			void *addr;
			size_t chars = buf->len;
			int error;

			if (chars > total_len)
				chars = total_len;

			addr = ops->map(filp, info, buf);
			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
			ops->unmap(info, buf);
			if (unlikely(error)) {
				if (!ret) ret = -EFAULT;
				break;
			}
			ret += chars;
			buf->offset += chars;
			buf->len -= chars;
			if (!buf->len) {
				buf->ops = NULL;
				ops->release(info, buf);
				curbuf = (curbuf + 1) & (PIPE_BUFFERS-1);
				info->curbuf = curbuf;
				info->nrbufs = --bufs;
				do_wakeup = 1;
			}
			total_len -= chars;
			if (!total_len)
				break;	/* common path: read succeeded */
		}
		if (bufs)	/* More to do? */
			continue