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v4.6
   1/*
   2 *  linux/fs/pipe.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5 */
   6
   7#include <linux/mm.h>
   8#include <linux/file.h>
   9#include <linux/poll.h>
  10#include <linux/slab.h>
  11#include <linux/module.h>
  12#include <linux/init.h>
  13#include <linux/fs.h>
  14#include <linux/log2.h>
  15#include <linux/mount.h>
  16#include <linux/magic.h>
  17#include <linux/pipe_fs_i.h>
  18#include <linux/uio.h>
  19#include <linux/highmem.h>
  20#include <linux/pagemap.h>
  21#include <linux/audit.h>
  22#include <linux/syscalls.h>
  23#include <linux/fcntl.h>
  24
  25#include <asm/uaccess.h>
  26#include <asm/ioctls.h>
  27
  28#include "internal.h"
  29
  30/*
  31 * The max size that a non-root user is allowed to grow the pipe. Can
  32 * be set by root in /proc/sys/fs/pipe-max-size
  33 */
  34unsigned int pipe_max_size = 1048576;
  35
  36/*
  37 * Minimum pipe size, as required by POSIX
  38 */
  39unsigned int pipe_min_size = PAGE_SIZE;
  40
  41/* Maximum allocatable pages per user. Hard limit is unset by default, soft
  42 * matches default values.
  43 */
  44unsigned long pipe_user_pages_hard;
  45unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  46
  47/*
  48 * We use a start+len construction, which provides full use of the 
  49 * allocated memory.
  50 * -- Florian Coosmann (FGC)
  51 * 
  52 * Reads with count = 0 should always return 0.
  53 * -- Julian Bradfield 1999-06-07.
  54 *
  55 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  56 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  57 *
  58 * pipe_read & write cleanup
  59 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  60 */
  61
  62static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  63{
  64	if (pipe->files)
  65		mutex_lock_nested(&pipe->mutex, subclass);
  66}
  67
  68void pipe_lock(struct pipe_inode_info *pipe)
  69{
  70	/*
  71	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  72	 */
  73	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  74}
  75EXPORT_SYMBOL(pipe_lock);
  76
  77void pipe_unlock(struct pipe_inode_info *pipe)
  78{
  79	if (pipe->files)
  80		mutex_unlock(&pipe->mutex);
  81}
  82EXPORT_SYMBOL(pipe_unlock);
  83
  84static inline void __pipe_lock(struct pipe_inode_info *pipe)
  85{
  86	mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  87}
  88
  89static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  90{
  91	mutex_unlock(&pipe->mutex);
  92}
  93
  94void pipe_double_lock(struct pipe_inode_info *pipe1,
  95		      struct pipe_inode_info *pipe2)
  96{
  97	BUG_ON(pipe1 == pipe2);
  98
  99	if (pipe1 < pipe2) {
 100		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
 101		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
 102	} else {
 103		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 104		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 105	}
 106}
 107
 108/* Drop the inode semaphore and wait for a pipe event, atomically */
 109void pipe_wait(struct pipe_inode_info *pipe)
 110{
 111	DEFINE_WAIT(wait);
 112
 113	/*
 114	 * Pipes are system-local resources, so sleeping on them
 115	 * is considered a noninteractive wait:
 116	 */
 117	prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 118	pipe_unlock(pipe);
 119	schedule();
 120	finish_wait(&pipe->wait, &wait);
 121	pipe_lock(pipe);
 122}
 123
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 124static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 125				  struct pipe_buffer *buf)
 126{
 127	struct page *page = buf->page;
 128
 129	/*
 130	 * If nobody else uses this page, and we don't already have a
 131	 * temporary page, let's keep track of it as a one-deep
 132	 * allocation cache. (Otherwise just release our reference to it)
 133	 */
 134	if (page_count(page) == 1 && !pipe->tmp_page)
 135		pipe->tmp_page = page;
 136	else
 137		put_page(page);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 138}
 
 139
 140/**
 141 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 142 * @pipe:	the pipe that the buffer belongs to
 143 * @buf:	the buffer to attempt to steal
 144 *
 145 * Description:
 146 *	This function attempts to steal the &struct page attached to
 147 *	@buf. If successful, this function returns 0 and returns with
 148 *	the page locked. The caller may then reuse the page for whatever
 149 *	he wishes; the typical use is insertion into a different file
 150 *	page cache.
 151 */
 152int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 153			   struct pipe_buffer *buf)
 154{
 155	struct page *page = buf->page;
 156
 157	/*
 158	 * A reference of one is golden, that means that the owner of this
 159	 * page is the only one holding a reference to it. lock the page
 160	 * and return OK.
 161	 */
 162	if (page_count(page) == 1) {
 163		lock_page(page);
 164		return 0;
 165	}
 166
 167	return 1;
 168}
 169EXPORT_SYMBOL(generic_pipe_buf_steal);
 170
 171/**
 172 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 173 * @pipe:	the pipe that the buffer belongs to
 174 * @buf:	the buffer to get a reference to
 175 *
 176 * Description:
 177 *	This function grabs an extra reference to @buf. It's used in
 178 *	in the tee() system call, when we duplicate the buffers in one
 179 *	pipe into another.
 180 */
 181void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 182{
 183	get_page(buf->page);
 184}
 185EXPORT_SYMBOL(generic_pipe_buf_get);
 186
 187/**
 188 * generic_pipe_buf_confirm - verify contents of the pipe buffer
 189 * @info:	the pipe that the buffer belongs to
 190 * @buf:	the buffer to confirm
 191 *
 192 * Description:
 193 *	This function does nothing, because the generic pipe code uses
 194 *	pages that are always good when inserted into the pipe.
 195 */
 196int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 197			     struct pipe_buffer *buf)
 198{
 199	return 0;
 200}
 201EXPORT_SYMBOL(generic_pipe_buf_confirm);
 202
 203/**
 204 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 205 * @pipe:	the pipe that the buffer belongs to
 206 * @buf:	the buffer to put a reference to
 207 *
 208 * Description:
 209 *	This function releases a reference to @buf.
 210 */
 211void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 212			      struct pipe_buffer *buf)
 213{
 214	put_page(buf->page);
 215}
 216EXPORT_SYMBOL(generic_pipe_buf_release);
 217
 218static const struct pipe_buf_operations anon_pipe_buf_ops = {
 219	.can_merge = 1,
 220	.confirm = generic_pipe_buf_confirm,
 221	.release = anon_pipe_buf_release,
 222	.steal = generic_pipe_buf_steal,
 223	.get = generic_pipe_buf_get,
 224};
 225
 226static const struct pipe_buf_operations packet_pipe_buf_ops = {
 227	.can_merge = 0,
 228	.confirm = generic_pipe_buf_confirm,
 229	.release = anon_pipe_buf_release,
 230	.steal = generic_pipe_buf_steal,
 231	.get = generic_pipe_buf_get,
 232};
 233
 234static ssize_t
 235pipe_read(struct kiocb *iocb, struct iov_iter *to)
 
 236{
 237	size_t total_len = iov_iter_count(to);
 238	struct file *filp = iocb->ki_filp;
 239	struct pipe_inode_info *pipe = filp->private_data;
 
 240	int do_wakeup;
 241	ssize_t ret;
 
 
 242
 
 243	/* Null read succeeds. */
 244	if (unlikely(total_len == 0))
 245		return 0;
 246
 247	do_wakeup = 0;
 248	ret = 0;
 249	__pipe_lock(pipe);
 
 250	for (;;) {
 251		int bufs = pipe->nrbufs;
 252		if (bufs) {
 253			int curbuf = pipe->curbuf;
 254			struct pipe_buffer *buf = pipe->bufs + curbuf;
 255			const struct pipe_buf_operations *ops = buf->ops;
 
 256			size_t chars = buf->len;
 257			size_t written;
 258			int error;
 259
 260			if (chars > total_len)
 261				chars = total_len;
 262
 263			error = ops->confirm(pipe, buf);
 264			if (error) {
 265				if (!ret)
 266					ret = error;
 267				break;
 268			}
 269
 270			written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 271			if (unlikely(written < chars)) {
 
 
 
 
 
 
 
 
 
 
 
 272				if (!ret)
 273					ret = -EFAULT;
 274				break;
 275			}
 276			ret += chars;
 277			buf->offset += chars;
 278			buf->len -= chars;
 279
 280			/* Was it a packet buffer? Clean up and exit */
 281			if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 282				total_len = chars;
 283				buf->len = 0;
 284			}
 285
 286			if (!buf->len) {
 287				buf->ops = NULL;
 288				ops->release(pipe, buf);
 289				curbuf = (curbuf + 1) & (pipe->buffers - 1);
 290				pipe->curbuf = curbuf;
 291				pipe->nrbufs = --bufs;
 292				do_wakeup = 1;
 293			}
 294			total_len -= chars;
 295			if (!total_len)
 296				break;	/* common path: read succeeded */
 297		}
 298		if (bufs)	/* More to do? */
 299			continue;
 300		if (!pipe->writers)
 301			break;
 302		if (!pipe->waiting_writers) {
 303			/* syscall merging: Usually we must not sleep
 304			 * if O_NONBLOCK is set, or if we got some data.
 305			 * But if a writer sleeps in kernel space, then
 306			 * we can wait for that data without violating POSIX.
 307			 */
 308			if (ret)
 309				break;
 310			if (filp->f_flags & O_NONBLOCK) {
 311				ret = -EAGAIN;
 312				break;
 313			}
 314		}
 315		if (signal_pending(current)) {
 316			if (!ret)
 317				ret = -ERESTARTSYS;
 318			break;
 319		}
 320		if (do_wakeup) {
 321			wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 322 			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 323		}
 324		pipe_wait(pipe);
 325	}
 326	__pipe_unlock(pipe);
 327
 328	/* Signal writers asynchronously that there is more room. */
 329	if (do_wakeup) {
 330		wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 331		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 332	}
 333	if (ret > 0)
 334		file_accessed(filp);
 335	return ret;
 336}
 337
 338static inline int is_packetized(struct file *file)
 339{
 340	return (file->f_flags & O_DIRECT) != 0;
 341}
 342
 343static ssize_t
 344pipe_write(struct kiocb *iocb, struct iov_iter *from)
 
 345{
 346	struct file *filp = iocb->ki_filp;
 347	struct pipe_inode_info *pipe = filp->private_data;
 348	ssize_t ret = 0;
 349	int do_wakeup = 0;
 350	size_t total_len = iov_iter_count(from);
 
 
 351	ssize_t chars;
 352
 
 353	/* Null write succeeds. */
 354	if (unlikely(total_len == 0))
 355		return 0;
 356
 357	__pipe_lock(pipe);
 
 
 
 358
 359	if (!pipe->readers) {
 360		send_sig(SIGPIPE, current, 0);
 361		ret = -EPIPE;
 362		goto out;
 363	}
 364
 365	/* We try to merge small writes */
 366	chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 367	if (pipe->nrbufs && chars != 0) {
 368		int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 369							(pipe->buffers - 1);
 370		struct pipe_buffer *buf = pipe->bufs + lastbuf;
 371		const struct pipe_buf_operations *ops = buf->ops;
 372		int offset = buf->offset + buf->len;
 373
 374		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 375			ret = ops->confirm(pipe, buf);
 376			if (ret)
 
 
 
 377				goto out;
 378
 379			ret = copy_page_from_iter(buf->page, offset, chars, from);
 380			if (unlikely(ret < chars)) {
 381				ret = -EFAULT;
 
 
 
 
 
 
 
 
 
 
 382				goto out;
 383			}
 384			do_wakeup = 1;
 385			buf->len += ret;
 386			if (!iov_iter_count(from))
 
 387				goto out;
 388		}
 389	}
 390
 391	for (;;) {
 392		int bufs;
 393
 394		if (!pipe->readers) {
 395			send_sig(SIGPIPE, current, 0);
 396			if (!ret)
 397				ret = -EPIPE;
 398			break;
 399		}
 400		bufs = pipe->nrbufs;
 401		if (bufs < pipe->buffers) {
 402			int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 403			struct pipe_buffer *buf = pipe->bufs + newbuf;
 404			struct page *page = pipe->tmp_page;
 405			int copied;
 
 406
 407			if (!page) {
 408				page = alloc_page(GFP_HIGHUSER);
 409				if (unlikely(!page)) {
 410					ret = ret ? : -ENOMEM;
 411					break;
 412				}
 413				pipe->tmp_page = page;
 414			}
 415			/* Always wake up, even if the copy fails. Otherwise
 416			 * we lock up (O_NONBLOCK-)readers that sleep due to
 417			 * syscall merging.
 418			 * FIXME! Is this really true?
 419			 */
 420			do_wakeup = 1;
 421			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 422			if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 423				if (!ret)
 424					ret = -EFAULT;
 425				break;
 426			}
 427			ret += copied;
 428
 429			/* Insert it into the buffer array */
 430			buf->page = page;
 431			buf->ops = &anon_pipe_buf_ops;
 432			buf->offset = 0;
 433			buf->len = copied;
 434			buf->flags = 0;
 435			if (is_packetized(filp)) {
 436				buf->ops = &packet_pipe_buf_ops;
 437				buf->flags = PIPE_BUF_FLAG_PACKET;
 438			}
 439			pipe->nrbufs = ++bufs;
 440			pipe->tmp_page = NULL;
 441
 442			if (!iov_iter_count(from))
 
 443				break;
 444		}
 445		if (bufs < pipe->buffers)
 446			continue;
 447		if (filp->f_flags & O_NONBLOCK) {
 448			if (!ret)
 449				ret = -EAGAIN;
 450			break;
 451		}
 452		if (signal_pending(current)) {
 453			if (!ret)
 454				ret = -ERESTARTSYS;
 455			break;
 456		}
 457		if (do_wakeup) {
 458			wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 459			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 460			do_wakeup = 0;
 461		}
 462		pipe->waiting_writers++;
 463		pipe_wait(pipe);
 464		pipe->waiting_writers--;
 465	}
 466out:
 467	__pipe_unlock(pipe);
 468	if (do_wakeup) {
 469		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 470		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 471	}
 472	if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 473		int err = file_update_time(filp);
 474		if (err)
 475			ret = err;
 476		sb_end_write(file_inode(filp)->i_sb);
 477	}
 478	return ret;
 479}
 480
 
 
 
 
 
 
 
 
 
 
 
 
 
 481static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 482{
 483	struct pipe_inode_info *pipe = filp->private_data;
 
 484	int count, buf, nrbufs;
 485
 486	switch (cmd) {
 487		case FIONREAD:
 488			__pipe_lock(pipe);
 
 489			count = 0;
 490			buf = pipe->curbuf;
 491			nrbufs = pipe->nrbufs;
 492			while (--nrbufs >= 0) {
 493				count += pipe->bufs[buf].len;
 494				buf = (buf+1) & (pipe->buffers - 1);
 495			}
 496			__pipe_unlock(pipe);
 497
 498			return put_user(count, (int __user *)arg);
 499		default:
 500			return -ENOIOCTLCMD;
 501	}
 502}
 503
 504/* No kernel lock held - fine */
 505static unsigned int
 506pipe_poll(struct file *filp, poll_table *wait)
 507{
 508	unsigned int mask;
 509	struct pipe_inode_info *pipe = filp->private_data;
 
 510	int nrbufs;
 511
 512	poll_wait(filp, &pipe->wait, wait);
 513
 514	/* Reading only -- no need for acquiring the semaphore.  */
 515	nrbufs = pipe->nrbufs;
 516	mask = 0;
 517	if (filp->f_mode & FMODE_READ) {
 518		mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 519		if (!pipe->writers && filp->f_version != pipe->w_counter)
 520			mask |= POLLHUP;
 521	}
 522
 523	if (filp->f_mode & FMODE_WRITE) {
 524		mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 525		/*
 526		 * Most Unices do not set POLLERR for FIFOs but on Linux they
 527		 * behave exactly like pipes for poll().
 528		 */
 529		if (!pipe->readers)
 530			mask |= POLLERR;
 531	}
 532
 533	return mask;
 534}
 535
 536static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 537{
 538	int kill = 0;
 539
 540	spin_lock(&inode->i_lock);
 541	if (!--pipe->files) {
 542		inode->i_pipe = NULL;
 543		kill = 1;
 544	}
 545	spin_unlock(&inode->i_lock);
 546
 547	if (kill)
 548		free_pipe_info(pipe);
 549}
 550
 551static int
 552pipe_release(struct inode *inode, struct file *file)
 553{
 554	struct pipe_inode_info *pipe = file->private_data;
 555
 556	__pipe_lock(pipe);
 557	if (file->f_mode & FMODE_READ)
 558		pipe->readers--;
 559	if (file->f_mode & FMODE_WRITE)
 560		pipe->writers--;
 561
 562	if (pipe->readers || pipe->writers) {
 
 
 563		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 564		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 565		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 566	}
 567	__pipe_unlock(pipe);
 568
 569	put_pipe_info(inode, pipe);
 570	return 0;
 571}
 572
 573static int
 574pipe_fasync(int fd, struct file *filp, int on)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 575{
 576	struct pipe_inode_info *pipe = filp->private_data;
 577	int retval = 0;
 
 
 
 
 
 
 
 
 578
 579	__pipe_lock(pipe);
 580	if (filp->f_mode & FMODE_READ)
 581		retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 582	if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 
 
 
 
 
 
 583		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 584		if (retval < 0 && (filp->f_mode & FMODE_READ))
 585			/* this can happen only if on == T */
 586			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 587	}
 588	__pipe_unlock(pipe);
 589	return retval;
 590}
 591
 592static void account_pipe_buffers(struct pipe_inode_info *pipe,
 593                                 unsigned long old, unsigned long new)
 
 
 
 
 
 
 
 
 
 
 
 
 
 594{
 595	atomic_long_add(new - old, &pipe->user->pipe_bufs);
 
 
 
 
 596}
 597
 598static bool too_many_pipe_buffers_soft(struct user_struct *user)
 
 599{
 600	return pipe_user_pages_soft &&
 601	       atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
 
 
 
 
 
 
 
 
 
 
 602}
 603
 604static bool too_many_pipe_buffers_hard(struct user_struct *user)
 
 605{
 606	return pipe_user_pages_hard &&
 607	       atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
 
 
 
 
 
 
 
 
 
 
 608}
 609
 610struct pipe_inode_info *alloc_pipe_info(void)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 611{
 612	struct pipe_inode_info *pipe;
 613
 614	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 615	if (pipe) {
 616		unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 617		struct user_struct *user = get_current_user();
 618
 619		if (!too_many_pipe_buffers_hard(user)) {
 620			if (too_many_pipe_buffers_soft(user))
 621				pipe_bufs = 1;
 622			pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
 623		}
 624
 625		if (pipe->bufs) {
 626			init_waitqueue_head(&pipe->wait);
 627			pipe->r_counter = pipe->w_counter = 1;
 628			pipe->buffers = pipe_bufs;
 629			pipe->user = user;
 630			account_pipe_buffers(pipe, 0, pipe_bufs);
 631			mutex_init(&pipe->mutex);
 632			return pipe;
 633		}
 634		free_uid(user);
 635		kfree(pipe);
 636	}
 637
 638	return NULL;
 639}
 640
 641void free_pipe_info(struct pipe_inode_info *pipe)
 642{
 643	int i;
 644
 645	account_pipe_buffers(pipe, pipe->buffers, 0);
 646	free_uid(pipe->user);
 647	for (i = 0; i < pipe->buffers; i++) {
 648		struct pipe_buffer *buf = pipe->bufs + i;
 649		if (buf->ops)
 650			buf->ops->release(pipe, buf);
 651	}
 652	if (pipe->tmp_page)
 653		__free_page(pipe->tmp_page);
 654	kfree(pipe->bufs);
 655	kfree(pipe);
 656}
 657
 
 
 
 
 
 
 658static struct vfsmount *pipe_mnt __read_mostly;
 659
 660/*
 661 * pipefs_dname() is called from d_path().
 662 */
 663static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 664{
 665	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 666				d_inode(dentry)->i_ino);
 667}
 668
 669static const struct dentry_operations pipefs_dentry_operations = {
 670	.d_dname	= pipefs_dname,
 671};
 672
 673static struct inode * get_pipe_inode(void)
 674{
 675	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 676	struct pipe_inode_info *pipe;
 677
 678	if (!inode)
 679		goto fail_inode;
 680
 681	inode->i_ino = get_next_ino();
 682
 683	pipe = alloc_pipe_info();
 684	if (!pipe)
 685		goto fail_iput;
 686
 687	inode->i_pipe = pipe;
 688	pipe->files = 2;
 689	pipe->readers = pipe->writers = 1;
 690	inode->i_fop = &pipefifo_fops;
 691
 692	/*
 693	 * Mark the inode dirty from the very beginning,
 694	 * that way it will never be moved to the dirty
 695	 * list because "mark_inode_dirty()" will think
 696	 * that it already _is_ on the dirty list.
 697	 */
 698	inode->i_state = I_DIRTY;
 699	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 700	inode->i_uid = current_fsuid();
 701	inode->i_gid = current_fsgid();
 702	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 703
 704	return inode;
 705
 706fail_iput:
 707	iput(inode);
 708
 709fail_inode:
 710	return NULL;
 711}
 712
 713int create_pipe_files(struct file **res, int flags)
 714{
 715	int err;
 716	struct inode *inode = get_pipe_inode();
 717	struct file *f;
 718	struct path path;
 719	static struct qstr name = { .name = "" };
 720
 
 
 721	if (!inode)
 722		return -ENFILE;
 723
 724	err = -ENOMEM;
 725	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
 726	if (!path.dentry)
 727		goto err_inode;
 728	path.mnt = mntget(pipe_mnt);
 729
 730	d_instantiate(path.dentry, inode);
 731
 732	f = alloc_file(&path, FMODE_WRITE, &pipefifo_fops);
 733	if (IS_ERR(f)) {
 734		err = PTR_ERR(f);
 735		goto err_dentry;
 736	}
 737
 738	f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
 739	f->private_data = inode->i_pipe;
 740
 741	res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
 742	if (IS_ERR(res[0])) {
 743		err = PTR_ERR(res[0]);
 744		goto err_file;
 745	}
 746
 747	path_get(&path);
 748	res[0]->private_data = inode->i_pipe;
 749	res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 750	res[1] = f;
 751	return 0;
 752
 753err_file:
 754	put_filp(f);
 755err_dentry:
 756	free_pipe_info(inode->i_pipe);
 757	path_put(&path);
 758	return err;
 759
 760err_inode:
 761	free_pipe_info(inode->i_pipe);
 762	iput(inode);
 763	return err;
 
 
 
 
 
 
 
 
 764}
 765
 766static int __do_pipe_flags(int *fd, struct file **files, int flags)
 767{
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 768	int error;
 769	int fdw, fdr;
 770
 771	if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 772		return -EINVAL;
 773
 774	error = create_pipe_files(files, flags);
 775	if (error)
 776		return error;
 
 
 
 
 777
 778	error = get_unused_fd_flags(flags);
 779	if (error < 0)
 780		goto err_read_pipe;
 781	fdr = error;
 782
 783	error = get_unused_fd_flags(flags);
 784	if (error < 0)
 785		goto err_fdr;
 786	fdw = error;
 787
 788	audit_fd_pair(fdr, fdw);
 
 
 789	fd[0] = fdr;
 790	fd[1] = fdw;
 
 791	return 0;
 792
 793 err_fdr:
 794	put_unused_fd(fdr);
 795 err_read_pipe:
 796	fput(files[0]);
 797	fput(files[1]);
 798	return error;
 799}
 800
 801int do_pipe_flags(int *fd, int flags)
 802{
 803	struct file *files[2];
 804	int error = __do_pipe_flags(fd, files, flags);
 805	if (!error) {
 806		fd_install(fd[0], files[0]);
 807		fd_install(fd[1], files[1]);
 808	}
 809	return error;
 810}
 811
 812/*
 813 * sys_pipe() is the normal C calling standard for creating
 814 * a pipe. It's not the way Unix traditionally does this, though.
 815 */
 816SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 817{
 818	struct file *files[2];
 819	int fd[2];
 820	int error;
 821
 822	error = __do_pipe_flags(fd, files, flags);
 823	if (!error) {
 824		if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 825			fput(files[0]);
 826			fput(files[1]);
 827			put_unused_fd(fd[0]);
 828			put_unused_fd(fd[1]);
 829			error = -EFAULT;
 830		} else {
 831			fd_install(fd[0], files[0]);
 832			fd_install(fd[1], files[1]);
 833		}
 834	}
 835	return error;
 836}
 837
 838SYSCALL_DEFINE1(pipe, int __user *, fildes)
 839{
 840	return sys_pipe2(fildes, 0);
 841}
 842
 843static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
 844{
 845	int cur = *cnt;	
 846
 847	while (cur == *cnt) {
 848		pipe_wait(pipe);
 849		if (signal_pending(current))
 850			break;
 851	}
 852	return cur == *cnt ? -ERESTARTSYS : 0;
 853}
 854
 855static void wake_up_partner(struct pipe_inode_info *pipe)
 856{
 857	wake_up_interruptible(&pipe->wait);
 858}
 859
 860static int fifo_open(struct inode *inode, struct file *filp)
 861{
 862	struct pipe_inode_info *pipe;
 863	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
 864	int ret;
 865
 866	filp->f_version = 0;
 867
 868	spin_lock(&inode->i_lock);
 869	if (inode->i_pipe) {
 870		pipe = inode->i_pipe;
 871		pipe->files++;
 872		spin_unlock(&inode->i_lock);
 873	} else {
 874		spin_unlock(&inode->i_lock);
 875		pipe = alloc_pipe_info();
 876		if (!pipe)
 877			return -ENOMEM;
 878		pipe->files = 1;
 879		spin_lock(&inode->i_lock);
 880		if (unlikely(inode->i_pipe)) {
 881			inode->i_pipe->files++;
 882			spin_unlock(&inode->i_lock);
 883			free_pipe_info(pipe);
 884			pipe = inode->i_pipe;
 885		} else {
 886			inode->i_pipe = pipe;
 887			spin_unlock(&inode->i_lock);
 888		}
 889	}
 890	filp->private_data = pipe;
 891	/* OK, we have a pipe and it's pinned down */
 892
 893	__pipe_lock(pipe);
 894
 895	/* We can only do regular read/write on fifos */
 896	filp->f_mode &= (FMODE_READ | FMODE_WRITE);
 897
 898	switch (filp->f_mode) {
 899	case FMODE_READ:
 900	/*
 901	 *  O_RDONLY
 902	 *  POSIX.1 says that O_NONBLOCK means return with the FIFO
 903	 *  opened, even when there is no process writing the FIFO.
 904	 */
 905		pipe->r_counter++;
 906		if (pipe->readers++ == 0)
 907			wake_up_partner(pipe);
 908
 909		if (!is_pipe && !pipe->writers) {
 910			if ((filp->f_flags & O_NONBLOCK)) {
 911				/* suppress POLLHUP until we have
 912				 * seen a writer */
 913				filp->f_version = pipe->w_counter;
 914			} else {
 915				if (wait_for_partner(pipe, &pipe->w_counter))
 916					goto err_rd;
 917			}
 918		}
 919		break;
 920	
 921	case FMODE_WRITE:
 922	/*
 923	 *  O_WRONLY
 924	 *  POSIX.1 says that O_NONBLOCK means return -1 with
 925	 *  errno=ENXIO when there is no process reading the FIFO.
 926	 */
 927		ret = -ENXIO;
 928		if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
 929			goto err;
 930
 931		pipe->w_counter++;
 932		if (!pipe->writers++)
 933			wake_up_partner(pipe);
 934
 935		if (!is_pipe && !pipe->readers) {
 936			if (wait_for_partner(pipe, &pipe->r_counter))
 937				goto err_wr;
 938		}
 939		break;
 940	
 941	case FMODE_READ | FMODE_WRITE:
 942	/*
 943	 *  O_RDWR
 944	 *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
 945	 *  This implementation will NEVER block on a O_RDWR open, since
 946	 *  the process can at least talk to itself.
 947	 */
 948
 949		pipe->readers++;
 950		pipe->writers++;
 951		pipe->r_counter++;
 952		pipe->w_counter++;
 953		if (pipe->readers == 1 || pipe->writers == 1)
 954			wake_up_partner(pipe);
 955		break;
 956
 957	default:
 958		ret = -EINVAL;
 959		goto err;
 960	}
 961
 962	/* Ok! */
 963	__pipe_unlock(pipe);
 964	return 0;
 965
 966err_rd:
 967	if (!--pipe->readers)
 968		wake_up_interruptible(&pipe->wait);
 969	ret = -ERESTARTSYS;
 970	goto err;
 971
 972err_wr:
 973	if (!--pipe->writers)
 974		wake_up_interruptible(&pipe->wait);
 975	ret = -ERESTARTSYS;
 976	goto err;
 977
 978err:
 979	__pipe_unlock(pipe);
 980
 981	put_pipe_info(inode, pipe);
 982	return ret;
 983}
 984
 985const struct file_operations pipefifo_fops = {
 986	.open		= fifo_open,
 987	.llseek		= no_llseek,
 988	.read_iter	= pipe_read,
 989	.write_iter	= pipe_write,
 990	.poll		= pipe_poll,
 991	.unlocked_ioctl	= pipe_ioctl,
 992	.release	= pipe_release,
 993	.fasync		= pipe_fasync,
 994};
 995
 996/*
 997 * Allocate a new array of pipe buffers and copy the info over. Returns the
 998 * pipe size if successful, or return -ERROR on error.
 999 */
1000static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1001{
1002	struct pipe_buffer *bufs;
1003
1004	/*
1005	 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1006	 * expect a lot of shrink+grow operations, just free and allocate
1007	 * again like we would do for growing. If the pipe currently
1008	 * contains more buffers than arg, then return busy.
1009	 */
1010	if (nr_pages < pipe->nrbufs)
1011		return -EBUSY;
1012
1013	bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
1014	if (unlikely(!bufs))
1015		return -ENOMEM;
1016
1017	/*
1018	 * The pipe array wraps around, so just start the new one at zero
1019	 * and adjust the indexes.
1020	 */
1021	if (pipe->nrbufs) {
1022		unsigned int tail;
1023		unsigned int head;
1024
1025		tail = pipe->curbuf + pipe->nrbufs;
1026		if (tail < pipe->buffers)
1027			tail = 0;
1028		else
1029			tail &= (pipe->buffers - 1);
1030
1031		head = pipe->nrbufs - tail;
1032		if (head)
1033			memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1034		if (tail)
1035			memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1036	}
1037
1038	account_pipe_buffers(pipe, pipe->buffers, nr_pages);
1039	pipe->curbuf = 0;
1040	kfree(pipe->bufs);
1041	pipe->bufs = bufs;
1042	pipe->buffers = nr_pages;
1043	return nr_pages * PAGE_SIZE;
1044}
1045
1046/*
1047 * Currently we rely on the pipe array holding a power-of-2 number
1048 * of pages.
1049 */
1050static inline unsigned int round_pipe_size(unsigned int size)
1051{
1052	unsigned long nr_pages;
1053
1054	nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1055	return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1056}
1057
1058/*
1059 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1060 * will return an error.
1061 */
1062int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1063		 size_t *lenp, loff_t *ppos)
1064{
1065	int ret;
1066
1067	ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1068	if (ret < 0 || !write)
1069		return ret;
1070
1071	pipe_max_size = round_pipe_size(pipe_max_size);
1072	return ret;
1073}
1074
1075/*
1076 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1077 * location, so checking ->i_pipe is not enough to verify that this is a
1078 * pipe.
1079 */
1080struct pipe_inode_info *get_pipe_info(struct file *file)
1081{
1082	return file->f_op == &pipefifo_fops ? file->private_data : NULL;
 
 
1083}
1084
1085long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1086{
1087	struct pipe_inode_info *pipe;
1088	long ret;
1089
1090	pipe = get_pipe_info(file);
1091	if (!pipe)
1092		return -EBADF;
1093
1094	__pipe_lock(pipe);
1095
1096	switch (cmd) {
1097	case F_SETPIPE_SZ: {
1098		unsigned int size, nr_pages;
1099
1100		size = round_pipe_size(arg);
1101		nr_pages = size >> PAGE_SHIFT;
1102
1103		ret = -EINVAL;
1104		if (!nr_pages)
1105			goto out;
1106
1107		if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1108			ret = -EPERM;
1109			goto out;
1110		} else if ((too_many_pipe_buffers_hard(pipe->user) ||
1111			    too_many_pipe_buffers_soft(pipe->user)) &&
1112		           !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
1113			ret = -EPERM;
1114			goto out;
1115		}
1116		ret = pipe_set_size(pipe, nr_pages);
1117		break;
1118		}
1119	case F_GETPIPE_SZ:
1120		ret = pipe->buffers * PAGE_SIZE;
1121		break;
1122	default:
1123		ret = -EINVAL;
1124		break;
1125	}
1126
1127out:
1128	__pipe_unlock(pipe);
1129	return ret;
1130}
1131
1132static const struct super_operations pipefs_ops = {
1133	.destroy_inode = free_inode_nonrcu,
1134	.statfs = simple_statfs,
1135};
1136
1137/*
1138 * pipefs should _never_ be mounted by userland - too much of security hassle,
1139 * no real gain from having the whole whorehouse mounted. So we don't need
1140 * any operations on the root directory. However, we need a non-trivial
1141 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1142 */
1143static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1144			 int flags, const char *dev_name, void *data)
1145{
1146	return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1147			&pipefs_dentry_operations, PIPEFS_MAGIC);
1148}
1149
1150static struct file_system_type pipe_fs_type = {
1151	.name		= "pipefs",
1152	.mount		= pipefs_mount,
1153	.kill_sb	= kill_anon_super,
1154};
1155
1156static int __init init_pipe_fs(void)
1157{
1158	int err = register_filesystem(&pipe_fs_type);
1159
1160	if (!err) {
1161		pipe_mnt = kern_mount(&pipe_fs_type);
1162		if (IS_ERR(pipe_mnt)) {
1163			err = PTR_ERR(pipe_mnt);
1164			unregister_filesystem(&pipe_fs_type);
1165		}
1166	}
1167	return err;
1168}
1169
 
 
 
 
 
 
1170fs_initcall(init_pipe_fs);
v3.1
   1/*
   2 *  linux/fs/pipe.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   5 */
   6
   7#include <linux/mm.h>
   8#include <linux/file.h>
   9#include <linux/poll.h>
  10#include <linux/slab.h>
  11#include <linux/module.h>
  12#include <linux/init.h>
  13#include <linux/fs.h>
  14#include <linux/log2.h>
  15#include <linux/mount.h>
 
  16#include <linux/pipe_fs_i.h>
  17#include <linux/uio.h>
  18#include <linux/highmem.h>
  19#include <linux/pagemap.h>
  20#include <linux/audit.h>
  21#include <linux/syscalls.h>
  22#include <linux/fcntl.h>
  23
  24#include <asm/uaccess.h>
  25#include <asm/ioctls.h>
  26
 
 
  27/*
  28 * The max size that a non-root user is allowed to grow the pipe. Can
  29 * be set by root in /proc/sys/fs/pipe-max-size
  30 */
  31unsigned int pipe_max_size = 1048576;
  32
  33/*
  34 * Minimum pipe size, as required by POSIX
  35 */
  36unsigned int pipe_min_size = PAGE_SIZE;
  37
 
 
 
 
 
 
  38/*
  39 * We use a start+len construction, which provides full use of the 
  40 * allocated memory.
  41 * -- Florian Coosmann (FGC)
  42 * 
  43 * Reads with count = 0 should always return 0.
  44 * -- Julian Bradfield 1999-06-07.
  45 *
  46 * FIFOs and Pipes now generate SIGIO for both readers and writers.
  47 * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  48 *
  49 * pipe_read & write cleanup
  50 * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  51 */
  52
  53static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  54{
  55	if (pipe->inode)
  56		mutex_lock_nested(&pipe->inode->i_mutex, subclass);
  57}
  58
  59void pipe_lock(struct pipe_inode_info *pipe)
  60{
  61	/*
  62	 * pipe_lock() nests non-pipe inode locks (for writing to a file)
  63	 */
  64	pipe_lock_nested(pipe, I_MUTEX_PARENT);
  65}
  66EXPORT_SYMBOL(pipe_lock);
  67
  68void pipe_unlock(struct pipe_inode_info *pipe)
  69{
  70	if (pipe->inode)
  71		mutex_unlock(&pipe->inode->i_mutex);
  72}
  73EXPORT_SYMBOL(pipe_unlock);
  74
 
 
 
 
 
 
 
 
 
 
  75void pipe_double_lock(struct pipe_inode_info *pipe1,
  76		      struct pipe_inode_info *pipe2)
  77{
  78	BUG_ON(pipe1 == pipe2);
  79
  80	if (pipe1 < pipe2) {
  81		pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  82		pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  83	} else {
  84		pipe_lock_nested(pipe2, I_MUTEX_PARENT);
  85		pipe_lock_nested(pipe1, I_MUTEX_CHILD);
  86	}
  87}
  88
  89/* Drop the inode semaphore and wait for a pipe event, atomically */
  90void pipe_wait(struct pipe_inode_info *pipe)
  91{
  92	DEFINE_WAIT(wait);
  93
  94	/*
  95	 * Pipes are system-local resources, so sleeping on them
  96	 * is considered a noninteractive wait:
  97	 */
  98	prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
  99	pipe_unlock(pipe);
 100	schedule();
 101	finish_wait(&pipe->wait, &wait);
 102	pipe_lock(pipe);
 103}
 104
 105static int
 106pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
 107			int atomic)
 108{
 109	unsigned long copy;
 110
 111	while (len > 0) {
 112		while (!iov->iov_len)
 113			iov++;
 114		copy = min_t(unsigned long, len, iov->iov_len);
 115
 116		if (atomic) {
 117			if (__copy_from_user_inatomic(to, iov->iov_base, copy))
 118				return -EFAULT;
 119		} else {
 120			if (copy_from_user(to, iov->iov_base, copy))
 121				return -EFAULT;
 122		}
 123		to += copy;
 124		len -= copy;
 125		iov->iov_base += copy;
 126		iov->iov_len -= copy;
 127	}
 128	return 0;
 129}
 130
 131static int
 132pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
 133		      int atomic)
 134{
 135	unsigned long copy;
 136
 137	while (len > 0) {
 138		while (!iov->iov_len)
 139			iov++;
 140		copy = min_t(unsigned long, len, iov->iov_len);
 141
 142		if (atomic) {
 143			if (__copy_to_user_inatomic(iov->iov_base, from, copy))
 144				return -EFAULT;
 145		} else {
 146			if (copy_to_user(iov->iov_base, from, copy))
 147				return -EFAULT;
 148		}
 149		from += copy;
 150		len -= copy;
 151		iov->iov_base += copy;
 152		iov->iov_len -= copy;
 153	}
 154	return 0;
 155}
 156
 157/*
 158 * Attempt to pre-fault in the user memory, so we can use atomic copies.
 159 * Returns the number of bytes not faulted in.
 160 */
 161static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
 162{
 163	while (!iov->iov_len)
 164		iov++;
 165
 166	while (len > 0) {
 167		unsigned long this_len;
 168
 169		this_len = min_t(unsigned long, len, iov->iov_len);
 170		if (fault_in_pages_writeable(iov->iov_base, this_len))
 171			break;
 172
 173		len -= this_len;
 174		iov++;
 175	}
 176
 177	return len;
 178}
 179
 180/*
 181 * Pre-fault in the user memory, so we can use atomic copies.
 182 */
 183static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
 184{
 185	while (!iov->iov_len)
 186		iov++;
 187
 188	while (len > 0) {
 189		unsigned long this_len;
 190
 191		this_len = min_t(unsigned long, len, iov->iov_len);
 192		fault_in_pages_readable(iov->iov_base, this_len);
 193		len -= this_len;
 194		iov++;
 195	}
 196}
 197
 198static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 199				  struct pipe_buffer *buf)
 200{
 201	struct page *page = buf->page;
 202
 203	/*
 204	 * If nobody else uses this page, and we don't already have a
 205	 * temporary page, let's keep track of it as a one-deep
 206	 * allocation cache. (Otherwise just release our reference to it)
 207	 */
 208	if (page_count(page) == 1 && !pipe->tmp_page)
 209		pipe->tmp_page = page;
 210	else
 211		page_cache_release(page);
 212}
 213
 214/**
 215 * generic_pipe_buf_map - virtually map a pipe buffer
 216 * @pipe:	the pipe that the buffer belongs to
 217 * @buf:	the buffer that should be mapped
 218 * @atomic:	whether to use an atomic map
 219 *
 220 * Description:
 221 *	This function returns a kernel virtual address mapping for the
 222 *	pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
 223 *	and the caller has to be careful not to fault before calling
 224 *	the unmap function.
 225 *
 226 *	Note that this function occupies KM_USER0 if @atomic != 0.
 227 */
 228void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 229			   struct pipe_buffer *buf, int atomic)
 230{
 231	if (atomic) {
 232		buf->flags |= PIPE_BUF_FLAG_ATOMIC;
 233		return kmap_atomic(buf->page, KM_USER0);
 234	}
 235
 236	return kmap(buf->page);
 237}
 238EXPORT_SYMBOL(generic_pipe_buf_map);
 239
 240/**
 241 * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
 242 * @pipe:	the pipe that the buffer belongs to
 243 * @buf:	the buffer that should be unmapped
 244 * @map_data:	the data that the mapping function returned
 245 *
 246 * Description:
 247 *	This function undoes the mapping that ->map() provided.
 248 */
 249void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 250			    struct pipe_buffer *buf, void *map_data)
 251{
 252	if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
 253		buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
 254		kunmap_atomic(map_data, KM_USER0);
 255	} else
 256		kunmap(buf->page);
 257}
 258EXPORT_SYMBOL(generic_pipe_buf_unmap);
 259
 260/**
 261 * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 262 * @pipe:	the pipe that the buffer belongs to
 263 * @buf:	the buffer to attempt to steal
 264 *
 265 * Description:
 266 *	This function attempts to steal the &struct page attached to
 267 *	@buf. If successful, this function returns 0 and returns with
 268 *	the page locked. The caller may then reuse the page for whatever
 269 *	he wishes; the typical use is insertion into a different file
 270 *	page cache.
 271 */
 272int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 273			   struct pipe_buffer *buf)
 274{
 275	struct page *page = buf->page;
 276
 277	/*
 278	 * A reference of one is golden, that means that the owner of this
 279	 * page is the only one holding a reference to it. lock the page
 280	 * and return OK.
 281	 */
 282	if (page_count(page) == 1) {
 283		lock_page(page);
 284		return 0;
 285	}
 286
 287	return 1;
 288}
 289EXPORT_SYMBOL(generic_pipe_buf_steal);
 290
 291/**
 292 * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 293 * @pipe:	the pipe that the buffer belongs to
 294 * @buf:	the buffer to get a reference to
 295 *
 296 * Description:
 297 *	This function grabs an extra reference to @buf. It's used in
 298 *	in the tee() system call, when we duplicate the buffers in one
 299 *	pipe into another.
 300 */
 301void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 302{
 303	page_cache_get(buf->page);
 304}
 305EXPORT_SYMBOL(generic_pipe_buf_get);
 306
 307/**
 308 * generic_pipe_buf_confirm - verify contents of the pipe buffer
 309 * @info:	the pipe that the buffer belongs to
 310 * @buf:	the buffer to confirm
 311 *
 312 * Description:
 313 *	This function does nothing, because the generic pipe code uses
 314 *	pages that are always good when inserted into the pipe.
 315 */
 316int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 317			     struct pipe_buffer *buf)
 318{
 319	return 0;
 320}
 321EXPORT_SYMBOL(generic_pipe_buf_confirm);
 322
 323/**
 324 * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 325 * @pipe:	the pipe that the buffer belongs to
 326 * @buf:	the buffer to put a reference to
 327 *
 328 * Description:
 329 *	This function releases a reference to @buf.
 330 */
 331void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 332			      struct pipe_buffer *buf)
 333{
 334	page_cache_release(buf->page);
 335}
 336EXPORT_SYMBOL(generic_pipe_buf_release);
 337
 338static const struct pipe_buf_operations anon_pipe_buf_ops = {
 339	.can_merge = 1,
 340	.map = generic_pipe_buf_map,
 341	.unmap = generic_pipe_buf_unmap,
 
 
 
 
 
 
 342	.confirm = generic_pipe_buf_confirm,
 343	.release = anon_pipe_buf_release,
 344	.steal = generic_pipe_buf_steal,
 345	.get = generic_pipe_buf_get,
 346};
 347
 348static ssize_t
 349pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 350	   unsigned long nr_segs, loff_t pos)
 351{
 
 352	struct file *filp = iocb->ki_filp;
 353	struct inode *inode = filp->f_path.dentry->d_inode;
 354	struct pipe_inode_info *pipe;
 355	int do_wakeup;
 356	ssize_t ret;
 357	struct iovec *iov = (struct iovec *)_iov;
 358	size_t total_len;
 359
 360	total_len = iov_length(iov, nr_segs);
 361	/* Null read succeeds. */
 362	if (unlikely(total_len == 0))
 363		return 0;
 364
 365	do_wakeup = 0;
 366	ret = 0;
 367	mutex_lock(&inode->i_mutex);
 368	pipe = inode->i_pipe;
 369	for (;;) {
 370		int bufs = pipe->nrbufs;
 371		if (bufs) {
 372			int curbuf = pipe->curbuf;
 373			struct pipe_buffer *buf = pipe->bufs + curbuf;
 374			const struct pipe_buf_operations *ops = buf->ops;
 375			void *addr;
 376			size_t chars = buf->len;
 377			int error, atomic;
 
 378
 379			if (chars > total_len)
 380				chars = total_len;
 381
 382			error = ops->confirm(pipe, buf);
 383			if (error) {
 384				if (!ret)
 385					ret = error;
 386				break;
 387			}
 388
 389			atomic = !iov_fault_in_pages_write(iov, chars);
 390redo:
 391			addr = ops->map(pipe, buf, atomic);
 392			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
 393			ops->unmap(pipe, buf, addr);
 394			if (unlikely(error)) {
 395				/*
 396				 * Just retry with the slow path if we failed.
 397				 */
 398				if (atomic) {
 399					atomic = 0;
 400					goto redo;
 401				}
 402				if (!ret)
 403					ret = error;
 404				break;
 405			}
 406			ret += chars;
 407			buf->offset += chars;
 408			buf->len -= chars;
 
 
 
 
 
 
 
 409			if (!buf->len) {
 410				buf->ops = NULL;
 411				ops->release(pipe, buf);
 412				curbuf = (curbuf + 1) & (pipe->buffers - 1);
 413				pipe->curbuf = curbuf;
 414				pipe->nrbufs = --bufs;
 415				do_wakeup = 1;
 416			}
 417			total_len -= chars;
 418			if (!total_len)
 419				break;	/* common path: read succeeded */
 420		}
 421		if (bufs)	/* More to do? */
 422			continue;
 423		if (!pipe->writers)
 424			break;
 425		if (!pipe->waiting_writers) {
 426			/* syscall merging: Usually we must not sleep
 427			 * if O_NONBLOCK is set, or if we got some data.
 428			 * But if a writer sleeps in kernel space, then
 429			 * we can wait for that data without violating POSIX.
 430			 */
 431			if (ret)
 432				break;
 433			if (filp->f_flags & O_NONBLOCK) {
 434				ret = -EAGAIN;
 435				break;
 436			}
 437		}
 438		if (signal_pending(current)) {
 439			if (!ret)
 440				ret = -ERESTARTSYS;
 441			break;
 442		}
 443		if (do_wakeup) {
 444			wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 445 			kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 446		}
 447		pipe_wait(pipe);
 448	}
 449	mutex_unlock(&inode->i_mutex);
 450
 451	/* Signal writers asynchronously that there is more room. */
 452	if (do_wakeup) {
 453		wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
 454		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 455	}
 456	if (ret > 0)
 457		file_accessed(filp);
 458	return ret;
 459}
 460
 
 
 
 
 
 461static ssize_t
 462pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 463	    unsigned long nr_segs, loff_t ppos)
 464{
 465	struct file *filp = iocb->ki_filp;
 466	struct inode *inode = filp->f_path.dentry->d_inode;
 467	struct pipe_inode_info *pipe;
 468	ssize_t ret;
 469	int do_wakeup;
 470	struct iovec *iov = (struct iovec *)_iov;
 471	size_t total_len;
 472	ssize_t chars;
 473
 474	total_len = iov_length(iov, nr_segs);
 475	/* Null write succeeds. */
 476	if (unlikely(total_len == 0))
 477		return 0;
 478
 479	do_wakeup = 0;
 480	ret = 0;
 481	mutex_lock(&inode->i_mutex);
 482	pipe = inode->i_pipe;
 483
 484	if (!pipe->readers) {
 485		send_sig(SIGPIPE, current, 0);
 486		ret = -EPIPE;
 487		goto out;
 488	}
 489
 490	/* We try to merge small writes */
 491	chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 492	if (pipe->nrbufs && chars != 0) {
 493		int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 494							(pipe->buffers - 1);
 495		struct pipe_buffer *buf = pipe->bufs + lastbuf;
 496		const struct pipe_buf_operations *ops = buf->ops;
 497		int offset = buf->offset + buf->len;
 498
 499		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
 500			int error, atomic = 1;
 501			void *addr;
 502
 503			error = ops->confirm(pipe, buf);
 504			if (error)
 505				goto out;
 506
 507			iov_fault_in_pages_read(iov, chars);
 508redo1:
 509			addr = ops->map(pipe, buf, atomic);
 510			error = pipe_iov_copy_from_user(offset + addr, iov,
 511							chars, atomic);
 512			ops->unmap(pipe, buf, addr);
 513			ret = error;
 514			do_wakeup = 1;
 515			if (error) {
 516				if (atomic) {
 517					atomic = 0;
 518					goto redo1;
 519				}
 520				goto out;
 521			}
 522			buf->len += chars;
 523			total_len -= chars;
 524			ret = chars;
 525			if (!total_len)
 526				goto out;
 527		}
 528	}
 529
 530	for (;;) {
 531		int bufs;
 532
 533		if (!pipe->readers) {
 534			send_sig(SIGPIPE, current, 0);
 535			if (!ret)
 536				ret = -EPIPE;
 537			break;
 538		}
 539		bufs = pipe->nrbufs;
 540		if (bufs < pipe->buffers) {
 541			int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 542			struct pipe_buffer *buf = pipe->bufs + newbuf;
 543			struct page *page = pipe->tmp_page;
 544			char *src;
 545			int error, atomic = 1;
 546
 547			if (!page) {
 548				page = alloc_page(GFP_HIGHUSER);
 549				if (unlikely(!page)) {
 550					ret = ret ? : -ENOMEM;
 551					break;
 552				}
 553				pipe->tmp_page = page;
 554			}
 555			/* Always wake up, even if the copy fails. Otherwise
 556			 * we lock up (O_NONBLOCK-)readers that sleep due to
 557			 * syscall merging.
 558			 * FIXME! Is this really true?
 559			 */
 560			do_wakeup = 1;
 561			chars = PAGE_SIZE;
 562			if (chars > total_len)
 563				chars = total_len;
 564
 565			iov_fault_in_pages_read(iov, chars);
 566redo2:
 567			if (atomic)
 568				src = kmap_atomic(page, KM_USER0);
 569			else
 570				src = kmap(page);
 571
 572			error = pipe_iov_copy_from_user(src, iov, chars,
 573							atomic);
 574			if (atomic)
 575				kunmap_atomic(src, KM_USER0);
 576			else
 577				kunmap(page);
 578
 579			if (unlikely(error)) {
 580				if (atomic) {
 581					atomic = 0;
 582					goto redo2;
 583				}
 584				if (!ret)
 585					ret = error;
 586				break;
 587			}
 588			ret += chars;
 589
 590			/* Insert it into the buffer array */
 591			buf->page = page;
 592			buf->ops = &anon_pipe_buf_ops;
 593			buf->offset = 0;
 594			buf->len = chars;
 
 
 
 
 
 595			pipe->nrbufs = ++bufs;
 596			pipe->tmp_page = NULL;
 597
 598			total_len -= chars;
 599			if (!total_len)
 600				break;
 601		}
 602		if (bufs < pipe->buffers)
 603			continue;
 604		if (filp->f_flags & O_NONBLOCK) {
 605			if (!ret)
 606				ret = -EAGAIN;
 607			break;
 608		}
 609		if (signal_pending(current)) {
 610			if (!ret)
 611				ret = -ERESTARTSYS;
 612			break;
 613		}
 614		if (do_wakeup) {
 615			wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 616			kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 617			do_wakeup = 0;
 618		}
 619		pipe->waiting_writers++;
 620		pipe_wait(pipe);
 621		pipe->waiting_writers--;
 622	}
 623out:
 624	mutex_unlock(&inode->i_mutex);
 625	if (do_wakeup) {
 626		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
 627		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 628	}
 629	if (ret > 0)
 630		file_update_time(filp);
 
 
 
 
 631	return ret;
 632}
 633
 634static ssize_t
 635bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
 636{
 637	return -EBADF;
 638}
 639
 640static ssize_t
 641bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
 642	   loff_t *ppos)
 643{
 644	return -EBADF;
 645}
 646
 647static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 648{
 649	struct inode *inode = filp->f_path.dentry->d_inode;
 650	struct pipe_inode_info *pipe;
 651	int count, buf, nrbufs;
 652
 653	switch (cmd) {
 654		case FIONREAD:
 655			mutex_lock(&inode->i_mutex);
 656			pipe = inode->i_pipe;
 657			count = 0;
 658			buf = pipe->curbuf;
 659			nrbufs = pipe->nrbufs;
 660			while (--nrbufs >= 0) {
 661				count += pipe->bufs[buf].len;
 662				buf = (buf+1) & (pipe->buffers - 1);
 663			}
 664			mutex_unlock(&inode->i_mutex);
 665
 666			return put_user(count, (int __user *)arg);
 667		default:
 668			return -EINVAL;
 669	}
 670}
 671
 672/* No kernel lock held - fine */
 673static unsigned int
 674pipe_poll(struct file *filp, poll_table *wait)
 675{
 676	unsigned int mask;
 677	struct inode *inode = filp->f_path.dentry->d_inode;
 678	struct pipe_inode_info *pipe = inode->i_pipe;
 679	int nrbufs;
 680
 681	poll_wait(filp, &pipe->wait, wait);
 682
 683	/* Reading only -- no need for acquiring the semaphore.  */
 684	nrbufs = pipe->nrbufs;
 685	mask = 0;
 686	if (filp->f_mode & FMODE_READ) {
 687		mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
 688		if (!pipe->writers && filp->f_version != pipe->w_counter)
 689			mask |= POLLHUP;
 690	}
 691
 692	if (filp->f_mode & FMODE_WRITE) {
 693		mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
 694		/*
 695		 * Most Unices do not set POLLERR for FIFOs but on Linux they
 696		 * behave exactly like pipes for poll().
 697		 */
 698		if (!pipe->readers)
 699			mask |= POLLERR;
 700	}
 701
 702	return mask;
 703}
 704
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 705static int
 706pipe_release(struct inode *inode, int decr, int decw)
 707{
 708	struct pipe_inode_info *pipe;
 709
 710	mutex_lock(&inode->i_mutex);
 711	pipe = inode->i_pipe;
 712	pipe->readers -= decr;
 713	pipe->writers -= decw;
 
 714
 715	if (!pipe->readers && !pipe->writers) {
 716		free_pipe_info(inode);
 717	} else {
 718		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
 719		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 720		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 721	}
 722	mutex_unlock(&inode->i_mutex);
 723
 
 724	return 0;
 725}
 726
 727static int
 728pipe_read_fasync(int fd, struct file *filp, int on)
 729{
 730	struct inode *inode = filp->f_path.dentry->d_inode;
 731	int retval;
 732
 733	mutex_lock(&inode->i_mutex);
 734	retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
 735	mutex_unlock(&inode->i_mutex);
 736
 737	return retval;
 738}
 739
 740
 741static int
 742pipe_write_fasync(int fd, struct file *filp, int on)
 743{
 744	struct inode *inode = filp->f_path.dentry->d_inode;
 745	int retval;
 746
 747	mutex_lock(&inode->i_mutex);
 748	retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
 749	mutex_unlock(&inode->i_mutex);
 750
 751	return retval;
 752}
 753
 754
 755static int
 756pipe_rdwr_fasync(int fd, struct file *filp, int on)
 757{
 758	struct inode *inode = filp->f_path.dentry->d_inode;
 759	struct pipe_inode_info *pipe = inode->i_pipe;
 760	int retval;
 761
 762	mutex_lock(&inode->i_mutex);
 763	retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 764	if (retval >= 0) {
 765		retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 766		if (retval < 0) /* this can happen only if on == T */
 
 767			fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 768	}
 769	mutex_unlock(&inode->i_mutex);
 770	return retval;
 771}
 772
 773
 774static int
 775pipe_read_release(struct inode *inode, struct file *filp)
 776{
 777	return pipe_release(inode, 1, 0);
 778}
 779
 780static int
 781pipe_write_release(struct inode *inode, struct file *filp)
 782{
 783	return pipe_release(inode, 0, 1);
 784}
 785
 786static int
 787pipe_rdwr_release(struct inode *inode, struct file *filp)
 788{
 789	int decr, decw;
 790
 791	decr = (filp->f_mode & FMODE_READ) != 0;
 792	decw = (filp->f_mode & FMODE_WRITE) != 0;
 793	return pipe_release(inode, decr, decw);
 794}
 795
 796static int
 797pipe_read_open(struct inode *inode, struct file *filp)
 798{
 799	int ret = -ENOENT;
 800
 801	mutex_lock(&inode->i_mutex);
 802
 803	if (inode->i_pipe) {
 804		ret = 0;
 805		inode->i_pipe->readers++;
 806	}
 807
 808	mutex_unlock(&inode->i_mutex);
 809
 810	return ret;
 811}
 812
 813static int
 814pipe_write_open(struct inode *inode, struct file *filp)
 815{
 816	int ret = -ENOENT;
 817
 818	mutex_lock(&inode->i_mutex);
 819
 820	if (inode->i_pipe) {
 821		ret = 0;
 822		inode->i_pipe->writers++;
 823	}
 824
 825	mutex_unlock(&inode->i_mutex);
 826
 827	return ret;
 828}
 829
 830static int
 831pipe_rdwr_open(struct inode *inode, struct file *filp)
 832{
 833	int ret = -ENOENT;
 834
 835	mutex_lock(&inode->i_mutex);
 836
 837	if (inode->i_pipe) {
 838		ret = 0;
 839		if (filp->f_mode & FMODE_READ)
 840			inode->i_pipe->readers++;
 841		if (filp->f_mode & FMODE_WRITE)
 842			inode->i_pipe->writers++;
 843	}
 844
 845	mutex_unlock(&inode->i_mutex);
 846
 847	return ret;
 848}
 849
 850/*
 851 * The file_operations structs are not static because they
 852 * are also used in linux/fs/fifo.c to do operations on FIFOs.
 853 *
 854 * Pipes reuse fifos' file_operations structs.
 855 */
 856const struct file_operations read_pipefifo_fops = {
 857	.llseek		= no_llseek,
 858	.read		= do_sync_read,
 859	.aio_read	= pipe_read,
 860	.write		= bad_pipe_w,
 861	.poll		= pipe_poll,
 862	.unlocked_ioctl	= pipe_ioctl,
 863	.open		= pipe_read_open,
 864	.release	= pipe_read_release,
 865	.fasync		= pipe_read_fasync,
 866};
 867
 868const struct file_operations write_pipefifo_fops = {
 869	.llseek		= no_llseek,
 870	.read		= bad_pipe_r,
 871	.write		= do_sync_write,
 872	.aio_write	= pipe_write,
 873	.poll		= pipe_poll,
 874	.unlocked_ioctl	= pipe_ioctl,
 875	.open		= pipe_write_open,
 876	.release	= pipe_write_release,
 877	.fasync		= pipe_write_fasync,
 878};
 879
 880const struct file_operations rdwr_pipefifo_fops = {
 881	.llseek		= no_llseek,
 882	.read		= do_sync_read,
 883	.aio_read	= pipe_read,
 884	.write		= do_sync_write,
 885	.aio_write	= pipe_write,
 886	.poll		= pipe_poll,
 887	.unlocked_ioctl	= pipe_ioctl,
 888	.open		= pipe_rdwr_open,
 889	.release	= pipe_rdwr_release,
 890	.fasync		= pipe_rdwr_fasync,
 891};
 892
 893struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
 894{
 895	struct pipe_inode_info *pipe;
 896
 897	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 898	if (pipe) {
 899		pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
 
 
 
 
 
 
 
 
 900		if (pipe->bufs) {
 901			init_waitqueue_head(&pipe->wait);
 902			pipe->r_counter = pipe->w_counter = 1;
 903			pipe->inode = inode;
 904			pipe->buffers = PIPE_DEF_BUFFERS;
 
 
 905			return pipe;
 906		}
 
 907		kfree(pipe);
 908	}
 909
 910	return NULL;
 911}
 912
 913void __free_pipe_info(struct pipe_inode_info *pipe)
 914{
 915	int i;
 916
 
 
 917	for (i = 0; i < pipe->buffers; i++) {
 918		struct pipe_buffer *buf = pipe->bufs + i;
 919		if (buf->ops)
 920			buf->ops->release(pipe, buf);
 921	}
 922	if (pipe->tmp_page)
 923		__free_page(pipe->tmp_page);
 924	kfree(pipe->bufs);
 925	kfree(pipe);
 926}
 927
 928void free_pipe_info(struct inode *inode)
 929{
 930	__free_pipe_info(inode->i_pipe);
 931	inode->i_pipe = NULL;
 932}
 933
 934static struct vfsmount *pipe_mnt __read_mostly;
 935
 936/*
 937 * pipefs_dname() is called from d_path().
 938 */
 939static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 940{
 941	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 942				dentry->d_inode->i_ino);
 943}
 944
 945static const struct dentry_operations pipefs_dentry_operations = {
 946	.d_dname	= pipefs_dname,
 947};
 948
 949static struct inode * get_pipe_inode(void)
 950{
 951	struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 952	struct pipe_inode_info *pipe;
 953
 954	if (!inode)
 955		goto fail_inode;
 956
 957	inode->i_ino = get_next_ino();
 958
 959	pipe = alloc_pipe_info(inode);
 960	if (!pipe)
 961		goto fail_iput;
 
 962	inode->i_pipe = pipe;
 963
 964	pipe->readers = pipe->writers = 1;
 965	inode->i_fop = &rdwr_pipefifo_fops;
 966
 967	/*
 968	 * Mark the inode dirty from the very beginning,
 969	 * that way it will never be moved to the dirty
 970	 * list because "mark_inode_dirty()" will think
 971	 * that it already _is_ on the dirty list.
 972	 */
 973	inode->i_state = I_DIRTY;
 974	inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 975	inode->i_uid = current_fsuid();
 976	inode->i_gid = current_fsgid();
 977	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 978
 979	return inode;
 980
 981fail_iput:
 982	iput(inode);
 983
 984fail_inode:
 985	return NULL;
 986}
 987
 988struct file *create_write_pipe(int flags)
 989{
 990	int err;
 991	struct inode *inode;
 992	struct file *f;
 993	struct path path;
 994	struct qstr name = { .name = "" };
 995
 996	err = -ENFILE;
 997	inode = get_pipe_inode();
 998	if (!inode)
 999		goto err;
1000
1001	err = -ENOMEM;
1002	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
1003	if (!path.dentry)
1004		goto err_inode;
1005	path.mnt = mntget(pipe_mnt);
1006
1007	d_instantiate(path.dentry, inode);
1008
1009	err = -ENFILE;
1010	f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
1011	if (!f)
1012		goto err_dentry;
1013	f->f_mapping = inode->i_mapping;
1014
1015	f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
1016	f->f_version = 0;
1017
1018	return f;
 
 
 
 
1019
1020 err_dentry:
1021	free_pipe_info(inode);
 
 
 
 
 
 
 
 
1022	path_put(&path);
1023	return ERR_PTR(err);
1024
1025 err_inode:
1026	free_pipe_info(inode);
1027	iput(inode);
1028 err:
1029	return ERR_PTR(err);
1030}
1031
1032void free_write_pipe(struct file *f)
1033{
1034	free_pipe_info(f->f_dentry->d_inode);
1035	path_put(&f->f_path);
1036	put_filp(f);
1037}
1038
1039struct file *create_read_pipe(struct file *wrf, int flags)
1040{
1041	/* Grab pipe from the writer */
1042	struct file *f = alloc_file(&wrf->f_path, FMODE_READ,
1043				    &read_pipefifo_fops);
1044	if (!f)
1045		return ERR_PTR(-ENFILE);
1046
1047	path_get(&wrf->f_path);
1048	f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
1049
1050	return f;
1051}
1052
1053int do_pipe_flags(int *fd, int flags)
1054{
1055	struct file *fw, *fr;
1056	int error;
1057	int fdw, fdr;
1058
1059	if (flags & ~(O_CLOEXEC | O_NONBLOCK))
1060		return -EINVAL;
1061
1062	fw = create_write_pipe(flags);
1063	if (IS_ERR(fw))
1064		return PTR_ERR(fw);
1065	fr = create_read_pipe(fw, flags);
1066	error = PTR_ERR(fr);
1067	if (IS_ERR(fr))
1068		goto err_write_pipe;
1069
1070	error = get_unused_fd_flags(flags);
1071	if (error < 0)
1072		goto err_read_pipe;
1073	fdr = error;
1074
1075	error = get_unused_fd_flags(flags);
1076	if (error < 0)
1077		goto err_fdr;
1078	fdw = error;
1079
1080	audit_fd_pair(fdr, fdw);
1081	fd_install(fdr, fr);
1082	fd_install(fdw, fw);
1083	fd[0] = fdr;
1084	fd[1] = fdw;
1085
1086	return 0;
1087
1088 err_fdr:
1089	put_unused_fd(fdr);
1090 err_read_pipe:
1091	path_put(&fr->f_path);
1092	put_filp(fr);
1093 err_write_pipe:
1094	free_write_pipe(fw);
 
 
 
 
 
 
 
 
 
1095	return error;
1096}
1097
1098/*
1099 * sys_pipe() is the normal C calling standard for creating
1100 * a pipe. It's not the way Unix traditionally does this, though.
1101 */
1102SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
1103{
 
1104	int fd[2];
1105	int error;
1106
1107	error = do_pipe_flags(fd, flags);
1108	if (!error) {
1109		if (copy_to_user(fildes, fd, sizeof(fd))) {
1110			sys_close(fd[0]);
1111			sys_close(fd[1]);
 
 
1112			error = -EFAULT;
 
 
 
1113		}
1114	}
1115	return error;
1116}
1117
1118SYSCALL_DEFINE1(pipe, int __user *, fildes)
1119{
1120	return sys_pipe2(fildes, 0);
1121}
1122
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1123/*
1124 * Allocate a new array of pipe buffers and copy the info over. Returns the
1125 * pipe size if successful, or return -ERROR on error.
1126 */
1127static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
1128{
1129	struct pipe_buffer *bufs;
1130
1131	/*
1132	 * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1133	 * expect a lot of shrink+grow operations, just free and allocate
1134	 * again like we would do for growing. If the pipe currently
1135	 * contains more buffers than arg, then return busy.
1136	 */
1137	if (nr_pages < pipe->nrbufs)
1138		return -EBUSY;
1139
1140	bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL);
1141	if (unlikely(!bufs))
1142		return -ENOMEM;
1143
1144	/*
1145	 * The pipe array wraps around, so just start the new one at zero
1146	 * and adjust the indexes.
1147	 */
1148	if (pipe->nrbufs) {
1149		unsigned int tail;
1150		unsigned int head;
1151
1152		tail = pipe->curbuf + pipe->nrbufs;
1153		if (tail < pipe->buffers)
1154			tail = 0;
1155		else
1156			tail &= (pipe->buffers - 1);
1157
1158		head = pipe->nrbufs - tail;
1159		if (head)
1160			memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1161		if (tail)
1162			memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1163	}
1164
 
1165	pipe->curbuf = 0;
1166	kfree(pipe->bufs);
1167	pipe->bufs = bufs;
1168	pipe->buffers = nr_pages;
1169	return nr_pages * PAGE_SIZE;
1170}
1171
1172/*
1173 * Currently we rely on the pipe array holding a power-of-2 number
1174 * of pages.
1175 */
1176static inline unsigned int round_pipe_size(unsigned int size)
1177{
1178	unsigned long nr_pages;
1179
1180	nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
1181	return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
1182}
1183
1184/*
1185 * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
1186 * will return an error.
1187 */
1188int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
1189		 size_t *lenp, loff_t *ppos)
1190{
1191	int ret;
1192
1193	ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
1194	if (ret < 0 || !write)
1195		return ret;
1196
1197	pipe_max_size = round_pipe_size(pipe_max_size);
1198	return ret;
1199}
1200
1201/*
1202 * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1203 * location, so checking ->i_pipe is not enough to verify that this is a
1204 * pipe.
1205 */
1206struct pipe_inode_info *get_pipe_info(struct file *file)
1207{
1208	struct inode *i = file->f_path.dentry->d_inode;
1209
1210	return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
1211}
1212
1213long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1214{
1215	struct pipe_inode_info *pipe;
1216	long ret;
1217
1218	pipe = get_pipe_info(file);
1219	if (!pipe)
1220		return -EBADF;
1221
1222	mutex_lock(&pipe->inode->i_mutex);
1223
1224	switch (cmd) {
1225	case F_SETPIPE_SZ: {
1226		unsigned int size, nr_pages;
1227
1228		size = round_pipe_size(arg);
1229		nr_pages = size >> PAGE_SHIFT;
1230
1231		ret = -EINVAL;
1232		if (!nr_pages)
1233			goto out;
1234
1235		if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
1236			ret = -EPERM;
1237			goto out;
 
 
 
 
 
1238		}
1239		ret = pipe_set_size(pipe, nr_pages);
1240		break;
1241		}
1242	case F_GETPIPE_SZ:
1243		ret = pipe->buffers * PAGE_SIZE;
1244		break;
1245	default:
1246		ret = -EINVAL;
1247		break;
1248	}
1249
1250out:
1251	mutex_unlock(&pipe->inode->i_mutex);
1252	return ret;
1253}
1254
1255static const struct super_operations pipefs_ops = {
1256	.destroy_inode = free_inode_nonrcu,
 
1257};
1258
1259/*
1260 * pipefs should _never_ be mounted by userland - too much of security hassle,
1261 * no real gain from having the whole whorehouse mounted. So we don't need
1262 * any operations on the root directory. However, we need a non-trivial
1263 * d_name - pipe: will go nicely and kill the special-casing in procfs.
1264 */
1265static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1266			 int flags, const char *dev_name, void *data)
1267{
1268	return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1269			&pipefs_dentry_operations, PIPEFS_MAGIC);
1270}
1271
1272static struct file_system_type pipe_fs_type = {
1273	.name		= "pipefs",
1274	.mount		= pipefs_mount,
1275	.kill_sb	= kill_anon_super,
1276};
1277
1278static int __init init_pipe_fs(void)
1279{
1280	int err = register_filesystem(&pipe_fs_type);
1281
1282	if (!err) {
1283		pipe_mnt = kern_mount(&pipe_fs_type);
1284		if (IS_ERR(pipe_mnt)) {
1285			err = PTR_ERR(pipe_mnt);
1286			unregister_filesystem(&pipe_fs_type);
1287		}
1288	}
1289	return err;
1290}
1291
1292static void __exit exit_pipe_fs(void)
1293{
1294	kern_unmount(pipe_mnt);
1295	unregister_filesystem(&pipe_fs_type);
1296}
1297
1298fs_initcall(init_pipe_fs);
1299module_exit(exit_pipe_fs);