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Commit ba5bb147 authored by Al Viro's avatar Al Viro
Browse files

pipe: take allocation and freeing of pipe_inode_info out of ->i_mutex 



* new field - pipe->files; number of struct file over that pipe (all
  sharing the same inode, of course); protected by inode->i_lock.
* pipe_release() decrements pipe->files, clears inode->i_pipe when
  if the counter has reached 0 (all under ->i_lock) and, in that case,
  frees pipe after having done pipe_unlock()
* fifo_open() starts with grabbing ->i_lock, and either bumps pipe->files
  if ->i_pipe was non-NULL or allocates a new pipe (dropping and regaining
  ->i_lock) and rechecks ->i_pipe; if it's still NULL, inserts new pipe
  there, otherwise bumps ->i_pipe->files and frees the one we'd allocated.
  At that point we know that ->i_pipe is non-NULL and won't go away, so
  we can do pipe_lock() on it and proceed as we used to.  If we end up
  failing, decrement pipe->files and if it reaches 0 clear ->i_pipe and
  free the sucker after pipe_unlock().

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 18c03cfd

fs/pipe.c

+51 −21
Original line number Diff line number Diff line
@@ -718,23 +718,30 @@ pipe_poll(struct file *filp, poll_table *wait) 
static int

pipe_release(struct inode *inode, struct file *file)

{

	struct pipe_inode_info *pipe;

	struct pipe_inode_info *pipe = inode->i_pipe;

	int kill = 0;



	mutex_lock(&inode->i_mutex);

	pipe = inode->i_pipe;

	pipe_lock(pipe);

	if (file->f_mode & FMODE_READ)

		pipe->readers--;

	if (file->f_mode & FMODE_WRITE)

		pipe->writers--;



	if (!pipe->readers && !pipe->writers) {

		free_pipe_info(inode);

	} else {

	if (pipe->readers || pipe->writers) {

		wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);

		kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);

		kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);

	}

	mutex_unlock(&inode->i_mutex);

	spin_lock(&inode->i_lock);

	if (!--pipe->files) {

		inode->i_pipe = NULL;

		kill = 1;

	}

	spin_unlock(&inode->i_lock);

	pipe_unlock(pipe);



	if (kill)

		__free_pipe_info(pipe);



	return 0;

}
@@ -827,8 +834,9 @@ static struct inode * get_pipe_inode(void) 
	pipe = alloc_pipe_info(inode);

	if (!pipe)

		goto fail_iput;

	inode->i_pipe = pipe;



	inode->i_pipe = pipe;

	pipe->files = 2;

	pipe->readers = pipe->writers = 1;

	inode->i_fop = &pipefifo_fops;
@@ -999,18 +1007,36 @@ static int fifo_open(struct inode *inode, struct file *filp) 
{

	struct pipe_inode_info *pipe;

	bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;

	int kill = 0;

	int ret;



	mutex_lock(&inode->i_mutex);

	filp->f_version = 0;



	spin_lock(&inode->i_lock);

	if (inode->i_pipe) {

		pipe = inode->i_pipe;

	if (!pipe) {

		ret = -ENOMEM;

		pipe->files++;

		spin_unlock(&inode->i_lock);

	} else {

		spin_unlock(&inode->i_lock);

		pipe = alloc_pipe_info(inode);

		if (!pipe)

			goto err_nocleanup;

			return -ENOMEM;

		pipe->files = 1;

		spin_lock(&inode->i_lock);

		if (unlikely(inode->i_pipe)) {

			inode->i_pipe->files++;

			spin_unlock(&inode->i_lock);

			__free_pipe_info(pipe);

			pipe = inode->i_pipe;

		} else {

			inode->i_pipe = pipe;

			spin_unlock(&inode->i_lock);

		}

	filp->f_version = 0;

	}

	/* OK, we have a pipe and it's pinned down */



	pipe_lock(pipe);



	/* We can only do regular read/write on fifos */

	filp->f_mode &= (FMODE_READ | FMODE_WRITE);
@@ -1080,7 +1106,7 @@ static int fifo_open(struct inode *inode, struct file *filp) 
	}



	/* Ok! */

	mutex_unlock(&inode->i_mutex);

	pipe_unlock(pipe);

	return 0;



err_rd:
@@ -1096,11 +1122,15 @@ err_wr: 
	goto err;



err:

	if (!pipe->readers && !pipe->writers)

		free_pipe_info(inode);



err_nocleanup:

	mutex_unlock(&inode->i_mutex);

	spin_lock(&inode->i_lock);

	if (!--pipe->files) {

		inode->i_pipe = NULL;

		kill = 1;

	}

	spin_unlock(&inode->i_lock);

	pipe_unlock(pipe);

	if (kill)

		__free_pipe_info(pipe);

	return ret;

}

include/linux/pipe_fs_i.h

+2 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ struct pipe_buffer { 
 *	@tmp_page: cached released page

 *	@readers: number of current readers of this pipe

 *	@writers: number of current writers of this pipe

 *	@files: number of struct file refering this pipe (protected by ->i_lock)

 *	@waiting_writers: number of writers blocked waiting for room

 *	@r_counter: reader counter

 *	@w_counter: writer counter
@@ -47,6 +48,7 @@ struct pipe_inode_info { 
	unsigned int nrbufs, curbuf, buffers;

	unsigned int readers;

	unsigned int writers;

	unsigned int files;

	unsigned int waiting_writers;

	unsigned int r_counter;

	unsigned int w_counter;