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Commit 6da61809 authored by Mark Fasheh's avatar Mark Fasheh Committed by Jens Axboe
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[PATCH] Introduce generic_file_splice_write_nolock() 



This allows file systems to manage their own i_mutex locking while
still re-using the generic_file_splice_write() logic.

OCFS2 in particular wants this so that it can order cluster locks within
i_mutex.

Signed-off-by: default avatarMark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 62752ee1

fs/splice.c

+66 −14
Original line number Diff line number Diff line
@@ -707,13 +707,12 @@ out_ret: 
 * key here is the 'actor' worker passed in that actually moves the data

 * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.

 */

ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,

			 loff_t *ppos, size_t len, unsigned int flags,

			 splice_actor *actor)

static ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,

				  struct file *out, loff_t *ppos, size_t len,

				  unsigned int flags, splice_actor *actor)

{

	int ret, do_wakeup, err;

	struct splice_desc sd;

	struct inode *inode = out->f_mapping->host;



	ret = 0;

	do_wakeup = 0;
@@ -723,14 +722,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 
	sd.file = out;

	sd.pos = *ppos;



	/*

	 * The actor worker might be calling ->prepare_write and

	 * ->commit_write. Most of the time, these expect i_mutex to

	 * be held. Since this may result in an ABBA deadlock with

	 * pipe->inode, we have to order lock acquiry here.

	 */

	inode_double_lock(inode, pipe->inode);



	for (;;) {

		if (pipe->nrbufs) {

			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
@@ -803,8 +794,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 
		pipe_wait(pipe);

	}



	inode_double_unlock(inode, pipe->inode);



	if (do_wakeup) {

		smp_mb();

		if (waitqueue_active(&pipe->wait))
@@ -815,6 +804,69 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 
	return ret;

}



ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,

			 loff_t *ppos, size_t len, unsigned int flags,

			 splice_actor *actor)

{

	ssize_t ret;

	struct inode *inode = out->f_mapping->host;



	/*

	 * The actor worker might be calling ->prepare_write and

	 * ->commit_write. Most of the time, these expect i_mutex to

	 * be held. Since this may result in an ABBA deadlock with

	 * pipe->inode, we have to order lock acquiry here.

	 */

	inode_double_lock(inode, pipe->inode);

	ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);

	inode_double_unlock(inode, pipe->inode);



	return ret;

}



/**

 * generic_file_splice_write_nolock - generic_file_splice_write without mutexes

 * @pipe:	pipe info

 * @out:	file to write to

 * @len:	number of bytes to splice

 * @flags:	splice modifier flags

 *

 * Will either move or copy pages (determined by @flags options) from

 * the given pipe inode to the given file. The caller is responsible

 * for acquiring i_mutex on both inodes.

 *

 */

ssize_t

generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,

				 loff_t *ppos, size_t len, unsigned int flags)

{

	struct address_space *mapping = out->f_mapping;

	struct inode *inode = mapping->host;

	ssize_t ret;

	int err;



	ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);

	if (ret > 0) {

		*ppos += ret;



		/*

		 * If file or inode is SYNC and we actually wrote some data,

		 * sync it.

		 */

		if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {

			err = generic_osync_inode(inode, mapping,

						  OSYNC_METADATA|OSYNC_DATA);



			if (err)

				ret = err;

		}

	}



	return ret;

}



EXPORT_SYMBOL(generic_file_splice_write_nolock);



/**

 * generic_file_splice_write - splice data from a pipe to a file

 * @pipe:	pipe info

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -1758,6 +1758,8 @@ extern ssize_t generic_file_splice_read(struct file *, loff_t *, 
		struct pipe_inode_info *, size_t, unsigned int);

extern ssize_t generic_file_splice_write(struct pipe_inode_info *,

		struct file *, loff_t *, size_t, unsigned int);

extern ssize_t generic_file_splice_write_nolock(struct pipe_inode_info *,

		struct file *, loff_t *, size_t, unsigned int);

extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,

		struct file *out, loff_t *, size_t len, unsigned int flags);

extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,