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Commit 2933970b authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Jens Axboe
Browse files

splice: remove i_mutex locking in splice_from_pipe() 



splice_from_pipe() is only called from two places:

  - generic_splice_sendpage()
  - splice_write_null()

Neither of these require i_mutex to be taken on the destination inode.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent b3c2d2dd

fs/splice.c

+2 −16
Original line number Diff line number Diff line
@@ -784,7 +784,7 @@ EXPORT_SYMBOL(__splice_from_pipe); 
 * @actor:	handler that splices the data

 *

 * Description:

 *    See __splice_from_pipe. This function locks the input and output inodes,

 *    See __splice_from_pipe. This function locks the pipe inode,

 *    otherwise it's identical to __splice_from_pipe().

 *

 */
@@ -793,7 +793,6 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 
			 splice_actor *actor)

{

	ssize_t ret;

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

	struct splice_desc sd = {

		.total_len = len,

		.flags = flags,
@@ -801,24 +800,11 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out, 
		.u.file = out,

	};



	/*

	 * The actor worker might be calling ->write_begin and

	 * ->write_end. 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.

	 *

	 * Outer lock must be inode->i_mutex, as pipe_wait() will

	 * release and reacquire pipe->inode->i_mutex, AND inode must

	 * never be a pipe.

	 */

	WARN_ON(S_ISFIFO(inode->i_mode));

	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);

	if (pipe->inode)

		mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD);

		mutex_lock(&pipe->inode->i_mutex);

	ret = __splice_from_pipe(pipe, &sd, actor);

	if (pipe->inode)

		mutex_unlock(&pipe->inode->i_mutex);

	mutex_unlock(&inode->i_mutex);



	return ret;

}