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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: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Miklos Szeredi 2009-04-14 19:48:37 +02:00 committed by Jens Axboe
parent b3c2d2ddd6
commit 2933970b96
1 changed files with 2 additions and 16 deletions

18
fs/splice.c
View File

@ -784,7 +784,7 @@ EXPORT_SYMBOL(__splice_from_pipe);
* @actor: handler that splices the data * @actor: handler that splices the data
* *
* Description: * 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(). * 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) splice_actor *actor)
{ {
ssize_t ret; ssize_t ret;
struct inode *inode = out->f_mapping->host;
struct splice_desc sd = { struct splice_desc sd = {
.total_len = len, .total_len = len,
.flags = flags, .flags = flags,
@ -801,24 +800,11 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
.u.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) 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); ret = __splice_from_pipe(pipe, &sd, actor);
if (pipe->inode) if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex); mutex_unlock(&pipe->inode->i_mutex);
mutex_unlock(&inode->i_mutex);
return ret; return ret;
} }