[patch 27/28] splice: fix i_mutex locking in generic_splice_write()

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Miklos Szeredi <miklos@xxxxxxxxxx>

commit eb443e5a25d43996deb62b9bcee1a4ce5dea2ead upstream.

Rearrange locking of i_mutex on destination so it's only held while
buffers are copied with the pipe_to_file() actor, and not while
waiting for more data on the pipe.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/splice.c |   34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

--- a/fs/splice.c
+++ b/fs/splice.c
@@ -893,17 +893,29 @@ generic_file_splice_write(struct pipe_in
 	};
 	ssize_t ret;
 
-	WARN_ON(S_ISFIFO(inode->i_mode));
-	mutex_lock_nested(&inode->i_mutex, I_MUTEX_PARENT);
-	ret = file_remove_suid(out);
-	if (likely(!ret)) {
-		if (pipe->inode)
-			mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_CHILD);
-		ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
-		if (pipe->inode)
-			mutex_unlock(&pipe->inode->i_mutex);
-	}
-	mutex_unlock(&inode->i_mutex);
+	if (pipe->inode)
+		mutex_lock_nested(&pipe->inode->i_mutex, I_MUTEX_PARENT);
+
+	splice_from_pipe_begin(&sd);
+	do {
+		ret = splice_from_pipe_next(pipe, &sd);
+		if (ret <= 0)
+			break;
+
+		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
+		ret = file_remove_suid(out);
+		if (!ret)
+			ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
+		mutex_unlock(&inode->i_mutex);
+	} while (ret > 0);
+	splice_from_pipe_end(pipe, &sd);
+
+	if (pipe->inode)
+		mutex_unlock(&pipe->inode->i_mutex);
+
+	if (sd.num_spliced)
+		ret = sd.num_spliced;
+
 	if (ret > 0) {
 		unsigned long nr_pages;
 


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