[patch 48/51] splice: fix i_mutex locking in generic_splice_write()

Greg KH
2009-05-14T22:59:25Z

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

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

From: Miklos Szeredi <miklos@szeredi.hu>

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@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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

--- a/fs/splice.c
+++ b/fs/splice.c
@@ -894,17 +894,29 @@ 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;