From 6e2631463f3a2ce430a295c68aead3ff228ca3cf Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Sun, 27 Jul 2014 22:32:27 -0400
Subject: ext4: fix incorrect locking in move_extent_per_page

If we have to copy data we must drop i_data_sem because of
get_blocks() will be called inside mext_page_mkuptodate(), but later we must
reacquire it again because we are about to change extent's tree

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 2484c7e..671a74b 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -1013,10 +1013,11 @@ data_copy:
 		*err = -EBUSY;
 		goto unlock_pages;
 	}
-
+	ext4_double_down_write_data_sem(orig_inode, donor_inode);
 	replaced_count = mext_replace_branches(handle, orig_inode, donor_inode,
 					       orig_blk_offset,
 					       block_len_in_page, err);
+	ext4_double_up_write_data_sem(orig_inode, donor_inode);
 	if (*err) {
 		if (replaced_count) {
 			block_len_in_page = replaced_count;
-- 
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