Btrfs: apply updated fallocate i_size fix

This version of the i_size fix for fallocate makes sure we only update
the i_size when the current fallocate is really operating outside of
i_size.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6782aa1..4deb280 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5799,7 +5799,9 @@
 		inode->i_ctime = CURRENT_TIME;
 		BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
 		if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-		    cur_offset > inode->i_size) {
+			(actual_len > inode->i_size) &&
+			(cur_offset > inode->i_size)) {
+
 			if (cur_offset > actual_len)
 				i_size  = actual_len;
 			else