Sync with mainline commit 992e9fd

 ext4: add some tracepoints in extent status tree
Sync rcu header with mainline

3fbfbf7 rcu: Add callback-free CPUs
Sync btrfs header with mainline
Sync with mainline commit fb57dc8

 Btrfs: parse parent 0 into correct value in tracepoint

This fix also apply to previous kernel version, thus no conditional is
required.
Sync with mainline commit 4520fb3

 ext4: split off ext4_journalled_invalidatepage()
Import private functions for ext4 tracepoints
Add required includes for ext4 tracepoints

The function ext4_ext_get_actual_len() called from ext4 tracepoints requires
additional includes.