writeback: Fix occasional slow sync(1)

In case when system contains no dirty pages, wakeup_flusher_threads()
will submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits
immediately without doing anything. Thus sync(1) will write all the
dirty inodes from a WB_SYNC_ALL writeback pass which is slow.

Fix the problem by using get_nr_dirty_pages() in
wakeup_flusher_threads() instead of calculating number of dirty pages
manually. That function also takes number of dirty inodes into account.

CC: stable@vger.kernel.org
Reported-by: Paul Taysom <taysom@chromium.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Cristoforo Cataldo <cristoforo.cataldo@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
USB force fast charging

-Use base from Chad Froebel <chadfroebel@gmail.com> so we continue to
use the same generic sysfs mechanism

-Referenced franco's git for drivers/usb/otg/msm_otg.c changes
https://github.com/franciscofranco/mako/commit/5a8a4c8e23c7e1df39c740b9ce1d5dda20b0ede3

Off by default

Turn on:
echo 1 > /sys/kernel/fast_charge/force_fast_charge

Turn off:
echo 0 > /sys/kernel/fast_charge/force_fast_charge

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>