f2fs: flush cp pack except cp pack 2 page at first

f2fs: flush cp pack except cp pack 2 page at first

BugLink: http://bugs.launchpad.net/bugs/1786352
[ Upstream commit 46706d5917f4457a6befe7a39a15c89dbb1ce9ca ]

Previously, we attempt to flush the whole cp pack in a single bio,
however, when suddenly powering off at this time, we could get into
an extreme scenario that cp pack 1 page and cp pack 2 page are updated
and latest, but payload or current summaries are still partially
outdated. (see reliable write in the UFS specification)

This patch submits the whole cp pack except cp pack 2 page at first,
and then writes the cp pack 2 page with an extra independent
bio with pre-io barrier.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>