The commit 84b89e5d943d8 ("f2fs: add auto tuning for small devices") add
tuning for small volume device, now support to tune alloce_mode to 'reuse'
if it's small size. But the alloc_mode will change to 'default' when do
remount on this small size dievce. This patch fo fix alloc_mode changed
when do remount for a small volume device.
Signed-off-by: Yuwei Guan <Yuwei.Guan@xxxxxxxxxxxxx>