xfs: remove nonblocking mode from xfs_vm_writepage

xfs: remove nonblocking mode from xfs_vm_writepage

Remove the nonblocking optimisation done for mapping lookups during
writeback. It's not clear that leaving a hole in the writeback range
just because we couldn't get a lock is really a win, as it makes us
do another small random IO later on rather than a large sequential
IO now.

As this gets in the way of sane error handling later on, just remove
for the moment and we can re-introduce an equivalent optimisation in
future if we see problems due to extent map lock contention.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
(cherry picked from commit 988ef927926aa3481cbf144f235c0cefd7deb9e4)

Orabug: 28193043

Signed-off-by: Shan Hai <shan.hai@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>