jbd2: revert must-not-fail allocation loops back to GFP_NOFAIL

jbd2: revert must-not-fail allocation loops back to GFP_NOFAIL

This basically reverts 47def82672b3 ("jbd2: Remove __GFP_NOFAIL from jbd2
layer").  The deprecation of __GFP_NOFAIL was a bad choice because it led
to open coding the endless loop around the allocator rather than removing
the dependency on the non failing allocation.  So the deprecation was a
clear failure and the reality tells us that __GFP_NOFAIL is not even close
to go away.

It is still true that __GFP_NOFAIL allocations are generally discouraged
and new uses should be evaluated and an alternative (pre-allocations or
reservations) should be considered but it doesn't make any sense to lie
the allocator about the requirements.  Allocator can take steps to help
making a progress if it knows the requirements.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vipul Pandya <vipul@chelsio.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>