mm: remove __GFP_NO_KSWAPD

mm: remove __GFP_NO_KSWAPD

When transparent huge pages were introduced, memory compaction and swap
storms were an issue, and the kernel had to be careful to not make THP
allocations cause pageout or compaction.

Now that we have working compaction deferral, kswapd is smart enough to
invoke compaction and the quadratic behaviour around isolate_free_pages
has been fixed, it should be safe to remove __GFP_NO_KSWAPD.

[[email protected]: Comment fix]
[[email protected]: Avoid direct reclaim for deferred compaction]
Cc: Andrea Arcangeli <[email protected]>
Signed-off-by: Rik van Riel <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>