Revert "revert "Revert "mm: remove __GFP_NO_KSWAPD""" and associated damage

This reverts commits a50915394f1fc02c2861d3b7ce7014788aa5066e and
d7c3b937bdf45f0b844400b7bf6fd3ed50bac604.

This is a revert of a revert of a revert.  In addition, it reverts the
even older i915 change to stop using the __GFP_NO_KSWAPD flag due to the
original commits in linux-next.

It turns out that the original patch really was bogus, and that the
original revert was the correct thing to do after all.  We thought we
had fixed the problem, and then reverted the revert, but the problem
really is fundamental: waking up kswapd simply isn't the right thing to
do, and direct reclaim sometimes simply _is_ the right thing to do.

When certain allocations fail, we simply should try some direct reclaim,
and if that fails, fail the allocation.  That's the right thing to do
for THP allocations, which can easily fail, and the GPU allocations want
to do that too.

So starting kswapd is sometimes simply wrong, and removing the flag that
said "don't start kswapd" was a mistake.  Let's hope we never revisit
this mistake again - and certainly not this many times ;)

Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8193809f3de0..7e208f0ad68c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2416,8 +2416,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
                 goto nopage;
 
 restart:
-        wake_all_kswapd(order, zonelist, high_zoneidx,
-                                        zone_idx(preferred_zone));
+        if (!(gfp_mask & __GFP_NO_KSWAPD))
+                wake_all_kswapd(order, zonelist, high_zoneidx,
+                                                zone_idx(preferred_zone));
 
         /*
          * OK, we're below the kswapd watermark and have kicked background
@@ -2494,7 +2495,7 @@ rebalance:
          * system then fail the allocation instead of entering direct reclaim.
          */
         if ((deferred_compaction || contended_compaction) &&
-            (gfp_mask & (__GFP_MOVABLE|__GFP_REPEAT)) == __GFP_MOVABLE)
+                                                (gfp_mask & __GFP_NO_KSWAPD))
                 goto nopage;
 
         /* Try direct reclaim and then allocating */