linux-kernel - [PATCH 1/2] mm: Guard a use of node_reclaim_distance with CONFIFG

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Message-Id: <20210226201721.510177-1-palmer@dabbelt.com>
Date:   Fri, 26 Feb 2021 12:17:20 -0800
From:   Palmer Dabbelt <palmer@...belt.com>
To:     akpm@...ux-foundation.org, atishp@...shpatra.org
Cc:     peterz@...radead.org, srikar@...ux.vnet.ibm.com,
        valentin.schneider@....com, vbabka@...e.cz, mpe@...erman.id.au,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@...roid.com
Subject: [PATCH 1/2] mm: Guard a use of node_reclaim_distance with CONFIFG_NUMA

From: Palmer Dabbelt <palmerdabbelt@...gle.com>

This is only useful under CONFIG_NUMA.  IIUC skipping the check is the
right thing to do here, as without CONFIG_NUMA there will never be any
large node distances on non-NUMA systems.

I expected this to manifest as a link failure under (!CONFIG_NUMA &&
CONFIG_TRANSPARENT_HUGE_PAGES), but I'm not actually seeing that.  I
think the reference is just getting pruned before it's checked, but I
didn't get that from reading the code so I'm worried I'm missing
something.

Either way, this is necessary to guard the definition of
node_reclaim_distance with CONFIG_NUMA.

Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
---
 mm/khugepaged.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a7d6cb912b05..b1bf191c3a54 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -819,8 +819,10 @@ static bool khugepaged_scan_abort(int nid)
 	for (i = 0; i < MAX_NUMNODES; i++) {
 		if (!khugepaged_node_load[i])
 			continue;
+#ifdef CONFIG_NUMA
 		if (node_distance(nid, i) > node_reclaim_distance)
 			return true;
+#endif
 	}
 	return false;
 }
-- 
2.30.1.766.gb4fecdf3b7-goog