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memory hotplug: reset pgdat->kswapd to NULL if creating kernel thread fails

PATCH In review Wen Congyang 2 participants 2 messages Aug 21, 2012

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Memory management MGLRU MM reclaim
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Wen Congyang

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#0 lore raw

PATCH 1/1 memory hotplug: reset pgdat->kswapd to NULL if creating kernel thread fails

If kthread_run() fails, pgdat->kswapd contains errno. When we stop this thread, we only check whether pgdat->kswapd is NULL and access it. If it contains errno, it will cause page fault. Reset pgdat->kswapd to NULL when creating kernel thread fails can avoid this problem.

Signed-off-by Wen Congyang <[email protected]>
---
 mm/vmscan.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
mm/vmscan.c +1 -0
index 347b3ff..1e8e2aa 100644
@@ -2953,6 +2953,7 @@ int kswapd_run(int nid)
 		/* failure at boot is fatal */
 		BUG_ON(system_state == SYSTEM_BOOTING);
 		printk("Failed to start kswapd on node %d\n",nid);
+		pgdat->kswapd = NULL;
 		ret = -1;
 	}
 	return ret;
Signature · 7 lines
1.7.1

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Reviewed-by on v1 1/1
#1 lore raw
Quoted 6 lines · Wen Congyang

If kthread_run() fails, pgdat->kswapd contains errno. When we stop this thread, we only check whether pgdat->kswapd is NULL and access it. If it contains errno, it will cause page fault. Reset pgdat->kswapd to NULL when creating kernel thread fails can avoid this problem.

Signed-off-by Wen Congyang <[email protected]>
Reviewed-by Minchan Kim <[email protected]>

Nitpick: Why doesn't online_pages check kswapd_run's return value?
I hope memory-hotplug can handle this error rightly without relying on this patch in the future.

Signature · 8 lines
Kind regards,
Minchan Kim

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