linux-kernel - Re: [PATCH v3] mm: fix panic in __alloc

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Date:   Tue, 21 Dec 2021 10:46:42 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Alexey Makhalov <amakhalov@...are.com>
Cc:     Dennis Zhou <dennis@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages

On Tue 21-12-21 05:46:16, Alexey Makhalov wrote:
> Hi Michal,
> 
> The patchset looks good to me. I didn’t find any issues during the testing.

Thanks a lot. Can I add your Tested-by: tag?

> I have one concern regarding dmesg output. Do you think this messaging is
> valid if possible node is not yet present?
> Or is it only the issue for virtual machines?
> 
>   Node XX uninitialized by the platform. Please report with boot dmesg.
>   Initmem setup node XX [mem 0x0000000000000000-0x0000000000000000]

AFAIU the Initmem part of the output is what concerns you, right? Yeah,
that really is more cryptic than necessary. Does this look any better?
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 34743dcd2d66..7e18a924be7e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7618,9 +7618,14 @@ static void __init free_area_init_node(int nid)
 	pgdat->node_start_pfn = start_pfn;
 	pgdat->per_cpu_nodestats = NULL;
 
-	pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
-		(u64)start_pfn << PAGE_SHIFT,
-		end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
+	if (start_pfn != end_pfn) {
+		pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid,
+			(u64)start_pfn << PAGE_SHIFT,
+			end_pfn ? ((u64)end_pfn << PAGE_SHIFT) - 1 : 0);
+	} else {
+		pr_info("Initmem setup node %d as memoryless\n", nid);
+	}
+
 	calculate_node_totalpages(pgdat, start_pfn, end_pfn);
 
 	alloc_node_mem_map(pgdat);
-- 
Michal Hocko
SUSE Labs