linux-kernel - Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in pGp

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Message-ID: <a9790427-1028-6acc-18e6-aafc1a5eb29d@redhat.com>
Date:   Mon, 1 Feb 2021 14:32:13 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Yafang Shao <laoar.shao@...il.com>,
        andriy.shevchenko@...ux.intel.com, vbabka@...e.cz,
        linmiaohe@...wei.com, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, linux@...musvillemoes.dk
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2 3/3] vsprintf: dump full information of page flags in
 pGp

On 01.02.21 14:23, David Hildenbrand wrote:
> On 01.02.21 12:56, Yafang Shao wrote:
>> Currently the pGp only shows the names of page flags, rather than
>> the full information including section, node, zone, last cpupid and
>> kasan tag. While it is not easy to parse these information manually
>> because there're so many flavors. Let's interpret them in pGp as well.
>>
>> - Before the patch,
>> [ 6343.396602] Slab 0x000000004382e02b objects=33 used=3 fp=0x000000009ae06ffc flags=0x17ffffc0010200(slab|head)
>>
>> - After the patch,
>> [ 6871.296131] Slab 0x00000000c0e19a37 objects=33 used=3 fp=0x00000000c4902159 flags=0x17ffffc0010200(Node 0,Zone 2,Lastcpupid 0x1fffff,slab|head)
> 
> For debugging purposes, it might be helpful to have the actual zone name
> (and to know if the value is sane). You could obtain it (without other
> modifications) via
> 
> const char zname = "Invalid";
> 
> if (zone < MAX_NR_ZONES)
> 	zname = first_online_pgdat()->node_zones[zone].name;
> 
> 
> Similarly, it might also be helpful to indicate if a node is
> online/offline/invalid/.
> 
> const char nstate = "Invalid";
> 
> if (node_online(nid))
> 	nstate = "Online";
> else if (node_possible(nid))
> 	nstate = "Offline";

Just remembering that we have to take care of nid limits:

if (nid >= 0 && nid < MAX_NUMNODES) {
	if (node_online(nid))
		nstate = "Online";
	else if (node_possible(nid))
		nstate = "Offline";
}

-- 
Thanks,

David / dhildenb