linux-kernel - Re: [PATCH v3] kho: init alloc tags when restoring pages from reserved memory

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Message-ID: <20260122042506.175897-1-ranxiaokai627@163.com>
Date: Thu, 22 Jan 2026 04:25:06 +0000
From: ranxiaokai627@....com
To: akpm@...ux-foundation.org
Cc: graf@...zon.com,
	kent.overstreet@...ux.dev,
	kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	pasha.tatashin@...een.com,
	pratyush@...nel.org,
	ran.xiaokai@....com.cn,
	ranxiaokai627@....com,
	rppt@...nel.org,
	surenb@...gle.com
Subject: Re: [PATCH v3] kho: init alloc tags when restoring pages from reserved memory

>> From: Ran Xiaokai <ran.xiaokai@....com.cn>
>> 
>> Memblock pages (including reserved memory) should have their allocation
>> tags initialized to CODETAG_EMPTY via clear_page_tag_ref() before being
>> released to the page allocator. When kho restores pages through
>> kho_restore_page(), missing this call causes mismatched
>> allocation/deallocation tracking and below warning message:
>> 
>> alloc_tag was not set
>> WARNING: include/linux/alloc_tag.h:164 at ___free_pages+0xb8/0x260, CPU#1: swapper/0/1
>> RIP: 0010:___free_pages+0xb8/0x260
>>  kho_restore_vmalloc+0x187/0x2e0
>>  kho_test_init+0x3c4/0xa30
>>  do_one_initcall+0x62/0x2b0
>>  kernel_init_freeable+0x25b/0x480
>>  kernel_init+0x1a/0x1c0
>>  ret_from_fork+0x2d1/0x360
>> 
>> Add missing clear_page_tag_ref() annotation in kho_restore_page() to
>> fix this.
>> 
>> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
>> ---
>> It is based on linux-next 20260120. I dont konw whether this base is ok ?
>
>It's awkward.
>
>Your v2 patch was based on Linus mainline.  This is appropriate, as the
>patch should be sent to Linus soon and it has cc:stable, so -stable
>maintainers will try to backport it into earlier kernels.
>
>However your v3 patch is dependent upon other material ("kho: simplify
>page initialization in kho_restore_page()") which is scheduled for
>6.20(?)-rc1.

I think i misunderstood Pratyush's last reply:
"I suggested a re-roll of this patch based on top of my cleanup patches
[1], since I think with those the end result is a bit nicer."

>For a prompt, backportable merge it's best to base the fix on latest
>Linus mainline, please.
>
>You didn't actually describe why v3 is different from v2.  If the
>v2->v3 changes are just nice-to-have then let's redo those and base
>them on linux-next in the usual fashion.

>Unless I'm missing something, your well-reviewed, decently-tested v2
>patch remains suitable for upstreaming during 6.18-rcX

v2 version just fixed the folio case(compound page), but didn't fix the
contiguous order 0 pages case. So i think it is better to send a v3 version
base on lastest Linus tree and drop the v2 version.