linux-kernel - Re: [PATCH v4 7/7] mm/mm_init: Use for_each_valid_pfn() in init_unavailable

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Message-ID: <c15100fcf6781a60b852c4dbb43bdc98a678fcf0.camel@infradead.org>
Date: Sat, 26 Apr 2025 00:04:46 +0100
From: David Woodhouse <dwmw2@...radead.org>
To: David Hildenbrand <david@...hat.com>, Mike Rapoport <rppt@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, "Sauerwein, David"
 <dssauerw@...zon.de>, Anshuman Khandual <anshuman.khandual@....com>, Ard
 Biesheuvel <ardb@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 Marc Zyngier <maz@...nel.org>,  Mark Rutland <mark.rutland@....com>, Mike
 Rapoport <rppt@...ux.ibm.com>, Will Deacon <will@...nel.org>, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, Ruihan Li <lrh2000@....edu.cn>
Subject: Re: [PATCH v4 7/7] mm/mm_init: Use for_each_valid_pfn() in
 init_unavailable_range()

On Fri, 2025-04-25 at 22:12 +0200, David Hildenbrand wrote:
> 
> In any case, trying to figure out why Lorenzo ran into an issue ... if 
> it's nit because of the pageblock, maybe something in for_each_valid_pfn 
> with sparsemem is still shaky.

Yep, I think this was it:

--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -2190,10 +2190,10 @@ static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_
        /*
         * Either every PFN within the section (or subsection for VMEMMAP) is
         * valid, or none of them are. So there's no point repeating the check
-        * for every PFN; only call first_valid_pfn() the first time, and when
-        * crossing a (sub)section boundary (i.e. !(pfn & ~PFN_VALID_MASK)).
+        * for every PFN; only call first_valid_pfn() again when crossing a
+        * (sub)section boundary (i.e. !(pfn & ~PAGE_{SUB,}SECTION_MASK)).
         */
-       if (pfn & (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
+       if (pfn & ~(IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
                   PAGE_SUBSECTION_MASK : PAGE_SECTION_MASK))
                return pfn;
 
I've pushed the fixed version out to 
https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/for_each_valid_pfn


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