linux-kernel - [PATCH v3 7/7] mm/mm_init: Use for_each_valid_pfn() in init_unavailable

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Message-ID: <20250423081828.608422-8-dwmw2@infradead.org>
Date: Wed, 23 Apr 2025 08:52:49 +0100
From: David Woodhouse <dwmw2@...radead.org>
To: 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>,
	David Hildenbrand <david@...hat.com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Mike Rapoport <rppt@...ux.ibm.com>,
	Will Deacon <will@...nel.org>,
	kvmarm@...ts.cs.columbia.edu,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Ruihan Li <lrh2000@....edu.cn>
Subject: [PATCH v3 7/7] mm/mm_init: Use for_each_valid_pfn() in init_unavailable_range()

From: David Woodhouse <dwmw@...zon.co.uk>

Currently, memmap_init initializes pfn_hole with 0 instead of
ARCH_PFN_OFFSET. Then init_unavailable_range will start iterating each
page from the page at address zero to the first available page, but it
won't do anything for pages below ARCH_PFN_OFFSET because pfn_valid
won't pass.

If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the
kernel is used as a library and loaded at a very high address), the
pointless iteration for pages below ARCH_PFN_OFFSET will take a very
long time, and the kernel will look stuck at boot time.

Use for_each_valid_pfn() to skip the pointless iterations.

Reported-by: Ruihan Li <lrh2000@....edu.cn>
Suggested-by: Mike Rapoport <rppt@...nel.org>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 mm/mm_init.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 41884f2155c4..0d1a4546825c 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -845,11 +845,7 @@ static void __init init_unavailable_range(unsigned long spfn,
 	unsigned long pfn;
 	u64 pgcnt = 0;
 
-	for (pfn = spfn; pfn < epfn; pfn++) {
-		if (!pfn_valid(pageblock_start_pfn(pfn))) {
-			pfn = pageblock_end_pfn(pfn) - 1;
-			continue;
-		}
+	for_each_valid_pfn(pfn, spfn, epfn) {
 		__init_single_page(pfn_to_page(pfn), pfn, zone, node);
 		__SetPageReserved(pfn_to_page(pfn));
 		pgcnt++;
-- 
2.49.0