+ mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memmap: prevent double scanning of memmap by kmemleak
has been added to the -mm mm-unstable branch.  Its filename is
     mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Guo Weikang <guoweikang.kernel@gmail.com>
Subject: mm/memmap: prevent double scanning of memmap by kmemleak
Date: Mon, 6 Jan 2025 10:11:25 +0800

kmemleak explicitly scans the mem_map through the valid struct page
objects.  However, memmap_alloc() was also adding this memory to the gray
object list, causing it to be scanned twice.  Remove memmap_alloc() from
the scan list and add a comment to clarify the behavior.

Link: https://lore.kernel.org/lkml/CAOm6qn=FVeTpH54wGDFMHuCOeYtvoTx30ktnv9-w3Nh8RMofEA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20250106021126.1678334-1-guoweikang.kernel@gmail.com
Signed-off-by: Guo Weikang <guoweikang.kernel@gmail.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/memblock.h |    4 ++++
 mm/mm_init.c             |    8 ++++++--
 mm/sparse-vmemmap.c      |    5 +++--
 3 files changed, 13 insertions(+), 4 deletions(-)

--- a/include/linux/memblock.h~mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak
+++ a/include/linux/memblock.h
@@ -378,6 +378,10 @@ static inline int memblock_get_region_no
 /* Flags for memblock allocation APIs */
 #define MEMBLOCK_ALLOC_ANYWHERE	(~(phys_addr_t)0)
 #define MEMBLOCK_ALLOC_ACCESSIBLE	0
+/*
+ *  MEMBLOCK_ALLOC_NOLEAKTRACE avoids kmemleak tracing. It implies
+ *  MEMBLOCK_ALLOC_ACCESSIBLE
+ */
 #define MEMBLOCK_ALLOC_NOLEAKTRACE	1
 
 /* We are using top down, so it is safe to use 0 here */
--- a/mm/mm_init.c~mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak
+++ a/mm/mm_init.c
@@ -1585,13 +1585,17 @@ void __init *memmap_alloc(phys_addr_t si
 {
 	void *ptr;
 
+	/*
+	 * Kmemleak will explicitly scan mem_map by traversing all valid
+	 * `struct *page`,so memblock does not need to be added to the scan list.
+	 */
 	if (exact_nid)
 		ptr = memblock_alloc_exact_nid_raw(size, align, min_addr,
-						   MEMBLOCK_ALLOC_ACCESSIBLE,
+						   MEMBLOCK_ALLOC_NOLEAKTRACE,
 						   nid);
 	else
 		ptr = memblock_alloc_try_nid_raw(size, align, min_addr,
-						 MEMBLOCK_ALLOC_ACCESSIBLE,
+						 MEMBLOCK_ALLOC_NOLEAKTRACE,
 						 nid);
 
 	if (ptr && size > 0)
--- a/mm/sparse-vmemmap.c~mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak
+++ a/mm/sparse-vmemmap.c
@@ -31,6 +31,8 @@
 #include <asm/dma.h>
 #include <asm/pgalloc.h>
 
+#include "internal.h"
+
 /*
  * Allocate a block of memory to be used to back the virtual memory map
  * or to back the page tables that are used to create the mapping.
@@ -42,8 +44,7 @@ static void * __ref __earlyonly_bootmem_
 				unsigned long align,
 				unsigned long goal)
 {
-	return memblock_alloc_try_nid_raw(size, align, goal,
-					       MEMBLOCK_ALLOC_ACCESSIBLE, node);
+	return memmap_alloc(size, align, goal, node, false);
 }
 
 void * __meminit vmemmap_alloc_block(unsigned long size, int node)
_

Patches currently in -mm which might be from guoweikang.kernel@gmail.com are

mm-kmemleak-fix-percpu-memory-leak-detection-failure.patch
mm-shmem-refactor-to-reuse-vfs_parse_monolithic_sep-for-option-parsing.patch
mm-early_ioremap-add-null-pointer-checks-to-prevent-null-pointer-dereference.patch
mm-memblock-add-memblock_alloc_or_panic-interface.patch
mm-memmap-prevent-double-scanning-of-memmap-by-kmemleak.patch