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mm/sparse: move sparse_init_one_section() to internal.h

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While at it, convert the BUG_ON to a VM_WARN_ON_ONCE, avoid long lines,
and merge sparse_encode_mem_map() into its only caller
sparse_init_one_section().

Clarify the comment a bit, pointing at page_to_pfn().

[david@kernel.org: s/VM_WARN_ON/VM_WARN_ON_ONCE/]
  Link: https://lkml.kernel.org/r/6b04c1a1-74e7-42e8-8523-a40802e5dacc@kernel.org
Link: https://lkml.kernel.org/r/20260320-sparsemem_cleanups-v2-13-096addc8800d@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand (Arm) 2026-03-20 23:13:45 +01:00 committed by Andrew Morton
parent b551ed94d9
commit f62a3bf227
3 changed files with 23 additions and 25 deletions
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2
include/linux/mmzone.h
View File

@ -1988,7 +1988,7 @@ struct mem_section {
/*
* This is, logically, a pointer to an array of struct
* pages. However, it is stored with some other magic.
* (see sparse.c::sparse_init_one_section())
* (see sparse_init_one_section())
*
* Additionally during early boot we encode node id of
* the location of the section here to guide allocation.

22
mm/internal.h
View File

@ -964,6 +964,28 @@ void memmap_init_range(unsigned long, int, unsigned long, unsigned long,
*/
#ifdef CONFIG_SPARSEMEM
void sparse_init(void);
static inline void sparse_init_one_section(struct mem_section *ms,
unsigned long pnum, struct page *mem_map,
struct mem_section_usage *usage, unsigned long flags)
{
unsigned long coded_mem_map;
BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
/*
* We encode the start PFN of the section into the mem_map such that
* page_to_pfn() on !CONFIG_SPARSEMEM_VMEMMAP can simply subtract it
* from the page pointer to obtain the PFN.
*/
coded_mem_map = (unsigned long)(mem_map - section_nr_to_pfn(pnum));
VM_WARN_ON_ONCE(coded_mem_map & ~SECTION_MAP_MASK);
ms->section_mem_map &= ~SECTION_MAP_MASK;
ms->section_mem_map |= coded_mem_map;
ms->section_mem_map |= flags | SECTION_HAS_MEM_MAP;
ms->usage = usage;
}
#else
static inline void sparse_init(void) {}
#endif /* CONFIG_SPARSEMEM */

24
mm/sparse.c
View File

@ -256,30 +256,6 @@ static void __init memblocks_present(void)
memory_present(nid, start, end);
}
/*
* Subtle, we encode the real pfn into the mem_map such that
* the identity pfn - section_mem_map will return the actual
* physical page frame number.
*/
static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
{
unsigned long coded_mem_map =
(unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT);
BUG_ON(coded_mem_map & ~SECTION_MAP_MASK);
return coded_mem_map;
}
static void __meminit sparse_init_one_section(struct mem_section *ms,
unsigned long pnum, struct page *mem_map,
struct mem_section_usage *usage, unsigned long flags)
{
ms->section_mem_map &= ~SECTION_MAP_MASK;
ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum)
| SECTION_HAS_MEM_MAP | flags;
ms->usage = usage;
}
static unsigned long usemap_size(void)
{
return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);