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mm: implement for_each_valid_pfn() for CONFIG_SPARSEMEM

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Implement for_each_valid_pfn() based on two helper functions.

The first_valid_pfn() function largely mirrors pfn_valid(), calling into a
pfn_section_first_valid() helper which is trivial for the !VMEMMAP case,
and in the VMEMMAP case will skip to the next subsection as needed.

Since next_valid_pfn() knows that its argument *is* a valid PFN, it
doesn't need to do any checking at all while iterating over the low bits
within a (sub)section mask; the whole (sub)section is either present or
not.

Note that the VMEMMAP version of pfn_section_first_valid() may return a
value *higher* than end_pfn when skipping to the next subsection, and
first_valid_pfn() happily returns that higher value.  This is fine.

[dwmw2@infradead.org: fix next_valid_pfn() for sparsemem]
  Link: https://lkml.kernel.org/r/c15100fcf6781a60b852c4dbb43bdc98a678fcf0.camel@infradead.org
Link: https://lkml.kernel.org/r/20250423133821.789413-4-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Woodhouse 2025-04-23 14:33:39 +01:00 committed by Andrew Morton
parent 928930c2e0
commit 037926316c
1 changed files with 78 additions and 0 deletions
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78
include/linux/mmzone.h
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@ -2075,11 +2075,37 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
return usage ? test_bit(idx, usage->subsection_map) : 0;
}
static inline bool pfn_section_first_valid(struct mem_section *ms, unsigned long *pfn)
{
struct mem_section_usage *usage = READ_ONCE(ms->usage);
int idx = subsection_map_index(*pfn);
unsigned long bit;
if (!usage)
return false;
if (test_bit(idx, usage->subsection_map))
return true;
/* Find the next subsection that exists */
bit = find_next_bit(usage->subsection_map, SUBSECTIONS_PER_SECTION, idx);
if (bit == SUBSECTIONS_PER_SECTION)
return false;
*pfn = (*pfn & PAGE_SECTION_MASK) + (bit * PAGES_PER_SUBSECTION);
return true;
}
#else
static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
{
return 1;
}
static inline bool pfn_section_first_valid(struct mem_section *ms, unsigned long *pfn)
{
return true;
}
#endif
void sparse_init_early_section(int nid, struct page *map, unsigned long pnum,
@ -2128,6 +2154,58 @@ static inline int pfn_valid(unsigned long pfn)
return ret;
}
/* Returns end_pfn or higher if no valid PFN remaining in range */
static inline unsigned long first_valid_pfn(unsigned long pfn, unsigned long end_pfn)
{
unsigned long nr = pfn_to_section_nr(pfn);
rcu_read_lock_sched();
while (nr <= __highest_present_section_nr && pfn < end_pfn) {
struct mem_section *ms = __pfn_to_section(pfn);
if (valid_section(ms) &&
(early_section(ms) || pfn_section_first_valid(ms, &pfn))) {
rcu_read_unlock_sched();
return pfn;
}
/* Nothing left in this section? Skip to next section */
nr++;
pfn = section_nr_to_pfn(nr);
}
rcu_read_unlock_sched();
return end_pfn;
}
static inline unsigned long next_valid_pfn(unsigned long pfn, unsigned long end_pfn)
{
pfn++;
if (pfn >= end_pfn)
return end_pfn;
/*
* 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() again when crossing a
* (sub)section boundary (i.e. !(pfn & ~PAGE_{SUB,}SECTION_MASK)).
*/
if (pfn & ~(IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) ?
PAGE_SUBSECTION_MASK : PAGE_SECTION_MASK))
return pfn;
return first_valid_pfn(pfn, end_pfn);
}
#define for_each_valid_pfn(_pfn, _start_pfn, _end_pfn) \
for ((_pfn) = first_valid_pfn((_start_pfn), (_end_pfn)); \
(_pfn) < (_end_pfn); \
(_pfn) = next_valid_pfn((_pfn), (_end_pfn)))
#endif
static inline int pfn_in_present_section(unsigned long pfn)