mm: introduce memdesc_flags_t

Patch series "Add and use memdesc_flags_t".

At some point struct page will be separated from struct slab and struct
folio.  This is a step towards that by introducing a type for the 'flags'
word of all three structures.  This gives us a certain amount of type
safety by establishing that some of these unsigned longs are different
from other unsigned longs in that they contain things like node ID,
section number and zone number in the upper bits.  That lets us have
functions that can be easily called by anyone who has a slab, folio or
page (but not easily by anyone else) to get the node or zone.

There's going to be some unusual merge problems with this as some odd bits
of the kernel decide they want to print out the flags value or something
similar by writing page->flags and now they'll need to write page->flags.f
instead.  That's most of the churn here.  Maybe we should be removing
these things from the debug output?


This patch (of 11):

Wrap the unsigned long flags in a typedef.  In upcoming patches, this will
provide a strong hint that you can't just pass a random unsigned long to
functions which take this as an argument.

[willy@infradead.org: s/flags/flags.f/ in several architectures]
  Link: https://lkml.kernel.org/r/aKMgPRLD-WnkPxYm@casper.infradead.org
[nicola.vetrini@gmail.com: mips: fix compilation error]
  Link: https://lore.kernel.org/lkml/CA+G9fYvkpmqGr6wjBNHY=dRp71PLCoi2341JxOudi60yqaeUdg@mail.gmail.com/
  Link: https://lkml.kernel.org/r/20250825214245.1838158-1-nicola.vetrini@gmail.com
Link: https://lkml.kernel.org/r/20250805172307.1302730-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20250805172307.1302730-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 11 insertions, 11 deletions

diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index 2a8155c4a882..44c1f757bfcf 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h
@@ -21,12 +21,12 @@ extern bool arch_hugetlb_migration_supported(struct hstate *h);
 
 static inline void arch_clear_hugetlb_flags(struct folio *folio)
 {
-	clear_bit(PG_dcache_clean, &folio->flags);
+	clear_bit(PG_dcache_clean, &folio->flags.f);
 
 #ifdef CONFIG_ARM64_MTE
 	if (system_supports_mte()) {
-		clear_bit(PG_mte_tagged, &folio->flags);
-		clear_bit(PG_mte_lock, &folio->flags);
+		clear_bit(PG_mte_tagged, &folio->flags.f);
+		clear_bit(PG_mte_lock, &folio->flags.f);
 	}
 #endif
 }
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index 6567df8ec8ca..3b5069f4683d 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -48,12 +48,12 @@ static inline void set_page_mte_tagged(struct page *page)
 	 * before the page flags update.
 	 */
 	smp_wmb();
-	set_bit(PG_mte_tagged, &page->flags);
+	set_bit(PG_mte_tagged, &page->flags.f);
 }
 
 static inline bool page_mte_tagged(struct page *page)
 {
-	bool ret = test_bit(PG_mte_tagged, &page->flags);
+	bool ret = test_bit(PG_mte_tagged, &page->flags.f);
 
 	VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page)));
 
@@ -82,7 +82,7 @@ static inline bool try_page_mte_tagging(struct page *page)
 {
 	VM_WARN_ON_ONCE(folio_test_hugetlb(page_folio(page)));
 
-	if (!test_and_set_bit(PG_mte_lock, &page->flags))
+	if (!test_and_set_bit(PG_mte_lock, &page->flags.f))
 		return true;
 
 	/*
@@ -90,7 +90,7 @@ static inline bool try_page_mte_tagging(struct page *page)
 	 * already. Check if the PG_mte_tagged flag has been set or wait
 	 * otherwise.
 	 */
-	smp_cond_load_acquire(&page->flags, VAL & (1UL << PG_mte_tagged));
+	smp_cond_load_acquire(&page->flags.f, VAL & (1UL << PG_mte_tagged));
 
 	return false;
 }
@@ -173,13 +173,13 @@ static inline void folio_set_hugetlb_mte_tagged(struct folio *folio)
 	 * before the folio flags update.
 	 */
 	smp_wmb();
-	set_bit(PG_mte_tagged, &folio->flags);
+	set_bit(PG_mte_tagged, &folio->flags.f);
 
 }
 
 static inline bool folio_test_hugetlb_mte_tagged(struct folio *folio)
 {
-	bool ret = test_bit(PG_mte_tagged, &folio->flags);
+	bool ret = test_bit(PG_mte_tagged, &folio->flags.f);
 
 	VM_WARN_ON_ONCE(!folio_test_hugetlb(folio));
 
@@ -196,7 +196,7 @@ static inline bool folio_try_hugetlb_mte_tagging(struct folio *folio)
 {
 	VM_WARN_ON_ONCE(!folio_test_hugetlb(folio));
 
-	if (!test_and_set_bit(PG_mte_lock, &folio->flags))
+	if (!test_and_set_bit(PG_mte_lock, &folio->flags.f))
 		return true;
 
 	/*
@@ -204,7 +204,7 @@ static inline bool folio_try_hugetlb_mte_tagging(struct folio *folio)
 	 * already. Check if the PG_mte_tagged flag has been set or wait
 	 * otherwise.
 	 */
-	smp_cond_load_acquire(&folio->flags, VAL & (1UL << PG_mte_tagged));
+	smp_cond_load_acquire(&folio->flags.f, VAL & (1UL << PG_mte_tagged));
 
 	return false;
 }