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>

7 files changed, 11 insertions, 11 deletions

diff --git a/arch/arm/include/asm/hugetlb.h b/arch/arm/include/asm/hugetlb.h
index b766c4b373f6..700055b1ccb3 100644
--- a/arch/arm/include/asm/hugetlb.h
+++ b/arch/arm/include/asm/hugetlb.h
@@ -17,7 +17,7 @@
 
 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);
 }
 #define arch_clear_hugetlb_flags arch_clear_hugetlb_flags
 
diff --git a/arch/arm/mm/copypage-v4mc.c b/arch/arm/mm/copypage-v4mc.c
index 7ddd82b9fe8b..ed843bb22020 100644
--- a/arch/arm/mm/copypage-v4mc.c
+++ b/arch/arm/mm/copypage-v4mc.c
@@ -67,7 +67,7 @@ void v4_mc_copy_user_highpage(struct page *to, struct page *from,
 	struct folio *src = page_folio(from);
 	void *kto = kmap_atomic(to);
 
-	if (!test_and_set_bit(PG_dcache_clean, &src->flags))
+	if (!test_and_set_bit(PG_dcache_clean, &src->flags.f))
 		__flush_dcache_folio(folio_flush_mapping(src), src);
 
 	raw_spin_lock(&minicache_lock);
diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
index a1a71f36d850..0710dba5c0bf 100644
--- a/arch/arm/mm/copypage-v6.c
+++ b/arch/arm/mm/copypage-v6.c
@@ -73,7 +73,7 @@ static void v6_copy_user_highpage_aliasing(struct page *to,
 	unsigned int offset = CACHE_COLOUR(vaddr);
 	unsigned long kfrom, kto;
 
-	if (!test_and_set_bit(PG_dcache_clean, &src->flags))
+	if (!test_and_set_bit(PG_dcache_clean, &src->flags.f))
 		__flush_dcache_folio(folio_flush_mapping(src), src);
 
 	/* FIXME: not highmem safe */
diff --git a/arch/arm/mm/copypage-xscale.c b/arch/arm/mm/copypage-xscale.c
index f1e29d3e8193..e16af68d709f 100644
--- a/arch/arm/mm/copypage-xscale.c
+++ b/arch/arm/mm/copypage-xscale.c
@@ -87,7 +87,7 @@ void xscale_mc_copy_user_highpage(struct page *to, struct page *from,
 	struct folio *src = page_folio(from);
 	void *kto = kmap_atomic(to);
 
-	if (!test_and_set_bit(PG_dcache_clean, &src->flags))
+	if (!test_and_set_bit(PG_dcache_clean, &src->flags.f))
 		__flush_dcache_folio(folio_flush_mapping(src), src);
 
 	raw_spin_lock(&minicache_lock);
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 88c2d68a69c9..08641a936394 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -718,7 +718,7 @@ static void __dma_page_dev_to_cpu(struct page *page, unsigned long off,
 			if (size < sz)
 				break;
 			if (!offset)
-				set_bit(PG_dcache_clean, &folio->flags);
+				set_bit(PG_dcache_clean, &folio->flags.f);
 			offset = 0;
 			size -= sz;
 			if (!size)
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index 39fd5df73317..91e488767783 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c
@@ -203,7 +203,7 @@ void update_mmu_cache_range(struct vm_fault *vmf, struct vm_area_struct *vma,
 
 	folio = page_folio(pfn_to_page(pfn));
 	mapping = folio_flush_mapping(folio);
-	if (!test_and_set_bit(PG_dcache_clean, &folio->flags))
+	if (!test_and_set_bit(PG_dcache_clean, &folio->flags.f))
 		__flush_dcache_folio(mapping, folio);
 	if (mapping) {
 		if (cache_is_vivt())
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 5219158d54cf..19470d938b23 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -304,7 +304,7 @@ void __sync_icache_dcache(pte_t pteval)
 	else
 		mapping = NULL;
 
-	if (!test_and_set_bit(PG_dcache_clean, &folio->flags))
+	if (!test_and_set_bit(PG_dcache_clean, &folio->flags.f))
 		__flush_dcache_folio(mapping, folio);
 
 	if (pte_exec(pteval))
@@ -343,8 +343,8 @@ void flush_dcache_folio(struct folio *folio)
 		return;
 
 	if (!cache_ops_need_broadcast() && cache_is_vipt_nonaliasing()) {
-		if (test_bit(PG_dcache_clean, &folio->flags))
-			clear_bit(PG_dcache_clean, &folio->flags);
+		if (test_bit(PG_dcache_clean, &folio->flags.f))
+			clear_bit(PG_dcache_clean, &folio->flags.f);
 		return;
 	}
 
@@ -352,14 +352,14 @@ void flush_dcache_folio(struct folio *folio)
 
 	if (!cache_ops_need_broadcast() &&
 	    mapping && !folio_mapped(folio))
-		clear_bit(PG_dcache_clean, &folio->flags);
+		clear_bit(PG_dcache_clean, &folio->flags.f);
 	else {
 		__flush_dcache_folio(mapping, folio);
 		if (mapping && cache_is_vivt())
 			__flush_dcache_aliases(mapping, folio);
 		else if (mapping)
 			__flush_icache_all();
-		set_bit(PG_dcache_clean, &folio->flags);
+		set_bit(PG_dcache_clean, &folio->flags.f);
 	}
 }
 EXPORT_SYMBOL(flush_dcache_folio);