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>

1 files changed, 6 insertions, 6 deletions

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index dfaa9fd86f7e..56d7e8960e77 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -87,9 +87,9 @@ static pte_t set_pte_filter_hash(pte_t pte, unsigned long addr)
 		struct folio *folio = maybe_pte_to_folio(pte);
 		if (!folio)
 			return pte;
-		if (!test_bit(PG_dcache_clean, &folio->flags)) {
+		if (!test_bit(PG_dcache_clean, &folio->flags.f)) {
 			flush_dcache_icache_folio(folio);
-			set_bit(PG_dcache_clean, &folio->flags);
+			set_bit(PG_dcache_clean, &folio->flags.f);
 		}
 	}
 	return pte;
@@ -127,13 +127,13 @@ static inline pte_t set_pte_filter(pte_t pte, unsigned long addr)
 		return pte;
 
 	/* If the page clean, we move on */
-	if (test_bit(PG_dcache_clean, &folio->flags))
+	if (test_bit(PG_dcache_clean, &folio->flags.f))
 		return pte;
 
 	/* If it's an exec fault, we flush the cache and make it clean */
 	if (is_exec_fault()) {
 		flush_dcache_icache_folio(folio);
-		set_bit(PG_dcache_clean, &folio->flags);
+		set_bit(PG_dcache_clean, &folio->flags.f);
 		return pte;
 	}
 
@@ -175,12 +175,12 @@ static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma,
 		goto bail;
 
 	/* If the page is already clean, we move on */
-	if (test_bit(PG_dcache_clean, &folio->flags))
+	if (test_bit(PG_dcache_clean, &folio->flags.f))
 		goto bail;
 
 	/* Clean the page and set PG_dcache_clean */
 	flush_dcache_icache_folio(folio);
-	set_bit(PG_dcache_clean, &folio->flags);
+	set_bit(PG_dcache_clean, &folio->flags.f);
 
  bail:
 	return pte_mkexec(pte);