mm: convert FPB_IGNORE_* into FPB_RESPECT_*

Patch series "mm: folio_pte_batch() improvements", v2.

Ever since we added folio_pte_batch() for fork() + munmap() purposes, a
lot more users appeared (and more are being proposed), and more
functionality was added.

Most of the users only need basic functionality, and could benefit from a
non-inlined version.

So let's clean up folio_pte_batch() and split it into a basic
folio_pte_batch() (no flags) and a more advanced folio_pte_batch_ext(). 
Using either variant will now look much cleaner.

This series will likely conflict with some changes in some (old+new)
folio_pte_batch() users, but conflicts should be trivial to resolve.


This patch (of 4):

Respecting these PTE bits is the exception, so let's invert the meaning.

With this change, most callers don't have to pass any flags.  This is a
preparation for splitting folio_pte_batch() into a non-inlined variant
that doesn't consume any flags.

Long-term, we want folio_pte_batch() to probably ignore most common PTE
bits (e.g., write/dirty/young/soft-dirty) that are not relevant for most
page table walkers: uffd-wp and protnone might be bits to consider in the
future.  Only walkers that care about them can opt-in to respect them.

No functional change intended.

Link: https://lkml.kernel.org/r/20250702104926.212243-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mathew Brost <matthew.brost@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/mm/internal.h b/mm/internal.h
index 2e235740128a..e530809ef7d2 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -202,17 +202,17 @@ static inline void vma_close(struct vm_area_struct *vma)
 /* Flags for folio_pte_batch(). */
 typedef int __bitwise fpb_t;
 
-/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */
-#define FPB_IGNORE_DIRTY		((__force fpb_t)BIT(0))
+/* Compare PTEs respecting the dirty bit. */
+#define FPB_RESPECT_DIRTY		((__force fpb_t)BIT(0))
 
-/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */
-#define FPB_IGNORE_SOFT_DIRTY		((__force fpb_t)BIT(1))
+/* Compare PTEs respecting the soft-dirty bit. */
+#define FPB_RESPECT_SOFT_DIRTY		((__force fpb_t)BIT(1))
 
 static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
 {
-	if (flags & FPB_IGNORE_DIRTY)
+	if (!(flags & FPB_RESPECT_DIRTY))
 		pte = pte_mkclean(pte);
-	if (likely(flags & FPB_IGNORE_SOFT_DIRTY))
+	if (likely(!(flags & FPB_RESPECT_SOFT_DIRTY)))
 		pte = pte_clear_soft_dirty(pte);
 	return pte_wrprotect(pte_mkold(pte));
 }
@@ -236,8 +236,8 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
  * pages of the same large folio.
  *
  * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN,
- * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and
- * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY).
+ * the accessed bit, writable bit, dirty bit (unless FPB_RESPECT_DIRTY is set)
+ * and soft-dirty bit (unless FPB_RESPECT_SOFT_DIRTY is set).
  *
  * start_ptep must map any page of the folio. max_nr must be at least one and
  * must be limited by the caller so scanning cannot exceed a single page table.