Re: [PATCH v3 35/40] mm: eliminate VMA_SPECIAL_FLAGS check in lru_gen_look_around()

A kernel-owned or fixed mapping is one which sets VMA_PFNMAP_BIT,
VMA_MIXEDMAP_BIT or VMA_DONTEXPAND_BIT, which is precisely what
VMA_SPECIAL_FLAGS tests for other than VMA_IO_BIT, which is safe to drop as
only kernel-owned mappings may set it.

Using these predicates rather than VMA_SPECIAL_FLAGS makes the check
self-documenting and helps eliminate the confusion around 'special' flags.

No functional change intended.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 mm/vmscan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 09ff20c3df5b..001f8b760266 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -4418,8 +4418,8 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw, unsigned int nr)
 	if (spin_is_contended(pvmw->ptl))
 		return true;
 
-	/* exclude special VMAs containing anon pages from COW */
-	if (vma->vm_flags & VM_SPECIAL)
+	/* exclude kernel-owned and fixed VMAs containing anon pages from COW */
+	if (vma_is_kernel_owned(vma) || vma_is_fixed_mapping(vma))
 		return true;