[PATCH 33/39] mm: eliminate VMA_SPECIAL_FLAGS usage when hugetlb explicitly tested
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Date: 2026-09-08 20:18:11
Also in:
bpf, dri-devel, fuse-devel, kvm, kvm-riscv, kvmarm, linux-arch, linux-doc, linux-fbdev, linux-fsdevel, linux-mm, linux-perf-users, linux-s390, linux-scsi, linux-sound, linux-trace-kernel, linux-usb, linuxppc-dev, lkml, selinux, sparclinux
Subsystem:
memory management, memory management - core, memory management - ksm (kernel samepage merging), memory management - mglru (multi-gen lru), memory management - reclaim, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Johannes Weiner, Linus Torvalds
It is now an invariant that VMA_IO_BIT is not set except by kernel-owned mappings, so each existing VMA_SPECIAL_FLAGS test need only test for VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT and VMA_MIXEDMAP_BIT. This is precisely a test for a kernel-owned or fixed mapping. Update a number of callsites which already explicitly handle hugetlb mappings. vma_supports_mlock() and ksm_compatible() also explicitly bail on droppable mappings - detecting kernel-owned, fixed or droppable mappings is handled by vma_is_persistent(), so in these cases use this predicate. should_skip_vma() tests for locked, kernel-owned or fixed memory (having already excluded hugetlb mappings) so simply test for those there. No functional change intended. Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> --- mm/internal.h | 4 +--- mm/ksm.c | 4 +--- mm/vmscan.c | 3 ++- 3 files changed, 4 insertions(+), 7 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 104bbca1eb57..6c004037913b 100644
--- a/mm/internal.h
+++ b/mm/internal.h@@ -1112,9 +1112,7 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, static inline bool vma_supports_mlock(const struct vm_area_struct *vma) { - if (vma_test_any_mask(vma, VMA_SPECIAL_FLAGS)) - return false; - if (vma_test_single_mask(vma, VMA_DROPPABLE)) + if (!vma_is_persistent(vma)) return false; if (vma_is_dax(vma) || vma_is_hugetlb(vma)) return false;
diff --git a/mm/ksm.c b/mm/ksm.c
index 624f37975e12..f80372bfd4b2 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c@@ -747,9 +747,7 @@ static bool ksm_compatible(const struct file *file, vma_flags_t vma_flags) if (vma_flags_test_any(&vma_flags, VMA_SHARED_BIT, VMA_MAYSHARE_BIT, VMA_HUGETLB_BIT)) return false; - if (vma_flags_test_single_mask(&vma_flags, VMA_DROPPABLE)) - return false; - if (vma_flags_test_any_mask(&vma_flags, VMA_SPECIAL_FLAGS)) + if (!vma_flags_is_persistent(&vma_flags)) return false; if (file_is_dax(file)) return false;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9cbfb90b0ad1..803754caf4fa 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c@@ -3419,7 +3419,8 @@ static int should_skip_vma(unsigned long start, unsigned long end, struct mm_wal if (!vma_has_recency(vma)) return true; - if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) + if (vma_test(vma, VMA_LOCKED_BIT) || vma_is_kernel_owned(vma) || + vma_is_fixed_mapping(vma)) return true; if (vma == get_gate_vma(vma->vm_mm))
--
2.55.0