The memory management (mm) subsystem is a fundamental low-level component
of the Linux kernel. Establishing const-correctness at this foundational
level enables higher-level subsystems, such as filesystems and drivers,
to also adopt const-correctness in their interfaces. This patch lays
the groundwork for broader const-correctness throughout the kernel
by starting with the core mm subsystem.
This patch adds const qualifiers to vm_area_struct, vm_fault, page, and
vmem_altmap pointer parameters in core mm functions that do not modify
the referenced memory, improving type safety and enabling compiler
optimizations.
Functions improved:
- assert_fault_locked()
- vma_is_temporary_stack()
- vma_is_foreign()
- vma_is_accessible()
- vma_is_shared_maywrite()
- stack_guard_start_gap()
- vm_start_gap()
- vm_end_gap()
- vma_pages()
- range_in_vma()
- gup_can_follow_protnone()
- page_is_guard()
- vmem_altmap_offset()
Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
---
include/linux/mm.h | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 23864c3519d6..08ea6e7c0329 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -703,7 +703,7 @@ static inline void release_fault_lock(struct vm_fault *vmf)
mmap_read_unlock(vmf->vma->vm_mm);
}
-static inline void assert_fault_locked(struct vm_fault *vmf)
+static inline void assert_fault_locked(struct vm_fault *const vmf)
{
if (vmf->flags & FAULT_FLAG_VMA_LOCK)
vma_assert_locked(vmf->vma);
@@ -716,7 +716,7 @@ static inline void release_fault_lock(struct vm_fault *vmf)
mmap_read_unlock(vmf->vma->vm_mm);
}
-static inline void assert_fault_locked(struct vm_fault *vmf)
+static inline void assert_fault_locked(const struct vm_fault *vmf)
{
mmap_assert_locked(vmf->vma->vm_mm);
}
@@ -859,7 +859,7 @@ static inline bool vma_is_initial_stack(const struct vm_area_struct *vma)
vma->vm_end >= vma->vm_mm->start_stack;
}
-static inline bool vma_is_temporary_stack(struct vm_area_struct *vma)
+static inline bool vma_is_temporary_stack(const struct vm_area_struct *const vma)
{
int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
@@ -873,7 +873,7 @@ static inline bool vma_is_temporary_stack(struct vm_area_struct *vma)
return false;
}
-static inline bool vma_is_foreign(struct vm_area_struct *vma)
+static inline bool vma_is_foreign(const struct vm_area_struct *const vma)
{
if (!current->mm)
return true;
@@ -884,7 +884,7 @@ static inline bool vma_is_foreign(struct vm_area_struct *vma)
return false;
}
-static inline bool vma_is_accessible(struct vm_area_struct *vma)
+static inline bool vma_is_accessible(const struct vm_area_struct *const vma)
{
return vma->vm_flags & VM_ACCESS_FLAGS;
}
@@ -895,7 +895,7 @@ static inline bool is_shared_maywrite(vm_flags_t vm_flags)
(VM_SHARED | VM_MAYWRITE);
}
-static inline bool vma_is_shared_maywrite(struct vm_area_struct *vma)
+static inline bool vma_is_shared_maywrite(const struct vm_area_struct *const vma)
{
return is_shared_maywrite(vma->vm_flags);
}
@@ -3488,7 +3488,7 @@ struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
return mtree_load(&mm->mm_mt, addr);
}
-static inline unsigned long stack_guard_start_gap(struct vm_area_struct *vma)
+static inline unsigned long stack_guard_start_gap(const struct vm_area_struct *const vma)
{
if (vma->vm_flags & VM_GROWSDOWN)
return stack_guard_gap;
@@ -3500,7 +3500,7 @@ static inline unsigned long stack_guard_start_gap(struct vm_area_struct *vma)
return 0;
}
-static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
+static inline unsigned long vm_start_gap(const struct vm_area_struct *const vma)
{
unsigned long gap = stack_guard_start_gap(vma);
unsigned long vm_start = vma->vm_start;
@@ -3511,7 +3511,7 @@ static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
return vm_start;
}
-static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
+static inline unsigned long vm_end_gap(const struct vm_area_struct *const vma)
{
unsigned long vm_end = vma->vm_end;
@@ -3523,7 +3523,7 @@ static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
return vm_end;
}
-static inline unsigned long vma_pages(struct vm_area_struct *vma)
+static inline unsigned long vma_pages(const struct vm_area_struct *const vma)
{
return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
}
@@ -3540,7 +3540,7 @@ static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
return vma;
}
-static inline bool range_in_vma(struct vm_area_struct *vma,
+static inline bool range_in_vma(const struct vm_area_struct *const vma,
unsigned long start, unsigned long end)
{
return (vma && vma->vm_start <= start && end <= vma->vm_end);
@@ -3656,7 +3656,7 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags)
* Indicates whether GUP can follow a PROT_NONE mapped page, or whether
* a (NUMA hinting) fault is required.
*/
-static inline bool gup_can_follow_protnone(struct vm_area_struct *vma,
+static inline bool gup_can_follow_protnone(const struct vm_area_struct *const vma,
unsigned int flags)
{
/*
@@ -3786,7 +3786,7 @@ static inline bool debug_guardpage_enabled(void)
return static_branch_unlikely(&_debug_guardpage_enabled);
}
-static inline bool page_is_guard(struct page *page)
+static inline bool page_is_guard(const struct page *const page)
{
if (!debug_guardpage_enabled())
return false;
@@ -3817,7 +3817,7 @@ static inline void debug_pagealloc_map_pages(struct page *page, int numpages) {}
static inline void debug_pagealloc_unmap_pages(struct page *page, int numpages) {}
static inline unsigned int debug_guardpage_minorder(void) { return 0; }
static inline bool debug_guardpage_enabled(void) { return false; }
-static inline bool page_is_guard(struct page *page) { return false; }
+static inline bool page_is_guard(const struct page *const page) { return false; }
static inline bool set_page_guard(struct zone *zone, struct page *page,
unsigned int order) { return false; }
static inline void clear_page_guard(struct zone *zone, struct page *page,
@@ -3899,7 +3899,7 @@ void vmemmap_free(unsigned long start, unsigned long end,
#endif
#ifdef CONFIG_SPARSEMEM_VMEMMAP
-static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+static inline unsigned long vmem_altmap_offset(const struct vmem_altmap *altmap)
{
/* number of pfns from base where pfn_to_page() is valid */
if (altmap)
@@ -3913,7 +3913,7 @@ static inline void vmem_altmap_free(struct vmem_altmap *altmap,
altmap->alloc -= nr_pfns;
}
#else
-static inline unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
+static inline unsigned long vmem_altmap_offset(const struct vmem_altmap *altmap)
{
return 0;
}
--
2.47.2
