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 rlimit, vm_area_struct, mm_struct,
and folio pointer parameters in mm/util.c and s390 arch code that do not
modify the referenced memory, improving type safety and enabling compiler
optimizations.
Functions improved:
- mmap_is_legacy() (both mm/util.c and s390)
- vma_is_stack_for_current()
- __vm_enough_memory()
- folio_mapping()
Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
---
arch/s390/mm/mmap.c | 2 +-
include/linux/mm.h | 6 +++---
include/linux/pagemap.h | 2 +-
mm/util.c | 11 ++++++-----
4 files changed, 11 insertions(+), 10 deletions(-)
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 547104ccc22a..c0f619fb9ab3 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -27,7 +27,7 @@ static unsigned long stack_maxrandom_size(void)
return STACK_RND_MASK << PAGE_SHIFT;
}
-static inline int mmap_is_legacy(struct rlimit *rlim_stack)
+static inline int mmap_is_legacy(const struct rlimit *const rlim_stack)
{
if (current->personality & ADDR_COMPAT_LAYOUT)
return 1;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f70c6b4d5f80..23864c3519d6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -986,7 +986,7 @@ static inline bool vma_is_shmem(const struct vm_area_struct *vma) { return false
static inline bool vma_is_anon_shmem(const struct vm_area_struct *vma) { return false; }
#endif
-int vma_is_stack_for_current(struct vm_area_struct *vma);
+int vma_is_stack_for_current(const struct vm_area_struct *vma);
/* flush_tlb_range() takes a vma, not a mm, and can care about flags */
#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }
@@ -2585,7 +2585,7 @@ void folio_add_pin(struct folio *folio);
int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc);
int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
- struct task_struct *task, bool bypass_rlim);
+ const struct task_struct *task, bool bypass_rlim);
struct kvec;
struct page *get_dump_page(unsigned long addr, int *locked);
@@ -3348,7 +3348,7 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
avc; avc = anon_vma_interval_tree_iter_next(avc, start, last))
/* mmap.c */
-extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
+extern int __vm_enough_memory(const struct mm_struct *mm, long pages, int cap_sys_admin);
extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
extern void exit_mmap(struct mm_struct *);
bool mmap_read_lock_maybe_expand(struct mm_struct *mm, struct vm_area_struct *vma,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 1d35f9e1416e..968b58a97236 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -551,7 +551,7 @@ static inline void filemap_nr_thps_dec(struct address_space *mapping)
#endif
}
-struct address_space *folio_mapping(struct folio *);
+struct address_space *folio_mapping(const struct folio *folio);
/**
* folio_flush_mapping - Find the file mapping this folio belongs to.
diff --git a/mm/util.c b/mm/util.c
index d235b74f7aff..f5a35efba7bf 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -315,7 +315,7 @@ void *memdup_user_nul(const void __user *src, size_t len)
EXPORT_SYMBOL(memdup_user_nul);
/* Check if the vma is being used as a stack by this task */
-int vma_is_stack_for_current(struct vm_area_struct *vma)
+int vma_is_stack_for_current(const struct vm_area_struct *const vma)
{
struct task_struct * __maybe_unused t = current;
@@ -410,7 +410,7 @@ unsigned long arch_mmap_rnd(void)
return rnd << PAGE_SHIFT;
}
-static int mmap_is_legacy(struct rlimit *rlim_stack)
+static int mmap_is_legacy(const struct rlimit *const rlim_stack)
{
if (current->personality & ADDR_COMPAT_LAYOUT)
return 1;
@@ -504,7 +504,7 @@ EXPORT_SYMBOL_IF_KUNIT(arch_pick_mmap_layout);
* * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
*/
int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
- struct task_struct *task, bool bypass_rlim)
+ const struct task_struct *const task, const bool bypass_rlim)
{
unsigned long locked_vm, limit;
int ret = 0;
@@ -688,7 +688,7 @@ struct anon_vma *folio_anon_vma(const struct folio *folio)
* You can call this for folios which aren't in the swap cache or page
* cache and it will return NULL.
*/
-struct address_space *folio_mapping(struct folio *folio)
+struct address_space *folio_mapping(const struct folio *const folio)
{
struct address_space *mapping;
@@ -926,7 +926,8 @@ EXPORT_SYMBOL_GPL(vm_memory_committed);
* Note this is a helper function intended to be used by LSMs which
* wish to use this logic.
*/
-int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
+int __vm_enough_memory(const struct mm_struct *const mm,
+ const long pages, const int cap_sys_admin)
{
long allowed;
unsigned long bytes_failed;
--
2.47.2
