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[2003:dc:6f1d:f00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b01902d0e99sm541005766b.12.2025.09.01.02.19.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Sep 2025 02:19:34 -0700 (PDT) From: Max Kellermann To: akpm@linux-foundation.org, david@redhat.com, axelrasmussen@google.com, yuanchu@google.com, willy@infradead.org, hughd@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, vishal.moola@gmail.com, linux@armlinux.org.uk, James.Bottomley@HansenPartnership.com, deller@gmx.de, agordeev@linux.ibm.com, gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, davem@davemloft.net, andreas@gaisler.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, weixugc@google.com, baolin.wang@linux.alibaba.com, rientjes@google.com, shakeel.butt@linux.dev, max.kellermann@ionos.com, thuth@redhat.com, broonie@kernel.org, osalvador@suse.de, jfalempe@redhat.com, mpe@ellerman.id.au, nysal@linux.ibm.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v4 06/12] mm/util, s390: add const to pointer parameters for improved const-correctness Date: Mon, 1 Sep 2025 11:19:09 +0200 Message-ID: <20250901091916.3002082-7-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250901091916.3002082-1-max.kellermann@ionos.com> References: <20250901091916.3002082-1-max.kellermann@ionos.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Vishal Moola (Oracle) --- 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; } =20 -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_st= ruct *vma) { return false static inline bool vma_is_anon_shmem(const struct vm_area_struct *vma) { r= eturn false; } #endif =20 -int vma_is_stack_for_current(struct vm_area_struct *vma); +int vma_is_stack_for_current(const struct vm_area_struct *vma); =20 /* flush_tlb_range() takes a vma, not a mm, and can care about flags */ #define TLB_FLUSH_VMA(mm,flags) { .vm_mm =3D (mm), .vm_flags =3D (flags) } @@ -2585,7 +2585,7 @@ void folio_add_pin(struct folio *folio); =20 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 in= c, - struct task_struct *task, bool bypass_rlim); + const struct task_struct *task, bool bypass_rlim); =20 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_ch= ain *node); avc; avc =3D anon_vma_interval_tree_iter_next(avc, start, last)) =20 /* mmap.c */ -extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sy= s_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_stru= ct *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_s= pace *mapping) #endif } =20 -struct address_space *folio_mapping(struct folio *); +struct address_space *folio_mapping(const struct folio *folio); =20 /** * 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 le= n) EXPORT_SYMBOL(memdup_user_nul); =20 /* 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 =3D current; =20 @@ -410,7 +410,7 @@ unsigned long arch_mmap_rnd(void) return rnd << PAGE_SHIFT; } =20 -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 in= c, - struct task_struct *task, bool bypass_rlim) + const struct task_struct *const task, const bool bypass_rlim) { unsigned long locked_vm, limit; int ret =3D 0; @@ -688,7 +688,7 @@ struct anon_vma *folio_anon_vma(const struct folio *fol= io) * 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; =20 @@ -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; --=20 2.47.2