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[2003:dc:6f1d:f00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b01902d0e99sm541005766b.12.2025.09.01.02.19.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Sep 2025 02:19:27 -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 02/12] mm/pagemap: add `const` to pointer parameters for improved const-correctness Date: Mon, 1 Sep 2025 11:19:05 +0200 Message-ID: <20250901091916.3002082-3-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 address_space, folio, vm_area_struct, readahead_control, and inode pointer parameters in pagemap.h functions that do not modify the referenced memory, improving type safety and enabling compiler optimizations. Functions improved: - mapping_empty() - mapping_shrinkable() - mapping_unevictable() - mapping_exiting() - mapping_use_writeback_tags() - mapping_inaccessible() - mapping_writeback_may_deadlock_on_reclaim() - mapping_gfp_mask() - mapping_gfp_constraint() - mapping_min_folio_nrpages() - mapping_min_folio_nrbytes() - mapping_align_index() - mapping_large_folio_support() - filemap_nr_thps() - folio_next_index() - folio_contains() - folio_pgoff() - linear_page_index() - readahead_pos() - readahead_length() - readahead_index() - readahead_count() - readahead_batch_length() - dir_pages() - folio_mkwrite_check_truncate() Constify pagemap related test functions for improved const-correctness. Signed-off-by: Max Kellermann Reviewed-by: Vishal Moola (Oracle) --- include/linux/pagemap.h | 57 +++++++++++++++++++++-------------------- 1 file changed, 29 insertions(+), 28 deletions(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index a3e16d74792f..1d35f9e1416e 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -140,7 +140,7 @@ static inline int inode_drain_writes(struct inode *inod= e) return filemap_write_and_wait(inode->i_mapping); } =20 -static inline bool mapping_empty(struct address_space *mapping) +static inline bool mapping_empty(const struct address_space *const mapping) { return xa_empty(&mapping->i_pages); } @@ -166,7 +166,7 @@ static inline bool mapping_empty(struct address_space *= mapping) * refcount and the referenced bit, which will be elevated or set in * the process of adding new cache pages to an inode. */ -static inline bool mapping_shrinkable(struct address_space *mapping) +static inline bool mapping_shrinkable(const struct address_space *const ma= pping) { void *head; =20 @@ -267,7 +267,7 @@ static inline void mapping_clear_unevictable(struct add= ress_space *mapping) clear_bit(AS_UNEVICTABLE, &mapping->flags); } =20 -static inline bool mapping_unevictable(struct address_space *mapping) +static inline bool mapping_unevictable(const struct address_space *const m= apping) { return mapping && test_bit(AS_UNEVICTABLE, &mapping->flags); } @@ -277,7 +277,7 @@ static inline void mapping_set_exiting(struct address_s= pace *mapping) set_bit(AS_EXITING, &mapping->flags); } =20 -static inline int mapping_exiting(struct address_space *mapping) +static inline int mapping_exiting(const struct address_space *const mappin= g) { return test_bit(AS_EXITING, &mapping->flags); } @@ -287,7 +287,7 @@ static inline void mapping_set_no_writeback_tags(struct= address_space *mapping) set_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags); } =20 -static inline int mapping_use_writeback_tags(struct address_space *mapping) +static inline int mapping_use_writeback_tags(const struct address_space *c= onst mapping) { return !test_bit(AS_NO_WRITEBACK_TAGS, &mapping->flags); } @@ -333,7 +333,7 @@ static inline void mapping_set_inaccessible(struct addr= ess_space *mapping) set_bit(AS_INACCESSIBLE, &mapping->flags); } =20 -static inline bool mapping_inaccessible(struct address_space *mapping) +static inline bool mapping_inaccessible(const struct address_space *const = mapping) { return test_bit(AS_INACCESSIBLE, &mapping->flags); } @@ -343,18 +343,18 @@ static inline void mapping_set_writeback_may_deadlock= _on_reclaim(struct address_ set_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags); } =20 -static inline bool mapping_writeback_may_deadlock_on_reclaim(struct addres= s_space *mapping) +static inline bool mapping_writeback_may_deadlock_on_reclaim(const struct = address_space *const mapping) { return test_bit(AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM, &mapping->flags); } =20 -static inline gfp_t mapping_gfp_mask(struct address_space * mapping) +static inline gfp_t mapping_gfp_mask(const struct address_space *const map= ping) { return mapping->gfp_mask; } =20 /* Restricts the given gfp_mask to what the mapping allows. */ -static inline gfp_t mapping_gfp_constraint(struct address_space *mapping, +static inline gfp_t mapping_gfp_constraint(const struct address_space *map= ping, gfp_t gfp_mask) { return mapping_gfp_mask(mapping) & gfp_mask; @@ -477,13 +477,13 @@ mapping_min_folio_order(const struct address_space *m= apping) } =20 static inline unsigned long -mapping_min_folio_nrpages(struct address_space *mapping) +mapping_min_folio_nrpages(const struct address_space *const mapping) { return 1UL << mapping_min_folio_order(mapping); } =20 static inline unsigned long -mapping_min_folio_nrbytes(struct address_space *mapping) +mapping_min_folio_nrbytes(const struct address_space *const mapping) { return mapping_min_folio_nrpages(mapping) << PAGE_SHIFT; } @@ -497,7 +497,7 @@ mapping_min_folio_nrbytes(struct address_space *mapping) * new folio to the page cache and need to know what index to give it, * call this function. */ -static inline pgoff_t mapping_align_index(struct address_space *mapping, +static inline pgoff_t mapping_align_index(const struct address_space *cons= t mapping, pgoff_t index) { return round_down(index, mapping_min_folio_nrpages(mapping)); @@ -507,7 +507,7 @@ static inline pgoff_t mapping_align_index(struct addres= s_space *mapping, * Large folio support currently depends on THP. These dependencies are * being worked on but are not yet fixed. */ -static inline bool mapping_large_folio_support(struct address_space *mappi= ng) +static inline bool mapping_large_folio_support(const struct address_space = *mapping) { /* AS_FOLIO_ORDER is only reasonable for pagecache folios */ VM_WARN_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON, @@ -522,7 +522,7 @@ static inline size_t mapping_max_folio_size(const struc= t address_space *mapping) return PAGE_SIZE << mapping_max_folio_order(mapping); } =20 -static inline int filemap_nr_thps(struct address_space *mapping) +static inline int filemap_nr_thps(const struct address_space *const mappin= g) { #ifdef CONFIG_READ_ONLY_THP_FOR_FS return atomic_read(&mapping->nr_thps); @@ -936,7 +936,7 @@ static inline struct page *grab_cache_page_nowait(struc= t address_space *mapping, * * Return: The index of the folio which follows this folio in the file. */ -static inline pgoff_t folio_next_index(struct folio *folio) +static inline pgoff_t folio_next_index(const struct folio *const folio) { return folio->index + folio_nr_pages(folio); } @@ -965,7 +965,7 @@ static inline struct page *folio_file_page(struct folio= *folio, pgoff_t index) * e.g., shmem did not move this folio to the swap cache. * Return: true or false. */ -static inline bool folio_contains(struct folio *folio, pgoff_t index) +static inline bool folio_contains(const struct folio *const folio, pgoff_t= index) { VM_WARN_ON_ONCE_FOLIO(folio_test_swapcache(folio), folio); return index - folio->index < folio_nr_pages(folio); @@ -1042,13 +1042,13 @@ static inline loff_t page_offset(struct page *page) /* * Get the offset in PAGE_SIZE (even for hugetlb folios). */ -static inline pgoff_t folio_pgoff(struct folio *folio) +static inline pgoff_t folio_pgoff(const struct folio *const folio) { return folio->index; } =20 -static inline pgoff_t linear_page_index(struct vm_area_struct *vma, - unsigned long address) +static inline pgoff_t linear_page_index(const struct vm_area_struct *const= vma, + const unsigned long address) { pgoff_t pgoff; pgoff =3D (address - vma->vm_start) >> PAGE_SHIFT; @@ -1468,7 +1468,7 @@ static inline unsigned int __readahead_batch(struct r= eadahead_control *rac, * readahead_pos - The byte offset into the file of this readahead request. * @rac: The readahead request. */ -static inline loff_t readahead_pos(struct readahead_control *rac) +static inline loff_t readahead_pos(const struct readahead_control *const r= ac) { return (loff_t)rac->_index * PAGE_SIZE; } @@ -1477,7 +1477,7 @@ static inline loff_t readahead_pos(struct readahead_c= ontrol *rac) * readahead_length - The number of bytes in this readahead request. * @rac: The readahead request. */ -static inline size_t readahead_length(struct readahead_control *rac) +static inline size_t readahead_length(const struct readahead_control *cons= t rac) { return rac->_nr_pages * PAGE_SIZE; } @@ -1486,7 +1486,7 @@ static inline size_t readahead_length(struct readahea= d_control *rac) * readahead_index - The index of the first page in this readahead request. * @rac: The readahead request. */ -static inline pgoff_t readahead_index(struct readahead_control *rac) +static inline pgoff_t readahead_index(const struct readahead_control *cons= t rac) { return rac->_index; } @@ -1495,7 +1495,7 @@ static inline pgoff_t readahead_index(struct readahea= d_control *rac) * readahead_count - The number of pages in this readahead request. * @rac: The readahead request. */ -static inline unsigned int readahead_count(struct readahead_control *rac) +static inline unsigned int readahead_count(const struct readahead_control = *const rac) { return rac->_nr_pages; } @@ -1504,12 +1504,12 @@ static inline unsigned int readahead_count(struct r= eadahead_control *rac) * readahead_batch_length - The number of bytes in the current batch. * @rac: The readahead request. */ -static inline size_t readahead_batch_length(struct readahead_control *rac) +static inline size_t readahead_batch_length(const struct readahead_control= *const rac) { return rac->_batch_count * PAGE_SIZE; } =20 -static inline unsigned long dir_pages(struct inode *inode) +static inline unsigned long dir_pages(const struct inode *const inode) { return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; @@ -1523,8 +1523,8 @@ static inline unsigned long dir_pages(struct inode *i= node) * Return: the number of bytes in the folio up to EOF, * or -EFAULT if the folio was truncated. */ -static inline ssize_t folio_mkwrite_check_truncate(struct folio *folio, - struct inode *inode) +static inline ssize_t folio_mkwrite_check_truncate(const struct folio *con= st folio, + const struct inode *const inode) { loff_t size =3D i_size_read(inode); pgoff_t index =3D size >> PAGE_SHIFT; @@ -1555,7 +1555,8 @@ static inline ssize_t folio_mkwrite_check_truncate(st= ruct folio *folio, * Return: The number of filesystem blocks covered by this folio. */ static inline -unsigned int i_blocks_per_folio(struct inode *inode, struct folio *folio) +unsigned int i_blocks_per_folio(const struct inode *const inode, + const struct folio *const folio) { return folio_size(folio) >> inode->i_blkbits; } --=20 2.47.2