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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     David Sterba <dsterba@suse.com>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        Nick Terrell <terrelln@fb.com>, linux-btrfs@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Kees Cook <keescook@chromium.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        "James E. J. Bottomley" <James.Bottomley@HansenPartnership.com>,
        Helge Deller <deller@gmx.de>,
        John David Anglin <dave.anglin@bell.net>,
        linux-parisc@vger.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
        David Sterba <dsterba@suse.cz>
Subject: [PATCH v5 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"
Date:   Mon,  4 Jul 2022 17:23:21 +0200
Message-Id: <20220704152322.20955-2-fmdefrancesco@gmail.com>
In-Reply-To: <20220704152322.20955-1-fmdefrancesco@gmail.com>
References: <20220704152322.20955-1-fmdefrancesco@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

__kunmap_ {local,atomic}() currently take pointers to void. However, this
is semantically incorrect, since these functions do not change the memory
their arguments point to.

Therefore, make this semantics explicit by modifying the
__kunmap_{local,atomic}() prototypes to take pointers to const void.

As a side effect, compilers will likely produce more efficient code.

Cc: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Sterba <dsterba@suse.cz>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
 arch/parisc/include/asm/cacheflush.h |  6 +++---
 arch/parisc/kernel/cache.c           |  2 +-
 include/linux/highmem-internal.h     | 10 +++++-----
 mm/highmem.c                         |  2 +-
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h
index 8d03b3b26229..0bdee6724132 100644
--- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -22,7 +22,7 @@ void flush_kernel_icache_range_asm(unsigned long, unsigned long);
 void flush_user_dcache_range_asm(unsigned long, unsigned long);
 void flush_kernel_dcache_range_asm(unsigned long, unsigned long);
 void purge_kernel_dcache_range_asm(unsigned long, unsigned long);
-void flush_kernel_dcache_page_asm(void *);
+void flush_kernel_dcache_page_asm(const void *addr);
 void flush_kernel_icache_page(void *);
 
 /* Cache flush operations */
@@ -31,7 +31,7 @@ void flush_cache_all_local(void);
 void flush_cache_all(void);
 void flush_cache_mm(struct mm_struct *mm);
 
-void flush_kernel_dcache_page_addr(void *addr);
+void flush_kernel_dcache_page_addr(const void *addr);
 
 #define flush_kernel_dcache_range(start,size) \
 	flush_kernel_dcache_range_asm((start), (start)+(size));
@@ -75,7 +75,7 @@ void flush_dcache_page_asm(unsigned long phys_addr, unsigned long vaddr);
 void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr);
 
 #define ARCH_HAS_FLUSH_ON_KUNMAP
-static inline void kunmap_flush_on_unmap(void *addr)
+static inline void kunmap_flush_on_unmap(const void *addr)
 {
 	flush_kernel_dcache_page_addr(addr);
 }
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index a9bc578e4c52..993999a65e54 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -549,7 +549,7 @@ extern void purge_kernel_dcache_page_asm(unsigned long);
 extern void clear_user_page_asm(void *, unsigned long);
 extern void copy_user_page_asm(void *, void *, unsigned long);
 
-void flush_kernel_dcache_page_addr(void *addr)
+void flush_kernel_dcache_page_addr(const void *addr)
 {
 	unsigned long flags;
 
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index cddb42ff0473..034b1106d022 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -8,7 +8,7 @@
 #ifdef CONFIG_KMAP_LOCAL
 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot);
 void *__kmap_local_page_prot(struct page *page, pgprot_t prot);
-void kunmap_local_indexed(void *vaddr);
+void kunmap_local_indexed(const void *vaddr);
 void kmap_local_fork(struct task_struct *tsk);
 void __kmap_local_sched_out(void);
 void __kmap_local_sched_in(void);
@@ -89,7 +89,7 @@ static inline void *kmap_local_pfn(unsigned long pfn)
 	return __kmap_local_pfn_prot(pfn, kmap_prot);
 }
 
-static inline void __kunmap_local(void *vaddr)
+static inline void __kunmap_local(const void *vaddr)
 {
 	kunmap_local_indexed(vaddr);
 }
@@ -121,7 +121,7 @@ static inline void *kmap_atomic_pfn(unsigned long pfn)
 	return __kmap_local_pfn_prot(pfn, kmap_prot);
 }
 
-static inline void __kunmap_atomic(void *addr)
+static inline void __kunmap_atomic(const void *addr)
 {
 	kunmap_local_indexed(addr);
 	pagefault_enable();
@@ -197,7 +197,7 @@ static inline void *kmap_local_pfn(unsigned long pfn)
 	return kmap_local_page(pfn_to_page(pfn));
 }
 
-static inline void __kunmap_local(void *addr)
+static inline void __kunmap_local(const void *addr)
 {
 #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
 	kunmap_flush_on_unmap(addr);
@@ -224,7 +224,7 @@ static inline void *kmap_atomic_pfn(unsigned long pfn)
 	return kmap_atomic(pfn_to_page(pfn));
 }
 
-static inline void __kunmap_atomic(void *addr)
+static inline void __kunmap_atomic(const void *addr)
 {
 #ifdef ARCH_HAS_FLUSH_ON_KUNMAP
 	kunmap_flush_on_unmap(addr);
diff --git a/mm/highmem.c b/mm/highmem.c
index 1a692997fac4..e32083e4ce0d 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -561,7 +561,7 @@ void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
 }
 EXPORT_SYMBOL(__kmap_local_page_prot);
 
-void kunmap_local_indexed(void *vaddr)
+void kunmap_local_indexed(const void *vaddr)
 {
 	unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
 	pte_t *kmap_pte;
-- 
2.36.1