[PATCH v3 0/2] Replace kmap() with kmap_local_page() in zstd.c

[PATCH v3 0/2] Replace kmap() with kmap_local_page() in zstd.c

[Fabio M. De Francesco]

This is a little series which serves the purpose to replace kmap() with
kmap_local_page() in btrfs/zstd.c. Actually this task is only
accomplished in patch 2/2. 

Instead patch 1/2 is a pre-requisite for the above-mentioned replacement,
but, above all else, it has the purpose to conform the prototypes of
__kunmap_{local,atomic}() to their own semantic. Since those functions
don't make changes to the memory pointed by their arguments, make those
arguments take pointers to const void.

This little series has version number 3, despite it's the first time the
two component patches have been re-united in a series. This may be a
questionable choice, however patch 1/2 should be at its v3 and patch 2/2
should be at its v2. I've tried to preserve the logs of version changes,
so, as said, this new series carries v3.

Fabio M. De Francesco (2):
  highmem: Make __kunmap_{local,atomic}() take "const void *"
  btrfs: Replace kmap() with kmap_local_page() in zstd.c

 arch/parisc/include/asm/cacheflush.h |  6 ++--
 arch/parisc/kernel/cache.c           |  2 +-
 fs/btrfs/zstd.c                      | 42 +++++++++++++++-------------
 include/linux/highmem-internal.h     | 10 +++----
 mm/highmem.c                         |  2 +-
 5 files changed, 33 insertions(+), 29 deletions(-)

-- 
2.36.1

[PATCH v3 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"

[Fabio M. De Francesco]

__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>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v2->v3: Fix compilation errors for ARCH=parisc.
	Reported-by: kernel test robot <lkp@intel.com>

v1->v2: Change the commit message to clearly explain why these functions
	should require pointers to const void. The fundamental argument 
	behind the commit message changes is semantic correctness.
	Obviously, there are no changes to the code.
	Many thanks to David Sterba and Ira Weiny for suggestions and
	reviews.

 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 c8a11fcecf4c..824064cafd61 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

[PATCH v3 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c

[Fabio M. De Francesco]

The use of kmap() is being deprecated in favor of kmap_local_page(). With
kmap_local_page(), the mapping is per thread, CPU local and not globally
visible.

Therefore, use kmap_local_page() / kunmap_local() in zstd.c because in
this file the mappings are per thread and are not visible in other
contexts; meanwhile refactor zstd_compress_pages() to comply with nested
local mapping / unmapping ordering rules.

Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM and
HIGHMEM64G enabled. These changes passed all tests of the "compress" group.

Cc: Filipe Manana <fdmanana@kernel.org>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v2->v3: Remove unnecessary casts to arguments of kunmap_local() now that
	this API can take pointers to const void.

v1->v2: No changes.

Thanks to Ira Weiny for his invaluable help and persevering support.
Thanks also to Filipe Manana for identifying a fundamental detail I had
overlooked in RFC:
https://lore.kernel.org/lkml/20220611093411.GA3779054@falcondesktop/


 fs/btrfs/zstd.c | 42 +++++++++++++++++++++++-------------------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 0fe31a6f6e68..5d2ab0bac9d2 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -391,6 +391,8 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 	*out_pages = 0;
 	*total_out = 0;
 	*total_in = 0;
+	workspace->in_buf.src = NULL;
+	workspace->out_buf.dst = NULL;
 
 	/* Initialize the stream */
 	stream = zstd_init_cstream(&params, len, workspace->mem,
@@ -403,7 +405,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
 	/* map in the first page of input data */
 	in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-	workspace->in_buf.src = kmap(in_page);
+	workspace->in_buf.src = kmap_local_page(in_page);
 	workspace->in_buf.pos = 0;
 	workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
 
@@ -415,7 +417,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 		goto out;
 	}
 	pages[nr_pages++] = out_page;
-	workspace->out_buf.dst = kmap(out_page);
+	workspace->out_buf.dst = kmap_local_page(out_page);
 	workspace->out_buf.pos = 0;
 	workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
 
@@ -450,9 +452,9 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 		if (workspace->out_buf.pos == workspace->out_buf.size) {
 			tot_out += PAGE_SIZE;
 			max_out -= PAGE_SIZE;
-			kunmap(out_page);
+			kunmap_local(workspace->out_buf.dst);
 			if (nr_pages == nr_dest_pages) {
-				out_page = NULL;
+				workspace->out_buf.dst = NULL;
 				ret = -E2BIG;
 				goto out;
 			}
@@ -462,7 +464,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 				goto out;
 			}
 			pages[nr_pages++] = out_page;
-			workspace->out_buf.dst = kmap(out_page);
+			workspace->out_buf.dst = kmap_local_page(out_page);
 			workspace->out_buf.pos = 0;
 			workspace->out_buf.size = min_t(size_t, max_out,
 							PAGE_SIZE);
@@ -477,15 +479,16 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 		/* Check if we need more input */
 		if (workspace->in_buf.pos == workspace->in_buf.size) {
 			tot_in += PAGE_SIZE;
-			kunmap(in_page);
+			kunmap_local(workspace->out_buf.dst);
+			kunmap_local(workspace->in_buf.src);
 			put_page(in_page);
-
 			start += PAGE_SIZE;
 			len -= PAGE_SIZE;
 			in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-			workspace->in_buf.src = kmap(in_page);
+			workspace->in_buf.src = kmap_local_page(in_page);
 			workspace->in_buf.pos = 0;
 			workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
+			workspace->out_buf.dst = kmap_local_page(out_page);
 		}
 	}
 	while (1) {
@@ -510,9 +513,9 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 
 		tot_out += PAGE_SIZE;
 		max_out -= PAGE_SIZE;
-		kunmap(out_page);
+		kunmap_local(workspace->out_buf.dst);
 		if (nr_pages == nr_dest_pages) {
-			out_page = NULL;
+			workspace->out_buf.dst = NULL;
 			ret = -E2BIG;
 			goto out;
 		}
@@ -522,7 +525,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 			goto out;
 		}
 		pages[nr_pages++] = out_page;
-		workspace->out_buf.dst = kmap(out_page);
+		workspace->out_buf.dst = kmap_local_page(out_page);
 		workspace->out_buf.pos = 0;
 		workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
 	}
@@ -538,12 +541,12 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
 out:
 	*out_pages = nr_pages;
 	/* Cleanup */
-	if (in_page) {
-		kunmap(in_page);
+	if (workspace->out_buf.dst)
+		kunmap_local(workspace->out_buf.dst);
+	if (workspace->in_buf.src) {
+		kunmap_local(workspace->in_buf.src);
 		put_page(in_page);
 	}
-	if (out_page)
-		kunmap(out_page);
 	return ret;
 }
 
@@ -567,7 +570,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 		goto done;
 	}
 
-	workspace->in_buf.src = kmap(pages_in[page_in_index]);
+	workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]);
 	workspace->in_buf.pos = 0;
 	workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
 
@@ -603,14 +606,15 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 			break;
 
 		if (workspace->in_buf.pos == workspace->in_buf.size) {
-			kunmap(pages_in[page_in_index++]);
+			kunmap_local(workspace->in_buf.src);
+			page_in_index++;
 			if (page_in_index >= total_pages_in) {
 				workspace->in_buf.src = NULL;
 				ret = -EIO;
 				goto done;
 			}
 			srclen -= PAGE_SIZE;
-			workspace->in_buf.src = kmap(pages_in[page_in_index]);
+			workspace->in_buf.src = kmap_local_page(pages_in[page_in_index]);
 			workspace->in_buf.pos = 0;
 			workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
 		}
@@ -619,7 +623,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	zero_fill_bio(cb->orig_bio);
 done:
 	if (workspace->in_buf.src)
-		kunmap(pages_in[page_in_index]);
+		kunmap_local(workspace->in_buf.src);
 	return ret;
 }
 
-- 
2.36.1

[PATCH v4 0/2] Replace kmap() with kmap_local_page() in zstd.c

[Fabio M. De Francesco]

This is a little series which serves the purpose to replace kmap() with
kmap_local_page() in btrfs/zstd.c. Actually this task is only
accomplished in patch 2/2. 

Instead patch 1/2 is a pre-requisite for the above-mentioned replacement,
but, above all else, it has the purpose to conform the prototypes of
__kunmap_{local,atomic}() to their own semantic. Since those functions
don't make changes to the memory pointed by their arguments, make those
arguments take pointers to const void.

This little series has version number 4, despite it's the first time the
two component patches have been re-united in a series. This may be a
questionable choice, however patch 1/2 should be at its v4 and patch 2/2
should be at its v3. I've tried to preserve the logs of version changes,
so, as said, this new series carries v4.

Furthermore, v4 is due to the fact that for v3 (where for the first time
the two above-mentioned patches had been united in a series) I forgot to
Cc several Maintainers and lists related to patch 1/2.

Sorry for the noise I provided to whom have received this same series
twice with no changes at all.

Fabio M. De Francesco (2):
  highmem: Make __kunmap_{local,atomic}() take "const void *"
  btrfs: Replace kmap() with kmap_local_page() in zstd.c

 arch/parisc/include/asm/cacheflush.h |  6 ++--
 arch/parisc/kernel/cache.c           |  2 +-
 fs/btrfs/zstd.c                      | 42 +++++++++++++++-------------
 include/linux/highmem-internal.h     | 10 +++----
 mm/highmem.c                         |  2 +-
 5 files changed, 33 insertions(+), 29 deletions(-)

-- 
2.36.1

[PATCH v3 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"

[Fabio M. De Francesco]

__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>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v3->v4: Cc Maintainers and lists which had been overlooked when sending
	v3.

v2->v3: Fix compilation errors for ARCH=parisc.
	Reported-by: kernel test robot <lkp@intel.com>

v1->v2: Change the commit message to clearly explain why these functions
	should require pointers to const void. The fundamental argument 
	behind the commit message changes is semantic correctness.
	Obviously, there are no changes to the code.
	Many thanks to David Sterba and Ira Weiny for suggestions and
	reviews.

 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 c8a11fcecf4c..824064cafd61 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

[PATCH v3 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"

[Fabio M. De Francesco]

__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>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v3->v4: Cc Maintainers and lists which had been overlooked when sending
	v3.

v2->v3: Fix compilation errors for ARCH=parisc.
	Reported-by: kernel test robot <lkp@intel.com>

v1->v2: Change the commit message to clearly explain why these functions
	should require pointers to const void. The fundamental argument 
	behind the commit message changes is semantic correctness.
	Obviously, there are no changes to the code.
	Many thanks to David Sterba and Ira Weiny for suggestions and
	reviews.

 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 c8a11fcecf4c..824064cafd61 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