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Subject[PATCH] highmem: Make __kunmap_{local,atomic}() take "const void *"
Date
Sometimes __kunmap_{local,atomic}() should take pointers to const void.
Currently their prototypes take pointers to void, therefore compilations
break in cases like the above-mentioned.

This is the output of GCC-12 when it encounters one those cases:

./linux/fs/btrfs/zstd.c:547:33: warning: passing
argument 1 of '__kunmap_local' discards 'const' qualifier from pointer
target type [-Wdiscarded-qualifiers]
547 | kunmap_local(workspace->in_buf.src);
| ~~~~~~~~~~~~~~~~~^~~~
./linux/include/linux/highmem-internal.h:284:17:
note: in definition of macro 'kunmap_local'
284 | __kunmap_local(__addr); \
| ^~~~~~
./linux/include/linux/highmem-internal.h:92:41:
note: expected 'void *' but argument is of type 'const void *'
92 | static inline void __kunmap_local(void *vaddr)
| ~~~~~~^~~~~

Make __kunmap_{local,atomic}() take pointers to const void.

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>
---
include/linux/highmem-internal.h | 10 +++++-----
mm/highmem.c | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)

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
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