* [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c
@ 2022-07-06 11:15 Fabio M. De Francesco
2022-07-06 11:15 ` [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Fabio M. De Francesco
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Fabio M. De Francesco @ 2022-07-06 11:15 UTC (permalink / raw)
To: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Andrew Morton,
Matthew Wilcox, Kees Cook, Sebastian Andrzej Siewior,
James E. J. Bottomley, Helge Deller, John David Anglin,
linux-parisc
Cc: 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,
however, above all else, it has the purpose to conform the prototypes of
__kunmap_{local,atomic}() to their own correct semantics. Since those
functions don't make changes to the memory pointed by their arguments,
change the type of those arguments to become pointers to const void.
v5 -> v6: Delete an unnecessary assignment in 2/2 (thanks to Ira Weiny).
v4 -> v5: Use plain page_address() for pages which cannot come from Highmem
(instead of kmapping them); remove unnecessary initializations to NULL
in 2/2 (thanks to Ira Weiny).
v3 -> v4: Resend and add linux-mm to the list of recipients (thanks to
Andrew Morton).
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 | 33 +++++++++++-----------------
include/linux/highmem-internal.h | 10 ++++-----
mm/highmem.c | 2 +-
5 files changed, 23 insertions(+), 30 deletions(-)
--
2.36.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"
2022-07-06 11:15 [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
@ 2022-07-06 11:15 ` Fabio M. De Francesco
2022-07-06 19:07 ` Andrew Morton
2022-07-06 11:15 ` [PATCH v6 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
2022-07-07 22:12 ` [PATCH v6 0/2] " David Sterba
2 siblings, 1 reply; 6+ messages in thread
From: Fabio M. De Francesco @ 2022-07-06 11:15 UTC (permalink / raw)
To: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Andrew Morton,
Matthew Wilcox, Kees Cook, Sebastian Andrzej Siewior,
James E. J. Bottomley, Helge Deller, John David Anglin,
linux-parisc
Cc: Fabio M. De Francesco, David Sterba
__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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v6 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c
2022-07-06 11:15 [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
2022-07-06 11:15 ` [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Fabio M. De Francesco
@ 2022-07-06 11:15 ` Fabio M. De Francesco
2022-07-07 22:12 ` [PATCH v6 0/2] " David Sterba
2 siblings, 0 replies; 6+ messages in thread
From: Fabio M. De Francesco @ 2022-07-06 11:15 UTC (permalink / raw)
To: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Andrew Morton,
Matthew Wilcox, Kees Cook, Sebastian Andrzej Siewior,
James E. J. Bottomley, Helge Deller, John David Anglin,
linux-parisc
Cc: Fabio M. De Francesco, Filipe Manana
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. In
the meanwhile use plain page_address() on pages allocated with the GFP_NOFS
flag instead of calling kmap*() on them (since they are always allocated
from ZONE_NORMAL).
Tested with xfstests on QEMU + KVM 32 bits VM with 4GB of RAM, booting a
kernel with HIGHMEM64G enabled.
Cc: Filipe Manana <fdmanana@kernel.org>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
fs/btrfs/zstd.c | 33 +++++++++++++--------------------
1 file changed, 13 insertions(+), 20 deletions(-)
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 0fe31a6f6e68..35a0224d4eb7 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -403,7 +403,7 @@ 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 +415,7 @@ 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 = page_address(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
@@ -450,9 +450,7 @@ 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);
if (nr_pages == nr_dest_pages) {
- out_page = NULL;
ret = -E2BIG;
goto out;
}
@@ -462,7 +460,7 @@ 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 = page_address(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out,
PAGE_SIZE);
@@ -477,13 +475,12 @@ 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->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);
}
@@ -510,9 +507,7 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
tot_out += PAGE_SIZE;
max_out -= PAGE_SIZE;
- kunmap(out_page);
if (nr_pages == nr_dest_pages) {
- out_page = NULL;
ret = -E2BIG;
goto out;
}
@@ -522,7 +517,7 @@ 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 = page_address(out_page);
workspace->out_buf.pos = 0;
workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
}
@@ -537,13 +532,10 @@ int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
*total_out = tot_out;
out:
*out_pages = nr_pages;
- /* Cleanup */
- if (in_page) {
- kunmap(in_page);
+ 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 +559,7 @@ 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 +595,15 @@ 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 +612,7 @@ 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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"
2022-07-06 11:15 ` [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Fabio M. De Francesco
@ 2022-07-06 19:07 ` Andrew Morton
2022-07-08 12:47 ` Helge Deller
0 siblings, 1 reply; 6+ messages in thread
From: Andrew Morton @ 2022-07-06 19:07 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Matthew Wilcox,
Kees Cook, Sebastian Andrzej Siewior, James E. J. Bottomley,
Helge Deller, John David Anglin, linux-parisc, David Sterba
On Wed, 6 Jul 2022 13:15:19 +0200 "Fabio M. De Francesco" <fmdefrancesco@gmail.com> wrote:
> __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.
>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Please include this in the btrfs tree if/when [2/2] is added.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c
2022-07-06 11:15 [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
2022-07-06 11:15 ` [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Fabio M. De Francesco
2022-07-06 11:15 ` [PATCH v6 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
@ 2022-07-07 22:12 ` David Sterba
2 siblings, 0 replies; 6+ messages in thread
From: David Sterba @ 2022-07-07 22:12 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Andrew Morton,
Matthew Wilcox, Kees Cook, Sebastian Andrzej Siewior,
James E. J. Bottomley, Helge Deller, John David Anglin,
linux-parisc
On Wed, Jul 06, 2022 at 01:15:18PM +0200, Fabio M. De Francesco wrote:
> 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,
> however, above all else, it has the purpose to conform the prototypes of
> __kunmap_{local,atomic}() to their own correct semantics. Since those
> functions don't make changes to the memory pointed by their arguments,
> change the type of those arguments to become pointers to const void.
>
> v5 -> v6: Delete an unnecessary assignment in 2/2 (thanks to Ira Weiny).
>
> v4 -> v5: Use plain page_address() for pages which cannot come from Highmem
> (instead of kmapping them); remove unnecessary initializations to NULL
> in 2/2 (thanks to Ira Weiny).
>
> v3 -> v4: Resend and add linux-mm to the list of recipients (thanks to
> Andrew Morton).
>
> Fabio M. De Francesco (2):
> highmem: Make __kunmap_{local,atomic}() take "const void *"
> btrfs: Replace kmap() with kmap_local_page() in zstd.c
Added to the kmap patch queue, thanks. With all the other conversion
there are 5 patches
highmem: Make __kunmap_{local,atomic}() take const void pointer
btrfs: zstd: replace kmap() with kmap_local_page()
btrfs: zlib: replace kmap() with kmap_local_page() in zlib_compress_pages()
btrfs: zlib: replace kmap() with kmap_local_page() in zlib_decompress_bio()
btrfs: replace kmap_atomic() with kmap_local_page()
and there are no kmap or kmap_atomic left in fs/btrfs, scheduled for 5.20.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *"
2022-07-06 19:07 ` Andrew Morton
@ 2022-07-08 12:47 ` Helge Deller
0 siblings, 0 replies; 6+ messages in thread
From: Helge Deller @ 2022-07-08 12:47 UTC (permalink / raw)
To: Andrew Morton, Fabio M. De Francesco
Cc: David Sterba, Chris Mason, Josef Bacik, Nick Terrell,
linux-btrfs, linux-mm, linux-kernel, Ira Weiny, Matthew Wilcox,
Kees Cook, Sebastian Andrzej Siewior, James E. J. Bottomley,
John David Anglin, linux-parisc, David Sterba
On 7/6/22 21:07, Andrew Morton wrote:
> On Wed, 6 Jul 2022 13:15:19 +0200 "Fabio M. De Francesco" <fmdefrancesco@gmail.com> wrote:
>
>> __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.
>>
>
> Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Helge Deller <deller@gmx.de> # parisc
> Please include this in the btrfs tree if/when [2/2] is added.
Yes, agreed. Please take both through btrfs.
Helge
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-07-08 12:48 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-07-06 11:15 [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
2022-07-06 11:15 ` [PATCH v6 1/2] highmem: Make __kunmap_{local,atomic}() take "const void *" Fabio M. De Francesco
2022-07-06 19:07 ` Andrew Morton
2022-07-08 12:47 ` Helge Deller
2022-07-06 11:15 ` [PATCH v6 2/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c Fabio M. De Francesco
2022-07-07 22:12 ` [PATCH v6 0/2] " David Sterba
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