[PATCH] use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

[PATCH] use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

[Jan Beulich]

After all that's what they are intended for.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

---
 fs/fuse/dev.c           |    2 +-
 kernel/kexec.c          |    2 +-
 kernel/power/snapshot.c |   14 +++++++-------
 kernel/power/swap.c     |    6 +++---
 mm/memory.c             |    2 +-
 5 files changed, 13 insertions(+), 13 deletions(-)

--- linux-2.6.36-rc3/fs/fuse/dev.c
+++ 2.6.36-rc3-use-clear_page/fs/fuse/dev.c
@@ -811,7 +811,7 @@ static int fuse_copy_page(struct fuse_co
 
 	if (page && zeroing && count < PAGE_SIZE) {
 		void *mapaddr = kmap_atomic(page, KM_USER1);
-		memset(mapaddr, 0, PAGE_SIZE);
+		clear_page(mapaddr);
 		kunmap_atomic(mapaddr, KM_USER1);
 	}
 	while (count) {
--- linux-2.6.36-rc3/kernel/kexec.c
+++ 2.6.36-rc3-use-clear_page/kernel/kexec.c
@@ -816,7 +816,7 @@ static int kimage_load_normal_segment(st
 
 		ptr = kmap(page);
 		/* Start with a clear page */
-		memset(ptr, 0, PAGE_SIZE);
+		clear_page(ptr);
 		ptr += maddr & ~PAGE_MASK;
 		mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);
 		if (mchunk > mbytes)
--- linux-2.6.36-rc3/kernel/power/snapshot.c
+++ 2.6.36-rc3-use-clear_page/kernel/power/snapshot.c
@@ -988,7 +988,7 @@ static void copy_data_page(unsigned long
 			 */
 			safe_copy_page(buffer, s_page);
 			dst = kmap_atomic(d_page, KM_USER0);
-			memcpy(dst, buffer, PAGE_SIZE);
+			copy_page(dst, buffer);
 			kunmap_atomic(dst, KM_USER0);
 		} else {
 			safe_copy_page(page_address(d_page), s_page);
@@ -1636,7 +1636,7 @@ int snapshot_read_next(struct snapshot_h
 		memory_bm_position_reset(&orig_bm);
 		memory_bm_position_reset(&copy_bm);
 	} else if (handle->cur <= nr_meta_pages) {
-		memset(buffer, 0, PAGE_SIZE);
+		clear_page(buffer);
 		pack_pfns(buffer, &orig_bm);
 	} else {
 		struct page *page;
@@ -1650,7 +1650,7 @@ int snapshot_read_next(struct snapshot_h
 			void *kaddr;
 
 			kaddr = kmap_atomic(page, KM_USER0);
-			memcpy(buffer, kaddr, PAGE_SIZE);
+			copy_page(buffer, kaddr);
 			kunmap_atomic(kaddr, KM_USER0);
 			handle->buffer = buffer;
 		} else {
@@ -1933,7 +1933,7 @@ static void copy_last_highmem_page(void)
 		void *dst;
 
 		dst = kmap_atomic(last_highmem_page, KM_USER0);
-		memcpy(dst, buffer, PAGE_SIZE);
+		copy_page(dst, buffer);
 		kunmap_atomic(dst, KM_USER0);
 		last_highmem_page = NULL;
 	}
@@ -2219,9 +2219,9 @@ swap_two_pages_data(struct page *p1, str
 
 	kaddr1 = kmap_atomic(p1, KM_USER0);
 	kaddr2 = kmap_atomic(p2, KM_USER1);
-	memcpy(buf, kaddr1, PAGE_SIZE);
-	memcpy(kaddr1, kaddr2, PAGE_SIZE);
-	memcpy(kaddr2, buf, PAGE_SIZE);
+	copy_page(buf, kaddr1);
+	copy_page(kaddr1, kaddr2);
+	copy_page(kaddr2, buf);
 	kunmap_atomic(kaddr1, KM_USER0);
 	kunmap_atomic(kaddr2, KM_USER1);
 }
--- linux-2.6.36-rc3/kernel/power/swap.c
+++ 2.6.36-rc3-use-clear_page/kernel/power/swap.c
@@ -249,7 +249,7 @@ static int write_page(void *buf, sector_
 	if (bio_chain) {
 		src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
 		if (src) {
-			memcpy(src, buf, PAGE_SIZE);
+			copy_page(src, buf);
 		} else {
 			WARN_ON_ONCE(1);
 			bio_chain = NULL;	/* Go synchronous */
@@ -323,7 +323,7 @@ static int swap_write_page(struct swap_m
 		error = write_page(handle->cur, handle->cur_swap, NULL);
 		if (error)
 			goto out;
-		memset(handle->cur, 0, PAGE_SIZE);
+		clear_page(handle->cur);
 		handle->cur_swap = offset;
 		handle->k = 0;
 	}
@@ -634,7 +634,7 @@ int swsusp_check(void)
 	hib_resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
 	if (!IS_ERR(hib_resume_bdev)) {
 		set_blocksize(hib_resume_bdev, PAGE_SIZE);
-		memset(swsusp_header, 0, PAGE_SIZE);
+		clear_page(swsusp_header);
 		error = hib_bio_read_page(swsusp_resume_block,
 					swsusp_header, NULL);
 		if (error)
--- linux-2.6.36-rc3/mm/memory.c
+++ 2.6.36-rc3-use-clear_page/mm/memory.c
@@ -2079,7 +2079,7 @@ static inline void cow_user_page(struct 
 		 * zeroes.
 		 */
 		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
-			memset(kaddr, 0, PAGE_SIZE);
+			clear_page(kaddr);
 		kunmap_atomic(kaddr, KM_USER0);
 		flush_dcache_page(dst);
 	} else

Re: [PATCH] use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

[Andrew Morton]

On Thu, 02 Sep 2010 13:30:37 +0100
"Jan Beulich" <JBeulich@novell.com> wrote:

> After all that's what they are intended for.
> 
> ...
>
> --- linux-2.6.36-rc3/fs/fuse/dev.c
> +++ 2.6.36-rc3-use-clear_page/fs/fuse/dev.c
> @@ -811,7 +811,7 @@ static int fuse_copy_page(struct fuse_co
>  
>  	if (page && zeroing && count < PAGE_SIZE) {
>  		void *mapaddr = kmap_atomic(page, KM_USER1);
> -		memset(mapaddr, 0, PAGE_SIZE);
> +		clear_page(mapaddr);
>  		kunmap_atomic(mapaddr, KM_USER1);
>  	}
>  	while (count) {

fuse wanted to use clear_highpage() here.  But clear_highpage() uses
KM_USER0.  I don't immediately see why fuse uses KM_USER1 here?

>
> ...
>
> --- linux-2.6.36-rc3/kernel/power/snapshot.c
> +++ 2.6.36-rc3-use-clear_page/kernel/power/snapshot.c
> @@ -988,7 +988,7 @@ static void copy_data_page(unsigned long
>  			 */
>  			safe_copy_page(buffer, s_page);
>  			dst = kmap_atomic(d_page, KM_USER0);
> -			memcpy(dst, buffer, PAGE_SIZE);
> +			copy_page(dst, buffer);
>  			kunmap_atomic(dst, KM_USER0);
>  		} else {
>  			safe_copy_page(page_address(d_page), s_page);
> @@ -1636,7 +1636,7 @@ int snapshot_read_next(struct snapshot_h
>  		memory_bm_position_reset(&orig_bm);
>  		memory_bm_position_reset(&copy_bm);
>  	} else if (handle->cur <= nr_meta_pages) {
> -		memset(buffer, 0, PAGE_SIZE);
> +		clear_page(buffer);
>  		pack_pfns(buffer, &orig_bm);
>  	} else {
>  		struct page *page;
> @@ -1650,7 +1650,7 @@ int snapshot_read_next(struct snapshot_h
>  			void *kaddr;
>  
>  			kaddr = kmap_atomic(page, KM_USER0);
> -			memcpy(buffer, kaddr, PAGE_SIZE);
> +			copy_page(buffer, kaddr);
>  			kunmap_atomic(kaddr, KM_USER0);
>  			handle->buffer = buffer;
>  		} else {
> @@ -1933,7 +1933,7 @@ static void copy_last_highmem_page(void)
>  		void *dst;
>  
>  		dst = kmap_atomic(last_highmem_page, KM_USER0);
> -		memcpy(dst, buffer, PAGE_SIZE);
> +		copy_page(dst, buffer);
>  		kunmap_atomic(dst, KM_USER0);
>  		last_highmem_page = NULL;
>  	}
> @@ -2219,9 +2219,9 @@ swap_two_pages_data(struct page *p1, str
>  
>  	kaddr1 = kmap_atomic(p1, KM_USER0);
>  	kaddr2 = kmap_atomic(p2, KM_USER1);
> -	memcpy(buf, kaddr1, PAGE_SIZE);
> -	memcpy(kaddr1, kaddr2, PAGE_SIZE);
> -	memcpy(kaddr2, buf, PAGE_SIZE);
> +	copy_page(buf, kaddr1);
> +	copy_page(kaddr1, kaddr2);
> +	copy_page(kaddr2, buf);
>  	kunmap_atomic(kaddr1, KM_USER0);
>  	kunmap_atomic(kaddr2, KM_USER1);
>  }

The page-copying functions in snapshot.c are magical.  The changes look
OK to me but I'd ask Rafael to double-check, please.

>
> ...
>

Re: [PATCH] use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

[Rafael J. Wysocki]

On Wednesday, September 15, 2010, Andrew Morton wrote:
> On Thu, 02 Sep 2010 13:30:37 +0100
> "Jan Beulich" <JBeulich@novell.com> wrote:
> 
> > After all that's what they are intended for.
> > 
> > ...
> >
> > --- linux-2.6.36-rc3/fs/fuse/dev.c
> > +++ 2.6.36-rc3-use-clear_page/fs/fuse/dev.c
> > @@ -811,7 +811,7 @@ static int fuse_copy_page(struct fuse_co
> >  
> >  	if (page && zeroing && count < PAGE_SIZE) {
> >  		void *mapaddr = kmap_atomic(page, KM_USER1);
> > -		memset(mapaddr, 0, PAGE_SIZE);
> > +		clear_page(mapaddr);
> >  		kunmap_atomic(mapaddr, KM_USER1);
> >  	}
> >  	while (count) {
> 
> fuse wanted to use clear_highpage() here.  But clear_highpage() uses
> KM_USER0.  I don't immediately see why fuse uses KM_USER1 here?
> 
> >
> > ...
> >
> > --- linux-2.6.36-rc3/kernel/power/snapshot.c
> > +++ 2.6.36-rc3-use-clear_page/kernel/power/snapshot.c
> > @@ -988,7 +988,7 @@ static void copy_data_page(unsigned long
> >  			 */
> >  			safe_copy_page(buffer, s_page);
> >  			dst = kmap_atomic(d_page, KM_USER0);
> > -			memcpy(dst, buffer, PAGE_SIZE);
> > +			copy_page(dst, buffer);
> >  			kunmap_atomic(dst, KM_USER0);
> >  		} else {
> >  			safe_copy_page(page_address(d_page), s_page);
> > @@ -1636,7 +1636,7 @@ int snapshot_read_next(struct snapshot_h
> >  		memory_bm_position_reset(&orig_bm);
> >  		memory_bm_position_reset(&copy_bm);
> >  	} else if (handle->cur <= nr_meta_pages) {
> > -		memset(buffer, 0, PAGE_SIZE);
> > +		clear_page(buffer);
> >  		pack_pfns(buffer, &orig_bm);
> >  	} else {
> >  		struct page *page;
> > @@ -1650,7 +1650,7 @@ int snapshot_read_next(struct snapshot_h
> >  			void *kaddr;
> >  
> >  			kaddr = kmap_atomic(page, KM_USER0);
> > -			memcpy(buffer, kaddr, PAGE_SIZE);
> > +			copy_page(buffer, kaddr);
> >  			kunmap_atomic(kaddr, KM_USER0);
> >  			handle->buffer = buffer;
> >  		} else {
> > @@ -1933,7 +1933,7 @@ static void copy_last_highmem_page(void)
> >  		void *dst;
> >  
> >  		dst = kmap_atomic(last_highmem_page, KM_USER0);
> > -		memcpy(dst, buffer, PAGE_SIZE);
> > +		copy_page(dst, buffer);
> >  		kunmap_atomic(dst, KM_USER0);
> >  		last_highmem_page = NULL;
> >  	}
> > @@ -2219,9 +2219,9 @@ swap_two_pages_data(struct page *p1, str
> >  
> >  	kaddr1 = kmap_atomic(p1, KM_USER0);
> >  	kaddr2 = kmap_atomic(p2, KM_USER1);
> > -	memcpy(buf, kaddr1, PAGE_SIZE);
> > -	memcpy(kaddr1, kaddr2, PAGE_SIZE);
> > -	memcpy(kaddr2, buf, PAGE_SIZE);
> > +	copy_page(buf, kaddr1);
> > +	copy_page(kaddr1, kaddr2);
> > +	copy_page(kaddr2, buf);
> >  	kunmap_atomic(kaddr1, KM_USER0);
> >  	kunmap_atomic(kaddr2, KM_USER1);
> >  }
> 
> The page-copying functions in snapshot.c are magical.  The changes look
> OK to me but I'd ask Rafael to double-check, please.

Well, they _look_ OK to me too.

Rafael

Re: [PATCH] use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

[Miklos Szeredi]

On Tue, 14 Sep 2010, Andrew Morton wrote:
> On Thu, 02 Sep 2010 13:30:37 +0100
> "Jan Beulich" <JBeulich@novell.com> wrote:
> 
> > After all that's what they are intended for.
> > 
> > ...
> >
> > --- linux-2.6.36-rc3/fs/fuse/dev.c
> > +++ 2.6.36-rc3-use-clear_page/fs/fuse/dev.c
> > @@ -811,7 +811,7 @@ static int fuse_copy_page(struct fuse_co
> >  
> >  	if (page && zeroing && count < PAGE_SIZE) {
> >  		void *mapaddr = kmap_atomic(page, KM_USER1);
> > -		memset(mapaddr, 0, PAGE_SIZE);
> > +		clear_page(mapaddr);
> >  		kunmap_atomic(mapaddr, KM_USER1);
> >  	}
> >  	while (count) {
> 
> fuse wanted to use clear_highpage() here.  But clear_highpage() uses
> KM_USER0.  I don't immediately see why fuse uses KM_USER1 here?

There used to be KM_USER0 kmaps in there, but now they've been
replaced with plain kmaps.  So switching to clear_highpage() should be
fine.

Incremental patch appended.

Thanks,
Miklos
----

Subject: fuse: use clear_highpage() and  KM_USER0 instead of KM_USER1
From: Miklos Szeredi <mszeredi@suse.cz>

Commit 7909b1c640 (fuse: don't use atomic kmap) removed KM_USER0 usage
from fuse/dev.c.  Switch KM_USER1 uses to KM_USER0 for clarity.  Also
replace open coded clear_highpage().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
 fs/fuse/dev.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

Index: linux-2.6/fs/fuse/dev.c
===================================================================
--- linux-2.6.orig/fs/fuse/dev.c	2010-09-15 08:22:34.000000000 +0200
+++ linux-2.6/fs/fuse/dev.c	2010-09-15 08:24:30.000000000 +0200
@@ -809,11 +809,9 @@ static int fuse_copy_page(struct fuse_co
 	int err;
 	struct page *page = *pagep;
 
-	if (page && zeroing && count < PAGE_SIZE) {
-		void *mapaddr = kmap_atomic(page, KM_USER1);
-		clear_page(mapaddr);
-		kunmap_atomic(mapaddr, KM_USER1);
-	}
+	if (page && zeroing && count < PAGE_SIZE)
+		clear_highpage(page);
+
 	while (count) {
 		if (cs->write && cs->pipebufs && page) {
 			return fuse_ref_page(cs, page, offset, count);
@@ -830,10 +828,10 @@ static int fuse_copy_page(struct fuse_co
 			}
 		}
 		if (page) {
-			void *mapaddr = kmap_atomic(page, KM_USER1);
+			void *mapaddr = kmap_atomic(page, KM_USER0);
 			void *buf = mapaddr + offset;
 			offset += fuse_copy_do(cs, &buf, &count);
-			kunmap_atomic(mapaddr, KM_USER1);
+			kunmap_atomic(mapaddr, KM_USER0);
 		} else
 			offset += fuse_copy_do(cs, NULL, &count);
 	}