[PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[Sumitra Sharma]

generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
The GFP_KERNEL is typical for kernel-internal allocations.
The caller requires ZONE_NORMAL or a lower zone for direct access.

Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
no need to map it with kmap().

Also, the kmap() is being deprecated in favor of kmap_local_page() [1].

Hence, use a plain page_address() directly.

Since the page passed to the page_address() is not from the highmem
zone, the page_address() function will always return a valid kernel
virtual address and will not return NULL. Hence, remove the check
'if (!ptr)'.

Remove the unused variable 'ptr' and label 'err_free_page'.

[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/

Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
---

- Link to v1: https://lore.kernel.org/bpf/20230613073020.GA359792@sumitra.com/T/
- Link to v2: https://lore.kernel.org/all/20230613071756.GA359746@sumitra.com/
- Link to v3: https://lore.kernel.org/all/20230622080729.GA426913@sumitra.com/

Changes in v4:
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202306230559.hU5Aonpl-lkp@intel.com/
	- Remove unused label 'err_free_page'.

Changes in v3:
Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
	- Remove the check 'if (!ptr)'.
	- Remove the unused variable 'ptr'.
	- Change the commit message.

Changes in v2:
Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
	- Remove the kmap() call and call page_address() instead.
	- Change the commit subject and message.

 lib/test_bpf.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index ade9ac672adb..a5cc5f9fc4e8 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -14381,25 +14381,17 @@ static void *generate_test_data(struct bpf_test *test, int sub)
 		 * single fragment to the skb, filled with
 		 * test->frag_data.
 		 */
-		void *ptr;
-
 		page = alloc_page(GFP_KERNEL);
 
 		if (!page)
 			goto err_kfree_skb;
 
-		ptr = kmap(page);
-		if (!ptr)
-			goto err_free_page;
-		memcpy(ptr, test->frag_data, MAX_DATA);
-		kunmap(page);
+		memcpy(page_address(page), test->frag_data, MAX_DATA);
 		skb_add_rx_frag(skb, 0, page, 0, MAX_DATA, MAX_DATA);
 	}
 
 	return skb;
 
-err_free_page:
-	__free_page(page);
 err_kfree_skb:
 	kfree_skb(skb);
 	return NULL;
-- 
2.25.1

Re: [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[Fabio M. De Francesco]

On venerdì 23 giugno 2023 17:16:44 CEST Sumitra Sharma wrote:
> generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
> The GFP_KERNEL is typical for kernel-internal allocations.
> The caller requires ZONE_NORMAL or a lower zone for direct access.
> 
> Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
> no need to map it with kmap().
> 
> Also, the kmap() is being deprecated in favor of kmap_local_page() [1].
> 
> Hence, use a plain page_address() directly.
> 
> Since the page passed to the page_address() is not from the highmem
> zone, the page_address() function will always return a valid kernel
> virtual address and will not return NULL. Hence, remove the check
> 'if (!ptr)'.
> 
> Remove the unused variable 'ptr' and label 'err_free_page'.
> 
> [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/
> 
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

I can't see no more things that prevent my tag, then it is...

Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>

Thanks for working on it for all the time it took to get to v4 and for 
listening to what you've been suggested to change.

Well done :-)

Fabio

> Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
> ---
> 
> - Link to v1:
> https://lore.kernel.org/bpf/20230613073020.GA359792@sumitra.com/T/ - Link to
> v2: https://lore.kernel.org/all/20230613071756.GA359746@sumitra.com/ - Link
> to v3: https://lore.kernel.org/all/20230622080729.GA426913@sumitra.com/
> 
> Changes in v4:
> Reported-by: kernel test robot <lkp@intel.com>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/202306230559.hU5Aonpl-lkp@intel.com/ -
> Remove unused label 'err_free_page'.
> 
> Changes in v3:
> Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> 	- Remove the check 'if (!ptr)'.
> 	- Remove the unused variable 'ptr'.
> 	- Change the commit message.
> 
> Changes in v2:
> Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> 	- Remove the kmap() call and call page_address() instead.
> 	- Change the commit subject and message.
> 
>  lib/test_bpf.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/lib/test_bpf.c b/lib/test_bpf.c
> index ade9ac672adb..a5cc5f9fc4e8 100644
> --- a/lib/test_bpf.c
> +++ b/lib/test_bpf.c
> @@ -14381,25 +14381,17 @@ static void *generate_test_data(struct bpf_test
> *test, int sub) * single fragment to the skb, filled with
>  		 * test->frag_data.
>  		 */
> -		void *ptr;
> -
>  		page = alloc_page(GFP_KERNEL);
> 
>  		if (!page)
>  			goto err_kfree_skb;
> 
> -		ptr = kmap(page);
> -		if (!ptr)
> -			goto err_free_page;
> -		memcpy(ptr, test->frag_data, MAX_DATA);
> -		kunmap(page);
> +		memcpy(page_address(page), test->frag_data, MAX_DATA);
>  		skb_add_rx_frag(skb, 0, page, 0, MAX_DATA, MAX_DATA);
>  	}
> 
>  	return skb;
> 
> -err_free_page:
> -	__free_page(page);
>  err_kfree_skb:
>  	kfree_skb(skb);
>  	return NULL;
> --
> 2.25.1

Re: [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[Sumitra Sharma]

On Mon, Jun 26, 2023 at 03:07:22PM +0200, Fabio M. De Francesco wrote:
> On venerdì 23 giugno 2023 17:16:44 CEST Sumitra Sharma wrote:
> > generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
> > The GFP_KERNEL is typical for kernel-internal allocations.
> > The caller requires ZONE_NORMAL or a lower zone for direct access.
> > 
> > Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
> > no need to map it with kmap().
> > 
> > Also, the kmap() is being deprecated in favor of kmap_local_page() [1].
> > 
> > Hence, use a plain page_address() directly.
> > 
> > Since the page passed to the page_address() is not from the highmem
> > zone, the page_address() function will always return a valid kernel
> > virtual address and will not return NULL. Hence, remove the check
> > 'if (!ptr)'.
> > 
> > Remove the unused variable 'ptr' and label 'err_free_page'.
> > 
> > [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/
> > 
> > Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> 
> I can't see no more things that prevent my tag, then it is...
> 
> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> 
> Thanks for working on it for all the time it took to get to v4 and for 
> listening to what you've been suggested to change.
> 
> Well done :-)

Thank you, Fabio and Ira, for your tags and kind words :)

Thanks & regards
Sumitra

> 
> Fabio
> 
> > Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
> > ---
> > 
> > - Link to v1:
> > https://lore.kernel.org/bpf/20230613073020.GA359792@sumitra.com/T/ - Link to
> > v2: https://lore.kernel.org/all/20230613071756.GA359746@sumitra.com/ - Link
> > to v3: https://lore.kernel.org/all/20230622080729.GA426913@sumitra.com/
> > 
> > Changes in v4:
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes:
> > https://lore.kernel.org/oe-kbuild-all/202306230559.hU5Aonpl-lkp@intel.com/ -
> > Remove unused label 'err_free_page'.
> > 
> > Changes in v3:
> > Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> > 	- Remove the check 'if (!ptr)'.
> > 	- Remove the unused variable 'ptr'.
> > 	- Change the commit message.
> > 
> > Changes in v2:
> > Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> > 	- Remove the kmap() call and call page_address() instead.
> > 	- Change the commit subject and message.
> > 
> >  lib/test_bpf.c | 10 +---------
> >  1 file changed, 1 insertion(+), 9 deletions(-)
> > 
> > diff --git a/lib/test_bpf.c b/lib/test_bpf.c
> > index ade9ac672adb..a5cc5f9fc4e8 100644
> > --- a/lib/test_bpf.c
> > +++ b/lib/test_bpf.c
> > @@ -14381,25 +14381,17 @@ static void *generate_test_data(struct bpf_test
> > *test, int sub) * single fragment to the skb, filled with
> >  		 * test->frag_data.
> >  		 */
> > -		void *ptr;
> > -
> >  		page = alloc_page(GFP_KERNEL);
> > 
> >  		if (!page)
> >  			goto err_kfree_skb;
> > 
> > -		ptr = kmap(page);
> > -		if (!ptr)
> > -			goto err_free_page;
> > -		memcpy(ptr, test->frag_data, MAX_DATA);
> > -		kunmap(page);
> > +		memcpy(page_address(page), test->frag_data, MAX_DATA);
> >  		skb_add_rx_frag(skb, 0, page, 0, MAX_DATA, MAX_DATA);
> >  	}
> > 
> >  	return skb;
> > 
> > -err_free_page:
> > -	__free_page(page);
> >  err_kfree_skb:
> >  	kfree_skb(skb);
> >  	return NULL;
> > --
> > 2.25.1
> 
> 
> 
> 

Re: [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[Ira Weiny]

Sumitra Sharma wrote:
> generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
> The GFP_KERNEL is typical for kernel-internal allocations.
> The caller requires ZONE_NORMAL or a lower zone for direct access.
> 
> Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
> no need to map it with kmap().
> 
> Also, the kmap() is being deprecated in favor of kmap_local_page() [1].
> 
> Hence, use a plain page_address() directly.
> 
> Since the page passed to the page_address() is not from the highmem
> zone, the page_address() function will always return a valid kernel
> virtual address and will not return NULL. Hence, remove the check
> 'if (!ptr)'.
> 
> Remove the unused variable 'ptr' and label 'err_free_page'.
> 
> [1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com/
> 
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>

Just saw the report from kernel bot...

Better on this version than I saw before!  :-D

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> ---
> 
> - Link to v1: https://lore.kernel.org/bpf/20230613073020.GA359792@sumitra.com/T/
> - Link to v2: https://lore.kernel.org/all/20230613071756.GA359746@sumitra.com/
> - Link to v3: https://lore.kernel.org/all/20230622080729.GA426913@sumitra.com/
> 
> Changes in v4:
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202306230559.hU5Aonpl-lkp@intel.com/
> 	- Remove unused label 'err_free_page'.
> 
> Changes in v3:
> Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> 	- Remove the check 'if (!ptr)'.
> 	- Remove the unused variable 'ptr'.
> 	- Change the commit message.
> 
> Changes in v2:
> Noted by: Fabio M. De Francesco<fmdefrancesco@gmail.com>
> 	- Remove the kmap() call and call page_address() instead.
> 	- Change the commit subject and message.
> 
>  lib/test_bpf.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/lib/test_bpf.c b/lib/test_bpf.c
> index ade9ac672adb..a5cc5f9fc4e8 100644
> --- a/lib/test_bpf.c
> +++ b/lib/test_bpf.c
> @@ -14381,25 +14381,17 @@ static void *generate_test_data(struct bpf_test *test, int sub)
>  		 * single fragment to the skb, filled with
>  		 * test->frag_data.
>  		 */
> -		void *ptr;
> -
>  		page = alloc_page(GFP_KERNEL);
>  
>  		if (!page)
>  			goto err_kfree_skb;
>  
> -		ptr = kmap(page);
> -		if (!ptr)
> -			goto err_free_page;
> -		memcpy(ptr, test->frag_data, MAX_DATA);
> -		kunmap(page);
> +		memcpy(page_address(page), test->frag_data, MAX_DATA);
>  		skb_add_rx_frag(skb, 0, page, 0, MAX_DATA, MAX_DATA);
>  	}
>  
>  	return skb;
>  
> -err_free_page:
> -	__free_page(page);
>  err_kfree_skb:
>  	kfree_skb(skb);
>  	return NULL;
> -- 
> 2.25.1
> 

Re: [PATCH v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Fri, 23 Jun 2023 08:16:44 -0700 you wrote:
> generate_test_data() acquires a page with alloc_page(GFP_KERNEL).
> The GFP_KERNEL is typical for kernel-internal allocations.
> The caller requires ZONE_NORMAL or a lower zone for direct access.
> 
> Therefore the page cannot come from ZONE_HIGHMEM. Thus there's
> no need to map it with kmap().
> 
> [...]

Here is the summary with links:
  - [v4] lib/test_bpf: Call page_address() on page acquired with GFP_KERNEL flag
    https://git.kernel.org/bpf/bpf-next/c/da1a055d01ed

You are awesome, thank you!
-- 
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