[PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[linmiaohe]

From: Miaohe Lin <linmiaohe@huawei.com>

The jump labels try_prev and none are not really needed
in find_mergeable_anon_vma(), eliminate them to improve
readability.

Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
-v2:
	Fix commit descriptions and further simplify the code
	as suggested by David Hildenbrand and John Hubbard.
-v3:
	Rewrite patch version info. Don't show this in commit log.
-v4:
	Get rid of var near completely as well.
---
 mm/mmap.c | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 91d5e097a4ed..4d93bda30eac 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1273,26 +1273,22 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
  */
 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
 {
-	struct anon_vma *anon_vma;
-	struct vm_area_struct *near;
-
-	near = vma->vm_next;
-	if (!near)
-		goto try_prev;
-
-	anon_vma = reusable_anon_vma(near, vma, near);
-	if (anon_vma)
-		return anon_vma;
-try_prev:
-	near = vma->vm_prev;
-	if (!near)
-		goto none;
-
-	anon_vma = reusable_anon_vma(near, near, vma);
-	if (anon_vma)
-		return anon_vma;
-none:
+	struct anon_vma *anon_vma = NULL;
+
+	/* Try next first. */
+	if (vma->vm_next) {
+		anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
+		if (anon_vma)
+			return anon_vma;
+	}
+
+	/* Try prev next. */
+	if (vma->vm_prev)
+		anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
+
 	/*
+	 * We might reach here with anon_vma == NULL if we can't find
+	 * any reusable anon_vma.
 	 * There's no absolute need to look only at touching neighbours:
 	 * we could search further afield for "compatible" anon_vmas.
 	 * But it would probably just be a waste of time searching,
@@ -1300,7 +1296,7 @@ struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
 	 * We're trying to allow mprotect remerging later on,
 	 * not trying to minimize memory used for anon_vmas.
 	 */
-	return NULL;
+	return anon_vma;
 }
 
 /*
-- 
2.21.GIT

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[Wei Yang]

On Mon, Nov 18, 2019 at 08:24:04PM +0800, linmiaohe wrote:
>From: Miaohe Lin <linmiaohe@huawei.com>
>
>The jump labels try_prev and none are not really needed
>in find_mergeable_anon_vma(), eliminate them to improve
>readability.
>
>Reviewed-by: David Hildenbrand <david@redhat.com>
>Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>

Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>

>---
>-v2:
>	Fix commit descriptions and further simplify the code
>	as suggested by David Hildenbrand and John Hubbard.
>-v3:
>	Rewrite patch version info. Don't show this in commit log.
>-v4:
>	Get rid of var near completely as well.
>---
> mm/mmap.c | 36 ++++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 20 deletions(-)
>
>diff --git a/mm/mmap.c b/mm/mmap.c
>index 91d5e097a4ed..4d93bda30eac 100644
>--- a/mm/mmap.c
>+++ b/mm/mmap.c
>@@ -1273,26 +1273,22 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
>  */
> struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
> {
>-	struct anon_vma *anon_vma;
>-	struct vm_area_struct *near;
>-
>-	near = vma->vm_next;
>-	if (!near)
>-		goto try_prev;
>-
>-	anon_vma = reusable_anon_vma(near, vma, near);
>-	if (anon_vma)
>-		return anon_vma;
>-try_prev:
>-	near = vma->vm_prev;
>-	if (!near)
>-		goto none;
>-
>-	anon_vma = reusable_anon_vma(near, near, vma);
>-	if (anon_vma)
>-		return anon_vma;
>-none:
>+	struct anon_vma *anon_vma = NULL;
>+
>+	/* Try next first. */
>+	if (vma->vm_next) {
>+		anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
>+		if (anon_vma)
>+			return anon_vma;
>+	}
>+
>+	/* Try prev next. */
>+	if (vma->vm_prev)
>+		anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
>+
> 	/*
>+	 * We might reach here with anon_vma == NULL if we can't find
>+	 * any reusable anon_vma.
> 	 * There's no absolute need to look only at touching neighbours:
> 	 * we could search further afield for "compatible" anon_vmas.
> 	 * But it would probably just be a waste of time searching,
>@@ -1300,7 +1296,7 @@ struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
> 	 * We're trying to allow mprotect remerging later on,
> 	 * not trying to minimize memory used for anon_vmas.
> 	 */
>-	return NULL;
>+	return anon_vma;
> }
> 
> /*
>-- 
>2.21.GIT

-- 
Wei Yang
Help you, Help me

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[David Hildenbrand]

On 18.11.19 13:24, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>
> 
> The jump labels try_prev and none are not really needed
> in find_mergeable_anon_vma(), eliminate them to improve
> readability.
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> -v2:
> 	Fix commit descriptions and further simplify the code
> 	as suggested by David Hildenbrand and John Hubbard.
> -v3:
> 	Rewrite patch version info. Don't show this in commit log.
> -v4:
> 	Get rid of var near completely as well.
> ---
>   mm/mmap.c | 36 ++++++++++++++++--------------------
>   1 file changed, 16 insertions(+), 20 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 91d5e097a4ed..4d93bda30eac 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1273,26 +1273,22 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
>    */
>   struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
>   {
> -	struct anon_vma *anon_vma;
> -	struct vm_area_struct *near;
> -
> -	near = vma->vm_next;
> -	if (!near)
> -		goto try_prev;
> -
> -	anon_vma = reusable_anon_vma(near, vma, near);
> -	if (anon_vma)
> -		return anon_vma;
> -try_prev:
> -	near = vma->vm_prev;
> -	if (!near)
> -		goto none;
> -
> -	anon_vma = reusable_anon_vma(near, near, vma);
> -	if (anon_vma)
> -		return anon_vma;
> -none:
> +	struct anon_vma *anon_vma = NULL;
> +
> +	/* Try next first. */
> +	if (vma->vm_next) {
> +		anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
> +		if (anon_vma)
> +			return anon_vma;
> +	}
> +
> +	/* Try prev next. */
> +	if (vma->vm_prev)
> +		anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
> +
>   	/*
> +	 * We might reach here with anon_vma == NULL if we can't find
> +	 * any reusable anon_vma.
>   	 * There's no absolute need to look only at touching neighbours:
>   	 * we could search further afield for "compatible" anon_vmas.
>   	 * But it would probably just be a waste of time searching,
> @@ -1300,7 +1296,7 @@ struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
>   	 * We're trying to allow mprotect remerging later on,
>   	 * not trying to minimize memory used for anon_vmas.
>   	 */
> -	return NULL;
> +	return anon_vma;
>   }
>   
>   /*
> 

Looks much better, thanks!

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 

Thanks,

David / dhildenb

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[David Rientjes]

On Mon, 18 Nov 2019, linmiaohe wrote:

> From: Miaohe Lin <linmiaohe@huawei.com>
> 
> The jump labels try_prev and none are not really needed
> in find_mergeable_anon_vma(), eliminate them to improve
> readability.
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[linmiaohe]

>>From: Miaohe Lin <linmiaohe@huawei.com>
>>
>>The jump labels try_prev and none are not really needed in 
>>find_mergeable_anon_vma(), eliminate them to improve readability.
>>
>>Reviewed-by: David Hildenbrand <david@redhat.com>
>>Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>>Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>
>Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
friendly ping ...

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[David Hildenbrand]

> Am 30.11.2019 um 08:23 schrieb linmiaohe <linmiaohe@huawei.com>:
> 
> 
>> 
>>> From: Miaohe Lin <linmiaohe@huawei.com>
>>> 
>>> The jump labels try_prev and none are not really needed in 
>>> find_mergeable_anon_vma(), eliminate them to improve readability.
>>> 
>>> Reviewed-by: David Hildenbrand <david@redhat.com>
>>> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
>>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> 
>> Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
> friendly ping ...
> 

We‘re currently in the merge phase, and U.S.A. just had Thanksgiving - so it might take some time to get picked up. Cheers!

Re: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()

[linmiaohe]

>
>> Am 30.11.2019 um 08:23 schrieb linmiaohe <linmiaohe@huawei.com>:
>> 
>> 
>>> 
>>>> From: Miaohe Lin <linmiaohe@huawei.com>
>>>> 
>>>> The jump labels try_prev and none are not really needed in 
>> friendly ping ...
>> 
>
>We‘re currently in the merge phase, and U.S.A. just had Thanksgiving - so it might take some time to get picked up. Cheers!

Hi,
Thanks for your remind. This patch have been silent for almost half a month, so
I send this ping. Thanks again.