2019-11-18 12:28:26

by Miaohe Lin

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

From: Miaohe Lin <[email protected]>

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 <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Signed-off-by: Miaohe Lin <[email protected]>
---
-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

2019-11-18 13:24:51

by Wei Yang

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

On Mon, Nov 18, 2019 at 08:24:04PM +0800, linmiaohe wrote:
>From: Miaohe Lin <[email protected]>
>
>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 <[email protected]>
>Reviewed-by: John Hubbard <[email protected]>
>Signed-off-by: Miaohe Lin <[email protected]>

Reviewed-by: Wei Yang <[email protected]>

>---
>-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

2019-11-18 13:51:07

by David Hildenbrand

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

On 18.11.19 13:24, linmiaohe wrote:
> From: Miaohe Lin <[email protected]>
>
> 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 <[email protected]>
> Reviewed-by: John Hubbard <[email protected]>
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> -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 <[email protected]>

--

Thanks,

David / dhildenb

2019-11-18 21:24:30

by David Rientjes

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

On Mon, 18 Nov 2019, linmiaohe wrote:

> From: Miaohe Lin <[email protected]>
>
> 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 <[email protected]>
> Reviewed-by: John Hubbard <[email protected]>
> Signed-off-by: Miaohe Lin <[email protected]>

Acked-by: David Rientjes <[email protected]>

2019-11-30 07:27:07

by Miaohe Lin

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

>>From: Miaohe Lin <[email protected]>
>>
>>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 <[email protected]>
>>Reviewed-by: John Hubbard <[email protected]>
>>Signed-off-by: Miaohe Lin <[email protected]>
>
>Reviewed-by: Wei Yang <[email protected]>
friendly ping ...

2019-11-30 08:19:50

by David Hildenbrand

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

> Am 30.11.2019 um 08:23 schrieb linmiaohe <[email protected]>:
>
> 
>>
>>> From: Miaohe Lin <[email protected]>
>>>
>>> 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 <[email protected]>
>>> Reviewed-by: John Hubbard <[email protected]>
>>> Signed-off-by: Miaohe Lin <[email protected]>
>>
>> Reviewed-by: Wei Yang <[email protected]>
> 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!

2019-11-30 08:40:22

by Miaohe Lin

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

>
>> Am 30.11.2019 um 08:23 schrieb linmiaohe <[email protected]>:
>>
>> 
>>>
>>>> From: Miaohe Lin <[email protected]>
>>>>
>>>> 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.