[PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[Tobias Klauser]

Remove the unused but set variable 'first_node' in
__bpf_lru_list_shrink_inactive() to fix the following GCC warning when
building with 'W=1':

  kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable]

Cc: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
---
 kernel/bpf/bpf_lru_list.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
index 89b7ef41c86b..d78501ee0609 100644
--- a/kernel/bpf/bpf_lru_list.c
+++ b/kernel/bpf/bpf_lru_list.c
@@ -213,11 +213,10 @@ __bpf_lru_list_shrink_inactive(struct bpf_lru *lru,
 			       enum bpf_lru_list_type tgt_free_type)
 {
 	struct list_head *inactive = &l->lists[BPF_LRU_LIST_T_INACTIVE];
-	struct bpf_lru_node *node, *tmp_node, *first_node;
+	struct bpf_lru_node *node, *tmp_node;
 	unsigned int nshrinked = 0;
 	unsigned int i = 0;
 
-	first_node = list_first_entry(inactive, struct bpf_lru_node, list);
 	list_for_each_entry_safe_reverse(node, tmp_node, inactive, list) {
 		if (bpf_lru_node_is_ref(node)) {
 			__bpf_lru_node_move(l, node, BPF_LRU_LIST_T_ACTIVE);
-- 
2.11.0

Re: [PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[Alexei Starovoitov]

On Tue, Jan 10, 2017 at 03:02:07PM +0100, Tobias Klauser wrote:
> Remove the unused but set variable 'first_node' in
> __bpf_lru_list_shrink_inactive() to fix the following GCC warning when
> building with 'W=1':
> 
>   kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable]
> 
> Cc: Martin KaFai Lau <kafai@fb.com>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
>  kernel/bpf/bpf_lru_list.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
> index 89b7ef41c86b..d78501ee0609 100644
> --- a/kernel/bpf/bpf_lru_list.c
> +++ b/kernel/bpf/bpf_lru_list.c
> @@ -213,11 +213,10 @@ __bpf_lru_list_shrink_inactive(struct bpf_lru *lru,
>  			       enum bpf_lru_list_type tgt_free_type)
>  {
>  	struct list_head *inactive = &l->lists[BPF_LRU_LIST_T_INACTIVE];
> -	struct bpf_lru_node *node, *tmp_node, *first_node;
> +	struct bpf_lru_node *node, *tmp_node;
>  	unsigned int nshrinked = 0;
>  	unsigned int i = 0;
>  
> -	first_node = list_first_entry(inactive, struct bpf_lru_node, list);
>  	list_for_each_entry_safe_reverse(node, tmp_node, inactive, list) {
>  		if (bpf_lru_node_is_ref(node)) {
>  			__bpf_lru_node_move(l, node, BPF_LRU_LIST_T_ACTIVE);

Martin,
I cannot tell whether it's actually copy-paste leftover
or this patch is needed:

diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
index 89b7ef41c86b..b9255a427c28 100644
--- a/kernel/bpf/bpf_lru_list.c
+++ b/kernel/bpf/bpf_lru_list.c
@@ -229,6 +229,7 @@ __bpf_lru_list_shrink_inactive(struct bpf_lru *lru,
                }

                if (++i == lru->nr_scans)
+               if (++i == lru->nr_scans || node == first_node)
                        break;
        }

Re: [PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[Martin KaFai Lau]

On Tue, Jan 10, 2017 at 04:25:23PM -0800, Alexei Starovoitov wrote:
> On Tue, Jan 10, 2017 at 03:02:07PM +0100, Tobias Klauser wrote:
> > Remove the unused but set variable 'first_node' in
> > __bpf_lru_list_shrink_inactive() to fix the following GCC warning when
> > building with 'W=1':
> >
> >   kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable]
> >
> > Cc: Martin KaFai Lau <kafai@fb.com>
> > Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> > ---
> >  kernel/bpf/bpf_lru_list.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
> > index 89b7ef41c86b..d78501ee0609 100644
> > --- a/kernel/bpf/bpf_lru_list.c
> > +++ b/kernel/bpf/bpf_lru_list.c
> > @@ -213,11 +213,10 @@ __bpf_lru_list_shrink_inactive(struct bpf_lru *lru,
> >  			       enum bpf_lru_list_type tgt_free_type)
> >  {
> >  	struct list_head *inactive = &l->lists[BPF_LRU_LIST_T_INACTIVE];
> > -	struct bpf_lru_node *node, *tmp_node, *first_node;
> > +	struct bpf_lru_node *node, *tmp_node;
> >  	unsigned int nshrinked = 0;
> >  	unsigned int i = 0;
> >
> > -	first_node = list_first_entry(inactive, struct bpf_lru_node, list);
> >  	list_for_each_entry_safe_reverse(node, tmp_node, inactive, list) {
> >  		if (bpf_lru_node_is_ref(node)) {
> >  			__bpf_lru_node_move(l, node, BPF_LRU_LIST_T_ACTIVE);
>
> Martin,
> I cannot tell whether it's actually copy-paste leftover
> or this patch is needed:
I made some changes to __bpf_lru_list_shrink_inactive() which made
first_node checking unnecessary but I did not remove first_node all
together by mistake.

__bpf_lru_list_rotate_active() pushes node back to the head, so we
need to remember the original first_node and break accordingly.

__bpf_lru_list_shrink_inactive() does not do that, so there is no
need to test against first_node.

Re: [PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[Martin KaFai Lau]

On Tue, Jan 10, 2017 at 03:02:07PM +0100, Tobias Klauser wrote:
> Remove the unused but set variable 'first_node' in
> __bpf_lru_list_shrink_inactive() to fix the following GCC warning when
> building with 'W=1':
>
>   kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable]
>
> Cc: Martin KaFai Lau <kafai@fb.com>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
>  kernel/bpf/bpf_lru_list.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/bpf_lru_list.c b/kernel/bpf/bpf_lru_list.c
> index 89b7ef41c86b..d78501ee0609 100644
> --- a/kernel/bpf/bpf_lru_list.c
> +++ b/kernel/bpf/bpf_lru_list.c
> @@ -213,11 +213,10 @@ __bpf_lru_list_shrink_inactive(struct bpf_lru *lru,
>  			       enum bpf_lru_list_type tgt_free_type)
>  {
>  	struct list_head *inactive = &l->lists[BPF_LRU_LIST_T_INACTIVE];
> -	struct bpf_lru_node *node, *tmp_node, *first_node;
> +	struct bpf_lru_node *node, *tmp_node;
>  	unsigned int nshrinked = 0;
>  	unsigned int i = 0;
>
> -	first_node = list_first_entry(inactive, struct bpf_lru_node, list);
>  	list_for_each_entry_safe_reverse(node, tmp_node, inactive, list) {
>  		if (bpf_lru_node_is_ref(node)) {
>  			__bpf_lru_node_move(l, node, BPF_LRU_LIST_T_ACTIVE);
> --
> 2.11.0
>
>
Thanks for the patch.

Acked-by: Martin KaFai Lau <kafai@fb.com>

Re: [PATCH net-next] bpf: Remove unused but set variable in __bpf_lru_list_shrink_inactive()

[David Miller]

From: Tobias Klauser <tklauser@distanz.ch>
Date: Tue, 10 Jan 2017 15:02:07 +0100

> Remove the unused but set variable 'first_node' in
> __bpf_lru_list_shrink_inactive() to fix the following GCC warning when
> building with 'W=1':
> 
>   kernel/bpf/bpf_lru_list.c:216:41: warning: variable ‘first_node’ set but not used [-Wunused-but-set-variable]
> 
> Cc: Martin KaFai Lau <kafai@fb.com>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Applied.