[PATCH -next 0/3] cpuset: code cleanup and redundancy removal

[PATCH -next 0/3] cpuset: code cleanup and redundancy removal

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

This patch series aims to clean up redundant code and remove unnecessary
checks in the cpuset subsystem.

Chen Ridong (3):
  cpuset: remove redundant special case for null input in node mask
    update
  cpuset: remove impossible warning in update_parent_effective_cpumask
  cpuset: remove is_prs_invalid helper

 kernel/cgroup/cpuset.c | 34 +++++++++++-----------------------
 1 file changed, 11 insertions(+), 23 deletions(-)

-- 
2.34.1

[PATCH -next 1/3] cpuset: remove redundant special case for null input in node mask update

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

The nodelist_parse function already handles empty nodemask input
appropriately, making it unnecessary to handle this case separately
during the node mask update process.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 535174ed7126..20dface3c3e0 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2847,22 +2847,16 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
 
 	/*
 	 * An empty mems_allowed is ok iff there are no tasks in the cpuset.
-	 * Since nodelist_parse() fails on an empty mask, we special case
-	 * that parsing.  The validate_change() call ensures that cpusets
-	 * with tasks have memory.
+	 * The validate_change() call ensures that cpusets with tasks have memory.
 	 */
-	if (!*buf) {
-		nodes_clear(trialcs->mems_allowed);
-	} else {
-		retval = nodelist_parse(buf, trialcs->mems_allowed);
-		if (retval < 0)
-			goto done;
+	retval = nodelist_parse(buf, trialcs->mems_allowed);
+	if (retval < 0)
+		goto done;
 
-		if (!nodes_subset(trialcs->mems_allowed,
-				  top_cpuset.mems_allowed)) {
-			retval = -EINVAL;
-			goto done;
-		}
+	if (!nodes_subset(trialcs->mems_allowed,
+			  top_cpuset.mems_allowed)) {
+		retval = -EINVAL;
+		goto done;
 	}
 
 	if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {
-- 
2.34.1

[PATCH -next 2/3] cpuset: remove impossible warning in update_parent_effective_cpumask

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

If the parent is not a valid partition, an error will be returned before
any partition update command is processed. This means the
WARN_ON_ONCE(!is_partition_valid(parent)) can never be triggered, so
it is safe to remove.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 20dface3c3e0..196645b38b24 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1923,7 +1923,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 		 * A partition error happens when parent has tasks and all
 		 * its effective CPUs will have to be distributed out.
 		 */
-		WARN_ON_ONCE(!is_partition_valid(parent));
 		if (nocpu) {
 			part_error = PERR_NOCPUS;
 			if (is_partition_valid(cs))
-- 
2.34.1

[PATCH -next 3/3] cpuset: remove is_prs_invalid helper

[Chen Ridong]

From: Chen Ridong <chenridong@huawei.com>

The is_prs_invalid helper function is redundant as it serves a similar
purpose to is_partition_invalid. It can be fully replaced by the existing
is_partition_invalid function, so this patch removes the is_prs_invalid
helper.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 196645b38b24..52468d2c178a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -132,11 +132,6 @@ static bool force_sd_rebuild;
 #define PRS_INVALID_ROOT	-1
 #define PRS_INVALID_ISOLATED	-2
 
-static inline bool is_prs_invalid(int prs_state)
-{
-	return prs_state < 0;
-}
-
 /*
  * Temporary cpumasks for working with partitions that are passed among
  * functions to avoid memory allocation in inner functions.
@@ -1767,7 +1762,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 	old_prs = new_prs = cs->partition_root_state;
 
 	if (cmd == partcmd_invalidate) {
-		if (is_prs_invalid(old_prs))
+		if (is_partition_invalid(cs))
 			return 0;
 
 		/*
@@ -1874,7 +1869,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 		 * For invalid partition:
 		 *   delmask = newmask & parent->effective_xcpus
 		 */
-		if (is_prs_invalid(old_prs)) {
+		if (is_partition_invalid(cs)) {
 			adding = false;
 			deleting = cpumask_and(tmp->delmask,
 					newmask, parent->effective_xcpus);
@@ -2964,7 +2959,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 	/*
 	 * Treat a previously invalid partition root as if it is a "member".
 	 */
-	if (new_prs && is_prs_invalid(old_prs))
+	if (new_prs && is_partition_invalid(cs))
 		old_prs = PRS_MEMBER;
 
 	if (alloc_tmpmasks(&tmpmask))
-- 
2.34.1

Re: [PATCH -next 1/3] cpuset: remove redundant special case for null input in node mask update

[Waiman Long]

On 9/22/25 9:02 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> The nodelist_parse function already handles empty nodemask input
> appropriately, making it unnecessary to handle this case separately
> during the node mask update process.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 22 ++++++++--------------
>   1 file changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 535174ed7126..20dface3c3e0 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2847,22 +2847,16 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
>   
>   	/*
>   	 * An empty mems_allowed is ok iff there are no tasks in the cpuset.
> -	 * Since nodelist_parse() fails on an empty mask, we special case
> -	 * that parsing.  The validate_change() call ensures that cpusets
> -	 * with tasks have memory.
> +	 * The validate_change() call ensures that cpusets with tasks have memory.
>   	 */
> -	if (!*buf) {
> -		nodes_clear(trialcs->mems_allowed);
> -	} else {
> -		retval = nodelist_parse(buf, trialcs->mems_allowed);
> -		if (retval < 0)
> -			goto done;
> +	retval = nodelist_parse(buf, trialcs->mems_allowed);
> +	if (retval < 0)
> +		goto done;
>   
> -		if (!nodes_subset(trialcs->mems_allowed,
> -				  top_cpuset.mems_allowed)) {
> -			retval = -EINVAL;
> -			goto done;
> -		}
> +	if (!nodes_subset(trialcs->mems_allowed,
> +			  top_cpuset.mems_allowed)) {
> +		retval = -EINVAL;
> +		goto done;
>   	}
>   
>   	if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed)) {

Right, the *buf check is no longer need with the current version fof 
nodelist_parse().

Reveiwed-by: Waiman Long <longman@redhat.com>

Re: [PATCH -next 2/3] cpuset: remove impossible warning in update_parent_effective_cpumask

[Waiman Long]

On 9/22/25 9:02 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> If the parent is not a valid partition, an error will be returned before
> any partition update command is processed. This means the
> WARN_ON_ONCE(!is_partition_valid(parent)) can never be triggered, so
> it is safe to remove.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 20dface3c3e0..196645b38b24 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -1923,7 +1923,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   		 * A partition error happens when parent has tasks and all
>   		 * its effective CPUs will have to be distributed out.
>   		 */
> -		WARN_ON_ONCE(!is_partition_valid(parent));
>   		if (nocpu) {
>   			part_error = PERR_NOCPUS;
>   			if (is_partition_valid(cs))
Acked-by: Waiman Long <longman@redhat.com>

Re: [PATCH -next 3/3] cpuset: remove is_prs_invalid helper

[Waiman Long]

On 9/22/25 9:02 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@huawei.com>
>
> The is_prs_invalid helper function is redundant as it serves a similar
> purpose to is_partition_invalid. It can be fully replaced by the existing
> is_partition_invalid function, so this patch removes the is_prs_invalid
> helper.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 11 +++--------
>   1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 196645b38b24..52468d2c178a 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -132,11 +132,6 @@ static bool force_sd_rebuild;
>   #define PRS_INVALID_ROOT	-1
>   #define PRS_INVALID_ISOLATED	-2
>   
> -static inline bool is_prs_invalid(int prs_state)
> -{
> -	return prs_state < 0;
> -}
> -
>   /*
>    * Temporary cpumasks for working with partitions that are passed among
>    * functions to avoid memory allocation in inner functions.
> @@ -1767,7 +1762,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   	old_prs = new_prs = cs->partition_root_state;
>   
>   	if (cmd == partcmd_invalidate) {
> -		if (is_prs_invalid(old_prs))
> +		if (is_partition_invalid(cs))
>   			return 0;
>   
>   		/*
> @@ -1874,7 +1869,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
>   		 * For invalid partition:
>   		 *   delmask = newmask & parent->effective_xcpus
>   		 */
> -		if (is_prs_invalid(old_prs)) {
> +		if (is_partition_invalid(cs)) {
>   			adding = false;
>   			deleting = cpumask_and(tmp->delmask,
>   					newmask, parent->effective_xcpus);
> @@ -2964,7 +2959,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>   	/*
>   	 * Treat a previously invalid partition root as if it is a "member".
>   	 */
> -	if (new_prs && is_prs_invalid(old_prs))
> +	if (new_prs && is_partition_invalid(cs))
>   		old_prs = PRS_MEMBER;
>   
>   	if (alloc_tmpmasks(&tmpmask))
Acked-by: Waiman Long <longman@redhat.com>

Re: [PATCH 0/3] cpuset: code cleanup and redundancy removal

[Tejun Heo]

> Chen Ridong (3):
>   cpuset: remove redundant special case for null input in node mask
>     update
>   cpuset: remove impossible warning in update_parent_effective_cpumask
>   cpuset: remove is_prs_invalid helper

Applied 1-3 to cgroup/for-6.18.

Thanks.

--
tejun