| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <f581b215-ade9-44c5-8e93-7181690d55ab@redhat.com>
Date: Mon, 25 Aug 2025 13:37:38 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, tj@...nel.org,
hannes@...xchg.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
lujialin4@...wei.com, chenridong@...wei.com
Subject: Re: [PATCH -next v5 2/3] cpuset: separate tmpmasks and cpuset
allocation logic
On 8/24/25 11:23 PM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> The original alloc_cpumasks() served dual purposes: allocating cpumasks
> for both temporary masks (tmpmasks) and cpuset structures. This patch:
>
> 1. Decouples these allocation paths for better code clarity
> 2. Introduces dedicated alloc_tmpmasks() and dup_or_alloc_cpuset()
> functions
> 3. Maintains symmetric pairing:
> - alloc_tmpmasks() ↔ free_tmpmasks()
> - dup_or_alloc_cpuset() ↔ free_cpuset()
>
> Signed-off-by: Chen Ridong <chenridong@...wei.com>
> ---
> kernel/cgroup/cpuset.c | 127 ++++++++++++++++++++++-------------------
> 1 file changed, 69 insertions(+), 58 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index aebda14cc67f..7b0b81c835bf 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -411,51 +411,47 @@ static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
> }
>
> /**
> - * alloc_cpumasks - allocate three cpumasks for cpuset
> - * @cs: the cpuset that have cpumasks to be allocated.
> - * @tmp: the tmpmasks structure pointer
> + * alloc_cpumasks - Allocate an array of cpumask variables
> + * @pmasks: Pointer to array of cpumask_var_t pointers
> + * @size: Number of cpumasks to allocate
> * Return: 0 if successful, -ENOMEM otherwise.
> *
> - * Only one of the two input arguments should be non-NULL.
> + * Allocates @size cpumasks and initializes them to empty. Returns 0 on
> + * success, -ENOMEM on allocation failure. On failure, any previously
> + * allocated cpumasks are freed.
> */
> -static inline int alloc_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
> +static inline int alloc_cpumasks(cpumask_var_t *pmasks[], u32 size)
> {
> - cpumask_var_t *pmask1, *pmask2, *pmask3, *pmask4;
> + int i;
>
> - if (cs) {
> - pmask1 = &cs->cpus_allowed;
> - pmask2 = &cs->effective_cpus;
> - pmask3 = &cs->effective_xcpus;
> - pmask4 = &cs->exclusive_cpus;
> - } else {
> - pmask1 = &tmp->new_cpus;
> - pmask2 = &tmp->addmask;
> - pmask3 = &tmp->delmask;
> - pmask4 = NULL;
> + for (i = 0; i < size; i++) {
> + if (!zalloc_cpumask_var(pmasks[i], GFP_KERNEL)) {
> + while (--i >= 0)
> + free_cpumask_var(*pmasks[i]);
> + return -ENOMEM;
> + }
> }
> -
> - if (!zalloc_cpumask_var(pmask1, GFP_KERNEL))
> - return -ENOMEM;
> -
> - if (!zalloc_cpumask_var(pmask2, GFP_KERNEL))
> - goto free_one;
> -
> - if (!zalloc_cpumask_var(pmask3, GFP_KERNEL))
> - goto free_two;
> -
> - if (pmask4 && !zalloc_cpumask_var(pmask4, GFP_KERNEL))
> - goto free_three;
> -
> -
> return 0;
> +}
>
> -free_three:
> - free_cpumask_var(*pmask3);
> -free_two:
> - free_cpumask_var(*pmask2);
> -free_one:
> - free_cpumask_var(*pmask1);
> - return -ENOMEM;
> +/**
> + * alloc_tmpmasks - Allocate temporary cpumasks for cpuset operations.
> + * @tmp: Pointer to tmpmasks structure to populate
> + * Return: 0 on success, -ENOMEM on allocation failure
> + */
> +static inline int alloc_tmpmasks(struct tmpmasks *tmp)
> +{
> + /*
> + * Array of pointers to the three cpumask_var_t fields in tmpmasks.
> + * Note: Array size must match actual number of masks (3)
> + */
> + cpumask_var_t *pmask[3] = {
> + &tmp->new_cpus,
> + &tmp->addmask,
> + &tmp->delmask
> + };
> +
> + return alloc_cpumasks(pmask, ARRAY_SIZE(pmask));
> }
>
> /**
> @@ -470,26 +466,46 @@ static inline void free_tmpmasks(struct tmpmasks *tmp)
> }
>
> /**
> - * alloc_trial_cpuset - allocate a trial cpuset
> - * @cs: the cpuset that the trial cpuset duplicates
> + * dup_or_alloc_cpuset - Duplicate or allocate a new cpuset
> + * @cs: Source cpuset to duplicate (NULL for a fresh allocation)
> + *
> + * Creates a new cpuset by either:
> + * 1. Duplicating an existing cpuset (if @cs is non-NULL), or
> + * 2. Allocating a fresh cpuset with zero-initialized masks (if @cs is NULL)
> + *
> + * Return: Pointer to newly allocated cpuset on success, NULL on failure
> */
> -static struct cpuset *alloc_trial_cpuset(struct cpuset *cs)
> +static struct cpuset *dup_or_alloc_cpuset(struct cpuset *cs)
> {
> struct cpuset *trial;
>
> - trial = kmemdup(cs, sizeof(*cs), GFP_KERNEL);
> + /* Allocate base structure */
> + trial = cs ? kmemdup(cs, sizeof(*cs), GFP_KERNEL) :
> + kzalloc(sizeof(*cs), GFP_KERNEL);
> if (!trial)
> return NULL;
>
> - if (alloc_cpumasks(trial, NULL)) {
> + /* Setup cpumask pointer array */
> + cpumask_var_t *pmask[4] = {
> + &trial->cpus_allowed,
> + &trial->effective_cpus,
> + &trial->effective_xcpus,
> + &trial->exclusive_cpus
> + };
> +
> + if (alloc_cpumasks(pmask, ARRAY_SIZE(pmask))) {
> kfree(trial);
> return NULL;
> }
>
> - cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
> - cpumask_copy(trial->effective_cpus, cs->effective_cpus);
> - cpumask_copy(trial->effective_xcpus, cs->effective_xcpus);
> - cpumask_copy(trial->exclusive_cpus, cs->exclusive_cpus);
> + /* Copy masks if duplicating */
> + if (cs) {
> + cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
> + cpumask_copy(trial->effective_cpus, cs->effective_cpus);
> + cpumask_copy(trial->effective_xcpus, cs->effective_xcpus);
> + cpumask_copy(trial->exclusive_cpus, cs->exclusive_cpus);
> + }
> +
> return trial;
> }
>
> @@ -2332,7 +2348,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
> if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
> return 0;
>
> - if (alloc_cpumasks(NULL, &tmp))
> + if (alloc_tmpmasks(&tmp))
> return -ENOMEM;
>
> if (old_prs) {
> @@ -2476,7 +2492,7 @@ static int update_exclusive_cpumask(struct cpuset *cs, struct cpuset *trialcs,
> if (retval)
> return retval;
>
> - if (alloc_cpumasks(NULL, &tmp))
> + if (alloc_tmpmasks(&tmp))
> return -ENOMEM;
>
> if (old_prs) {
> @@ -2820,7 +2836,7 @@ int cpuset_update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
> int spread_flag_changed;
> int err;
>
> - trialcs = alloc_trial_cpuset(cs);
> + trialcs = dup_or_alloc_cpuset(cs);
> if (!trialcs)
> return -ENOMEM;
>
> @@ -2881,7 +2897,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
> if (new_prs && is_prs_invalid(old_prs))
> old_prs = PRS_MEMBER;
>
> - if (alloc_cpumasks(NULL, &tmpmask))
> + if (alloc_tmpmasks(&tmpmask))
> return -ENOMEM;
>
> err = update_partition_exclusive_flag(cs, new_prs);
> @@ -3223,7 +3239,7 @@ ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
> if (!is_cpuset_online(cs))
> goto out_unlock;
>
> - trialcs = alloc_trial_cpuset(cs);
> + trialcs = dup_or_alloc_cpuset(cs);
> if (!trialcs) {
> retval = -ENOMEM;
> goto out_unlock;
> @@ -3456,15 +3472,10 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
> if (!parent_css)
> return &top_cpuset.css;
>
> - cs = kzalloc(sizeof(*cs), GFP_KERNEL);
> + cs = dup_or_alloc_cpuset(NULL);
> if (!cs)
> return ERR_PTR(-ENOMEM);
>
> - if (alloc_cpumasks(cs, NULL)) {
> - kfree(cs);
> - return ERR_PTR(-ENOMEM);
> - }
> -
> __set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
> fmeter_init(&cs->fmeter);
> cs->relax_domain_level = -1;
> @@ -3920,7 +3931,7 @@ static void cpuset_handle_hotplug(void)
> bool on_dfl = is_in_v2_mode();
> struct tmpmasks tmp, *ptmp = NULL;
>
> - if (on_dfl && !alloc_cpumasks(NULL, &tmp))
> + if (on_dfl && !alloc_tmpmasks(&tmp))
> ptmp = &tmp;
>
> lockdep_assert_cpus_held();
Reviewed-by: Waiman Long <longman@...hat.com>
Powered by blists - more mailing lists