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Message-Id: <20250813082904.1091651-4-chenridong@huaweicloud.com>
Date: Wed, 13 Aug 2025 08:29:03 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com,
longman@...hat.com
Cc: cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
lujialin4@...wei.com,
chenridong@...wei.com,
christophe.jaillet@...adoo.fr
Subject: [-next v2 3/4] cpuset: separate tmpmasks and cpuset allocation logic
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 | 128 ++++++++++++++++++++++-------------------
1 file changed, 69 insertions(+), 59 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index aebda14cc67f..3c5e44f824d1 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -411,51 +411,46 @@ 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
- * Return: 0 if successful, -ENOMEM otherwise.
+ * alloc_cpumasks - Allocate an array of cpumask variables
+ * @cpumasks: Pointer to array of cpumask_var_t pointers
+ * @size: Number of cpumasks to allocate
*
- * 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 +465,46 @@ 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 +2347,7 @@ 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 +2491,7 @@ 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 +2835,7 @@ 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 +2896,7 @@ 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 +3238,7 @@ 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 +3471,10 @@ 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 +3930,7 @@ 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();
--
2.34.1
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