[xen staging] xen/cpupool: use ERR_PTR() for returning error cause from cpupool_create()

[patchbot@xxxxxxx]

commit 841f660b16b7e5ab9c6100d665f276074735e04c
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon Dec 7 16:19:17 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 7 16:19:17 2020 +0100

    xen/cpupool: use ERR_PTR() for returning error cause from cpupool_create()
    
    Instead of a pointer to an error variable as parameter just use
    ERR_PTR() to return the cause of an error in cpupool_create().
    
    This propagates to scheduler_alloc(), too.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
 xen/common/sched/core.c    | 13 ++++++-------
 xen/common/sched/cpupool.c | 38 ++++++++++++++++++++------------------
 xen/common/sched/private.h |  2 +-
 3 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 6063f6d9ea..a429fc7640 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -3233,26 +3233,25 @@ struct scheduler *scheduler_get_default(void)
     return &ops;
 }
 
-struct scheduler *scheduler_alloc(unsigned int sched_id, int *perr)
+struct scheduler *scheduler_alloc(unsigned int sched_id)
 {
     int i;
+    int ret;
     struct scheduler *sched;
 
     for ( i = 0; i < NUM_SCHEDULERS; i++ )
         if ( schedulers[i] && schedulers[i]->sched_id == sched_id )
             goto found;
-    *perr = -ENOENT;
-    return NULL;
+    return ERR_PTR(-ENOENT);
 
  found:
-    *perr = -ENOMEM;
     if ( (sched = xmalloc(struct scheduler)) == NULL )
-        return NULL;
+        return ERR_PTR(-ENOMEM);
     memcpy(sched, schedulers[i], sizeof(*sched));
-    if ( (*perr = sched_init(sched)) != 0 )
+    if ( (ret = sched_init(sched)) != 0 )
     {
         xfree(sched);
-        sched = NULL;
+        sched = ERR_PTR(ret);
     }
 
     return sched;
diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index 714cd47ae9..0db7d77219 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -240,15 +240,15 @@ void cpupool_put(struct cpupool *pool)
  * - poolid already used
  * - unknown scheduler
  */
-static struct cpupool *cpupool_create(
-    unsigned int poolid, unsigned int sched_id, int *perr)
+static struct cpupool *cpupool_create(unsigned int poolid,
+                                      unsigned int sched_id)
 {
     struct cpupool *c;
     struct cpupool *q;
+    int ret;
 
-    *perr = -ENOMEM;
     if ( (c = alloc_cpupool_struct()) == NULL )
-        return NULL;
+        return ERR_PTR(-ENOMEM);
 
     /* One reference for caller, one reference for cpupool_destroy(). */
     atomic_set(&c->refcnt, 2);
@@ -267,7 +267,7 @@ static struct cpupool *cpupool_create(
             list_add_tail(&c->list, &q->list);
             if ( q->cpupool_id == poolid )
             {
-                *perr = -EEXIST;
+                ret = -EEXIST;
                 goto err;
             }
         }
@@ -294,15 +294,15 @@ static struct cpupool *cpupool_create(
     }
 
     if ( poolid == 0 )
-    {
         c->sched = scheduler_get_default();
-    }
     else
+        c->sched = scheduler_alloc(sched_id);
+    if ( IS_ERR(c->sched) )
     {
-        c->sched = scheduler_alloc(sched_id, perr);
-        if ( c->sched == NULL )
-            goto err;
+        ret = PTR_ERR(c->sched);
+        goto err;
     }
+
     c->sched->cpupool = c;
     c->gran = opt_sched_granularity;
     c->sched_gran = sched_granularity;
@@ -312,15 +312,16 @@ static struct cpupool *cpupool_create(
     debugtrace_printk("Created cpupool %u with scheduler %s (%s)\n",
                       c->cpupool_id, c->sched->name, c->sched->opt_name);
 
-    *perr = 0;
     return c;
 
  err:
     list_del(&c->list);
 
     spin_unlock(&cpupool_lock);
+
     free_cpupool_struct(c);
-    return NULL;
+
+    return ERR_PTR(ret);
 }
 /*
  * destroys the given cpupool
@@ -767,7 +768,7 @@ static void cpupool_cpu_remove_forced(unsigned int cpu)
  */
 int cpupool_do_sysctl(struct xen_sysctl_cpupool_op *op)
 {
-    int ret;
+    int ret = 0;
     struct cpupool *c;
 
     switch ( op->op )
@@ -779,8 +780,10 @@ int cpupool_do_sysctl(struct xen_sysctl_cpupool_op *op)
 
         poolid = (op->cpupool_id == XEN_SYSCTL_CPUPOOL_PAR_ANY) ?
             CPUPOOLID_NONE: op->cpupool_id;
-        c = cpupool_create(poolid, op->sched_id, &ret);
-        if ( c != NULL )
+        c = cpupool_create(poolid, op->sched_id);
+        if ( IS_ERR(c) )
+            ret = PTR_ERR(c);
+        else
         {
             op->cpupool_id = c->cpupool_id;
             cpupool_put(c);
@@ -1003,12 +1006,11 @@ static struct notifier_block cpu_nfb = {
 static int __init cpupool_init(void)
 {
     unsigned int cpu;
-    int err;
 
     cpupool_gran_init();
 
-    cpupool0 = cpupool_create(0, 0, &err);
-    BUG_ON(cpupool0 == NULL);
+    cpupool0 = cpupool_create(0, 0);
+    BUG_ON(IS_ERR(cpupool0));
     cpupool_put(cpupool0);
     register_cpu_notifier(&cpu_nfb);
 
diff --git a/xen/common/sched/private.h b/xen/common/sched/private.h
index 6953cefa6e..92d0d49610 100644
--- a/xen/common/sched/private.h
+++ b/xen/common/sched/private.h
@@ -597,7 +597,7 @@ void sched_rm_cpu(unsigned int cpu);
 const cpumask_t *sched_get_opt_cpumask(enum sched_gran opt, unsigned int cpu);
 void schedule_dump(struct cpupool *c);
 struct scheduler *scheduler_get_default(void);
-struct scheduler *scheduler_alloc(unsigned int sched_id, int *perr);
+struct scheduler *scheduler_alloc(unsigned int sched_id);
 void scheduler_free(struct scheduler *sched);
 int cpu_disable_scheduler(unsigned int cpu);
 int schedule_cpu_add(unsigned int cpu, struct cpupool *c);
--
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