Re: [PATCH] cgroup/cpuset: Adjust exception handling in generate_sched_domains()

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On 1/1/24 03:56, Markus Elfring wrote:
Two resource allocation failures triggered further actions
over the label “done” so far.

* Jump to the statement “ndoms = 1;” in three cases directly
    by using the label “set_ndoms” instead.

* Delete an assignment for the variable “ndoms” in one if branch.
---
   kernel/cgroup/cpuset.c | 8 ++++----
   1 file changed, 4 insertions(+), 4 deletions(-)
@@ -973,10 +973,9 @@ static int generate_sched_domains(cpumask_var_t **domains,

       /* Special case for the 99% of systems with one, full, sched domain */
       if (root_load_balance && !top_cpuset.nr_subparts) {
-        ndoms = 1;
           doms = alloc_sched_domains(ndoms);
           if (!doms)
-            goto done;
+            goto set_ndoms;

           dattr = kmalloc(sizeof(struct sched_domain_attr), GFP_KERNEL);
           if (dattr) {
@@ -1123,6 +1122,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
        * See comments in partition_sched_domains().
        */
       if (doms == NULL)
+set_ndoms:
           ndoms = 1;

       *domains    = doms;
Please clarify what this patch is for. Is it just a cleanup with no functional changes or is there a bug that is being fixed?
The development opinions might vary for the presented transformation.
I suggest to reconsider the number of relevant variable assignments here.
Would you categorise an extra statement still as a desirable implementation detail?

My understanding of the patch is just to avoid an unnecessary call to kfree() as kfree(NULL) is basically a NOP. By jumping inside the "if" part of the conditional statement, however, it makes it a bit harder to read. As generate_sched_domains() is not in the fast path, I would rather have a patch that can simplify the logic than to make it harder to understand.

Cheers,
Longman





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