[bpf-next,3/5] bpf: Replace bpf_cpumask_any* with bpf_cpumask_any_distribute*

Commit Message

David Vernet June 10, 2023, 3:50 a.m. UTC

We currently export the bpf_cpumask_any() and bpf_cpumask_any_and()
kfuncs. Intuitively, one would expect these to choose any CPU in the
cpumask, but what they actually do is alias to cpumask_first() and
cpmkas_first_and().

This is useless given that we already export bpf_cpumask_first() and
bpf_cpumask_first_and(), so this patch replaces them with kfuncs that
call cpumask_any_distribute() and cpumask_any_and_distribute(), which
actually choose any CPU from the cpumask (or the AND of two cpumasks for
the latter).

Signed-off-by: David Vernet <[e-mail]>
---
 kernel/bpf/cpumask.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

Comments

Yonghong Song June 12, 2023, 3:22 p.m. UTC | #1

On 6/9/23 8:50 PM, David Vernet wrote:
> We currently export the bpf_cpumask_any() and bpf_cpumask_any_and()
> kfuncs. Intuitively, one would expect these to choose any CPU in the
> cpumask, but what they actually do is alias to cpumask_first() and
> cpmkas_first_and().
> 
> This is useless given that we already export bpf_cpumask_first() and
> bpf_cpumask_first_and(), so this patch replaces them with kfuncs that
> call cpumask_any_distribute() and cpumask_any_and_distribute(), which
> actually choose any CPU from the cpumask (or the AND of two cpumasks for
> the latter).
> 
> Signed-off-by: David Vernet <[e-mail]>

Acked-by: Yonghong Song <[e-mail]>

Patch

diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 9416c8ac8a04..938a60ff4295 100644
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -382,7 +382,7 @@  __bpf_kfunc void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask
 }
 
 /**
- * bpf_cpumask_any() - Return a random set CPU from a cpumask.
+ * bpf_cpumask_any_distribute() - Return a random set CPU from a cpumask.
  * @cpumask: The cpumask being queried.
  *
  * Return:
@@ -391,26 +391,28 @@  __bpf_kfunc void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask
  *
  * A struct bpf_cpumask pointer may be safely passed to @src.
  */
-__bpf_kfunc u32 bpf_cpumask_any(const struct cpumask *cpumask)
+__bpf_kfunc u32 bpf_cpumask_any_distribute(const struct cpumask *cpumask)
 {
-	return cpumask_any(cpumask);
+	return cpumask_any_distribute(cpumask);
 }
 
 /**
- * bpf_cpumask_any_and() - Return a random set CPU from the AND of two
- *			   cpumasks.
+ * bpf_cpumask_any_and_distribute() - Return a random set CPU from the AND of
+ *				      two cpumasks.
  * @src1: The first cpumask.
  * @src2: The second cpumask.
  *
  * Return:
- * * A random set bit within [0, num_cpus) if at least one bit is set.
+ * * A random set bit within [0, num_cpus) from the AND of two cpumasks, if at
+ *   least one bit is set.
  * * >= num_cpus if no bit is set.
  *
  * struct bpf_cpumask pointers may be safely passed to @src1 and @src2.
  */
-__bpf_kfunc u32 bpf_cpumask_any_and(const struct cpumask *src1, const struct cpumask *src2)
+__bpf_kfunc u32 bpf_cpumask_any_and_distribute(const struct cpumask *src1,
+					       const struct cpumask *src2)
 {
-	return cpumask_any_and(src1, src2);
+	return cpumask_any_and_distribute(src1, src2);
 }
 
 __diag_pop();
@@ -438,8 +440,8 @@  BTF_ID_FLAGS(func, bpf_cpumask_subset, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_empty, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_full, KF_RCU)
 BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU)
-BTF_ID_FLAGS(func, bpf_cpumask_any, KF_RCU)
-BTF_ID_FLAGS(func, bpf_cpumask_any_and, KF_RCU)
+BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU)
+BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU)
 BTF_SET8_END(cpumask_kfunc_btf_ids)
 
 static const struct btf_kfunc_id_set cpumask_kfunc_set = {