From: Xu Kuohai <xukuohai@xxxxxxxxxx>
[ Upstream commit 4b45cd81f737d79d0fbfc0d320a1e518e7f0bbf0 ]
pcpu_freelist_populate() initializes nr_elems / num_possible_cpus() + 1
free nodes for some CPUs, and then possibly one CPU with fewer nodes,
followed by remaining cpus with 0 nodes. For example, when nr_elems == 256
and num_possible_cpus() == 32, CPU 0~27 each gets 9 free nodes, CPU 28 gets
4 free nodes, CPU 29~31 get 0 free nodes, while in fact each CPU should get
8 nodes equally.
This patch initializes nr_elems / num_possible_cpus() free nodes for each
CPU firstly, then allocates the remaining free nodes by one for each CPU
until no free nodes left.
Fixes: e19494edab82 ("bpf: introduce percpu_freelist")
Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
Link: https://lore.kernel.org/bpf/20221110122128.105214-1-xukuohai@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/bpf/percpu_freelist.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
diff --git a/kernel/bpf/percpu_freelist.c b/kernel/bpf/percpu_freelist.c
index 3d897de89061..bbab8bb4b2fd 100644
--- a/kernel/bpf/percpu_freelist.c
+++ b/kernel/bpf/percpu_freelist.c
@@ -102,22 +102,21 @@ void pcpu_freelist_populate(struct pcpu_freelist *s, void *buf, u32 elem_size,
u32 nr_elems)
{
struct pcpu_freelist_head *head;
- int i, cpu, pcpu_entries;
+ unsigned int cpu, cpu_idx, i, j, n, m;
- pcpu_entries = nr_elems / num_possible_cpus() + 1;
- i = 0;
+ n = nr_elems / num_possible_cpus();
+ m = nr_elems % num_possible_cpus();
+ cpu_idx = 0;
for_each_possible_cpu(cpu) {
-again:
head = per_cpu_ptr(s->freelist, cpu);
- /* No locking required as this is not visible yet. */
- pcpu_freelist_push_node(head, buf);
- i++;
- buf += elem_size;
- if (i == nr_elems)
- break;
- if (i % pcpu_entries)
- goto again;
+ j = n + (cpu_idx < m ? 1 : 0);
+ for (i = 0; i < j; i++) {
+ /* No locking required as this is not visible yet. */
+ pcpu_freelist_push_node(head, buf);
+ buf += elem_size;
+ }
+ cpu_idx++;
}
}
--
2.35.1
