From: Alexei Starovoitov <ast@xxxxxxxxxx>
Introduce sysctl kernel.bpf_force_dyn_alloc to force dynamic allocation in bpf
hash map. All selftests/bpf should pass with bpf_force_dyn_alloc 0 or 1 and all
bpf programs (both sleepable and not) should not see any functional difference.
The sysctl's observable behavior should only be improved memory usage.
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/filter.h | 2 ++
kernel/bpf/core.c | 2 ++
kernel/bpf/hashtab.c | 5 +++++
kernel/bpf/syscall.c | 9 +++++++++
4 files changed, 18 insertions(+)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index a5f21dc3c432..eb4d4a0c0bde 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1009,6 +1009,8 @@ bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
}
#endif
+extern int bpf_force_dyn_alloc;
+
#ifdef CONFIG_BPF_JIT
extern int bpf_jit_enable;
extern int bpf_jit_harden;
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 639437f36928..a13e78ea4b90 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -533,6 +533,8 @@ void bpf_prog_kallsyms_del_all(struct bpf_prog *fp)
bpf_prog_kallsyms_del(fp);
}
+int bpf_force_dyn_alloc __read_mostly;
+
#ifdef CONFIG_BPF_JIT
/* All BPF JIT sysctl knobs here. */
int bpf_jit_enable __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 89f26cbddef5..f68a3400939e 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -505,6 +505,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
bpf_map_init_from_attr(&htab->map, attr);
+ if (!lru && bpf_force_dyn_alloc) {
+ prealloc = false;
+ htab->map.map_flags |= BPF_F_NO_PREALLOC;
+ }
+
if (percpu_lru) {
/* ensure each CPU's lru list has >=1 elements.
* since we are at it, make each lru list has the same
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 074c901fbb4e..5c631244b63b 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5299,6 +5299,15 @@ static struct ctl_table bpf_syscall_table[] = {
.mode = 0644,
.proc_handler = bpf_stats_handler,
},
+ {
+ .procname = "bpf_force_dyn_alloc",
+ .data = &bpf_force_dyn_alloc,
+ .maxlen = sizeof(int),
+ .mode = 0600,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
{ }
};
--
2.30.2
