mirrors/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-02-12 12:25:07 -05:00
Code Issues Packages Projects Releases Wiki Activity

bpf: drop KF_ACQUIRE flag on BPF kfunc bpf_get_root_mem_cgroup()

Browse Source 
With the BPF verifier now treating pointers to struct types returned
from BPF kfuncs as implicitly trusted by default, there is no need for
bpf_get_root_mem_cgroup() to be annotated with the KF_ACQUIRE flag.

bpf_get_root_mem_cgroup() does not acquire any references, but rather
simply returns a NULL pointer or a pointer to a struct mem_cgroup
object that is valid for the entire lifetime of the kernel.

This simplifies BPF programs using this kfunc by removing the
requirement to pair the call with bpf_put_mem_cgroup().

Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260113083949.2502978-2-mattbobrowski@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Matt Bobrowski
2026-01-13 08:39:48 +00:00
committed by Alexei Starovoitov
parent f8ade2342e
commit e463b6de9d
1 changed files with 7 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
mm/bpf_memcontrol.c
View File

@@ -13,12 +13,12 @@ __bpf_kfunc_start_defs();
/**
* bpf_get_root_mem_cgroup - Returns a pointer to the root memory cgroup
*
* The function has KF_ACQUIRE semantics, even though the root memory
* cgroup is never destroyed after being created and doesn't require
* reference counting. And it's perfectly safe to pass it to
* bpf_put_mem_cgroup()
*
* Return: A pointer to the root memory cgroup.
* Return: A pointer to the root memory cgroup. Notably, the pointer to the
* returned struct mem_cgroup is trusted by default, so it's perfectably
* acceptable to also pass this pointer into other BPF kfuncs (e.g.,
* bpf_mem_cgroup_usage()). Additionally, this BPF kfunc does not make use of
* KF_ACQUIRE semantics, so there's no requirement for the BPF program to call
* bpf_put_mem_cgroup() on the pointer returned by this BPF kfunc.
*/
__bpf_kfunc struct mem_cgroup *bpf_get_root_mem_cgroup(void)
{
@@ -162,7 +162,7 @@ __bpf_kfunc void bpf_mem_cgroup_flush_stats(struct mem_cgroup *memcg)
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(bpf_memcontrol_kfuncs)
BTF_ID_FLAGS(func, bpf_get_root_mem_cgroup, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_get_root_mem_cgroup, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_get_mem_cgroup, KF_ACQUIRE | KF_RET_NULL | KF_RCU)
BTF_ID_FLAGS(func, bpf_put_mem_cgroup, KF_RELEASE)