diff mbox series

[v2,bpf-next,3/6] bpf: Use bpf_mem_free_rcu when bpf_obj_dropping non-refcounted nodes

Message ID 20231107085639.3016113-4-davemarchevsky@fb.com (mailing list archive)
State Accepted
Commit cf1ec20de34b6741e898b02c5f44c792a0437008
Delegated to: BPF
Headers show
Series Allow bpf_refcount_acquire of mapval obtained via direct LD | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1393 this patch: 1393
netdev/cc_maintainers warning 7 maintainers not CCed: jolsa@kernel.org sdf@google.com john.fastabend@gmail.com kpsingh@kernel.org song@kernel.org haoluo@google.com martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 1379 this patch: 1379
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1421 this patch: 1421
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 11 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
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Commit Message

Dave Marchevsky Nov. 7, 2023, 8:56 a.m. UTC 
The use of bpf_mem_free_rcu to free refcounted local kptrs was added
in commit 7e26cd12ad1c ("bpf: Use bpf_mem_free_rcu when
bpf_obj_dropping refcounted nodes"). In the cover letter for the
series containing that patch [0] I commented:

    Perhaps it makes sense to move to mem_free_rcu for _all_
    non-owning refs in the future, not just refcounted. This might
    allow custom non-owning ref lifetime + invalidation logic to be
    entirely subsumed by MEM_RCU handling. IMO this needs a bit more
    thought and should be tackled outside of a fix series, so it's not
    attempted here.

It's time to start moving in the "non-owning refs have MEM_RCU
lifetime" direction. As mentioned in that comment, using
bpf_mem_free_rcu for all local kptrs - not just refcounted - is
necessarily the first step towards that goal. This patch does so.

After this patch the memory pointed to by all local kptrs will not be
reused until RCU grace period elapses. The verifier's understanding of
non-owning ref validity and the clobbering logic it uses to enforce
that understanding are not changed here, that'll happen gradually in
future work, including further patches in the series.

  [0]: https://lore.kernel.org/all/20230821193311.3290257-1-davemarchevsky@fb.com/

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
---
 kernel/bpf/helpers.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 6e1874cc9c13..9895c30f6810 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1932,10 +1932,7 @@  void __bpf_obj_drop_impl(void *p, const struct btf_record *rec, bool percpu)
 		ma = &bpf_global_percpu_ma;
 	else
 		ma = &bpf_global_ma;
-	if (rec && rec->refcount_off >= 0)
-		bpf_mem_free_rcu(ma, p);
-	else
-		bpf_mem_free(ma, p);
+	bpf_mem_free_rcu(ma, p);
 }
 
 __bpf_kfunc void bpf_obj_drop_impl(void *p__alloc, void *meta__ign)