diff mbox series

[v3,bpf-next] bpf: Reduce smap->elem_size

Message ID 20221221013036.3427431-1-martin.lau@linux.dev (mailing list archive)
State Accepted
Commit 552d42a356ebf78df9d2f4b73e077d2459966fac
Delegated to: BPF
Headers show
Series [v3,bpf-next] bpf: Reduce smap->elem_size | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers warning 6 maintainers not CCed: kpsingh@kernel.org haoluo@google.com song@kernel.org sdf@google.com john.fastabend@gmail.com jolsa@kernel.org
netdev/build_clang success Errors and warnings before: 1 this patch: 1
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
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: 2 this patch: 2
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 10 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-1 success Logs for ShellCheck
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bpf/vmtest-bpf-next-VM_Test-11 pending Logs for test_maps on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-9 success Logs for test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-10 success Logs for test_maps on aarch64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-12 success Logs for test_maps on x86_64 with gcc
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bpf/vmtest-bpf-next-VM_Test-23 fail Logs for test_progs_no_alu32 on x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-24 success Logs for test_progs_no_alu32_parallel on aarch64 with gcc
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bpf/vmtest-bpf-next-VM_Test-36 success Logs for test_verifier on s390x with gcc
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bpf/vmtest-bpf-next-VM_Test-31 success Logs for test_progs_parallel on s390x with gcc
bpf/vmtest-bpf-next-PR fail PR summary

Commit Message

Martin KaFai Lau Dec. 21, 2022, 1:30 a.m. UTC 
From: Martin KaFai Lau <martin.lau@kernel.org>

'struct bpf_local_storage_elem' has an unused 56 byte padding at the
end due to struct's cache-line alignment requirement. This padding
space is overlapped by storage value contents, so if we use sizeof()
to calculate the total size, we overinflate it by 56 bytes. Use
offsetof() instead to calculate more exact memory use.

Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
v3:
  Use one offsetof and save a '+' operator (Andrii)

v2:
  Rephrase the commit message (Andrii and Yonghong)
  Use offsetofend instead of offsetof (Andrii)

 kernel/bpf/bpf_local_storage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

patchwork-bot+netdevbpf@kernel.org Dec. 21, 2022, 2:50 p.m. UTC | #1 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Tue, 20 Dec 2022 17:30:36 -0800 you wrote:
> From: Martin KaFai Lau <martin.lau@kernel.org>
> 
> 'struct bpf_local_storage_elem' has an unused 56 byte padding at the
> end due to struct's cache-line alignment requirement. This padding
> space is overlapped by storage value contents, so if we use sizeof()
> to calculate the total size, we overinflate it by 56 bytes. Use
> offsetof() instead to calculate more exact memory use.
> 
> [...]

Here is the summary with links:
  - [v3,bpf-next] bpf: Reduce smap->elem_size
    https://git.kernel.org/bpf/bpf-next/c/552d42a356eb

You are awesome, thank you!
diff mbox series

Patch

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index b39a46e8fb08..373c3c2c75bc 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -580,8 +580,8 @@  static struct bpf_local_storage_map *__bpf_local_storage_map_alloc(union bpf_att
 		raw_spin_lock_init(&smap->buckets[i].lock);
 	}
 
-	smap->elem_size =
-		sizeof(struct bpf_local_storage_elem) + attr->value_size;
+	smap->elem_size = offsetof(struct bpf_local_storage_elem,
+				   sdata.data[attr->value_size]);
 
 	return smap;
 }