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* [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset()
@ 2021-09-09 15:49 Yonghong Song
  2021-09-09 21:57 ` Liam Howlett
  2021-09-10 20:30 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 3+ messages in thread
From: Yonghong Song @ 2021-09-09 15:49 UTC (permalink / raw)
  To: bpf, linux-mm
  Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann,
	kernel-team, Luigi Rizzo, Jason Gunthorpe

Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning:

  [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0
  [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod]
  [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G        W  O      5.14.0+ #53
  [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
  [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0
  [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8
  [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246
  [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000
  [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
  [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe
  [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0
  [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0
  [ 1411.304501] FS:  00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000
  [ 1411.304504] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0
  [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  [ 1411.304512] Call Trace:
  [ 1411.304517]  stack_map_get_build_id_offset+0x17c/0x260
  [ 1411.304528]  __bpf_get_stack+0x18f/0x230
  [ 1411.304541]  bpf_get_stack_raw_tp+0x5a/0x70
  [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000
  [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
  [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04
  [ 1411.306978]  bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c
  [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0
  [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108
  [ 1411.309074]  bpf_trace_run2+0x8f/0x1a0
  [ 1411.309891] FS:  00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000
  [ 1411.309896] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [ 1411.311221]  syscall_trace_enter.isra.20+0x161/0x1f0
  [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0
  [ 1411.312291]  do_syscall_64+0x15/0x80
  [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  [ 1411.313803]  entry_SYSCALL_64_after_hwframe+0x44/0xae
  [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  [ 1411.315082] RIP: 0033:0x7f00ad80a0e0
  [ 1411.315626] Call Trace:
  [ 1411.315632]  stack_map_get_build_id_offset+0x17c/0x260

To reproduce, first build `test_progs` binary:
  make -C tools/testing/selftests/bpf -j60
and then run the binary at tools/testing/selftests/bpf directory:
  ./test_progs -t get_stack_raw_tp

The warning is due to commit 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked()
annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function.
The mmap_assert_locked() function asserts that mm->mmap_lock needs to be held. But this
is not the case for bpf_get_stack() or bpf_get_stackid() helper (kernel/bpf/stackmap.c),
which uses mmap_read_trylock_non_owner() instead. Since mm->mmap_lock is not held
in bpf_get_stack[id]() use case, the above warning is emitted during test run.

This patch fixed the issue by (1). using mmap_read_trylock() instead of
mmap_read_trylock_non_owner() to satisfy lockdep checking in find_vma(),
and (2). droping lockdep for mmap_lock right before the irq_work_queue().
The function mmap_read_trylock_non_owner() is also removed since after
this patch nobody calls it any more.

Cc: Luigi Rizzo <lrizzo@google.com>
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Fixes: 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()")
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 include/linux/mmap_lock.h |  9 ---------
 kernel/bpf/stackmap.c     | 10 ++++++++--
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
index 0540f0156f58..3af8f7fb067d 100644
--- a/include/linux/mmap_lock.h
+++ b/include/linux/mmap_lock.h
@@ -144,15 +144,6 @@ static inline void mmap_read_unlock(struct mm_struct *mm)
 	__mmap_lock_trace_released(mm, false);
 }
 
-static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
-{
-	if (mmap_read_trylock(mm)) {
-		rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
-		return true;
-	}
-	return false;
-}
-
 static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
 {
 	up_read_non_owner(&mm->mmap_lock);
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index e8eefdf8cf3e..09a3fd97d329 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -179,7 +179,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 	 * with build_id.
 	 */
 	if (!user || !current || !current->mm || irq_work_busy ||
-	    !mmap_read_trylock_non_owner(current->mm)) {
+	    !mmap_read_trylock(current->mm)) {
 		/* cannot access current->mm, fall back to ips */
 		for (i = 0; i < trace_nr; i++) {
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
@@ -204,9 +204,15 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 	}
 
 	if (!work) {
-		mmap_read_unlock_non_owner(current->mm);
+		mmap_read_unlock(current->mm);
 	} else {
 		work->mm = current->mm;
+
+		/* The lock will be released once we're out of interrupt
+		 * context. Tell lockdep that we've released it now so
+		 * it doesn't complain that we forgot to release it.
+		 */
+		rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
 		irq_work_queue(&work->irq_work);
 	}
 }
-- 
2.30.2



^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset()
  2021-09-09 15:49 [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset() Yonghong Song
@ 2021-09-09 21:57 ` Liam Howlett
  2021-09-10 20:30 ` patchwork-bot+netdevbpf
  1 sibling, 0 replies; 3+ messages in thread
From: Liam Howlett @ 2021-09-09 21:57 UTC (permalink / raw)
  To: Yonghong Song
  Cc: bpf, linux-mm, Alexei Starovoitov, Andrii Nakryiko,
	Daniel Borkmann, kernel-team, Luigi Rizzo, Jason Gunthorpe

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

* Yonghong Song <yhs@fb.com> [210909 11:50]:
> Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning:
> 
>   [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0
>   [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod]
>   [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G        W  O      5.14.0+ #53
>   [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
>   [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0
>   [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8
>   [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246
>   [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000
>   [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
>   [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe
>   [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0
>   [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0
>   [ 1411.304501] FS:  00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000
>   [ 1411.304504] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0
>   [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   [ 1411.304512] Call Trace:
>   [ 1411.304517]  stack_map_get_build_id_offset+0x17c/0x260
>   [ 1411.304528]  __bpf_get_stack+0x18f/0x230
>   [ 1411.304541]  bpf_get_stack_raw_tp+0x5a/0x70
>   [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000
>   [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
>   [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04
>   [ 1411.306978]  bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c
>   [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0
>   [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108
>   [ 1411.309074]  bpf_trace_run2+0x8f/0x1a0
>   [ 1411.309891] FS:  00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000
>   [ 1411.309896] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [ 1411.311221]  syscall_trace_enter.isra.20+0x161/0x1f0
>   [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0
>   [ 1411.312291]  do_syscall_64+0x15/0x80
>   [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   [ 1411.313803]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>   [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   [ 1411.315082] RIP: 0033:0x7f00ad80a0e0
>   [ 1411.315626] Call Trace:
>   [ 1411.315632]  stack_map_get_build_id_offset+0x17c/0x260
> 
> To reproduce, first build `test_progs` binary:
>   make -C tools/testing/selftests/bpf -j60
> and then run the binary at tools/testing/selftests/bpf directory:
>   ./test_progs -t get_stack_raw_tp
> 
> The warning is due to commit 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked()
> annotations to find_vma*()") which added mmap_assert_locked() in find_vma() function.
> The mmap_assert_locked() function asserts that mm->mmap_lock needs to be held. But this
> is not the case for bpf_get_stack() or bpf_get_stackid() helper (kernel/bpf/stackmap.c),
> which uses mmap_read_trylock_non_owner() instead. Since mm->mmap_lock is not held
> in bpf_get_stack[id]() use case, the above warning is emitted during test run.
> 
> This patch fixed the issue by (1). using mmap_read_trylock() instead of
> mmap_read_trylock_non_owner() to satisfy lockdep checking in find_vma(),
> and (2). droping lockdep for mmap_lock right before the irq_work_queue().
> The function mmap_read_trylock_non_owner() is also removed since after
> this patch nobody calls it any more.
> 
> Cc: Luigi Rizzo <lrizzo@google.com>
> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
> Fixes: 5b78ed24e8ec("mm/pagemap: add mmap_assert_locked() annotations to find_vma*()")
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
>  include/linux/mmap_lock.h |  9 ---------
>  kernel/bpf/stackmap.c     | 10 ++++++++--
>  2 files changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
> index 0540f0156f58..3af8f7fb067d 100644
> --- a/include/linux/mmap_lock.h
> +++ b/include/linux/mmap_lock.h
> @@ -144,15 +144,6 @@ static inline void mmap_read_unlock(struct mm_struct *mm)
>  	__mmap_lock_trace_released(mm, false);
>  }
>  
> -static inline bool mmap_read_trylock_non_owner(struct mm_struct *mm)
> -{
> -	if (mmap_read_trylock(mm)) {
> -		rwsem_release(&mm->mmap_lock.dep_map, _RET_IP_);
> -		return true;
> -	}
> -	return false;
> -}
> -
>  static inline void mmap_read_unlock_non_owner(struct mm_struct *mm)
>  {
>  	up_read_non_owner(&mm->mmap_lock);
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index e8eefdf8cf3e..09a3fd97d329 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -179,7 +179,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>  	 * with build_id.
>  	 */
>  	if (!user || !current || !current->mm || irq_work_busy ||
> -	    !mmap_read_trylock_non_owner(current->mm)) {
> +	    !mmap_read_trylock(current->mm)) {
>  		/* cannot access current->mm, fall back to ips */
>  		for (i = 0; i < trace_nr; i++) {
>  			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> @@ -204,9 +204,15 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>  	}
>  
>  	if (!work) {
> -		mmap_read_unlock_non_owner(current->mm);
> +		mmap_read_unlock(current->mm);
>  	} else {
>  		work->mm = current->mm;
> +
> +		/* The lock will be released once we're out of interrupt
> +		 * context. Tell lockdep that we've released it now so
> +		 * it doesn't complain that we forgot to release it.
> +		 */
> +		rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
>  		irq_work_queue(&work->irq_work);
>  	}
>  }
> -- 
> 2.30.2
> 
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset()
  2021-09-09 15:49 [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset() Yonghong Song
  2021-09-09 21:57 ` Liam Howlett
@ 2021-09-10 20:30 ` patchwork-bot+netdevbpf
  1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-09-10 20:30 UTC (permalink / raw)
  To: Yonghong Song
  Cc: bpf, linux-mm, ast, andrii, daniel, kernel-team, lrizzo, jgg

Hello:

This patch was applied to bpf/bpf.git (refs/heads/master):

On Thu, 9 Sep 2021 08:49:59 -0700 you wrote:
> Current bpf-next bpf selftest "get_stack_raw_tp" triggered the warning:
> 
>   [ 1411.304463] WARNING: CPU: 3 PID: 140 at include/linux/mmap_lock.h:164 find_vma+0x47/0xa0
>   [ 1411.304469] Modules linked in: bpf_testmod(O) [last unloaded: bpf_testmod]
>   [ 1411.304476] CPU: 3 PID: 140 Comm: systemd-journal Tainted: G        W  O      5.14.0+ #53
>   [ 1411.304479] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
>   [ 1411.304481] RIP: 0010:find_vma+0x47/0xa0
>   [ 1411.304484] Code: de 48 89 ef e8 ba f5 fe ff 48 85 c0 74 2e 48 83 c4 08 5b 5d c3 48 8d bf 28 01 00 00 be ff ff ff ff e8 2d 9f d8 00 85 c0 75 d4 <0f> 0b 48 89 de 48 8
>   [ 1411.304487] RSP: 0018:ffffabd440403db8 EFLAGS: 00010246
>   [ 1411.304490] RAX: 0000000000000000 RBX: 00007f00ad80a0e0 RCX: 0000000000000000
>   [ 1411.304492] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
>   [ 1411.304494] RBP: ffff9cf5c2f50000 R08: ffff9cf5c3eb25d8 R09: 00000000fffffffe
>   [ 1411.304496] R10: 0000000000000001 R11: 00000000ef974e19 R12: ffff9cf5c39ae0e0
>   [ 1411.304498] R13: 0000000000000000 R14: 0000000000000000 R15: ffff9cf5c39ae0e0
>   [ 1411.304501] FS:  00007f00ae754780(0000) GS:ffff9cf5fba00000(0000) knlGS:0000000000000000
>   [ 1411.304504] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [ 1411.304506] CR2: 000000003e34343c CR3: 0000000103a98005 CR4: 0000000000370ee0
>   [ 1411.304508] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   [ 1411.304510] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   [ 1411.304512] Call Trace:
>   [ 1411.304517]  stack_map_get_build_id_offset+0x17c/0x260
>   [ 1411.304528]  __bpf_get_stack+0x18f/0x230
>   [ 1411.304541]  bpf_get_stack_raw_tp+0x5a/0x70
>   [ 1411.305752] RAX: 0000000000000000 RBX: 5541f689495641d7 RCX: 0000000000000000
>   [ 1411.305756] RDX: 0000000000000001 RSI: ffffffff9776b144 RDI: ffffffff977e1b0e
>   [ 1411.305758] RBP: ffff9cf5c02b2f40 R08: ffff9cf5ca7606c0 R09: ffffcbd43ee02c04
>   [ 1411.306978]  bpf_prog_32007c34f7726d29_bpf_prog1+0xaf/0xd9c
>   [ 1411.307861] R10: 0000000000000001 R11: 0000000000000044 R12: ffff9cf5c2ef60e0
>   [ 1411.307865] R13: 0000000000000005 R14: 0000000000000000 R15: ffff9cf5c2ef6108
>   [ 1411.309074]  bpf_trace_run2+0x8f/0x1a0
>   [ 1411.309891] FS:  00007ff485141700(0000) GS:ffff9cf5fae00000(0000) knlGS:0000000000000000
>   [ 1411.309896] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   [ 1411.311221]  syscall_trace_enter.isra.20+0x161/0x1f0
>   [ 1411.311600] CR2: 00007ff48514d90e CR3: 0000000107114001 CR4: 0000000000370ef0
>   [ 1411.312291]  do_syscall_64+0x15/0x80
>   [ 1411.312941] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>   [ 1411.313803]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>   [ 1411.314223] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>   [ 1411.315082] RIP: 0033:0x7f00ad80a0e0
>   [ 1411.315626] Call Trace:
>   [ 1411.315632]  stack_map_get_build_id_offset+0x17c/0x260
> 
> [...]

Here is the summary with links:
  - [bpf-next/mm,v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset()
    https://git.kernel.org/bpf/bpf/c/2f1aaf3ea666

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html




^ permalink raw reply	[flat|nested] 3+ messages in thread
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2021-09-09 15:49 [PATCH bpf-next/mm v5] bpf/mm: fix lockdep warning triggered by stack_map_get_build_id_offset() Yonghong Song
2021-09-09 21:57 ` Liam Howlett
2021-09-10 20:30 ` patchwork-bot+netdevbpf

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