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bpf, cgroup: Add BPF support for cgroup1 hierarchy #631

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bpf, cgroup: Add BPF support for cgroup1 hierarchy #631

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danielocfb
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Pull request for series with
subject: bpf, cgroup: Add BPF support for cgroup1 hierarchy
version: 3
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378

@danielocfb
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Upstream branch: f2fbb90
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

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Upstream branch: ff269e2
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@danielocfb
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Upstream branch: cb3c6a5
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

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Upstream branch: b4e59c1
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@danielocfb danielocfb added needs-ack and removed new labels Nov 9, 2023
@danielocfb danielocfb force-pushed the bpf-next_base branch 3 times, most recently from 902178a to bc1b833 Compare November 9, 2023 18:41
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Upstream branch: 3815f89
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@danielocfb danielocfb force-pushed the bpf-next_base branch 2 times, most recently from 0fbe9f3 to b0d20d2 Compare November 9, 2023 19:02
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Upstream branch: 6f101db
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@danielocfb danielocfb force-pushed the bpf-next_base branch 2 times, most recently from 1e02037 to a98cbca Compare November 9, 2023 19:19
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@laoar @d-e-s-o
cgroup: Remove unnecessary list_empty()
7a03d97 
The root hasn't been removed from the root_list, so the list can't be NULL.
However, if it had been removed, attempting to destroy it once more is not
possible. Let's replace this with WARN_ON_ONCE() for clarity.

Signed-off-by: Yafang Shao <[email protected]>
Acked-by: Tejun Heo <[email protected]>
@laoar @d-e-s-o
cgroup: Make operations on the cgroup root_list RCU safe
4bf4eaa 
At present, when we perform operations on the cgroup root_list, we must
hold the cgroup_mutex, which is a relatively heavyweight lock. In reality,
we can make operations on this list RCU-safe, eliminating the need to hold
the cgroup_mutex during traversal. Modifications to the list only occur in
the cgroup root setup and destroy paths, which should be infrequent in a
production environment. In contrast, traversal may occur frequently.
Therefore, making it RCU-safe would be beneficial.

Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
cgroup: Eliminate the need for cgroup_mutex in proc_cgroup_show()
6134b7c 
The cgroup root_list is already RCU-safe. Therefore, we can replace the
cgroup_mutex with the RCU read lock in some particular paths. This change
will be particularly beneficial for frequent operations, such as
`cat /proc/self/cgroup`, in a cgroup1-based container environment.

I did stress tests with this change, as outlined below
(with CONFIG_PROVE_RCU_LIST enabled):

- Continuously mounting and unmounting named cgroups in some tasks,
  for example:

  cgrp_name=$1
  while true
  do
      mount -t cgroup -o none,name=$cgrp_name none /$cgrp_name
      umount /$cgrp_name
  done

- Continuously triggering proc_cgroup_show() in some tasks concurrently,
  for example:
  while true; do cat /proc/self/cgroup > /dev/null; done

They can ran successfully after implementing this change, with no RCU
warnings in dmesg.

Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
cgroup: Add annotation for holding namespace_sem in current_cgns_cgro…
0d40ede 
…up_from_root()

When I initially examined the function current_cgns_cgroup_from_root(), I
was perplexed by its lack of holding cgroup_mutex. However, after Michal
explained the reason[0] to me, I realized that it already holds the
namespace_sem. I believe this intricacy could also confuse others, so it
would be advisable to include an annotation for clarification.

After we replace the cgroup_mutex with RCU read lock, if current doesn't
hold the namespace_sem, the root cgroup will be NULL. So let's add a
WARN_ON_ONCE() for it.

[0]. https://lore.kernel.org/bpf/afdnpo3jz2ic2ampud7swd6so5carkilts2mkygcaw67vbw6yh@5b5mncf7qyet

Signed-off-by: Yafang Shao <[email protected]>
Cc: Michal Koutný <[email protected]>
@laoar @d-e-s-o
cgroup: Add a new helper for cgroup1 hierarchy
96ddadc 
A new helper is added for cgroup1 hierarchy:

- task_get_cgroup1
  Acquires the associated cgroup of a task within a specific cgroup1
  hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.

This helper function is added to facilitate the tracing of tasks within
a particular container or cgroup dir in BPF programs. It's important to
note that this helper is designed specifically for cgroup1 only.

Suggested-by: Tejun Heo <[email protected]>
Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
bpf: Add a new kfunc for cgroup1 hierarchy
4bb8501 
A new kfunc is added to acquire cgroup1 of a task:

- bpf_task_get_cgroup1
  Acquires the associated cgroup of a task whithin a specific cgroup1
  hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.

This new kfunc enables the tracing of tasks within a designated
container or cgroup directory in BPF programs.

Suggested-by: Tejun Heo <[email protected]>
Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
selftests/bpf: Fix issues in setup_classid_environment()
0d0d0c9 
If the net_cls subsystem is already mounted, attempting to mount it again
in setup_classid_environment() will result in a failure with the error code
EBUSY. Despite this, tmpfs will have been successfully mounted at
/sys/fs/cgroup/net_cls. Consequently, the /sys/fs/cgroup/net_cls directory
will be empty, causing subsequent setup operations to fail.

Here's an error log excerpt illustrating the issue when net_cls has already
been mounted at /sys/fs/cgroup/net_cls prior to running
setup_classid_environment():

- Before that change

  $ tools/testing/selftests/bpf/test_progs --name=cgroup_v1v2
  test_cgroup_v1v2:PASS:server_fd 0 nsec
  test_cgroup_v1v2:PASS:client_fd 0 nsec
  test_cgroup_v1v2:PASS:cgroup_fd 0 nsec
  test_cgroup_v1v2:PASS:server_fd 0 nsec
  run_test:PASS:skel_open 0 nsec
  run_test:PASS:prog_attach 0 nsec
  test_cgroup_v1v2:PASS:cgroup-v2-only 0 nsec
  (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup.procs
  (cgroup_helpers.c:540: errno: No such file or directory) Opening cgroup classid: /sys/fs/cgroup/net_cls/cgroup-test-work-dir/net_cls.classid
  run_test:PASS:skel_open 0 nsec
  run_test:PASS:prog_attach 0 nsec
  (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup-test-work-dir/cgroup.procs
  run_test:FAIL:join_classid unexpected error: 1 (errno 2)
  test_cgroup_v1v2:FAIL:cgroup-v1v2 unexpected error: -1 (errno 2)
  (cgroup_helpers.c:248: errno: No such file or directory) Opening Cgroup Procs: /sys/fs/cgroup/net_cls/cgroup.procs
  #44      cgroup_v1v2:FAIL
  Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED

- After that change
  $ tools/testing/selftests/bpf/test_progs --name=cgroup_v1v2
  #44      cgroup_v1v2:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
selftests/bpf: Add parallel support for classid
d9fa44b 
Include the current pid in the classid cgroup path. This way, different
testers relying on classid-based configurations will have distinct classid
cgroup directories, enabling them to run concurrently. Additionally, we
leverage the current pid as the classid, ensuring unique identification.

Signed-off-by: Yafang Shao <[email protected]>
@danielocfb
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Upstream branch: e80742d
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=797378
version: 3

@laoar @d-e-s-o
selftests/bpf: Add a new cgroup helper get_classid_cgroup_id()
567f6aa 
Introduce a new helper function to retrieve the cgroup ID from a net_cls
cgroup directory.

Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
selftests/bpf: Add a new cgroup helper get_cgroup_hierarchy_id()
b1d13ff 
A new cgroup helper function, get_cgroup1_hierarchy_id(), has been
introduced to obtain the ID of a cgroup1 hierarchy based on the provided
cgroup name. This cgroup name can be obtained from the /proc/self/cgroup
file.

Signed-off-by: Yafang Shao <[email protected]>
@laoar @d-e-s-o
selftests/bpf: Add selftests for cgroup1 hierarchy
cfd8dba 
Add selftests for cgroup1 hierarchy.
The result as follows,

  $ tools/testing/selftests/bpf/test_progs --name=cgroup1_hierarchy
  #36/1    cgroup1_hierarchy/test_cgroup1_hierarchy:OK
  #36/2    cgroup1_hierarchy/test_root_cgid:OK
  #36/3    cgroup1_hierarchy/test_invalid_level:OK
  #36/4    cgroup1_hierarchy/test_invalid_cgid:OK
  #36/5    cgroup1_hierarchy/test_invalid_hid:OK
  #36/6    cgroup1_hierarchy/test_invalid_cgrp_name:OK
  #36/7    cgroup1_hierarchy/test_invalid_cgrp_name2:OK
  #36/8    cgroup1_hierarchy/test_sleepable_prog:OK
  #36      cgroup1_hierarchy:OK
  Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED

Besides, I also did some stress test similar to the patch #2 in this
series, as follows (with CONFIG_PROVE_RCU_LIST enabled):

- Continuously mounting and unmounting named cgroups in some tasks,
  for example:

  cgrp_name=$1
  while true
  do
      mount -t cgroup -o none,name=$cgrp_name none /$cgrp_name
      umount /$cgrp_name
  done

- Continuously run this selftest concurrently,
  while true; do ./test_progs --name=cgroup1_hierarchy; done

They can ran successfully without any RCU warnings in dmesg.

Signed-off-by: Yafang Shao <[email protected]>
@danielocfb
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=797378 expired. Closing PR.

@danielocfb danielocfb closed this Nov 9, 2023
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