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Subject[PATCH] cgroup, docs: document cgroup v2 device controller
Date
Add the corresponding section in cgroup v2 documentation.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Documentation/cgroup-v2.txt | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index 2cddab7efb20..d6efabb487e3 100644
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -53,10 +53,11 @@ v1 is available under Documentation/cgroup-v1/.
5-3-2. Writeback
5-4. PID
5-4-1. PID Interface Files
- 5-5. RDMA
- 5-5-1. RDMA Interface Files
- 5-6. Misc
- 5-6-1. perf_event
+ 5-5. Device
+ 5-6. RDMA
+ 5-6-1. RDMA Interface Files
+ 5-7. Misc
+ 5-7-1. perf_event
6. Namespace
6-1. Basics
6-2. The Root and Views
@@ -1429,6 +1430,30 @@ through fork() or clone(). These will return -EAGAIN if the creation
of a new process would cause a cgroup policy to be violated.


+Device controller
+-----------------
+
+Device controller manages access to device files. It includes both
+creation of new device files (using mknod), and access to the
+existing device files.
+
+Cgroup v2 device controller has no interface files and is implemented
+on top of cgroup BPF. To control access to device files, a user may
+create bpf programs of the BPF_CGROUP_DEVICE type and attach them
+to cgroups. On an attempt to access a device file, corresponding
+BPF programs will be executed, and depending on the return value
+the attempt will succeed or fail with -EPERM.
+
+A BPF_CGROUP_DEVICE program takes a pointer to the bpf_cgroup_dev_ctx
+structure, which describes the device access attempt: access type
+(mknod/read/write) and device (type, major and minor numbers).
+If the program returns 0, the attempt fails with -EPERM, otherwise
+it succeeds.
+
+An example of BPF_CGROUP_DEVICE program may be found in the kernel
+source tree in the tools/testing/selftests/bpf/dev_cgroup.c file.
+
+
RDMA
----

--
2.14.3
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