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List:       linux-cgroups
Subject:    [PATCH] cgroup: Add named hierarchy disabling to cgroup_no_v1 boot param
From:       Tejun Heo <tj () kernel ! org>
Date:       2018-12-28 18:31:07
Message-ID: 20181228183107.GL2509588 () devbig004 ! ftw2 ! facebook ! com
[Download RAW message or body]

It can be useful to inhibit all cgroup1 hierarchies especially during
transition and for debugging.  cgroup_no_v1 can block hierarchies with
controllers which leaves out the named hierarchies.  Expand it to
cover the named hierarchies so that "cgroup_no_v1=all,named" disables
all cgroup1 hierarchies.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Marcin Pawlowski <mpawlowski@fb.com>w
---
Will append to for-4.21 pull request.

Thanks.

 Documentation/admin-guide/kernel-parameters.txt |    8 ++++++--
 kernel/cgroup/cgroup-v1.c                       |   14 +++++++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt \
b/Documentation/admin-guide/kernel-parameters.txt index ff4daa780ae8..b7c9040f547e \
                100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -486,10 +486,14 @@
 			cut the overhead, others just disable the usage. So
 			only cgroup_disable=memory is actually worthy}
 
-	cgroup_no_v1=	[KNL] Disable one, multiple, all cgroup controllers in v1
-			Format: { controller[,controller...] | "all" }
+	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
+			Format: { { controller | "all" | "named" }
+			          [,{ controller | "all" | "named" }...] }
 			Like cgroup_disable, but only applies to cgroup v1;
 			the blacklisted controllers remain available in cgroup2.
+			"all" blacklists all controllers and "named" disables
+			named mounts. Specifying both "all" and "named" disables
+			all v1 hierarchies.
 
 	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
 			Format: <string>
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 51063e7a93c2..583b969b0c0e 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -27,6 +27,9 @@
 /* Controllers blocked by the commandline in v1 */
 static u16 cgroup_no_v1_mask;
 
+/* disable named v1 mounts */
+static bool cgroup_no_v1_named;
+
 /*
  * pidlist destructions need to be flushed on cgroup destruction.  Use a
  * separate workqueue as flush domain.
@@ -963,6 +966,10 @@ static int parse_cgroupfs_options(char *data, struct \
cgroup_sb_opts *opts)  }
 		if (!strncmp(token, "name=", 5)) {
 			const char *name = token + 5;
+
+			/* blocked by boot param? */
+			if (cgroup_no_v1_named)
+				return -ENOENT;
 			/* Can't specify an empty name */
 			if (!strlen(name))
 				return -EINVAL;
@@ -1292,7 +1299,12 @@ static int __init cgroup_no_v1(char *str)
 
 		if (!strcmp(token, "all")) {
 			cgroup_no_v1_mask = U16_MAX;
-			break;
+			continue;
+		}
+
+		if (!strcmp(token, "named")) {
+			cgroup_no_v1_named = true;
+			continue;
 		}
 
 		for_each_subsys(ss, i) {


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