From: Aristeu Rozanski <aris@redhat.com>
To: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Cc: Li Zefan <lizefan@huawei.com>, Tejun Heo <tj@kernel.org>,
Hugh Dickins <hughd@google.com>, Hillf Danton <dhillf@gmail.com>,
Lennart Poettering <lpoetter@redhat.com>
Subject: [PATCH 1/2] cgroups: add documentation on extended attributes usage
Date: Wed, 05 Sep 2012 14:31:33 -0400 [thread overview]
Message-ID: <20120905183133.162440150@napanee.usersys.redhat.com> (raw)
In-Reply-To: 20120905183132.806473183@napanee.usersys.redhat.com
[-- Attachment #1: doc.patch --]
[-- Type: text/plain, Size: 1680 bytes --]
Cc: Li Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Lennart Poettering <lpoetter@redhat.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
---
Documentation/cgroups/00-INDEX | 2 ++
Documentation/cgroups/xattr.txt | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)
--- a/Documentation/cgroups/00-INDEX 2010-07-29 22:53:28.000000000 -0400
+++ b/Documentation/cgroups/00-INDEX 2012-08-30 12:32:18.419879863 -0400
@@ -16,3 +16,5 @@ memory.txt
- Memory Resource Controller; design, accounting, interface, testing.
resource_counter.txt
- Resource Counter API.
+xattr.txt
+ - Extended attributes support and usage in cgroup filesystem
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ b/Documentation/cgroups/xattr.txt 2012-08-30 13:02:56.585865106 -0400
@@ -0,0 +1,21 @@
+Extended Attributes Usage in cgroup Filesystem
+
+1. Usage
+
+cgroup filesystem supports certain types of extended attributes in its
+directories and files. The current supported types are:
+ - Trusted (XATTR_TRUSTED)
+ - Security (XATTR_SECURITY)
+
+Both require CAP_SYS_ADMIN capability to set.
+
+Like in tmpfs, the extended attributes in cgroup filesystem are stored
+using kernel memory and it's advised to keep the usage at minimum. This
+is the reason why user defined extended attributes are not supported, since
+any user can do it and there's no limit in the value size.
+
+2. Users
+
+The current known users for this feature are SELinux to limit cgroup usage
+in containers and systemd for assorted meta data like main PID in a cgroup
+(systemd creates a cgroup per service).
next prev parent reply other threads:[~2012-09-05 18:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-05 18:31 [PATCH 0/2] cgroups: add documentation on extended attributes and simple_xattr functions Aristeu Rozanski
2012-09-05 18:31 ` Aristeu Rozanski [this message]
2012-09-05 22:49 ` [PATCH 1/2] cgroups: add documentation on extended attributes usage Tejun Heo
2012-09-05 18:31 ` [PATCH 2/2] fs: add documentation to simple_xattr functions Aristeu Rozanski
2012-09-05 22:50 ` Tejun Heo
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