Re: [PATCH] clone.2: Document CLONE_INTO_CGROUP
From: Michael Kerrisk (man-pages) <hidden>
Date: 2020-04-10 20:18:14
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Hi Christian, Thank you for writing this! On 4/10/20 12:41 PM, Christian Brauner wrote:
quoted hunk ↗ jump to hunk
From: Christian Brauner <redacted> Signed-off-by: Christian Brauner <redacted> --- man2/clone.2 | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)diff --git a/man2/clone.2 b/man2/clone.2 index 39cec4c86..8d9aa9f99 100644 --- a/man2/clone.2 +++ b/man2/clone.2@@ -197,6 +197,7 @@ struct clone_args { u64 tls; /* Location of new TLS */ u64 set_tid; /* Pointer to a \fIpid_t\fP array */ u64 set_tid_size; /* Number of elements in \fIset_tid\fP */ + u64 cgroup; /* Target cgroup file descriptor for the child process */ }; .EE .in@@ -448,6 +449,25 @@ Specifying this flag together with .B CLONE_SIGHAND is nonsensical and disallowed. .TP +.BR CLONE_INTO_CGROUP " (since Linux 5.7)" +.\" commit ef2c41cf38a7559bbf91af42d5b6a4429db8fc68 +By default, the child process will belong to the same cgroup as its parent.
s/belong to/be placed in/ s/cgroup/version 2 cgroup/
+If this flag is specified the child process will be created in a +different cgroup than its parent. + +When using +.RB clone3 () +the target cgroup can be specified by setting the +.I cl_args.cgroup +member to the file descriptor of the target cgroup. The cgroup file
We need to say something about how this file descriptor is obtained. Is it by opening a directory in the v2 cgroup hierarchy? With what flags? O_RDONLY? or is O_PATH also possible? Yes, these are some rhetorical questions (I read your nice commit message); these things need to be explicit in the manual page though. Also, your commit message mentions a nice list of use cases. I think it would be well worth capturing those in a paragraph in the manual page text.
+descriptor must refer to a cgroup in a cgroup v2 hierarchy +(see +.BR cgroup (2)).
s/cgroup/cgroups/ s/2/7/
+ +Note that all usual cgroup v2 process migration restrictions apply. See +.BR cgroup (2)
s/cgroup/cgroups/ s/2/7/ Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/