From: Christian Brauner <christian.brauner@ubuntu.com>
To: Mike Christie <michael.christie@oracle.com>, hch@infradead.org
Cc: hdanton@sina.com, stefanha@redhat.com, jasowang@redhat.com,
mst@redhat.com, sgarzare@redhat.com,
virtualization@lists.linux-foundation.org, axboe@kernel.dk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 5/9] fork: add helper to clone a process
Date: Wed, 22 Sep 2021 14:50:06 +0200 [thread overview]
Message-ID: <20210922125006.3i2k26durdwghgto@wittgenstein> (raw)
In-Reply-To: <20210921215218.89844-6-michael.christie@oracle.com>
On Tue, Sep 21, 2021 at 04:52:14PM -0500, Mike Christie wrote:
> The vhost layer has similar requirements as io_uring where its worker
> threads need to access the userspace thread's memory, want to inherit the
> parents's cgroups and namespaces, and be checked against the parent's
> RLIMITs. Right now, the vhost layer uses the kthread API which has
> kthread_use_mm for mem access, and those threads can use
> cgroup_attach_task_all for v1 cgroups, but there are no helpers for the
> other items.
>
> This adds a helper to clone a process so we can inherit everything we
> want in one call. It's a more generic version of create_io_thread which
> will be used by the vhost layer and io_uring in later patches in this set.
>
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> ---
Looks good to me.
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Christoph, does this match what you had in mind too?
> include/linux/sched/task.h | 6 ++++-
> kernel/fork.c | 48 ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 53 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
> index e165cc67fd3c..ba0499b6627c 100644
> --- a/include/linux/sched/task.h
> +++ b/include/linux/sched/task.h
> @@ -87,7 +87,11 @@ extern void exit_files(struct task_struct *);
> extern void exit_itimers(struct signal_struct *);
>
> extern pid_t kernel_clone(struct kernel_clone_args *kargs);
> -struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
> +struct task_struct *create_io_thread(int (*fn)(void *i), void *arg, int node);
> +struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
> + unsigned long clone_flags, u32 worker_flags);
> +__printf(2, 3)
> +void kernel_worker_start(struct task_struct *tsk, const char namefmt[], ...);
> struct task_struct *fork_idle(int);
> struct mm_struct *copy_init_mm(void);
> extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 98264cf1d6a6..3f3fcabffa5f 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2540,6 +2540,54 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
> return copy_process(NULL, 0, node, &args);
> }
>
> +/**
> + * kernel_worker - create a copy of a process to be used by the kernel
> + * @fn: thread stack
> + * @arg: data to be passed to fn
> + * @node: numa node to allocate task from
> + * @clone_flags: CLONE flags
> + * @worker_flags: KERN_WORKER flags
> + *
> + * This returns a created task, or an error pointer. The returned task is
> + * inactive, and the caller must fire it up through kernel_worker_start(). If
> + * this is an PF_IO_WORKER all singals but KILL and STOP are blocked.
> + */
> +struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
> + unsigned long clone_flags, u32 worker_flags)
> +{
> + struct kernel_clone_args args = {
> + .flags = ((lower_32_bits(clone_flags) | CLONE_VM |
> + CLONE_UNTRACED) & ~CSIGNAL),
> + .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL),
> + .stack = (unsigned long)fn,
> + .stack_size = (unsigned long)arg,
> + .worker_flags = KERN_WORKER_USER | worker_flags,
> + };
> +
> + return copy_process(NULL, 0, node, &args);
> +}
> +EXPORT_SYMBOL_GPL(kernel_worker);
> +
> +/**
> + * kernel_worker_start - Start a task created with kernel_worker
> + * @tsk: task to wake up
> + * @namefmt: printf-style format string for the thread name
> + * @arg: arguments for @namefmt
> + */
> +void kernel_worker_start(struct task_struct *tsk, const char namefmt[], ...)
> +{
> + char name[TASK_COMM_LEN];
> + va_list args;
> +
> + va_start(args, namefmt);
> + vsnprintf(name, sizeof(name), namefmt, args);
> + set_task_comm(tsk, name);
> + va_end(args);
> +
> + wake_up_new_task(tsk);
> +}
> +EXPORT_SYMBOL_GPL(kernel_worker_start);
> +
> /*
> * Ok, this is the main fork-routine.
> *
> --
> 2.25.1
>
next prev parent reply other threads:[~2021-09-22 12:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 21:52 [PATCH V2 0/9] Use copy_process/create_io_thread in vhost layer Mike Christie
2021-09-21 21:52 ` [PATCH V2 1/9] fork: Make IO worker options flag based Mike Christie
2021-09-22 12:44 ` Christian Brauner
2021-09-21 21:52 ` [PATCH V2 2/9] fork: pass worker_flags to copy_thread Mike Christie
2021-09-22 12:42 ` Christian Brauner
2021-09-22 14:18 ` Geert Uytterhoeven
2021-09-21 21:52 ` [PATCH V2 3/9] fork: move PF_IO_WORKER's kernel frame setup to new flag Mike Christie
2021-09-22 12:32 ` Geert Uytterhoeven
2021-09-22 12:39 ` Christian Brauner
2021-09-22 12:45 ` Christian Brauner
2021-09-21 21:52 ` [PATCH V2 4/9] fork: add option to not clone or dup files Mike Christie
2021-09-22 12:46 ` Christian Brauner
2021-09-21 21:52 ` [PATCH V2 5/9] fork: add helper to clone a process Mike Christie
2021-09-22 12:50 ` Christian Brauner [this message]
2021-09-21 21:52 ` [PATCH V2 6/9] io_uring: switch to kernel_worker Mike Christie
2021-09-22 12:53 ` Christian Brauner
2021-09-21 21:52 ` [PATCH V2 7/9] fork: Add worker flag to ignore signals Mike Christie
2021-09-22 12:52 ` Christian Brauner
2021-09-21 21:52 ` [PATCH V2 8/9] vhost: move worker thread fields to new struct Mike Christie
2021-10-04 13:12 ` Michael S. Tsirkin
2021-09-21 21:52 ` [PATCH V2 9/9] vhost: use kernel_worker to check RLIMITs and inherit v2 cgroups Mike Christie
2021-10-04 13:12 ` Michael S. Tsirkin
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