The following patches were made over Eric's tree:
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git
and his kthread-cleanups-for-v5.19 branch. They allow the vhost layer to
do a copy_process on the thread that does the VHOST_SET_OWNER ioctl like how
io_uring does a copy_process against its userspace app. This allows the
vhost layer's worker threads to inherit cgroups, namespaces, address
space, etc and this worker thread will also be accounted for against that
owner/parent process's RLIMIT_NPROC limit.
If you are not familiar with qemu and vhost here is more detailed
problem description:
Qemu will create vhost devices in the kernel which perform network, SCSI,
etc IO and management operations from worker threads created by the
kthread API. Because the kthread API does a copy_process on the kthreadd
thread, the vhost layer has to use kthread_use_mm to access the Qemu
thread's memory and cgroup_attach_task_all to add itself to the Qemu
thread's cgroups.
The problem with this approach is that we then have to add new functions/
args/functionality for every thing we want to inherit. I started doing
that here:
https://lkml.org/lkml/2021/6/23/1233
for the RLIMIT_NPROC check, but it seems it might be easier to just
inherit everything from the beginning, becuase I'd need to do something
like that patch several times.
V9:
- Rebase against Eric's kthread-cleanups-for-v5.19 branch. Drop patches
no longer needed due to kernel clone arg and pf io worker patches in that
branch.
V8:
- Fix kzalloc GFP use.
- Fix email subject version number.
V7:
- Drop generic user_worker_* helpers and replace with vhost_task specific
ones.
- Drop autoreap patch. Use kernel_wait4 instead.
- Fix issue where vhost.ko could be removed while the worker function is
still running.
V6:
- Rename kernel_worker to user_worker and fix prefixes.
- Add better patch descriptions.
V5:
- Handle kbuild errors by building patchset against current kernel that
has all deps merged. Also add patch to remove create_io_thread code as
it's not used anymore.
- Rebase patchset against current kernel and handle a new vm PF_IO_WORKER
case added in 5.16-rc1.
- Add PF_USER_WORKER flag so we can check it later after the initial
thread creation for the wake up, vm and singal cses.
- Added patch to auto reap the worker thread.
V4:
- Drop NO_SIG patch and replaced with Christian's SIG_IGN patch.
- Merged Christian's kernel_worker_flags_valid helpers into patch 5 that
added the new kernel worker functions.
- Fixed extra "i" issue.
- Added PF_USER_WORKER flag and added check that kernel_worker_start users
had that flag set. Also dropped patches that passed worker flags to
copy_thread and replaced with PF_USER_WORKER check.
V3:
- Add parentheses in p->flag and work_flags check in copy_thread.
- Fix check in arm/arm64 which was doing the reverse of other archs
where it did likely(!flags) instead of unlikely(flags).
V2:
- Rename kernel_copy_process to kernel_worker.
- Instead of exporting functions, make kernel_worker() a proper
function/API that does common work for the caller.
- Instead of adding new fields to kernel_clone_args for each option
make it flag based similar to CLONE_*.
- Drop unused completion struct in vhost.
- Fix compile warnings by merging vhost cgroup cleanup patch and
vhost conversion patch.
This adds a new flag, PF_USER_WORKER, that's used for behavior common to
to both PF_IO_WORKER and users like vhost which will use a new helper
instead of create_io_thread because they require different behavior for
operations like signal handling.
The common behavior PF_USER_WORKER covers is the vm reclaim handling.
Signed-off-by: Mike Christie <[email protected]>
---
include/linux/sched.h | 1 +
include/linux/sched/task.h | 3 ++-
kernel/fork.c | 4 ++++
mm/vmscan.c | 4 ++--
4 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a8911b1f35aa..0fa66a098183 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1700,6 +1700,7 @@ extern struct pid *cad_pid;
#define PF_MEMALLOC 0x00000800 /* Allocating memory */
#define PF_NPROC_EXCEEDED 0x00001000 /* set_user() noticed that RLIMIT_NPROC was exceeded */
#define PF_USED_MATH 0x00002000 /* If unset the fpu must be initialized before use */
+#define PF_USER_WORKER 0x00004000 /* Kernel thread cloned from userspace thread */
#define PF_NOFREEZE 0x00008000 /* This thread should not be frozen */
#define PF_FROZEN 0x00010000 /* Frozen for system suspend */
#define PF_KSWAPD 0x00020000 /* I am kswapd */
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index b0a9d6c75bcc..9e20fa18c41f 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -18,7 +18,8 @@ struct css_set;
/* All the bits taken by the old clone syscall. */
#define CLONE_LEGACY_FLAGS 0xffffffffULL
-#define USER_WORKER_IO BIT(0)
+#define USER_WORKER BIT(0)
+#define USER_WORKER_IO BIT(1)
struct kernel_clone_args {
u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index f4f2c88d9a2a..19293bcca001 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2071,6 +2071,10 @@ static __latent_entropy struct task_struct *copy_process(
p->flags &= ~PF_KTHREAD;
if (args->kthread)
p->flags |= PF_KTHREAD;
+
+ if (args->worker_flags & USER_WORKER)
+ p->flags |= PF_USER_WORKER;
+
if (args->worker_flags & USER_WORKER_IO) {
/*
* Mark us an IO worker, and block any signal that isn't
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1678802e03e7..0f58587862ef 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1051,12 +1051,12 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
DEFINE_WAIT(wait);
/*
- * Do not throttle IO workers, kthreads other than kswapd or
+ * Do not throttle user workers, kthreads other than kswapd or
* workqueues. They may be required for reclaim to make
* forward progress (e.g. journalling workqueues or kthreads).
*/
if (!current_is_kswapd() &&
- current->flags & (PF_IO_WORKER|PF_KTHREAD)) {
+ current->flags & (PF_USER_WORKER|PF_KTHREAD)) {
cond_resched();
return;
}
--
2.25.1
For vhost workers we use the kthread API which inherit's its values from
and checks against the kthreadd thread. This results in the wrong RLIMITs
being checked, so while tools like libvirt try to control the number of
threads based on the nproc rlimit setting we can end up creating more
threads than the user wanted.
This patch has us use the vhost_task helpers which will inherit its
values/checks from the thread that owns the device similar to if we did
a clone in userspace. The vhost threads will now be counted in the nproc
rlimits. And we get features like cgroups and mm sharing automatically,
so we can remove those calls.
Signed-off-by: Mike Christie <[email protected]>
---
drivers/vhost/vhost.c | 58 ++++++++-----------------------------------
drivers/vhost/vhost.h | 4 +--
2 files changed, 13 insertions(+), 49 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 8fd8aff2201c..91180c0e2b77 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -22,11 +22,11 @@
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/kthread.h>
-#include <linux/cgroup.h>
#include <linux/module.h>
#include <linux/sort.h>
#include <linux/sched/mm.h>
#include <linux/sched/signal.h>
+#include <linux/sched/vhost_task.h>
#include <linux/interval_tree_generic.h>
#include <linux/nospec.h>
#include <linux/kcov.h>
@@ -264,7 +264,7 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
* test_and_set_bit() implies a memory barrier.
*/
llist_add(&work->node, &dev->worker->work_list);
- wake_up_process(dev->worker->task);
+ wake_up_process(dev->worker->vtsk->task);
}
}
EXPORT_SYMBOL_GPL(vhost_work_queue);
@@ -344,17 +344,14 @@ static void vhost_vq_reset(struct vhost_dev *dev,
static int vhost_worker(void *data)
{
struct vhost_worker *worker = data;
- struct vhost_dev *dev = worker->dev;
struct vhost_work *work, *work_next;
struct llist_node *node;
- kthread_use_mm(dev->mm);
-
for (;;) {
/* mb paired w/ kthread_stop */
set_current_state(TASK_INTERRUPTIBLE);
- if (kthread_should_stop()) {
+ if (vhost_task_should_stop(worker->vtsk)) {
__set_current_state(TASK_RUNNING);
break;
}
@@ -376,7 +373,7 @@ static int vhost_worker(void *data)
schedule();
}
}
- kthread_unuse_mm(dev->mm);
+
return 0;
}
@@ -517,31 +514,6 @@ long vhost_dev_check_owner(struct vhost_dev *dev)
}
EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
-struct vhost_attach_cgroups_struct {
- struct vhost_work work;
- struct task_struct *owner;
- int ret;
-};
-
-static void vhost_attach_cgroups_work(struct vhost_work *work)
-{
- struct vhost_attach_cgroups_struct *s;
-
- s = container_of(work, struct vhost_attach_cgroups_struct, work);
- s->ret = cgroup_attach_task_all(s->owner, current);
-}
-
-static int vhost_attach_cgroups(struct vhost_dev *dev)
-{
- struct vhost_attach_cgroups_struct attach;
-
- attach.owner = current;
- vhost_work_init(&attach.work, vhost_attach_cgroups_work);
- vhost_work_queue(dev, &attach.work);
- vhost_work_dev_flush(dev);
- return attach.ret;
-}
-
/* Caller should have device mutex */
bool vhost_dev_has_owner(struct vhost_dev *dev)
{
@@ -588,14 +560,14 @@ static void vhost_worker_free(struct vhost_dev *dev)
dev->worker = NULL;
WARN_ON(!llist_empty(&worker->work_list));
- kthread_stop(worker->task);
+ vhost_task_stop(worker->vtsk);
kfree(worker);
}
static int vhost_worker_create(struct vhost_dev *dev)
{
struct vhost_worker *worker;
- struct task_struct *task;
+ struct vhost_task *vtsk;
int ret;
worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
@@ -603,27 +575,19 @@ static int vhost_worker_create(struct vhost_dev *dev)
return -ENOMEM;
dev->worker = worker;
- worker->dev = dev;
worker->kcov_handle = kcov_common_handle();
init_llist_head(&worker->work_list);
- task = kthread_create(vhost_worker, worker, "vhost-%d", current->pid);
- if (IS_ERR(task)) {
- ret = PTR_ERR(task);
+ vtsk = vhost_task_create(vhost_worker, worker, NUMA_NO_NODE);
+ if (!vtsk) {
+ ret = -ENOMEM;
goto free_worker;
}
- worker->task = task;
- wake_up_process(task); /* avoid contributing to loadavg */
-
- ret = vhost_attach_cgroups(dev);
- if (ret)
- goto stop_worker;
-
+ worker->vtsk = vtsk;
+ vhost_task_start(vtsk, "vhost-%d", current->pid);
return 0;
-stop_worker:
- kthread_stop(worker->task);
free_worker:
kfree(worker);
dev->worker = NULL;
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 102ce25e4e13..c9f391326dd5 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -16,6 +16,7 @@
#include <linux/irqbypass.h>
struct vhost_work;
+struct vhost_task;
typedef void (*vhost_work_fn_t)(struct vhost_work *work);
#define VHOST_WORK_QUEUED 1
@@ -26,9 +27,8 @@ struct vhost_work {
};
struct vhost_worker {
- struct task_struct *task;
+ struct vhost_task *vtsk;
struct llist_head work_list;
- struct vhost_dev *dev;
u64 kcov_handle;
};
--
2.25.1
From: Christian Brauner <[email protected]>
Since:
commit 10ab825bdef8 ("change kernel threads to ignore signals instead of
blocking them")
kthreads have been ignoring signals by default, and the vhost layer has
never had a need to change that. This patch adds an option flag,
USER_WORKER_SIG_IGN, handled in copy_process() after copy_sighand()
and copy_signals() so vhost_tasks added in the next patches can continue
to ignore singals.
Signed-off-by: Christian Brauner <[email protected]>
Signed-off-by: Mike Christie <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
include/linux/sched/task.h | 1 +
kernel/fork.c | 3 +++
2 files changed, 4 insertions(+)
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 7f6364e5aa1a..9fbb489b2512 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -21,6 +21,7 @@ struct css_set;
#define USER_WORKER BIT(0)
#define USER_WORKER_IO BIT(1)
#define USER_WORKER_NO_FILES BIT(2)
+#define USER_WORKER_SIG_IGN BIT(3)
struct kernel_clone_args {
u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index 43213bc926c6..84346fa6232e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2258,6 +2258,9 @@ static __latent_entropy struct task_struct *copy_process(
if (retval)
goto bad_fork_cleanup_io;
+ if (args->worker_flags & USER_WORKER_SIG_IGN)
+ ignore_signals(p);
+
stackleak_task_init(p);
if (pid != &init_struct_pid) {
--
2.25.1
Each vhost device gets a thread that is used to perform IO and management
operations. Instead of a thread that is accessing a device, the thread is
part of the device, so when it creates a thread using a helper based on
copy_process we can't dup or clone the parent's files/FDS because it
would do an extra increment on ourself.
Later, when we do:
Qemu process exits:
do_exit -> exit_files -> put_files_struct -> close_files
we would leak the device's resources because of that extra refcount
on the fd or file_struct.
This patch adds a no_files option so these worker threads can prevent
taking an extra refcount on themselves.
Signed-off-by: Mike Christie <[email protected]>
Acked-by: Christian Brauner <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
include/linux/sched/task.h | 1 +
kernel/fork.c | 11 +++++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 9e20fa18c41f..7f6364e5aa1a 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -20,6 +20,7 @@ struct css_set;
#define USER_WORKER BIT(0)
#define USER_WORKER_IO BIT(1)
+#define USER_WORKER_NO_FILES BIT(2)
struct kernel_clone_args {
u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index 19293bcca001..43213bc926c6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1600,7 +1600,8 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
return 0;
}
-static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
+static int copy_files(unsigned long clone_flags, struct task_struct *tsk,
+ int no_files)
{
struct files_struct *oldf, *newf;
int error = 0;
@@ -1612,6 +1613,11 @@ static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
if (!oldf)
goto out;
+ if (no_files) {
+ tsk->files = NULL;
+ goto out;
+ }
+
if (clone_flags & CLONE_FILES) {
atomic_inc(&oldf->count);
goto out;
@@ -2226,7 +2232,8 @@ static __latent_entropy struct task_struct *copy_process(
retval = copy_semundo(clone_flags, p);
if (retval)
goto bad_fork_cleanup_security;
- retval = copy_files(clone_flags, p);
+ retval = copy_files(clone_flags, p,
+ args->worker_flags & USER_WORKER_NO_FILES);
if (retval)
goto bad_fork_cleanup_semundo;
retval = copy_fs(clone_flags, p);
--
2.25.1
Qemu will create vhost devices in the kernel which perform network, SCSI,
etc IO and management operations from worker threads created by the
kthread API. Because the kthread API does a copy_process on the kthreadd
thread, the vhost layer has to use kthread_use_mm to access the Qemu
thread's memory and cgroup_attach_task_all to add itself to the Qemu
thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result
in VMs creating more threads than the admin expected.
This patch adds a new struct vhost_task which can be used instead of
kthreads. They allow the vhost layer to use copy_process and inherit
the userspace process's mm and cgroups, the task is accounted for
under the userspace's nproc count and can be seen in its process tree,
and other features like namespaces work and are inherited by default.
Signed-off-by: Mike Christie <[email protected]>
---
MAINTAINERS | 2 +
drivers/vhost/Kconfig | 5 ++
include/linux/sched/vhost_task.h | 23 ++++++
kernel/Makefile | 1 +
kernel/vhost_task.c | 122 +++++++++++++++++++++++++++++++
5 files changed, 153 insertions(+)
create mode 100644 include/linux/sched/vhost_task.h
create mode 100644 kernel/vhost_task.c
diff --git a/MAINTAINERS b/MAINTAINERS
index e8c52d0192a6..94c77f4a1ecb 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20919,7 +20919,9 @@ L: [email protected]
L: [email protected]
S: Maintained
T: git git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git
+F: kernel/vhost_task.c
F: drivers/vhost/
+F: include/linux/sched/vhost_task.h
F: include/linux/vhost_iotlb.h
F: include/uapi/linux/vhost.h
diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 587fbae06182..b455d9ab6f3d 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -13,9 +13,14 @@ config VHOST_RING
This option is selected by any driver which needs to access
the host side of a virtio ring.
+config VHOST_TASK
+ bool
+ default n
+
config VHOST
tristate
select VHOST_IOTLB
+ select VHOST_TASK
help
This option is selected by any driver which needs to access
the core of vhost.
diff --git a/include/linux/sched/vhost_task.h b/include/linux/sched/vhost_task.h
new file mode 100644
index 000000000000..50d02a25d37b
--- /dev/null
+++ b/include/linux/sched/vhost_task.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_VHOST_TASK_H
+#define _LINUX_VHOST_TASK_H
+
+#include <linux/completion.h>
+
+struct task_struct;
+
+struct vhost_task {
+ int (*fn)(void *data);
+ void *data;
+ struct completion exited;
+ unsigned long flags;
+ struct task_struct *task;
+};
+
+struct vhost_task *vhost_task_create(int (*fn)(void *), void *arg, int node);
+__printf(2, 3)
+void vhost_task_start(struct vhost_task *vtsk, const char namefmt[], ...);
+void vhost_task_stop(struct vhost_task *vtsk);
+bool vhost_task_should_stop(struct vhost_task *vtsk);
+
+#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index 847a82bfe0e3..7fbf3eb6a86b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -15,6 +15,7 @@ obj-y = fork.o exec_domain.o panic.o \
obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o
obj-$(CONFIG_MODULES) += kmod.o
obj-$(CONFIG_MULTIUSER) += groups.o
+obj-$(CONFIG_VHOST_TASK) += vhost_task.o
ifdef CONFIG_FUNCTION_TRACER
# Do not trace internal ftrace files
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
new file mode 100644
index 000000000000..517dd166bb2b
--- /dev/null
+++ b/kernel/vhost_task.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Oracle Corporation
+ */
+#include <linux/slab.h>
+#include <linux/completion.h>
+#include <linux/sched/task.h>
+#include <linux/sched/vhost_task.h>
+#include <linux/sched/signal.h>
+
+enum vhost_task_flags {
+ VHOST_TASK_FLAGS_STOP,
+};
+
+static int vhost_task_fn(void *data)
+{
+ struct vhost_task *vtsk = data;
+ int ret;
+
+ ret = vtsk->fn(vtsk->data);
+ complete(&vtsk->exited);
+ do_exit(ret);
+}
+
+/**
+ * vhost_task_stop - stop a vhost_task
+ * @vtsk: vhost_task to stop
+ *
+ * Callers must call vhost_task_should_stop and return from their worker
+ * function when it returns true;
+ */
+void vhost_task_stop(struct vhost_task *vtsk)
+{
+ pid_t pid = vtsk->task->pid;
+
+ set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
+ wake_up_process(vtsk->task);
+ /*
+ * Make sure vhost_task_fn is no longer accessing the vhost_task before
+ * freeing it below. If userspace crashed or exited without closing,
+ * then the vhost_task->task could already be marked dead so
+ * kernel_wait will return early.
+ */
+ wait_for_completion(&vtsk->exited);
+ /*
+ * If we are just closing/removing a device and the parent process is
+ * not exiting then reap the task.
+ */
+ kernel_wait4(pid, NULL, __WCLONE, NULL);
+ kfree(vtsk);
+}
+EXPORT_SYMBOL_GPL(vhost_task_stop);
+
+/**
+ * vhost_task_should_stop - should the vhost task return from the work function
+ */
+bool vhost_task_should_stop(struct vhost_task *vtsk)
+{
+ return test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
+}
+EXPORT_SYMBOL_GPL(vhost_task_should_stop);
+
+/**
+ * vhost_task_create - 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
+ *
+ * This returns a specialized task for use by the vhost layer or NULL on
+ * failure. The returned task is inactive, and the caller must fire it up
+ * through vhost_task_start().
+ */
+struct vhost_task *vhost_task_create(int (*fn)(void *), void *arg, int node)
+{
+ struct kernel_clone_args args = {
+ .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM,
+ .exit_signal = 0,
+ .worker_flags = USER_WORKER | USER_WORKER_NO_FILES |
+ USER_WORKER_SIG_IGN,
+ .fn = vhost_task_fn,
+ };
+ struct vhost_task *vtsk;
+ struct task_struct *tsk;
+
+ vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);
+ if (!vtsk)
+ return ERR_PTR(-ENOMEM);
+ init_completion(&vtsk->exited);
+ vtsk->data = arg;
+ vtsk->fn = fn;
+
+ args.fn_arg = vtsk;
+
+ tsk = copy_process(NULL, 0, node, &args);
+ if (IS_ERR(tsk)) {
+ kfree(vtsk);
+ return NULL;
+ }
+
+ vtsk->task = tsk;
+ return vtsk;
+}
+EXPORT_SYMBOL_GPL(vhost_task_create);
+
+/**
+ * vhost_task_start - start a vhost_task created with vhost_task_create
+ * @vtsk: vhost_task to wake up
+ * @namefmt: printf-style format string for the thread name
+ */
+void vhost_task_start(struct vhost_task *vtsk, const char namefmt[], ...)
+{
+ char name[TASK_COMM_LEN];
+ va_list args;
+
+ va_start(args, namefmt);
+ vsnprintf(name, sizeof(name), namefmt, args);
+ set_task_comm(vtsk->task, name);
+ va_end(args);
+
+ wake_up_new_task(vtsk->task);
+}
+EXPORT_SYMBOL_GPL(vhost_task_start);
--
2.25.1
On Thu, May 12, 2022 at 04:46:56PM -0500, Mike Christie wrote:
> The following patches were made over Eric's tree:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git
>
> and his kthread-cleanups-for-v5.19 branch. They allow the vhost layer to
> do a copy_process on the thread that does the VHOST_SET_OWNER ioctl like how
> io_uring does a copy_process against its userspace app. This allows the
> vhost layer's worker threads to inherit cgroups, namespaces, address
> space, etc and this worker thread will also be accounted for against that
> owner/parent process's RLIMIT_NPROC limit.
>
> If you are not familiar with qemu and vhost here is more detailed
> problem description:
>
> Qemu will create vhost devices in the kernel which perform network, SCSI,
> etc IO and management operations from worker threads created by the
> kthread API. Because the kthread API does a copy_process on the kthreadd
> thread, the vhost layer has to use kthread_use_mm to access the Qemu
> thread's memory and cgroup_attach_task_all to add itself to the Qemu
> thread's cgroups.
>
> The problem with this approach is that we then have to add new functions/
> args/functionality for every thing we want to inherit. I started doing
> that here:
>
> https://lkml.org/lkml/2021/6/23/1233
>
> for the RLIMIT_NPROC check, but it seems it might be easier to just
> inherit everything from the beginning, becuase I'd need to do something
> like that patch several times.
Series:
Acked-by: Michael S. Tsirkin <[email protected]>
Who is going to merge this?
> V9:
> - Rebase against Eric's kthread-cleanups-for-v5.19 branch. Drop patches
> no longer needed due to kernel clone arg and pf io worker patches in that
> branch.
> V8:
> - Fix kzalloc GFP use.
> - Fix email subject version number.
> V7:
> - Drop generic user_worker_* helpers and replace with vhost_task specific
> ones.
> - Drop autoreap patch. Use kernel_wait4 instead.
> - Fix issue where vhost.ko could be removed while the worker function is
> still running.
> V6:
> - Rename kernel_worker to user_worker and fix prefixes.
> - Add better patch descriptions.
> V5:
> - Handle kbuild errors by building patchset against current kernel that
> has all deps merged. Also add patch to remove create_io_thread code as
> it's not used anymore.
> - Rebase patchset against current kernel and handle a new vm PF_IO_WORKER
> case added in 5.16-rc1.
> - Add PF_USER_WORKER flag so we can check it later after the initial
> thread creation for the wake up, vm and singal cses.
> - Added patch to auto reap the worker thread.
> V4:
> - Drop NO_SIG patch and replaced with Christian's SIG_IGN patch.
> - Merged Christian's kernel_worker_flags_valid helpers into patch 5 that
> added the new kernel worker functions.
> - Fixed extra "i" issue.
> - Added PF_USER_WORKER flag and added check that kernel_worker_start users
> had that flag set. Also dropped patches that passed worker flags to
> copy_thread and replaced with PF_USER_WORKER check.
> V3:
> - Add parentheses in p->flag and work_flags check in copy_thread.
> - Fix check in arm/arm64 which was doing the reverse of other archs
> where it did likely(!flags) instead of unlikely(flags).
> V2:
> - Rename kernel_copy_process to kernel_worker.
> - Instead of exporting functions, make kernel_worker() a proper
> function/API that does common work for the caller.
> - Instead of adding new fields to kernel_clone_args for each option
> make it flag based similar to CLONE_*.
> - Drop unused completion struct in vhost.
> - Fix compile warnings by merging vhost cgroup cleanup patch and
> vhost conversion patch.
>
>
>
On 5/12/22 4:46 PM, Mike Christie wrote:
> The following patches were made over Eric's tree:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git
>
> and his kthread-cleanups-for-v5.19 branch.
Hi Eric,
Did you have more review comments for the patches or are you ok with them
now? I haven't seen any comments the last couple of postings. I've
been watching your trees, so I know you are doing cleanup/improvements
in the areas I needed help with so I know it's still on your radar, but
now I'm worried I'm missing emails/reviews from you :)
Are you also going to push the kthread-cleanups for 5.19 still or is that
going to be 5.20? I have patches that depend and/or have conflicts with
this set so I'm trying to figure out what I should be rebasing and testing
against.