linux-kernel - [PATCH V8 1/8] fork: Make IO worker options flag based

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Message-Id: <20220209232939.9169-2-michael.christie@oracle.com>
Date:   Wed,  9 Feb 2022 17:29:32 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     geert@...ux-m68k.org, hdanton@...a.com, hch@...radead.org,
        stefanha@...hat.com, jasowang@...hat.com, mst@...hat.com,
        sgarzare@...hat.com, virtualization@...ts.linux-foundation.org,
        christian.brauner@...ntu.com, axboe@...nel.dk,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH V8 1/8] fork: Make IO worker options flag based

This patchset adds a couple new options to kernel_clone_args for the vhost
layer which is going to work like PF_IO_WORKER but will differ enough that
we will need to add several fields to kernel_clone_args. This patch moves
us to a flags based approach for these types of users.

Signed-off-by: Mike Christie <michael.christie@...cle.com>
Suggested-by: Christian Brauner <christian.brauner@...ntu.com>
Acked-by: Christian Brauner <christian.brauner@...ntu.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 include/linux/sched/task.h | 4 +++-
 kernel/fork.c              | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index b9198a1b3a84..0bf95966ae7d 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -18,8 +18,11 @@ struct css_set;
 /* All the bits taken by the old clone syscall. */
 #define CLONE_LEGACY_FLAGS 0xffffffffULL
 
+#define USER_WORKER_IO		BIT(0)
+
 struct kernel_clone_args {
 	u64 flags;
+	u32 worker_flags;
 	int __user *pidfd;
 	int __user *child_tid;
 	int __user *parent_tid;
@@ -31,7 +34,6 @@ struct kernel_clone_args {
 	/* Number of elements in *set_tid */
 	size_t set_tid_size;
 	int cgroup;
-	int io_thread;
 	struct cgroup *cgrp;
 	struct css_set *cset;
 };
diff --git a/kernel/fork.c b/kernel/fork.c
index d75a528f7b21..9273fd81a329 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1998,7 +1998,7 @@ static __latent_entropy struct task_struct *copy_process(
 	p = dup_task_struct(current, node);
 	if (!p)
 		goto fork_out;
-	if (args->io_thread) {
+	if (args->worker_flags & USER_WORKER_IO) {
 		/*
 		 * Mark us an IO worker, and block any signal that isn't
 		 * fatal or STOP
@@ -2497,7 +2497,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 		.exit_signal	= (lower_32_bits(flags) & CSIGNAL),
 		.stack		= (unsigned long)fn,
 		.stack_size	= (unsigned long)arg,
-		.io_thread	= 1,
+		.worker_flags	= USER_WORKER_IO,
 	};
 
 	return copy_process(NULL, 0, node, &args);
-- 
2.25.1