linux-kernel - [PATCH 05/11] fork/vm: Move common PF_IO

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Message-Id: <20230310220332.5309-6-michael.christie@oracle.com>
Date:   Fri, 10 Mar 2023 16:03:26 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, brauner@...nel.org,
        ebiederm@...ssion.com, torvalds@...ux-foundation.org,
        konrad.wilk@...cle.com, linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>
Subject: [PATCH 05/11] fork/vm: Move common PF_IO_WORKER behavior to new flag

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 <michael.christie@...cle.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
---
 include/linux/sched.h      | 2 +-
 include/linux/sched/task.h | 1 +
 kernel/fork.c              | 3 +++
 mm/vmscan.c                | 4 ++--
 4 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 853d08f7562b..2ca9269332c1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1723,7 +1723,7 @@ 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__HOLE__00004000	0x00004000
+#define PF_USER_WORKER		0x00004000	/* Kernel thread cloned from userspace thread */
 #define PF_NOFREEZE		0x00008000	/* This thread should not be frozen */
 #define PF__HOLE__00010000	0x00010000
 #define PF_KSWAPD		0x00020000	/* I am kswapd */
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 268c77a42155..2950e83d5382 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -27,6 +27,7 @@ struct kernel_clone_args {
 	int exit_signal;
 	u32 kthread:1;
 	u32 io_thread:1;
+	u32 user_worker:1;
 	unsigned long stack;
 	unsigned long stack_size;
 	unsigned long tls;
diff --git a/kernel/fork.c b/kernel/fork.c
index cb8f85c88c75..0dec38276363 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2100,6 +2100,8 @@ static __latent_entropy struct task_struct *copy_process(
 	p->flags &= ~PF_KTHREAD;
 	if (args->kthread)
 		p->flags |= PF_KTHREAD;
+	if (args->user_worker)
+		p->flags |= PF_USER_WORKER;
 	if (args->io_thread) {
 		/*
 		 * Mark us an IO worker, and block any signal that isn't
@@ -2627,6 +2629,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 		.fn		= fn,
 		.fn_arg		= arg,
 		.io_thread	= 1,
+		.user_worker	= 1,
 	};
 
 	return copy_process(NULL, 0, node, &args);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bf3eedf0209c..86c27b08041e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1141,12 +1141,12 @@ 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