[PATCH 05/11] fork/vm: Move common PF_IO_WORKER behavior to new flag

Mike Christie
2023-03-10T22:05:57Z

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@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.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