[PATCH 1/5] fs: gate final fput task_work on PF_NO_TASKWORK

[Jens Axboe <axboe@kernel.dk>]

Rather than hardwire this to kernel threads, add a task flag that tells
us whether the task in question runs task_work or not. At fork time,
this flag is set for kernel threads. This is in preparation for allowing
kernel threads to signal that they will run deferred task_work.

No functional changes in this patch.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/file_table.c       | 2 +-
 include/linux/sched.h | 2 +-
 kernel/fork.c         | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index 5c00dc38558d..d824f1330d6e 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -520,7 +520,7 @@ void fput(struct file *file)
 			file_free(file);
 			return;
 		}
-		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
+		if (likely(!in_interrupt() && !(task->flags & PF_NO_TASKWORK))) {
 			init_task_work(&file->f_task_work, ____fput);
 			if (!task_work_add(task, &file->f_task_work, TWA_RESUME))
 				return;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9c15365a30c0..301f5dda6a06 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1709,7 +1709,7 @@ extern struct pid *cad_pid;
 						 * I am cleaning dirty pages from some other bdi. */
 #define PF_KTHREAD		0x00200000	/* I am a kernel thread */
 #define PF_RANDOMIZE		0x00400000	/* Randomize virtual address space */
-#define PF__HOLE__00800000	0x00800000
+#define PF_NO_TASKWORK		0x00800000	/* task doesn't run task_work */
 #define PF__HOLE__01000000	0x01000000
 #define PF__HOLE__02000000	0x02000000
 #define PF_NO_SETAFFINITY	0x04000000	/* Userland is not allowed to meddle with cpus_mask */
diff --git a/kernel/fork.c b/kernel/fork.c
index 735405a9c5f3..3745407624c7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2235,7 +2235,7 @@ __latent_entropy struct task_struct *copy_process(
 		goto fork_out;
 	p->flags &= ~PF_KTHREAD;
 	if (args->kthread)
-		p->flags |= PF_KTHREAD;
+		p->flags |= PF_KTHREAD | PF_NO_TASKWORK;
 	if (args->user_worker) {
 		/*
 		 * Mark us a user worker, and block any signal that isn't
-- 
2.49.0