[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 4f03beed4737..d7c6685afbcb 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -477,7 +477,7 @@ 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 61591ac6eab6..1393d557f05e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1635,7 +1635,7 @@ extern struct pid *cad_pid;
 #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__HOLE__00010000	0x00010000
+#define PF_NO_TASKWORK		0x00010000	/* task doesn't run task_work */
 #define PF_KSWAPD		0x00020000	/* I am kswapd */
 #define PF_MEMALLOC_NOFS	0x00040000	/* All allocations inherit GFP_NOFS. See memalloc_nfs_save() */
 #define PF_MEMALLOC_NOIO	0x00080000	/* All allocations inherit GFP_NOIO. See memalloc_noio_save() */
diff --git a/kernel/fork.c b/kernel/fork.c
index 99076dbe27d8..156bf8778d18 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2222,7 +2222,7 @@ __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
-- 
2.43.0