linux-kernel - [PATCH 2/2] userfaultfd: Set the corresponding flag in IOU worker context

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Message-Id: <20250422104545.1199433-3-qq282012236@gmail.com>
Date: Tue, 22 Apr 2025 10:45:45 +0000
From: Zhiwei Jiang <qq282012236@...il.com>
To: viro@...iv.linux.org.uk
Cc: brauner@...nel.org,
	jack@...e.cz,
	akpm@...ux-foundation.org,
	peterx@...hat.com,
	axboe@...nel.dk,
	asml.silence@...il.com,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	io-uring@...r.kernel.org,
	Zhiwei Jiang <qq282012236@...il.com>
Subject: [PATCH 2/2] userfaultfd: Set the corresponding flag in IOU worker context

Set this to avoid premature return from schedule in IOU worker threads,
ensuring it sleeps and waits to be woken up as in normal cases.

Signed-off-by: Zhiwei Jiang <qq282012236@...il.com>
---
 fs/userfaultfd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index d80f94346199..74bead069e85 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -32,6 +32,7 @@
 #include <linux/swapops.h>
 #include <linux/miscdevice.h>
 #include <linux/uio.h>
+#include "../io_uring/io-wq.h"
 
 static int sysctl_unprivileged_userfaultfd __read_mostly;
 
@@ -369,7 +370,10 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	vm_fault_t ret = VM_FAULT_SIGBUS;
 	bool must_wait;
 	unsigned int blocking_state;
+	struct io_worker *worker = current->worker_private;
 
+	if (worker)
+		set_userfault_flag_for_ioworker(worker);
 	/*
 	 * We don't do userfault handling for the final child pid update
 	 * and when coredumping (faults triggered by get_dump_page()).
@@ -506,6 +510,9 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
 
 	__set_current_state(TASK_RUNNING);
 
+	if (worker)
+		clear_userfault_flag_for_ioworker(worker);
+
 	/*
 	 * Here we race with the list_del; list_add in
 	 * userfaultfd_ctx_read(), however because we don't ever run
-- 
2.34.1