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From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     linux-arch@vger.kernel.org
Cc:     Tejun Heo <tj@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Al Viro <viro@ZenIV.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        "Eric W. Biederman" <ebiederm@xmission.com>
Date:   Fri,  6 May 2022 09:15:10 -0500
Message-Id: <20220506141512.516114-5-ebiederm@xmission.com>
In-Reply-To: <87mtfu4up3.fsf@email.froward.int.ebiederm.org>
References: <87mtfu4up3.fsf@email.froward.int.ebiederm.org>
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Subject: [PATCH 5/7] init: Deal with the init process being a user mode process
Precedence: bulk

It is silly for user_mode_thread to leave PF_KTHREAD set
on the resulting task.  Update the init process so that
it does not care if PF_KTHREAD is set or not.

Ensure do_populate_rootfs flushes all delayed fput work by calling
task_work_run.  In the rare instance that async_schedule_domain calls
do_populate_rootfs synchronously it is possible do_populate_rootfs
will be called directly from the init process.  At which point fput
will call "task_work_add(current, ..., TWA_RESUME)".  The files on the
initramfs need to be completely put before we attempt to exec them
(which is before the code enters userspace).  So call task_work_run
just in case there are any pending fput operations.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 init/initramfs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/init/initramfs.c b/init/initramfs.c
index 2f3d96dc3db6..41e7857d510d 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -15,6 +15,7 @@
 #include <linux/mm.h>
 #include <linux/namei.h>
 #include <linux/init_syscalls.h>
+#include <linux/task_work.h>
 #include <linux/umh.h>
 
 static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
@@ -703,6 +704,7 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie)
 	initrd_end = 0;
 
 	flush_delayed_fput();
+	task_work_run();
 }
 
 static ASYNC_DOMAIN_EXCLUSIVE(initramfs_domain);
-- 
2.35.3