fs/nilfs2: convert timers to use timer_setup()

In preparation for unconditionally passing the struct timer_list pointer
to all timer callbacks, switch to using the new timer_setup() and
from_timer() to pass the timer pointer explicitly.  This requires adding
a pointer to hold the timer's target task, as the lifetime of sc_task
doesn't appear to match the timer's task.

Link: http://lkml.kernel.org/r/20171016235900.GA102729@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/segment.c

@@ -2400,11 +2400,11 @@ static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 	return err;
 }
 
-static void nilfs_construction_timeout(unsigned long data)
+static void nilfs_construction_timeout(struct timer_list *t)
 {
-	struct task_struct *p = (struct task_struct *)data;
+	struct nilfs_sc_info *sci = from_timer(sci, t, sc_timer);
 
-	wake_up_process(p);
+	wake_up_process(sci->sc_timer_task);
 }
 
 static void
@@ -2542,8 +2542,7 @@ static int nilfs_segctor_thread(void *arg)
 	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
 	int timeout = 0;
 
-	sci->sc_timer.data = (unsigned long)current;
-	sci->sc_timer.function = nilfs_construction_timeout;
+	sci->sc_timer_task = current;
 
 	/* start sync. */
 	sci->sc_task = current;
@@ -2674,7 +2673,7 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
 	INIT_LIST_HEAD(&sci->sc_gc_inodes);
 	INIT_LIST_HEAD(&sci->sc_iput_queue);
 	INIT_WORK(&sci->sc_iput_work, nilfs_iput_work_func);
-	init_timer(&sci->sc_timer);
+	timer_setup(&sci->sc_timer, nilfs_construction_timeout, 0);
 
 	sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
 	sci->sc_mjcp_freq = HZ * NILFS_SC_DEFAULT_SR_FREQ;

fs/nilfs2/segment.h

@@ -180,6 +180,7 @@ struct nilfs_sc_info {
 	unsigned long		sc_watermark;
 
 	struct timer_list	sc_timer;
+	struct task_struct     *sc_timer_task;
 	struct task_struct     *sc_task;
 };