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Commit c1955ce3 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

writeback: remove wb_list 



The wb_list member of struct backing_device_info always has exactly one
element.  Just use the direct bdi->wb pointer instead and simplify some
code.

Also remove bdi_task_init which is now trivial to prepare for the next
patch.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 4c4762d1

fs/fs-writeback.c

+2 −2
Original line number Diff line number Diff line
@@ -73,9 +73,9 @@ static void bdi_queue_work(struct backing_dev_info *bdi, 
	 * If the default thread isn't there, make sure we add it. When

	 * it gets created and wakes up, we'll run this work.

	 */

	if (unlikely(list_empty_careful(&bdi->wb_list)))

	if (unlikely(!bdi->wb.task)) {

		wake_up_process(default_backing_dev_info.wb.task);

	else {

	} else {

		struct bdi_writeback *wb = &bdi->wb;



		if (wb->task)

include/linux/backing-dev.h

+1 −4
Original line number Diff line number Diff line
@@ -45,8 +45,6 @@ enum bdi_stat_item { 
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))



struct bdi_writeback {

	struct list_head list;			/* hangs off the bdi */



	struct backing_dev_info *bdi;		/* our parent bdi */

	unsigned int nr;
@@ -80,8 +78,7 @@ struct backing_dev_info { 
	unsigned int max_ratio, max_prop_frac;



	struct bdi_writeback wb;  /* default writeback info for this bdi */

	spinlock_t wb_lock;	  /* protects update side of wb_list */

	struct list_head wb_list; /* the flusher threads hanging off this bdi */

	spinlock_t wb_lock;	  /* protects work_list */



	struct list_head work_list;

mm/backing-dev.c

+29 −54
Original line number Diff line number Diff line
@@ -65,28 +65,21 @@ static void bdi_debug_init(void) 
static int bdi_debug_stats_show(struct seq_file *m, void *v)

{

	struct backing_dev_info *bdi = m->private;

	struct bdi_writeback *wb;

	struct bdi_writeback *wb = &bdi->wb;

	unsigned long background_thresh;

	unsigned long dirty_thresh;

	unsigned long bdi_thresh;

	unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;

	struct inode *inode;



	/*

	 * inode lock is enough here, the bdi->wb_list is protected by

	 * RCU on the reader side

	 */

	nr_wb = nr_dirty = nr_io = nr_more_io = 0;

	spin_lock(&inode_lock);

	list_for_each_entry(wb, &bdi->wb_list, list) {

		nr_wb++;

	list_for_each_entry(inode, &wb->b_dirty, i_list)

		nr_dirty++;

	list_for_each_entry(inode, &wb->b_io, i_list)

		nr_io++;

	list_for_each_entry(inode, &wb->b_more_io, i_list)

		nr_more_io++;

	}

	spin_unlock(&inode_lock);



	get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
@@ -98,19 +91,16 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v) 
		   "BdiDirtyThresh:   %8lu kB\n"

		   "DirtyThresh:      %8lu kB\n"

		   "BackgroundThresh: %8lu kB\n"

		   "WritebackThreads: %8lu\n"

		   "b_dirty:          %8lu\n"

		   "b_io:             %8lu\n"

		   "b_more_io:        %8lu\n"

		   "bdi_list:         %8u\n"

		   "state:            %8lx\n"

		   "wb_list:          %8u\n",

		   "state:            %8lx\n",

		   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),

		   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),

		   K(bdi_thresh), K(dirty_thresh),

		   K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,

		   !list_empty(&bdi->bdi_list), bdi->state,

		   !list_empty(&bdi->wb_list));

		   K(background_thresh), nr_dirty, nr_io, nr_more_io,

		   !list_empty(&bdi->bdi_list), bdi->state);

#undef K



	return 0;
@@ -270,24 +260,6 @@ static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi) 
	INIT_LIST_HEAD(&wb->b_more_io);

}



static void bdi_task_init(struct backing_dev_info *bdi,

			  struct bdi_writeback *wb)

{

	struct task_struct *tsk = current;



	spin_lock(&bdi->wb_lock);

	list_add_tail_rcu(&wb->list, &bdi->wb_list);

	spin_unlock(&bdi->wb_lock);



	tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;

	set_freezable();



	/*

	 * Our parent may run at a different priority, just set us to normal

	 */

	set_user_nice(tsk, 0);

}



static int bdi_start_fn(void *ptr)

{

	struct bdi_writeback *wb = ptr;
@@ -301,7 +273,13 @@ static int bdi_start_fn(void *ptr) 
	list_add_rcu(&bdi->bdi_list, &bdi_list);

	spin_unlock_bh(&bdi_lock);



	bdi_task_init(bdi, wb);

	current->flags |= PF_FLUSHER | PF_SWAPWRITE;

	set_freezable();



	/*

	 * Our parent may run at a different priority, just set us to normal

	 */

	set_user_nice(current, 0);



	/*

	 * Clear pending bit and wakeup anybody waiting to tear us down
@@ -312,12 +290,7 @@ static int bdi_start_fn(void *ptr) 


	ret = bdi_writeback_task(wb);



	/*

	 * Remove us from the list

	 */

	spin_lock(&bdi->wb_lock);

	list_del_rcu(&wb->list);

	spin_unlock(&bdi->wb_lock);

	wb->task = NULL;



	/*

	 * Flush any work that raced with us exiting. No new work
@@ -326,7 +299,6 @@ static int bdi_start_fn(void *ptr) 
	if (!list_empty(&bdi->work_list))

		wb_do_writeback(wb, 1);



	wb->task = NULL;

	return ret;

}
@@ -391,7 +363,13 @@ static int bdi_forker_task(void *ptr) 
{

	struct bdi_writeback *me = ptr;



	bdi_task_init(me->bdi, me);

	current->flags |= PF_FLUSHER | PF_SWAPWRITE;

	set_freezable();



	/*

	 * Our parent may run at a different priority, just set us to normal

	 */

	set_user_nice(current, 0);



	for (;;) {

		struct backing_dev_info *bdi, *tmp;
@@ -598,8 +576,6 @@ EXPORT_SYMBOL(bdi_register_dev); 
 */

static void bdi_wb_shutdown(struct backing_dev_info *bdi)

{

	struct bdi_writeback *wb;



	if (!bdi_cap_writeback_dirty(bdi))

		return;
@@ -615,14 +591,14 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi) 
	bdi_remove_from_list(bdi);



	/*

	 * Finally, kill the kernel threads. We don't need to be RCU

	 * Finally, kill the kernel thread. We don't need to be RCU

	 * safe anymore, since the bdi is gone from visibility. Force

	 * unfreeze of the thread before calling kthread_stop(), otherwise

	 * it would never exet if it is currently stuck in the refrigerator.

	 */

	list_for_each_entry(wb, &bdi->wb_list, list) {

		thaw_process(wb->task);

		kthread_stop(wb->task);

	if (bdi->wb.task) {

		thaw_process(bdi->wb.task);

		kthread_stop(bdi->wb.task);

	}

}
@@ -667,7 +643,6 @@ int bdi_init(struct backing_dev_info *bdi) 
	spin_lock_init(&bdi->wb_lock);

	INIT_RCU_HEAD(&bdi->rcu_head);

	INIT_LIST_HEAD(&bdi->bdi_list);

	INIT_LIST_HEAD(&bdi->wb_list);

	INIT_LIST_HEAD(&bdi->work_list);



	bdi_wb_init(&bdi->wb, bdi);