writeback: move backing_dev_info->state into bdi_writeback

Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
and the role of the separation is unclear.  For cgroup support for
writeback IOs, a bdi will be updated to host multiple wb's where each
wb serves writeback IOs of a different cgroup on the bdi.  To achieve
that, a wb should carry all states necessary for servicing writeback
IOs for a cgroup independently.

This patch moves bdi->state into wb.

* enum bdi_state is renamed to wb_state and the prefix of all enums is
  changed from BDI_ to WB_.

* Explicit zeroing of bdi->state is removed without adding zeoring of
  wb->state as the whole data structure is zeroed on init anyway.

* As there's still only one bdi_writeback per backing_dev_info, all
  uses of bdi->state are mechanically replaced with bdi->wb.state
  introducing no behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: drbd-dev@lists.linbit.com
Cc: Neil Brown <neilb@suse.de>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-core.c

@@ -621,7 +621,6 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 
 	q->backing_dev_info.ra_pages =
 			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
-	q->backing_dev_info.state = 0;
 	q->backing_dev_info.capabilities = 0;
 	q->backing_dev_info.name = "block";
 	q->node = node_id;

drivers/block/drbd/drbd_main.c

@@ -2359,7 +2359,7 @@ static void drbd_cleanup(void)
  * @congested_data:	User data
  * @bdi_bits:		Bits the BDI flusher thread is currently interested in
  *
- * Returns 1<<BDI_async_congested and/or 1<<BDI_sync_congested if we are congested.
+ * Returns 1<<WB_async_congested and/or 1<<WB_sync_congested if we are congested.
  */
 static int drbd_congested(void *congested_data, int bdi_bits)
 {
@@ -2376,14 +2376,14 @@ static int drbd_congested(void *congested_data, int bdi_bits)
 	}
 
 	if (test_bit(CALLBACK_PENDING, &first_peer_device(device)->connection->flags)) {
-		r |= (1 << BDI_async_congested);
+		r |= (1 << WB_async_congested);
 		/* Without good local data, we would need to read from remote,
 		 * and that would need the worker thread as well, which is
 		 * currently blocked waiting for that usermode helper to
 		 * finish.
 		 */
 		if (!get_ldev_if_state(device, D_UP_TO_DATE))
-			r |= (1 << BDI_sync_congested);
+			r |= (1 << WB_sync_congested);
 		else
 			put_ldev(device);
 		r &= bdi_bits;
@@ -2399,9 +2399,9 @@ static int drbd_congested(void *congested_data, int bdi_bits)
 			reason = 'b';
 	}
 
-	if (bdi_bits & (1 << BDI_async_congested) &&
+	if (bdi_bits & (1 << WB_async_congested) &&
 	    test_bit(NET_CONGESTED, &first_peer_device(device)->connection->flags)) {
-		r |= (1 << BDI_async_congested);
+		r |= (1 << WB_async_congested);
 		reason = reason == 'b' ? 'a' : 'n';
 	}
 

drivers/md/dm.c

@@ -2074,7 +2074,7 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
 			 * the query about congestion status of request_queue
 			 */
 			if (dm_request_based(md))
-				r = md->queue->backing_dev_info.state &
+				r = md->queue->backing_dev_info.wb.state &
 				    bdi_bits;
 			else
 				r = dm_table_any_congested(map, bdi_bits);

drivers/md/raid1.c

@@ -745,7 +745,7 @@ static int raid1_congested(struct mddev *mddev, int bits)
 	struct r1conf *conf = mddev->private;
 	int i, ret = 0;
 
-	if ((bits & (1 << BDI_async_congested)) &&
+	if ((bits & (1 << WB_async_congested)) &&
 	    conf->pending_count >= max_queued_requests)
 		return 1;
 
@@ -760,7 +760,7 @@ static int raid1_congested(struct mddev *mddev, int bits)
 			/* Note the '|| 1' - when read_balance prefers
 			 * non-congested targets, it can be removed
 			 */
-			if ((bits & (1<<BDI_async_congested)) || 1)
+			if ((bits & (1 << WB_async_congested)) || 1)
 				ret |= bdi_congested(&q->backing_dev_info, bits);
 			else
 				ret &= bdi_congested(&q->backing_dev_info, bits);

drivers/md/raid10.c

@@ -914,7 +914,7 @@ static int raid10_congested(struct mddev *mddev, int bits)
 	struct r10conf *conf = mddev->private;
 	int i, ret = 0;
 
-	if ((bits & (1 << BDI_async_congested)) &&
+	if ((bits & (1 << WB_async_congested)) &&
 	    conf->pending_count >= max_queued_requests)
 		return 1;
 

fs/fs-writeback.c

@@ -74,7 +74,7 @@ unsigned int dirtytime_expire_interval = 12 * 60 * 60;
  */
 int writeback_in_progress(struct backing_dev_info *bdi)
 {
-	return test_bit(BDI_writeback_running, &bdi->state);
+	return test_bit(WB_writeback_running, &bdi->wb.state);
 }
 EXPORT_SYMBOL(writeback_in_progress);
 
@@ -112,7 +112,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(wbc_writepage);
 static void bdi_wakeup_thread(struct backing_dev_info *bdi)
 {
 	spin_lock_bh(&bdi->wb_lock);
-	if (test_bit(BDI_registered, &bdi->state))
+	if (test_bit(WB_registered, &bdi->wb.state))
 		mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
 	spin_unlock_bh(&bdi->wb_lock);
 }
@@ -123,7 +123,7 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
 	trace_writeback_queue(bdi, work);
 
 	spin_lock_bh(&bdi->wb_lock);
-	if (!test_bit(BDI_registered, &bdi->state)) {
+	if (!test_bit(WB_registered, &bdi->wb.state)) {
 		if (work->done)
 			complete(work->done);
 		goto out_unlock;
@@ -1057,7 +1057,7 @@ static long wb_do_writeback(struct bdi_writeback *wb)
 	struct wb_writeback_work *work;
 	long wrote = 0;
 
-	set_bit(BDI_writeback_running, &wb->bdi->state);
+	set_bit(WB_writeback_running, &wb->state);
 	while ((work = get_next_work_item(bdi)) != NULL) {
 
 		trace_writeback_exec(bdi, work);
@@ -1079,7 +1079,7 @@ static long wb_do_writeback(struct bdi_writeback *wb)
 	 */
 	wrote += wb_check_old_data_flush(wb);
 	wrote += wb_check_background_flush(wb);
-	clear_bit(BDI_writeback_running, &wb->bdi->state);
+	clear_bit(WB_writeback_running, &wb->state);
 
 	return wrote;
 }
@@ -1099,7 +1099,7 @@ void bdi_writeback_workfn(struct work_struct *work)
 	current->flags |= PF_SWAPWRITE;
 
 	if (likely(!current_is_workqueue_rescuer() ||
-		   !test_bit(BDI_registered, &bdi->state))) {
+		   !test_bit(WB_registered, &wb->state))) {
 		/*
 		 * The normal path.  Keep writing back @bdi until its
 		 * work_list is empty.  Note that this path is also taken
@@ -1323,7 +1323,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
 			spin_unlock(&inode->i_lock);
 			spin_lock(&bdi->wb.list_lock);
 			if (bdi_cap_writeback_dirty(bdi)) {
-				WARN(!test_bit(BDI_registered, &bdi->state),
+				WARN(!test_bit(WB_registered, &bdi->wb.state),
 				     "bdi-%s not registered\n", bdi->name);
 
 				/*

include/linux/backing-dev.h

@@ -25,13 +25,13 @@ struct device;
 struct dentry;
 
 /*
- * Bits in backing_dev_info.state
+ * Bits in bdi_writeback.state
  */
-enum bdi_state {
-	BDI_async_congested,	/* The async (write) queue is getting full */
-	BDI_sync_congested,	/* The sync queue is getting full */
-	BDI_registered,		/* bdi_register() was done */
-	BDI_writeback_running,	/* Writeback is in progress */
+enum wb_state {
+	WB_async_congested,	/* The async (write) queue is getting full */
+	WB_sync_congested,	/* The sync queue is getting full */
+	WB_registered,		/* bdi_register() was done */
+	WB_writeback_running,	/* Writeback is in progress */
 };
 
 typedef int (congested_fn)(void *, int);
@@ -49,6 +49,7 @@ enum bdi_stat_item {
 struct bdi_writeback {
 	struct backing_dev_info *bdi;	/* our parent bdi */
 
+	unsigned long state;		/* Always use atomic bitops on this */
 	unsigned long last_old_flush;	/* last old data flush */
 
 	struct delayed_work dwork;	/* work item used for writeback */
@@ -62,7 +63,6 @@ struct bdi_writeback {
 struct backing_dev_info {
 	struct list_head bdi_list;
 	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */
-	unsigned long state;	/* Always use atomic bitops on this */
 	unsigned int capabilities; /* Device capabilities */
 	congested_fn *congested_fn; /* Function pointer if device is md/dm */
 	void *congested_data;	/* Pointer to aux data for congested func */
@@ -250,23 +250,23 @@ static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
 {
 	if (bdi->congested_fn)
 		return bdi->congested_fn(bdi->congested_data, bdi_bits);
-	return (bdi->state & bdi_bits);
+	return (bdi->wb.state & bdi_bits);
 }
 
 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 {
-	return bdi_congested(bdi, 1 << BDI_sync_congested);
+	return bdi_congested(bdi, 1 << WB_sync_congested);
 }
 
 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 {
-	return bdi_congested(bdi, 1 << BDI_async_congested);
+	return bdi_congested(bdi, 1 << WB_async_congested);
 }
 
 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 {
-	return bdi_congested(bdi, (1 << BDI_sync_congested) |
-				  (1 << BDI_async_congested));
+	return bdi_congested(bdi, (1 << WB_sync_congested) |
+				  (1 << WB_async_congested));
 }
 
 enum {

mm/backing-dev.c

@@ -96,7 +96,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 		   nr_io,
 		   nr_more_io,
 		   nr_dirty_time,
-		   !list_empty(&bdi->bdi_list), bdi->state);
+		   !list_empty(&bdi->bdi_list), bdi->wb.state);
 #undef K
 
 	return 0;
@@ -280,7 +280,7 @@ void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
 
 	timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
 	spin_lock_bh(&bdi->wb_lock);
-	if (test_bit(BDI_registered, &bdi->state))
+	if (test_bit(WB_registered, &bdi->wb.state))
 		queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
 	spin_unlock_bh(&bdi->wb_lock);
 }
@@ -315,7 +315,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 	bdi->dev = dev;
 
 	bdi_debug_register(bdi, dev_name(dev));
-	set_bit(BDI_registered, &bdi->state);
+	set_bit(WB_registered, &bdi->wb.state);
 
 	spin_lock_bh(&bdi_lock);
 	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
@@ -339,7 +339,7 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 {
 	/* Make sure nobody queues further work */
 	spin_lock_bh(&bdi->wb_lock);
-	if (!test_and_clear_bit(BDI_registered, &bdi->state)) {
+	if (!test_and_clear_bit(WB_registered, &bdi->wb.state)) {
 		spin_unlock_bh(&bdi->wb_lock);
 		return;
 	}
@@ -492,11 +492,11 @@ static atomic_t nr_bdi_congested[2];
 
 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 {
-	enum bdi_state bit;
+	enum wb_state bit;
 	wait_queue_head_t *wqh = &congestion_wqh[sync];
 
-	bit = sync ? BDI_sync_congested : BDI_async_congested;
-	if (test_and_clear_bit(bit, &bdi->state))
+	bit = sync ? WB_sync_congested : WB_async_congested;
+	if (test_and_clear_bit(bit, &bdi->wb.state))
 		atomic_dec(&nr_bdi_congested[sync]);
 	smp_mb__after_atomic();
 	if (waitqueue_active(wqh))
@@ -506,10 +506,10 @@ EXPORT_SYMBOL(clear_bdi_congested);
 
 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 {
-	enum bdi_state bit;
+	enum wb_state bit;
 
-	bit = sync ? BDI_sync_congested : BDI_async_congested;
-	if (!test_and_set_bit(bit, &bdi->state))
+	bit = sync ? WB_sync_congested : WB_async_congested;
+	if (!test_and_set_bit(bit, &bdi->wb.state))
 		atomic_inc(&nr_bdi_congested[sync]);
 }
 EXPORT_SYMBOL(set_bdi_congested);