[PATCH 02/23][SRU][OEM-5.14] mm: hide laptop_mode_wb_timer entirely behind the BDI API

[Koba Ko]

From: Christoph Hellwig <hch at lst.de>

BugLink: https://bugs.launchpad.net/bugs/1958850 

Don't leak the detaіls of the timer into the block layer, instead
initialize the timer in bdi_alloc and delete it in bdi_unregister.
Note that this means the timer is initialized (but not armed) for
non-block queues as well now.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Jan Kara <jack at suse.cz>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn at wdc.com>
Link: https://lore.kernel.org/r/20210809141744.1203023-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe at kernel.dk>
(cherry picked from commit 5ed964f8e54eb3191b8b7b45aeb52672a0c995dc)
Signed-off-by: Koba Ko <koba.ko at canonical.com>
---
 block/blk-core.c    | 4 ----
 mm/backing-dev.c    | 3 +++
 mm/page-writeback.c | 2 --
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 569494002f3f8..facaaffbe6d70 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -393,8 +393,6 @@ void blk_cleanup_queue(struct request_queue *q)
 	/* for synchronous bio-based driver finish in-flight integrity i/o */
 	blk_flush_integrity();
 
-	/* @q won't process any more request, flush async actions */
-	del_timer_sync(&q->backing_dev_info->laptop_mode_wb_timer);
 	blk_sync_queue(q);
 
 	if (queue_is_mq(q)) {
@@ -547,8 +545,6 @@ struct request_queue *blk_alloc_queue(int node_id)
 
 	atomic_set(&q->nr_active_requests_shared_sbitmap, 0);
 
-	timer_setup(&q->backing_dev_info->laptop_mode_wb_timer,
-		    laptop_mode_timer_fn, 0);
 	timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
 	INIT_WORK(&q->timeout_work, blk_timeout_work);
 	INIT_LIST_HEAD(&q->icq_list);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 140683c588c91..74b7adefb4d4a 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -807,6 +807,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
 	bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
 	bdi->ra_pages = VM_READAHEAD_PAGES;
 	bdi->io_pages = VM_READAHEAD_PAGES;
+	timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
 	return bdi;
 }
 EXPORT_SYMBOL(bdi_alloc);
@@ -928,6 +929,8 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
 
 void bdi_unregister(struct backing_dev_info *bdi)
 {
+	del_timer_sync(&bdi->laptop_mode_wb_timer);
+
 	/* make sure nobody finds us on the bdi_list anymore */
 	bdi_remove_from_list(bdi);
 	wb_shutdown(&bdi->wb);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 9f63548f247c3..c12f67cbfa19a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2010,7 +2010,6 @@ int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
 	return ret;
 }
 
-#ifdef CONFIG_BLOCK
 void laptop_mode_timer_fn(struct timer_list *t)
 {
 	struct backing_dev_info *backing_dev_info =
@@ -2045,7 +2044,6 @@ void laptop_sync_completion(void)
 
 	rcu_read_unlock();
 }
-#endif
 
 /*
  * If ratelimit_pages is too high then we can get into dirty-data overload
-- 
2.25.1