[Devel] [PATCH vz9 v2 29/65] dm-ploop: BAT use only one list for writeback

[Konstantin Khorenko]

From: Alexander Atanasov <alexander.atanasov at virtuozzo.com>

remove the wb_batch_list_prio, use only wb_batch_list and
use the md high_prio flag for immediate submission.

https://virtuozzo.atlassian.net/browse/VSTOR-91817
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>

======
Patchset description:
ploop: optimistations and scalling

Ploop processes requsts in a different threads in parallel
where possible which results in significant improvement in
performance and makes further optimistations possible.

Known bugs:
  - delayed metadata writeback is not working and is missing error handling
     - patch to disable it until fixed
  - fast path is not working - causes rcu lockups - patch to disable it

Further improvements:
  - optimize md pages lookups

Alexander Atanasov (50):
  dm-ploop: md_pages map all pages at creation time
  dm-ploop: Use READ_ONCE/WRITE_ONCE to access md page data
  dm-ploop: fsync after all pios are sent
  dm-ploop: move md status to use proper bitops
  dm-ploop: convert wait_list and wb_batch_llist to use lockless lists
  dm-ploop: convert enospc handling to use lockless lists
  dm-ploop: convert suspended_pios list to use lockless list
  dm-ploop: convert the rest of the lists to use llist variant
  dm-ploop: combine processing of pios thru prepare list and remove
    fsync worker
  dm-ploop: move from wq to kthread
  dm-ploop: move preparations of pios into the caller from worker
  dm-ploop: fast path execution for reads
  dm-ploop: do not use a wrapper for set_bit to make a page writeback
  dm-ploop: BAT use only one list for writeback
  dm-ploop: make md writeback timeout to be per page
  dm-ploop: add interface to disable bat writeback delay
  dm-ploop: convert wb_batch_list to lockless variant
  dm-ploop: convert high_prio to status
  dm-ploop: split cow processing into two functions
  dm-ploop: convert md page rw lock to spin lock
  dm-ploop: convert bat_rwlock to bat_lock spinlock
  dm-ploop: prepare bat updates under bat_lock
  dm-ploop: make ploop_bat_write_complete ready for parallel pio
    completion
  dm-ploop: make ploop_submit_metadata_writeback return number of
    requests sent
  dm-ploop: introduce pio runner threads
  dm-ploop: add pio list ids to be used when passing pios to runners
  dm-ploop: process pios via runners
  dm-ploop: disable metadata writeback delay
  dm-ploop: disable fast path
  dm-ploop: use lockless lists for chained cow updates list
  dm-ploop: use lockless lists for data ready pios
  dm-ploop: give runner threads better name
  dm-ploop: resize operation - add holes bitmap locking
  dm-ploop: remove unnecessary operations
  dm-ploop: use filp per thread
  dm-ploop: catch if we try to advance pio past bio end
  dm-ploop: support REQ_FUA for data pios
  dm-ploop: proplerly access nr_bat_entries
  dm-ploop: fix locking and improve error handling when submitting pios
  dm-ploop: fix how ENOTBLK is handled
  dm-ploop: sync when suspended or stopping
  dm-ploop: rework bat completion logic
  dm-ploop: rework logic in pio processing
  dm-ploop: end fsync pios in parallel
  dm-ploop: make filespace preallocations async
  dm-ploop: resubmit enospc pios from dispatcher thread
  dm-ploop: dm-ploop: simplify discard completion
  dm-ploop: use GFP_ATOMIC instead of GFP_NOIO
  dm-ploop: fix locks used in mixed context
  dm-ploop: fix how current flags are managed inside threads

Andrey Zhadchenko (13):
  dm-ploop: do not flush after metadata writes
  dm-ploop: set IOCB_DSYNC on all FUA requests
  dm-ploop: remove extra ploop_cluster_is_in_top_delta()
  dm-ploop: introduce per-md page locking
  dm-ploop: reduce BAT accesses on discard completion
  dm-ploop: simplify llseek
  dm-ploop: speed up ploop_prepare_bat_update()
  dm-ploop: make new allocations immediately visible in BAT
  dm-ploop: drop ploop_cluster_is_in_top_delta()
  dm-ploop: do not wait for BAT update for non-FUA requests
  dm-ploop: add delay for metadata writeback
  dm-ploop: submit all postponed metadata on REQ_OP_FLUSH
  dm-ploop: handle REQ_PREFLUSH

Feature: dm-ploop: ploop target driver
---
 drivers/md/dm-ploop-map.c    | 70 +++++++++++++++---------------------
 drivers/md/dm-ploop-target.c |  1 -
 drivers/md/dm-ploop.h        |  1 -
 3 files changed, 29 insertions(+), 43 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 993a8ff1447b..f2e0d0b317de 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -579,10 +579,6 @@ static void ploop_md_up_prio(struct ploop *ploop, struct md_page *md)
 
 	md->high_prio = true;
 	WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));
-
-	list_del(&md->wb_link);
-	list_add(&md->wb_link, &ploop->wb_batch_list_prio);
-
 out:
 	write_unlock_irqrestore(&ploop->bat_rwlock, flags);
 }
@@ -1829,43 +1825,41 @@ static void ploop_process_resubmit_pios(struct ploop *ploop,
 	}
 }
 
-static void ploop_submit_metadata_writeback_from_list(struct ploop *ploop,
-						      struct list_head *list)
+static void ploop_submit_metadata_writeback(struct ploop *ploop)
 {
-	struct md_page *md;
+	ktime_t ktime, ktimeout;
+	LIST_HEAD(ll_skipped);
+	struct md_page *md, *mtmp;
+	int send_all;
 
-	while (1) {
+	ktime = ktime_get();
+	ktimeout = ktime_add_ms(ktime, ploop->md_submit_delay_ms);
+	send_all = ktime_after(ktime, ktimeout);
+	/*
+	 * Pages are set dirty so no one must touch lists
+	 * if new md entries are dirtied they are added at the start of the list
+	 */
+	list_for_each_entry_safe(md, mtmp, &ploop->wb_batch_list, wb_link) {
 		write_lock_irq(&ploop->bat_rwlock);
-		md = list_first_entry_or_null(list, struct md_page, wb_link);
-		if (!md) {
+		list_del_init(&md->wb_link);
+		if (md->high_prio || send_all) {
+			/* L1L2 mustn't be redirtyed, when wb in-flight! */
+			WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));
+			WARN_ON_ONCE(test_bit(MD_WRITEBACK, &md->status));
+			set_bit(MD_WRITEBACK, &md->status);
+			clear_bit(MD_DIRTY, &md->status);
+			md->high_prio = false;
+			write_unlock_irq(&ploop->bat_rwlock);
+			ploop_index_wb_submit(ploop, md->piwb);
+		} else {
+			list_add_tail(&md->wb_link, &ll_skipped);
 			write_unlock_irq(&ploop->bat_rwlock);
-			break;
 		}
-		list_del_init(&md->wb_link);
-		/* L1L2 mustn't be redirtyed, when wb in-flight! */
-
-		WARN_ON_ONCE(!test_bit(MD_DIRTY, &md->status));
-		WARN_ON_ONCE(test_bit(MD_WRITEBACK, &md->status));
-		set_bit(MD_WRITEBACK, &md->status);
-		clear_bit(MD_DIRTY, &md->status);
-		md->high_prio = false;
-		write_unlock_irq(&ploop->bat_rwlock);
-
-		ploop_index_wb_submit(ploop, md->piwb);
 	}
-}
-
-static void ploop_submit_metadata_writeback(struct ploop *ploop)
-{
-	ktime_t time;
-
-	ploop_submit_metadata_writeback_from_list(ploop, &ploop->wb_batch_list_prio);
+	write_lock_irq(&ploop->bat_rwlock);
+	list_splice(&ll_skipped, &ploop->wb_batch_list);
+	write_unlock_irq(&ploop->bat_rwlock);
 
-	time = ktime_get();
-	if (ktime_after(time, ktime_add_ms(ploop->last_md_submit, ploop->md_submit_delay_ms))) {
-		ploop->last_md_submit = time;
-		ploop_submit_metadata_writeback_from_list(ploop, &ploop->wb_batch_list);
-	}
 }
 
 static void process_ploop_fsync_work(struct ploop *ploop, struct llist_node *llflush_pios)
@@ -2014,16 +2008,10 @@ static void ploop_prepare_flush(struct ploop *ploop, struct pio *pio)
 
 	write_lock_irq(&ploop->bat_rwlock);
 
-	list_for_each_entry(md, &ploop->wb_batch_list_prio, wb_link) {
-		md_inflight++;
-		md->piwb->flush_pio = flush_pio;
-	}
-
 	list_for_each_entry_safe(md, n, &ploop->wb_batch_list, wb_link) {
 		md_inflight++;
 		md->piwb->flush_pio = flush_pio;
-		list_del(&md->wb_link);
-		list_add_tail(&md->wb_link, &ploop->wb_batch_list_prio);
+		md->high_prio = true;
 	}
 
 	atomic_set(&flush_pio->md_inflight, md_inflight);
diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index f714c2cb540f..87827b90aeef 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -423,7 +423,6 @@ static int ploop_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	INIT_LIST_HEAD(&ploop->cluster_lk_list);
 	init_llist_head(&ploop->wb_batch_llist);
 	INIT_LIST_HEAD(&ploop->wb_batch_list);
-	INIT_LIST_HEAD(&ploop->wb_batch_list_prio);
 	ploop->last_md_submit = 0;
 	ploop->md_submit_delay_ms = PLOOP_DEFAULT_METADATA_SUBMIT_DELAY;
 
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index b19fbdbc8423..909ddf877a7f 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -178,7 +178,6 @@ struct ploop {
 
 	struct llist_head wb_batch_llist;
 	struct list_head wb_batch_list;
-	struct list_head wb_batch_list_prio;
 
 	ktime_t last_md_submit;
 #define PLOOP_DEFAULT_METADATA_SUBMIT_DELAY 10000
-- 
2.43.5