[Devel] [PATCH vz9 v2 19/65] dm-ploop: reduce BAT accesses on discard completion

[Konstantin Khorenko]

From: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>

Drop extra ploop_cluster_is_in_top_delta() as we are planning to
access BAT anyway

https://virtuozzo.atlassian.net/browse/VSTOR-91817
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko 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 | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 296b44511b8c..2706a1731ca4 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -713,12 +713,15 @@ static void ploop_complete_cow(struct ploop_cow *cow, blk_status_t bi_status)
 	kmem_cache_free(cow_cache, cow);
 }
 
-static void ploop_release_cluster(struct ploop *ploop, u32 clu)
+static void ploop_piwb_discard_completed(struct ploop *ploop,
+					 bool success, u32 clu, u32 new_dst_clu)
 {
 	u32 id, *bat_entries, dst_clu;
 	struct md_page *md;
+	u8 level;
 
-	lockdep_assert_held(&ploop->bat_rwlock);
+	if (new_dst_clu)
+		return;
 
 	id = ploop_bat_clu_to_page_nr(clu);
 	md = ploop_md_page_find(ploop, id);
@@ -728,22 +731,15 @@ static void ploop_release_cluster(struct ploop *ploop, u32 clu)
 
 	bat_entries = md->kmpage;
 	dst_clu = READ_ONCE(bat_entries[clu]);
-	WRITE_ONCE(bat_entries[clu], BAT_ENTRY_NONE);
-	WRITE_ONCE(md->bat_levels[clu], 0);
-
-	ploop_hole_set_bit(dst_clu, ploop);
-}
-
-static void ploop_piwb_discard_completed(struct ploop *ploop,
-					 bool success, u32 clu, u32 new_dst_clu)
-{
-	if (new_dst_clu)
-		return;
+	level = md->bat_levels[clu];
 
-	if (ploop_cluster_is_in_top_delta(ploop, clu)) {
+	if (!(dst_clu == BAT_ENTRY_NONE || level < ploop_top_level(ploop))) {
 		WARN_ON_ONCE(ploop->nr_deltas != 1);
-		if (success)
-			ploop_release_cluster(ploop, clu);
+		if (success) {
+			WRITE_ONCE(bat_entries[clu], BAT_ENTRY_NONE);
+			WRITE_ONCE(md->bat_levels[clu], 0);
+			ploop_hole_set_bit(dst_clu, ploop);
+		}
 	}
 }
 
-- 
2.43.5