[Devel] [PATCH vz9 v2 21/65] dm-ploop: speed up ploop_prepare_bat_update()

[Konstantin Khorenko]

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

Drop ploop_cluster_is_in_top_delta(), because
 - it internally searches md on every call
 - it takes read lock every time

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 | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 8a2d9c27ef64..e34bc4aafc79 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -900,13 +900,14 @@ static void ploop_bat_write_complete(struct pio *pio, void *piwb_ptr,
 static int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
 				    enum piwb_type type)
 {
-	u32 i, off, last, *bat_entries;
+	u32 i, off, last, *bat_entries, clu;
 	struct ploop_index_wb *piwb;
 	bool is_last_page = true;
 	u32 page_id = md->id;
 	struct page *page;
 	struct pio *pio;
 	map_index_t *to;
+	u8 level;
 
 	piwb = kmalloc(sizeof(*piwb), GFP_NOIO);
 	if (!piwb)
@@ -928,6 +929,8 @@ static int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
 
 	piwb->page_id = page_id;
 	to = kmap_local_page(page);
+
+	read_lock_irq(&md->lock);
 	memcpy((void *)to, bat_entries, PAGE_SIZE);
 
 	/* Absolute number of first index in page (negative for page#0) */
@@ -946,10 +949,14 @@ static int ploop_prepare_bat_update(struct ploop *ploop, struct md_page *md,
 
 	/* Copy BAT (BAT goes right after hdr, see .ctr) */
 	for (; i < last; i++) {
-		if (ploop_cluster_is_in_top_delta(ploop, i + off))
-			continue;
-		to[i] = 0;
+		level = md->bat_levels[i];
+		clu = READ_ONCE(bat_entries[i]);
+
+		if (clu == BAT_ENTRY_NONE || level < ploop_top_level(ploop))
+			to[i] = 0;
 	}
+	read_unlock_irq(&md->lock);
+
 	if (is_last_page) {
 	/* Fill tail of page with 0 */
 		for (i = last; i < PAGE_SIZE / sizeof(map_index_t); i++)
-- 
2.43.5