[Devel] [PATCH vz9 v2 64/65] dm-ploop: fix locks used in mixed context

[Konstantin Khorenko]

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

These locks are used in both interrupt and user context so we must
preserve interrupts state.

https://virtuozzo.atlassian.net/browse/VSTOR-98471
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 | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index f7e7dd04773e..0b934b83a176 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -1408,6 +1408,7 @@ static void ploop_check_standby_mode(struct ploop *ploop, long res)
 {
 	struct request_queue *q = ploop_blk_queue(ploop);
 	int prev;
+	unsigned long flags;
 
 	if (!blk_queue_standby_en(q))
 		return;
@@ -1416,9 +1417,9 @@ static void ploop_check_standby_mode(struct ploop *ploop, long res)
 	if (res != -EBUSY && res != -ENOTCONN && res != -EIO)
 		return;
 
-	spin_lock_irq(&q->queue_lock);
+	spin_lock_irqsave(&q->queue_lock, flags);
 	prev = blk_queue_flag_test_and_set(QUEUE_FLAG_STANDBY, q);
-	spin_unlock_irq(&q->queue_lock);
+	spin_unlock_irqrestore(&q->queue_lock, flags);
 
 	if (!prev)
 		PL_INFO("was switched into the standby mode");
@@ -1540,12 +1541,13 @@ static bool ploop_postpone_if_cluster_locked(struct ploop *ploop,
 					     struct pio *pio, u32 clu)
 {
 	struct pio *e_h; /* Exclusively locked */
+	unsigned long flags;
 
-	spin_lock_irq(&ploop->deferred_lock);
+	spin_lock_irqsave(&ploop->deferred_lock, flags);
 	e_h = ploop_find_lk_of_cluster(ploop, clu);
 	if (e_h && pio)
 		ploop_add_endio_pio(e_h, pio);
-	spin_unlock_irq(&ploop->deferred_lock);
+	spin_unlock_irqrestore(&ploop->deferred_lock, flags);
 
 	return e_h != NULL;
 }
-- 
2.43.5