[Devel] [PATCH RHEL9 COMMIT] dm-ploop: add interface to disable bat writeback delay

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.44.1.vz9.80.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.44.1.vz9.80.6
------>
commit c694f26e94c33b9b71b5ba49fd09155c14a59954
Author: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
Date:   Fri Jan 24 17:36:03 2025 +0200

    dm-ploop: add interface to disable bat writeback delay
    
    Add conditions that prevent writeback delay:
    - if we have a pending pios
    - if doing utility operations we do not want to delay writeout too
    
    Add interface to disable delay.
    Hook it into suspend/resuming of sending pios. Which is done before
    ops that require it.
    
    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-cmd.c |  2 ++
 drivers/md/dm-ploop-map.c | 15 ++++++++++++++-
 drivers/md/dm-ploop.h     |  7 ++++++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
index 26dc1ff04e8e..f98542e952e1 100644
--- a/drivers/md/dm-ploop-cmd.c
+++ b/drivers/md/dm-ploop-cmd.c
@@ -129,6 +129,7 @@ static void ploop_resume_submitting_pios(struct ploop *ploop)
 {
 	struct llist_node *suspended_pending;
 
+	ploop_enable_writeback_delay(ploop);
 	spin_lock_irq(&ploop->deferred_lock);
 	WARN_ON_ONCE(!ploop->stop_submitting_pios);
 	ploop->stop_submitting_pios = false;
@@ -143,6 +144,7 @@ static int ploop_suspend_submitting_pios(struct ploop *ploop)
 {
 	int ret;
 
+	ploop_disable_writeback_delay(ploop);
 	spin_lock_irq(&ploop->deferred_lock);
 	WARN_ON_ONCE(ploop->stop_submitting_pios);
 	ploop->stop_submitting_pios = true;
diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 40c3cb00856d..cc75b99908a2 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -585,6 +585,17 @@ static void ploop_md_up_prio(struct ploop *ploop, struct md_page *md)
 	write_unlock_irqrestore(&ploop->bat_rwlock, flags);
 }
 
+void ploop_disable_writeback_delay(struct ploop *ploop)
+{
+	ploop->force_md_writeback = true;
+	ploop_schedule_work(ploop);
+}
+
+void ploop_enable_writeback_delay(struct ploop *ploop)
+{
+	ploop->force_md_writeback = false;
+}
+
 static bool ploop_pio_endio_if_all_zeros(struct pio *pio)
 {
 	struct bvec_iter bi = {
@@ -1842,7 +1853,9 @@ static void ploop_submit_metadata_writeback(struct ploop *ploop)
 	list_for_each_entry_safe(md, mtmp, &ploop->wb_batch_list, wb_link) {
 		write_lock_irq(&ploop->bat_rwlock);
 		list_del_init(&md->wb_link);
-		if (md->high_prio || time_before(md->dirty_timeout, timeout)) {
+		if (!llist_empty(&md->wait_llist) || md->high_prio ||
+		    time_before(md->dirty_timeout, timeout) ||
+		    ploop->force_md_writeback) {
 			/* 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));
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index fa2b02910296..b0cf01bb3003 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -181,6 +181,7 @@ struct ploop {
 	struct list_head wb_batch_list;
 
 	ktime_t last_md_submit;
+	bool	force_md_writeback;
 #define PLOOP_DEFAULT_METADATA_SUBMIT_DELAY 10000
 	uint64_t md_submit_delay_ms;
 
@@ -608,6 +609,10 @@ extern void ploop_call_rw_iter(struct file *file, loff_t pos, unsigned rw,
 extern void ploop_enospc_timer(struct timer_list *timer);
 extern loff_t ploop_llseek_hole(struct dm_target *ti, loff_t offset, int whence);
 
-int ploop_worker(void *data);
+extern int ploop_worker(void *data);
+
+extern void ploop_disable_writeback_delay(struct ploop *ploop);
+extern void ploop_enable_writeback_delay(struct ploop *ploop);
+
 
 #endif /* __DM_PLOOP_H */