[Devel] [PATCH RHEL9 COMMIT] dm-ploop: submit all postponed metadata on REQ_OP_FLUSH

[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 e039c9267ba62f2db1f77febb90b0c46a3ac7871
Author: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Date:   Fri Jan 24 17:35:58 2025 +0200

    dm-ploop: submit all postponed metadata on REQ_OP_FLUSH
    
    On every flush request we should submit all accumulated metadata
    changes, wait for their completion and only then do the flush.
    
    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 | 42 ++++++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-ploop.h     |  3 +++
 2 files changed, 45 insertions(+)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 92844d032810..fdbf20145223 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -67,6 +67,7 @@ void ploop_index_wb_init(struct ploop_index_wb *piwb, struct ploop *ploop)
 	piwb->completed = false;
 	piwb->page_id = PAGE_NR_NONE;
 	piwb->type = PIWB_TYPE_ALLOC;
+	piwb->flush_pio = NULL;
 }
 
 void ploop_init_pio(struct ploop *ploop, unsigned int bi_op, struct pio *pio)
@@ -873,6 +874,7 @@ static void ploop_bat_write_complete(struct pio *pio, void *piwb_ptr,
 				     blk_status_t bi_status)
 {
 	struct ploop_index_wb *piwb = piwb_ptr;
+	struct pio *flush_pio = piwb->flush_pio;
 	struct ploop *ploop = piwb->ploop;
 	struct pio *aux_pio;
 	struct ploop_cow *cow;
@@ -911,6 +913,12 @@ static void ploop_bat_write_complete(struct pio *pio, void *piwb_ptr,
 		ploop_complete_cow(cow, bi_status);
 	}
 
+	if (flush_pio) {
+		if (atomic_dec_and_test(&flush_pio->md_inflight))
+			ploop_dispatch_pios(ploop, flush_pio, NULL);
+		piwb->flush_pio = NULL;
+	}
+
 	/*
 	 * In case of update BAT is failed, dst_clusters will be
 	 * set back to holes_bitmap on last put_piwb().
@@ -1972,6 +1980,35 @@ int ploop_worker(void *data)
 	return 0;
 }
 
+static void ploop_prepare_flush(struct ploop *ploop, struct pio *pio)
+{
+	struct md_page *md, *n;
+	int md_inflight = 0;
+
+	write_lock_irq(&ploop->bat_rwlock);
+
+	list_for_each_entry(md, &ploop->wb_batch_list_prio, wb_link) {
+		md_inflight++;
+		md->piwb->flush_pio = pio;
+	}
+
+	list_for_each_entry_safe(md, n, &ploop->wb_batch_list, wb_link) {
+		md_inflight++;
+		md->piwb->flush_pio = pio;
+		list_del(&md->wb_link);
+		list_add_tail(&md->wb_link, &ploop->wb_batch_list_prio);
+	}
+
+	atomic_set(&pio->md_inflight, md_inflight);
+
+	write_unlock_irq(&ploop->bat_rwlock);
+
+	if (md_inflight)
+		ploop_schedule_work(ploop);
+	else
+		ploop_dispatch_pios(ploop, pio, NULL);
+}
+
 static void ploop_submit_embedded_pio(struct ploop *ploop, struct pio *pio)
 {
 	struct ploop_rq *prq = pio->endio_cb_data;
@@ -1994,6 +2031,11 @@ static void ploop_submit_embedded_pio(struct ploop *ploop, struct pio *pio)
 
 	ploop_inc_nr_inflight(ploop, pio);
 
+	if ((pio->bi_op & REQ_OP_MASK) == REQ_OP_FLUSH) {
+		ploop_prepare_flush(ploop, pio);
+		return;
+	}
+
 	if (pio->queue_list_id == PLOOP_LIST_FLUSH) {
 		/* Let the FLUSH go last from the queue , do not run here to preserve ordering */
 		llist_add((struct llist_node *)(&pio->list), &ploop->pios[PLOOP_LIST_PREPARE]);
diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
index 8bfc5e87a24e..c08acb1a3cc9 100644
--- a/drivers/md/dm-ploop.h
+++ b/drivers/md/dm-ploop.h
@@ -108,6 +108,7 @@ struct ploop_index_wb {
 	blk_status_t bi_status;
 	u32 page_id;
 	struct bio_vec aux_bvec;
+	struct pio *flush_pio;
 };
 
 /* Metadata page */
@@ -300,6 +301,8 @@ struct pio {
 	int ret; /* iocb result */
 	void (*complete)(struct pio *me);
 	void *data;
+
+	atomic_t md_inflight;
 };
 
 /* Delta COW private */