[Devel] [PATCH RHEL9 COMMIT] dm-ploop: handle REQ_PREFLUSH

[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 649ec1bdd004cde5c9ef89c53e852b226eca901b
Author: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
Date:   Fri Jan 24 17:35:59 2025 +0200

    dm-ploop: handle REQ_PREFLUSH
    
    Create new flush pio when we see REQ_PREFLUSH flag. Call original
    pio after the flush is done.
    
    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 | 39 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index fdbf20145223..553603b95bf8 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -1980,33 +1980,62 @@ int ploop_worker(void *data)
 	return 0;
 }
 
+static void ploop_preflush_endio(struct pio *pio, void *orig_pio_ptr,
+					blk_status_t bi_status)
+{
+	struct pio *original = orig_pio_ptr;
+
+	if (bi_status) {
+		original->bi_status = bi_status;
+		ploop_pio_endio(original);
+	} else {
+		ploop_dispatch_pios(pio->ploop, original, NULL);
+	}
+}
+
 static void ploop_prepare_flush(struct ploop *ploop, struct pio *pio)
 {
+	struct pio *flush_pio = pio;
 	struct md_page *md, *n;
 	int md_inflight = 0;
 
+	if (pio->bi_op & REQ_PREFLUSH && (pio->bi_op & REQ_OP_MASK) != REQ_OP_FLUSH) {
+		flush_pio = ploop_alloc_pio(ploop, GFP_NOIO);
+		if (!flush_pio) {
+			pio->bi_status = BLK_STS_RESOURCE;
+			ploop_pio_endio(pio);
+			return;
+		}
+
+		ploop_init_pio(ploop, REQ_OP_FLUSH, flush_pio);
+		flush_pio->endio_cb = ploop_preflush_endio;
+		flush_pio->endio_cb_data = pio;
+		flush_pio->queue_list_id = PLOOP_LIST_FLUSH;
+		flush_pio->free_on_endio = true;
+	}
+
 	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;
+		md->piwb->flush_pio = flush_pio;
 	}
 
 	list_for_each_entry_safe(md, n, &ploop->wb_batch_list, wb_link) {
 		md_inflight++;
-		md->piwb->flush_pio = pio;
+		md->piwb->flush_pio = flush_pio;
 		list_del(&md->wb_link);
 		list_add_tail(&md->wb_link, &ploop->wb_batch_list_prio);
 	}
 
-	atomic_set(&pio->md_inflight, md_inflight);
+	atomic_set(&flush_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);
+		ploop_dispatch_pios(ploop, flush_pio, NULL);
 }
 
 static void ploop_submit_embedded_pio(struct ploop *ploop, struct pio *pio)
@@ -2031,7 +2060,7 @@ 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) {
+	if ((pio->bi_op & REQ_OP_MASK) == REQ_OP_FLUSH || pio->bi_op & REQ_PREFLUSH) {
 		ploop_prepare_flush(ploop, pio);
 		return;
 	}