[Devel] [PATCH RHEL9 COMMIT] dm-ploop: split cow processing into two functions

[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 36a162bb4c5809e95f540eac112dbf10d55423b4
Author: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
Date:   Fri Jan 24 17:36:06 2025 +0200

    dm-ploop: split cow processing into two functions
    
    Split ploop_process_delta_cow in two - list iterator and processing
    functions, unify handling with other pio types.
    We need this to be able to call pio by pio from threads.
    
    https://virtuozzo.atlassian.net/browse/VSTOR-91821
    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 | 52 +++++++++++++++++++++++++----------------------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 55d619cefe50..4b5992335e04 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -1472,39 +1472,43 @@ static void ploop_submit_cow_index_wb(struct ploop_cow *cow)
 	ploop_complete_cow(cow, BLK_STS_RESOURCE);
 }
 
+static void ploop_process_one_delta_cow(struct ploop *ploop, struct pio *aux_pio)
+{
+	struct ploop_cow *cow;
+
+	cow = aux_pio->endio_cb_data;
+	if (unlikely(aux_pio->bi_status != BLK_STS_OK)) {
+		ploop_complete_cow(cow, aux_pio->bi_status);
+		return;
+	}
+	/* until type is changed */
+	INIT_LIST_HEAD(&aux_pio->list);
+	if (cow->dst_clu == BAT_ENTRY_NONE) {
+		/*
+		 * Stage #1: assign dst_clu and write data
+		 * to top delta.
+		 */
+		ploop_submit_cluster_write(cow);
+	} else {
+		/*
+		 * Stage #2: data is written to top delta.
+		 * Update index.
+		 */
+		ploop_submit_cow_index_wb(cow);
+	}
+}
+
 static void ploop_process_delta_cow(struct ploop *ploop,
 				    struct llist_node *cow_llist)
 {
-	struct ploop_cow *cow;
-	struct pio *aux_pio;
 	struct llist_node *pos, *t;
+	struct pio *aux_pio;
 
 	llist_for_each_safe(pos, t, cow_llist) {
 		aux_pio = list_entry((struct list_head *)pos, typeof(*aux_pio), list);
-		cow = aux_pio->endio_cb_data;
-		if (unlikely(aux_pio->bi_status != BLK_STS_OK)) {
-			ploop_complete_cow(cow, aux_pio->bi_status);
-			continue;
-		}
-		/* until type is changed */
-		INIT_LIST_HEAD(&aux_pio->list);
-
-		if (cow->dst_clu == BAT_ENTRY_NONE) {
-			/*
-			 * Stage #1: assign dst_clu and write data
-			 * to top delta.
-			 */
-			ploop_submit_cluster_write(cow);
-		} else {
-			/*
-			 * Stage #2: data is written to top delta.
-			 * Update index.
-			 */
-			ploop_submit_cow_index_wb(cow);
-		}
+		ploop_process_one_delta_cow(ploop, aux_pio);
 	}
 }
-
 /*
  * This allocates a new clu (if clu wb is not pending yet),
  * or tries to attach a bio to a planned page index wb.