[Devel] [PATCH vz9 v1 56/63] dm-ploop: rework logic in pio processing

[Alexander Atanasov]

improve how and when we wait for pios to complete
before proceeding with next pios.
force writing of pending md pages in case we have a sync pios.
remove now unused functions.

https://virtuozzo.atlassian.net/browse/VSTOR-91821
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 drivers/md/dm-ploop-map.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 35d12fd54050..f9904e708c35 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -2049,6 +2049,7 @@ void do_ploop_run_work(struct ploop *ploop)
 	struct llist_node *llflush_pios;
 	unsigned int old_flags = current->flags;
 	int npios;
+	int force_md_update;
 
 	current->flags |= PF_IO_THREAD|PF_LOCAL_THROTTLE|PF_MEMALLOC_NOIO;
 
@@ -2064,8 +2065,7 @@ void do_ploop_run_work(struct ploop *ploop)
 		ploop_runners_add_work_list(ploop, lldeferred_pios);
 
 	if (llembedded_pios)
-		ploop_prepare_embedded_pios(ploop, llist_reverse_order(llembedded_pios),
-					    &deferred_pios);
+		ploop_prepare_embedded_pios(ploop, llembedded_pios, &deferred_pios);
 
 	llflush_pios = llist_del_all(&ploop->pios[PLOOP_LIST_FLUSH]);
 
@@ -2080,23 +2080,28 @@ void do_ploop_run_work(struct ploop *ploop)
 	if (llcow_pios)
 		ploop_runners_add_work_list(ploop, llcow_pios);
 
-	/* wait for all pios to be executed before metadata updates */
+	/*
+	 * put stick in the wheel - wait for all pios to be executed before doing metadata
+	 * we could gain a bit more iops if we can skip this wait but for now we can not
+	 */
 	current->flags = old_flags;
-	wait_event_interruptible(ploop->dispatcher_wq_data, (!ploop_runners_have_pending(ploop)));
+	wait_event_interruptible(ploop->dispatcher_wq_data,
+				 (!ploop_runners_have_pending(ploop)));
 	current->flags |= PF_IO_THREAD|PF_LOCAL_THROTTLE|PF_MEMALLOC_NOIO;
 
 	/* if we have a flush we must sync md data too */
-	npios = ploop_submit_metadata_writeback(ploop, !!llflush_pios | ploop->force_md_writeback);
+	force_md_update = !!llflush_pios | ploop->force_md_writeback;
+	npios = ploop_submit_metadata_writeback(ploop, force_md_update);
 
-	if (llflush_pios) {
-		if (npios) {
-			/* wait for metadata writeback to complete */
-			current->flags = old_flags;
-			/* First wait all pios to be processed */
-			wait_event_interruptible(ploop->dispatcher_wq_data,
-						 (!ploop_runners_have_pending(ploop)));
-			current->flags |= PF_IO_THREAD|PF_LOCAL_THROTTLE|PF_MEMALLOC_NOIO;
-		}
+	if (npios) {
+		/* wait for metadata writeback to complete */
+		current->flags = old_flags;
+		/* First wait all pios to be processed */
+		wait_event_interruptible(ploop->dispatcher_wq_data,
+					 (!ploop_runners_have_pending(ploop)));
+		current->flags |= PF_IO_THREAD|PF_LOCAL_THROTTLE|PF_MEMALLOC_NOIO;
+	}
+	if (llflush_pios || npios) {
 		/* Now process fsync pios after we have done all other */
 		npios = process_ploop_fsync_work(ploop, llflush_pios);
 		/* Since dispatcher is single thread no other work can be queued */
-- 
2.43.0