[Devel] [PATCH hci-8.1 v5 2/6] block/blk-throttle: account a throttled write in CBT

[Pavel Tikhomirov]

submit_bio_noacct() accounts a write in CBT only when blk-throttle does
not hold it: a throttled bio is later issued from the throttle dispatch
work with submit_bio_noacct_nocheck(), which skips CBT. So writes delayed
by an IO limit never reach CBT, and incremental backups miss them.

Account the bio in CBT when the dispatch work issues it. The work runs
in process context with no locks held, so CBT may allocate there as it
does at submission.

https://virtuozzo.atlassian.net/browse/VSTOR-149268
Feature: cbt: changed block tracking (for backup)
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 block/blk-throttle.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 397b6a410f9e5..e1e008a30bf2c 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1223,8 +1223,11 @@ static void blk_throtl_dispatch_work_fn(struct work_struct *work)
 
 	if (!bio_list_empty(&bio_list_on_stack)) {
 		blk_start_plug(&plug);
-		while ((bio = bio_list_pop(&bio_list_on_stack)))
+		while ((bio = bio_list_pop(&bio_list_on_stack))) {
+			/* submit_bio_noacct() did not account it in CBT */
+			blk_cbt_bio_queue(q, bio);
 			submit_bio_noacct_nocheck(bio);
+		}
 		blk_finish_plug(&plug);
 	}
 }

-- 
2.55.0