From e0f2224433b15a57125d6ac5d46182f99c6c9d08 Mon Sep 17 00:00:00 2001 From: Vasileios Almpanis Date: Wed, 30 Sep 2026 14:32:26 +0000 Subject: [PATCH] block: drop the cached plug time when blk_add_rq_to_plug() flushes blk_time_get_ns() caches the current time in the task's plug. The idea is that the cache lives for one plug and is dropped when the plug is flushed. __blk_flush_plug() and finish_task_switch() do that. blk_add_rq_to_plug() also flushes, when the plug has too many requests or the last request is at least BLK_PLUG_FLUSH_SIZE. But it calls blk_mq_flush_plug_list() directly and never drops the cached time. So a task that keeps submitting without sleeping stamps every request after that with the time first cached in the plug. start_time_ns and io_start_time_ns are stale and the disk stats charge each request for the whole time since the plug began. Drop the cached time after the flush, same as __blk_flush_plug() does. Fixes: da4c8c3d0975 ("block: cache current nsec time in struct blk_plug") Cc: stable@vger.kernel.org Signed-off-by: Vasileios Almpanis Link: https://patch.msgid.link/20260930-blk-plug-ts-flush-v1-1-bf8ca7bc5cd6@virtuozzo.com Signed-off-by: Jens Axboe --- block/blk-mq.c | 1 + 1 file changed, 1 insertion(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index a26a11c73ee3..7a37d9f1647d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1384,6 +1384,7 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq) (!blk_queue_nomerges(rq->q) && blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) { blk_mq_flush_plug_list(plug, false); + blk_plug_invalidate_ts(); last = NULL; trace_block_plug(rq->q); }