From: Chunguang Xu <brookxu@xxxxxxxxxxx> On the IO submission path, blk_account_io_start() may interrupt the system interruption. When the interruption returns, the value of part->stamp may have been updated by other cores, so the time value collected before the interruption may be less than part-> stamp. So when this happens, we should do nothing to make io_ticks more accurate? For kernels less than 5.0, this may cause io_ticks to become smaller, which in turn may cause abnormal ioutil values. v3: update the commit log v2: sorry, fix compile error due to the missed ')' Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx> --- block/blk-core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-core.c b/block/blk-core.c index 514838c..bbf56ae 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1243,7 +1243,7 @@ static void update_io_ticks(struct block_device *part, unsigned long now, unsigned long stamp; again: stamp = READ_ONCE(part->bd_stamp); - if (unlikely(stamp != now)) { + if (unlikely(time_after(now, stamp))) { if (likely(cmpxchg(&part->bd_stamp, stamp, now) == stamp)) __part_stat_add(part, io_ticks, end ? now - stamp : 1); } -- 1.8.3.1