From: Chunguang Xu <brookxu@xxxxxxxxxxx> [ Upstream commit d80c228d44640f0b47b57a2ca4afa26ef87e16b0 ] 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. Signed-off-by: Chunguang Xu <brookxu@xxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Link: https://lore.kernel.org/r/1625521646-1069-1-git-send-email-brookxu.cn@xxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 fc60ff208497..e34dfa13b7bc 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1255,7 +1255,7 @@ 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); } -- 2.30.2
