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block: fix the problem of io_ticks becoming smaller 

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@tencent.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/1625521646-1069-1-git-send-email-brookxu.cn@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Chunguang Xu 2021-07-06 05:47:26 +08:00 committed by Jens Axboe
parent c6af8db92b
commit d80c228d44
1 changed files with 1 additions and 1 deletions
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2
block/blk-core.c
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@ -1241,7 +1241,7 @@ 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);
}