OK. Thanks for our explanation. ^_^
Feng fei
-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de]
发送时间: 2021年8月31日 9:35
收件人: xifengfei (RD) [off-list ref]
抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org; kent.overstreet@gmail.com
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
On 8/30/21 2:29 PM, Xifengfei wrote:
quoted hunk
（Sorry, there was an obvious typo in the last email）
Thanks a lot. I understand the purpose.
So is the original judgment process too complicated? Can we judge
bi_size directly? This will be more concise
@@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
+ if (bio->bi_iter.bi_size)
i->sequential += bio->bi_iter.bi_size;
i->last = bio_end_sector(bio);
The above change works, but the code readability decreased because how/why i->sequential is maintained is not that directly visible.
This is a difference of coding styles. IMHO for this particular case, the readability is more important than less CPU instructions.
Thanks.
Coly Li
Thanks
Fengfei
-----邮件原件-----
发件人: Coly Li [mailto:colyli@suse.de]
发送时间: 2021年8月29日 15:50
收件人: xifengfei (RD) [off-list ref]
抄送: linux-bcache@vger.kernel.org; linux-kernel@vger.kernel.org;
kent.overstreet@gmail.com
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size
On 8/29/21 12:49 PM, Fengfei Xi wrote:
quoted
The bi_size is unsigned int type data not less than 0, so we can
directly add bi_size without extra judgment
Signed-off-by: Fengfei Xi <redacted>
NACK. The check is necessary to avoid redundant and unnecessary memory write.
Coly Li
quoted
---
drivers/md/bcache/request.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/md/bcache/request.c
b/drivers/md/bcache/request.c index 6d1de889b..2788eec3a 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
- i->sequential += bio->bi_iter.bi_size;
-
+ i->sequential += bio->bi_iter.bi_size;
i->last = bio_end_sector(bio);
i->jiffies = jiffies + msecs_to_jiffies(5000);
task->sequential_io = i->sequential;