[PATCH] f2fs: fix is_idle() check for discard type

[PATCH] f2fs: fix is_idle() check for discard type

[Sahitya Tummala]

The discard thread should issue upto dpolicy->max_requests at once
and wait for all those discard requests at once it reaches
dpolicy->max_requests. It should then sleep for dpolicy->min_interval
timeout before issuing the next batch of discard requests. But in the
current code of is_idle(), it checks for dcc_info->queued_discard and
aborts issuing the discard batch of max_requests. This
dcc_info->queued_discard will be true always once one discard command
is issued.

It is thus resulting into this type of discard request pattern -

- Issue discard request#1
- is_idle() returns false, discard thread waits for request#1 and then
  sleeps for min_interval 50ms.
- Issue discard request#2
- is_idle() returns false, discard thread waits for request#2 and then
  sleeps for min_interval 50ms.
- and so on for all other discard requests, assuming f2fs is idle w.r.t
  other conditions.

With this fix, the pattern will look like this -

- Issue discard request#1
- Issue discard request#2
  and so on upto max_requests of 8
- Issue discard request#8
- wait for min_interval 50ms.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
---
 fs/f2fs/f2fs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 95adedb..ea34fef 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2209,7 +2209,7 @@ static inline bool is_idle(struct f2fs_sb_info *sbi, int type)
 		get_pages(sbi, F2FS_DIO_WRITE))
 		return false;
 
-	if (SM_I(sbi) && SM_I(sbi)->dcc_info &&
+	if (type != DISCARD_TIME && SM_I(sbi) && SM_I(sbi)->dcc_info &&
 			atomic_read(&SM_I(sbi)->dcc_info->queued_discard))
 		return false;
 
-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

Re: [PATCH] f2fs: fix is_idle() check for discard type

[Chao Yu]

On 2019/6/6 17:38, Sahitya Tummala wrote:
> The discard thread should issue upto dpolicy->max_requests at once
> and wait for all those discard requests at once it reaches
> dpolicy->max_requests. It should then sleep for dpolicy->min_interval
> timeout before issuing the next batch of discard requests. But in the
> current code of is_idle(), it checks for dcc_info->queued_discard and
> aborts issuing the discard batch of max_requests. This
> dcc_info->queued_discard will be true always once one discard command
> is issued.
> 
> It is thus resulting into this type of discard request pattern -
> 
> - Issue discard request#1
> - is_idle() returns false, discard thread waits for request#1 and then
>   sleeps for min_interval 50ms.
> - Issue discard request#2
> - is_idle() returns false, discard thread waits for request#2 and then
>   sleeps for min_interval 50ms.
> - and so on for all other discard requests, assuming f2fs is idle w.r.t
>   other conditions.
> 
> With this fix, the pattern will look like this -
> 
> - Issue discard request#1
> - Issue discard request#2
>   and so on upto max_requests of 8
> - Issue discard request#8
> - wait for min_interval 50ms.
> 

Fixes: fef4129ec2e6 ("f2fs: fix to be aware discard/preflush/dio command in
is_idle()")

> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>

Ah, thanks for fixing this bug.

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

Re: [f2fs-dev] [PATCH] f2fs: fix is_idle() check for discard type

[Chao Yu]

On 2019/6/6 17:38, Sahitya Tummala wrote:
> The discard thread should issue upto dpolicy->max_requests at once
> and wait for all those discard requests at once it reaches
> dpolicy->max_requests. It should then sleep for dpolicy->min_interval
> timeout before issuing the next batch of discard requests. But in the
> current code of is_idle(), it checks for dcc_info->queued_discard and
> aborts issuing the discard batch of max_requests. This
> dcc_info->queued_discard will be true always once one discard command
> is issued.
> 
> It is thus resulting into this type of discard request pattern -
> 
> - Issue discard request#1
> - is_idle() returns false, discard thread waits for request#1 and then
>   sleeps for min_interval 50ms.
> - Issue discard request#2
> - is_idle() returns false, discard thread waits for request#2 and then
>   sleeps for min_interval 50ms.
> - and so on for all other discard requests, assuming f2fs is idle w.r.t
>   other conditions.
> 
> With this fix, the pattern will look like this -
> 
> - Issue discard request#1
> - Issue discard request#2
>   and so on upto max_requests of 8
> - Issue discard request#8
> - wait for min_interval 50ms.
> 

Fixes: fef4129ec2e6 ("f2fs: fix to be aware discard/preflush/dio command in
is_idle()")

> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>

Ah, thanks for fixing this bug.

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,


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