linux-kernel - Re: [PATCH] f2fs: enable atgc if atgc_age_threshold from user is less than elapsed

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Message-ID: <446c7e4a-2a1e-402d-8238-2eee7cdfd5c2@kernel.org>
Date: Mon, 3 Jun 2024 15:41:06 +0800
From: Chao Yu <chao@...nel.org>
To: Zhiguo Niu <zhiguo.niu@...soc.com>, jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
 niuzhiguo84@...il.com, ke.wang@...soc.com
Subject: Re: [PATCH] f2fs: enable atgc if atgc_age_threshold from user is less
 than elapsed_time

On 2024/5/20 19:36, Zhiguo Niu wrote:
> Now atgc can be enabled based on the following conditions:
> -ATGC mount option is set
> -elapsed_time is more than atgc_age_threshold already
> but these conditions are check when umounted->mounted device again.
> If the device has not be umounted->mounted for a long time, atgc can
> not work even the above conditions met.
> 
> It is better to enable atgc dynamiclly when user change atgc_age_threshold
> meanwhile this vale is less than elapsed_time and ATGC mount option is on.
> 
> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> ---
>   fs/f2fs/f2fs.h    |  1 +
>   fs/f2fs/segment.c |  9 ++++-----
>   fs/f2fs/sysfs.c   | 16 ++++++++++++++++
>   3 files changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1974b6a..e441d2d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3694,6 +3694,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi,
>   int f2fs_init_inmem_curseg(struct f2fs_sb_info *sbi);
>   void f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi);
>   void f2fs_restore_inmem_curseg(struct f2fs_sb_info *sbi);
> +int f2fs_init_atgc_curseg(struct f2fs_sb_info *sbi);
>   int f2fs_allocate_segment_for_resize(struct f2fs_sb_info *sbi, int type,
>   					unsigned int start, unsigned int end);
>   int f2fs_allocate_new_section(struct f2fs_sb_info *sbi, int type, bool force);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 71dc8042..44923d4 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -2931,14 +2931,11 @@ static int get_atssr_segment(struct f2fs_sb_info *sbi, int type,
>   	return ret;
>   }
>   
> -static int __f2fs_init_atgc_curseg(struct f2fs_sb_info *sbi)
> +int f2fs_init_atgc_curseg(struct f2fs_sb_info *sbi)
>   {
>   	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_ALL_DATA_ATGC);
>   	int ret = 0;
>   
> -	if (!sbi->am.atgc_enabled)
> -		return 0;
> -
>   	f2fs_down_read(&SM_I(sbi)->curseg_lock);
>   
>   	mutex_lock(&curseg->curseg_mutex);
> @@ -2955,7 +2952,9 @@ static int __f2fs_init_atgc_curseg(struct f2fs_sb_info *sbi)
>   }
>   int f2fs_init_inmem_curseg(struct f2fs_sb_info *sbi)
>   {
> -	return __f2fs_init_atgc_curseg(sbi);
> +	if (!sbi->am.atgc_enabled)
> +		return 0;
> +	return f2fs_init_atgc_curseg(sbi);
>   }
>   
>   static void __f2fs_save_inmem_curseg(struct f2fs_sb_info *sbi, int type)
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index 09d3ecf..72676c5 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -673,6 +673,22 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>   		return count;
>   	}
>   
> +	if (!strcmp(a->attr.name, "atgc_age_threshold")) {
> +		if (t < 0)
> +			return -EINVAL;
> +		sbi->am.age_threshold = t;
> +		if (sbi->am.atgc_enabled)
> +			return count;
> +
> +		if (test_opt(sbi, ATGC) &&
> +			le64_to_cpu(sbi->ckpt->elapsed_time) >= t) {

Oh, I guess you want to fix this:

static void init_atgc_management(struct f2fs_sb_info *sbi)
{
...
	if (test_opt(sbi, ATGC) &&
		SIT_I(sbi)->elapsed_time >= DEF_GC_THREAD_AGE_THRESHOLD)
		am->atgc_enabled = true;

What about enabling atgc_enabled during checkpoint once elapsed time is
satisfed w/ the condition? I guess this can give another chance whenever
CP is been triggered, and it can avoid the racing condition as well.

Thanks,

> +			if (f2fs_init_atgc_curseg(sbi))
> +				return -EINVAL;
> +			sbi->am.atgc_enabled = true;
> +		}
> +		return count;
> +	}
> +
>   	if (!strcmp(a->attr.name, "gc_segment_mode")) {
>   		if (t < MAX_GC_MODE)
>   			sbi->gc_segment_mode = t;