linux-kernel - Re: [PATCH v3] f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable

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Message-ID: <9825b1c1-9d24-48d1-a807-d1e6e25c4157@vivo.com>
Date: Wed, 23 Oct 2024 07:40:43 +0000
From: 韩棋 <hanqi@...o.com>
To: "jaegeuk@...nel.org" <jaegeuk@...nel.org>, "chao@...nel.org"
	<chao@...nel.org>
CC: "linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Zhiguo Niu <niuzhiguo84@...il.com>
Subject: Re: [PATCH v3] f2fs: modify f2fs_is_checkpoint_ready logic to allow
 more data to be written with the CP disable

在 2024/10/23 10:59, Qi Han 写道:
> When the free segment is used up during CP disable, many write or
> ioctl operations will get ENOSPC error codes, even if there are
> still many blocks available. We can reproduce it in the following
> steps:
>
> dd if=/dev/zero of=f2fs.img bs=1M count=65
> mkfs.f2fs -f f2fs.img
> mount f2fs.img f2fs_dir -o checkpoint=disable:10%
> cd f2fs_dir
> i=1 ; while [[ $i -lt 50 ]] ; do (file_name=./2M_file$i ; dd \
> if=/dev/random of=$file_name bs=1M count=2); i=$((i+1)); done
> sync
> i=1 ; while [[ $i -lt 50 ]] ; do (file_name=./2M_file$i ; truncate \
> -s 1K $file_name); i=$((i+1)); done
> sync
> dd if=/dev/zero of=./file bs=1M count=20
>
> In f2fs_need_SSR() function, it is allowed to use SSR to allocate
> blocks when CP is disabled, so in f2fs_is_checkpoint_ready function,
> can we judge the number of invalid blocks when free segment is not
> enough, and return ENOSPC only if the number of invalid blocks is
> also not enough?
>
> Signed-off-by: Qi Han <hanqi@...o.com>
> ---
>   fs/f2fs/segment.h | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 71adb4a43bec..20b568eaa95e 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -637,12 +637,29 @@ static inline bool has_enough_free_secs(struct f2fs_sb_info *sbi,
>   	return !has_not_enough_free_secs(sbi, freed, needed);
>   }
>   
> +static inline bool has_enough_free_blks(struct f2fs_sb_info *sbi)
> +{
> +	unsigned int total_free_blocks = 0;
> +	unsigned int avail_user_block_count;
> +
> +	spin_lock(&sbi->stat_lock);
> +
> +	avail_user_block_count = get_available_block_count(sbi, NULL, true);
> +	total_free_blocks = avail_user_block_count - (unsigned int)valid_user_blocks(sbi);
> +
> +	spin_unlock(&sbi->stat_lock);
> +
> +	return total_free_blocks > 0;
> +}
> +
>   static inline bool f2fs_is_checkpoint_ready(struct f2fs_sb_info *sbi)
>   {
>   	if (likely(!is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
>   		return true;
>   	if (likely(has_enough_free_secs(sbi, 0, 0)))
>   		return true;

Hi, Chao,

After Zhiguo's reminder, I just saw your previous patch:
f2fs: fix to account dirty data in __get_secs_required(),
the current modification may still return true if the segment
is found to be insufficient when LFS and CP is closed, should
I add the LFS mode restriction here?

Thanks.

> +	if (likely(has_enough_free_blks(sbi)))
> +		return true;
>   	return false;
>   }
>