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

[Chao Yu]

On 2024/10/9 18:27, Qi Han wrote:
> 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=55
> mkfs.f2fs -f f2fs.img
> mount f2fs.img f2fs_dir -o checkpoint=disable:10%
> cd f2fs_dir
> dd if=/dev/zero of=bigfile bs=1M count=50
> sync
> rm bigfile
> i=1; while [[ $i -lt 10000000 ]]; do (file_name=./file$i; dd \
> if=/dev/random of=$file_name bs=1M count=0); i=$((i+1)); done
> stat -f ./
>
> 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?

Can you please try below patch?

From 38b7c97dcc55ba83de4220c3dc54c2eb66148dd5 Mon Sep 17 00:00:00 2001
From: Chao Yu <chao@xxxxxxxxxx>
Date: Thu, 17 Oct 2024 17:07:05 +0800
Subject: [PATCH] f2fs: revalidate empty segment when checkpoint is disabled

If checkpoint is off, let's set segment as free once all newly
written datas were removed.

Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
 fs/f2fs/segment.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index f8d6e601e084..9bad13d70afb 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -853,6 +853,17 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 	valid_blocks = get_valid_blocks(sbi, segno, false);
 	ckpt_valid_blocks = get_ckpt_valid_blocks(sbi, segno, false);

+	/*
+	 * If checkpoint is off, let's set segment as free once all newly
+	 * written datas were removed.
+	 */
+	if (is_sbi_flag_set(sbi, SBI_CP_DISABLED) &&
+		valid_blocks == 0 && ckpt_valid_blocks == 0) {
+		__remove_dirty_segment(sbi, segno, DIRTY);
+		__set_test_and_free(sbi, segno, false);
+		goto out_lock;
+	}
+
 	if (valid_blocks == 0 && (!is_sbi_flag_set(sbi, SBI_CP_DISABLED) ||
 		ckpt_valid_blocks == usable_blocks)) {
 		__locate_dirty_segment(sbi, segno, PRE);
@@ -863,7 +874,7 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 		/* Recovery routine with SSR needs this */
 		__remove_dirty_segment(sbi, segno, DIRTY);
 	}
-
+out_lock:
 	mutex_unlock(&dirty_i->seglist_lock);
 }

--
2.40.1

> Signed-off-by: Qi Han <hanqi@xxxxxxxx>
> ---
>   fs/f2fs/segment.h | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
>
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 71adb4a43bec..9bf0cf3a6a31 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -637,12 +637,33 @@ 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_available_blocks(struct f2fs_sb_info *sbi)
> +{
> +	unsigned int total_free_blocks = sbi->user_block_count -
> +					valid_user_blocks(sbi) -
> +					sbi->current_reserved_blocks;
> +
> +	if (total_free_blocks <= sbi->unusable_block_count)
> +		total_free_blocks = 0;
> +	else
> +		total_free_blocks -= sbi->unusable_block_count;
> +
> +	if (total_free_blocks > F2FS_OPTION(sbi).root_reserved_blocks)
> +		total_free_blocks -= F2FS_OPTION(sbi).root_reserved_blocks;
> +	else
> +		total_free_blocks = 0;
> +
> +	return (total_free_blocks > 0) ? true : false;
> +}
> +
>   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;
> +	if (likely(has_enough_available_blocks(sbi)))
> +		return true;
>   	return false;
>   }
>