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
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

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@vivo.com>
---
 fs/f2fs/segment.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 71adb4a43bec..b7af84a07435 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -637,12 +637,31 @@ 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)
+{
+	long long total_free_blocks = 0;
+	block_t avail_user_block_count;
+	block_t valid_block_count;
+
+	spin_lock(&sbi->stat_lock);
+
+	avail_user_block_count = get_available_block_count(sbi, NULL, true);
+	valid_block_count = valid_user_blocks(sbi);
+	total_free_blocks = avail_user_block_count - valid_block_count;
+
+	spin_unlock(&sbi->stat_lock);
+
+	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_free_blks(sbi)))
+		return true;
 	return false;
 }
 
-- 
2.39.0

On 2024/10/22 17:15, 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=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
> 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

'dd if=/dev/zero of=./file bs=1M count=20' will be more quick to
trigger SSR allocation.

> 
> 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@vivo.com>
> ---
>   fs/f2fs/segment.h | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
> 
> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
> index 71adb4a43bec..b7af84a07435 100644
> --- a/fs/f2fs/segment.h
> +++ b/fs/f2fs/segment.h
> @@ -637,12 +637,31 @@ 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)
> +{
> +	long long total_free_blocks = 0;
> +	block_t avail_user_block_count;

long long avail_user_block_count;

> +	block_t valid_block_count;
> +
> +	spin_lock(&sbi->stat_lock);
> +
> +	avail_user_block_count = get_available_block_count(sbi, NULL, true);
> +	valid_block_count = valid_user_blocks(sbi);
> +	total_free_blocks = avail_user_block_count - valid_block_count;

total_free_blocks =
	avail_user_block_count - (long long)valid_user_blocks(sbi);

Then, we can avoid allocating & assigning valid_block_count variable.

> +
> +	spin_unlock(&sbi->stat_lock);
> +
> +	return (total_free_blocks > 0) ? true : false;

return total_free_blocks > 0;

Thanks,

> +}
> +
>   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_free_blks(sbi)))
> +		return true;
>   	return false;
>   }
>