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

[韩棋 <hanqi@vivo.com>]

在 2024/10/22 10:53, Chao Yu 写道:
> 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?
>>
>> Signed-off-by: Qi Han <hanqi@vivo.com>
>> ---
>>   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;
>
> Can you please reuse get_available_block_count() as much as possible?
> and cover it w/ stat_lock?
>
> Thanks,

Thank you for your suggestion. I will send the v2 version patch later.

>
>> +}
>> +
>>   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;
>>   }
>
>