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

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Message-ID: <37129398-430d-4a2a-b17a-a38cdc2bd9e6@vivo.com>
Date: Tue, 22 Oct 2024 03:45:36 +0000
From: 韩棋 <hanqi@...o.com>
To: Chao Yu <chao@...nel.org>, "jaegeuk@...nel.org" <jaegeuk@...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>
Subject: Re: [PATCH] f2fs: modify f2fs_is_checkpoint_ready logic to allow more
 data to be written with the CP disable

在 2024/10/22 11:39, Chao Yu 写道:
> On 2024/10/22 11:14, 韩棋 wrote:
>> 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@...o.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.
>
> BTW, it looks your testcase won't create sparse available space in
> segment for following reuse by SSR, can you please update your
> testcase?
>
> Thanks,

Okay, I got it. I'll update later. Thank you for your advice.

>
>>
>>>
>>>> +}
>>>> +
>>>>    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;
>>>>    }
>>>
>>>
>>
>
>