linux-kernel - Re: [PATCH] f2fs: compress: remove unneed check condition

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Date:   Thu, 22 Apr 2021 14:51:04 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH] f2fs: compress: remove unneed check condition

On 2021/4/22 12:04, Jaegeuk Kim wrote:
> On 04/21, Chao Yu wrote:
>> In only call path of __cluster_may_compress(), __f2fs_write_data_pages()
>> has checked SBI_POR_DOING condition, and also cluster_may_compress()
>> has checked CP_ERROR_FLAG condition, so remove redundant check condition
>> in __cluster_may_compress() for cleanup.
> 
> I think cp_error can get any time without synchronization. Is it safe to say
> it's redundant?

Yes,

But no matter how late we check cp_error, cp_error can happen after our
check points, it won't cause regression if we remove cp_error check there,
because for compress write, it uses OPU, it won't overwrite any existed data
in device.

Seems it will be more appropriate to check cp_error in
f2fs_write_compressed_pages() like we did in f2fs_write_single_data_page()
rather than in __cluster_may_compress().

BTW, shouldn't we rename __cluster_may_compress() to
cluster_beyond_filesize() for better readability?

Thanks,

> 
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>>   fs/f2fs/compress.c | 5 -----
>>   1 file changed, 5 deletions(-)
>>
>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>> index 3c9d797dbdd6..532c311e3a89 100644
>> --- a/fs/f2fs/compress.c
>> +++ b/fs/f2fs/compress.c
>> @@ -906,11 +906,6 @@ static bool __cluster_may_compress(struct compress_ctx *cc)
>>   
>>   		f2fs_bug_on(sbi, !page);
>>   
>> -		if (unlikely(f2fs_cp_error(sbi)))
>> -			return false;
>> -		if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
>> -			return false;
>> -
>>   		/* beyond EOF */
>>   		if (page->index >= nr_pages)
>>   			return false;
>> -- 
>> 2.29.2
> .
>