Re: [f2fs-dev] 答复: [RFC PATCH] f2fs: compress: remove unneeded read when rewrite whole cluster

[Chao Yu <yuchao0@huawei.com>]

On 2021/5/25 20:05, changfengnan@vivo.com wrote:
> yes, I just check wheather the whole page was dirty, because of when write
> cache f2fs_prepare_compress_overwrite will be called again,
> when update whole cluster,  cc in prepare_compress_overwrite will be empty,
> so will not submit bio.
> when only update one page in cluster,  cc in prepare_compress_overwrite will
> not be empty, so will submit bio.
> This is my thinking, not sure if I've missed anything

Well, it looks more like we did for mmap() write case.

So I guess we can change as below:

To Jaegeuk, comments?

---
  fs/f2fs/data.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 2ea887a114c8..723c59df51b7 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3323,7 +3323,7 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
  	}

  #ifdef CONFIG_F2FS_FS_COMPRESSION
-	if (f2fs_compressed_file(inode)) {
+	if (f2fs_compressed_file(inode) && len != PAGE_SIZE) {
  		int ret;

  		*fsdata = NULL;
-- 
2.29.2

Thanks,

> 
> 
> -----邮件原件-----
> 发件人: Chao Yu <yuchao0@huawei.com>
> 发送时间: 2021年5月24日 19:39
> 收件人: Fengnan Chang <changfengnan@vivo.com>; jaegeuk@kernel.org;
> chao@kernel.org; linux-f2fs-devel@lists.sourceforge.net
> 主题: Re: [f2fs-dev] [RFC PATCH] f2fs: compress: remove unneeded read when
> rewrite whole cluster
> 
> On 2021/5/18 20:51, Fengnan Chang wrote:
>> For now,when overwrite compressed file, we need read old data to page
>> cache first and update pages.
>> But when we need overwrite whole cluster, we don't need old data
>> anymore.
> 
> I only see you just check the whole page was dirty as below rather than the
> whole cluster is dirty during write().
> 
> Thanks,
> 
>> +	if (len == PAGE_SIZE)
>> +		return 0;
>>    	/* compressed case */
>>    	prealloc = (ret < cc->cluster_size);
>>    
> 
> 
> .
> 


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