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

[<changfengnan@vivo.com>]

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


-----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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