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

[changfengnan--- via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

Hi Jaegeuk:

	Any comments about this patch?
 
Thanks.

-----邮件原件-----
发件人: Chao Yu <yuchao0@huawei.com> 
发送时间: 2021年5月29日 9:13
收件人: changfengnan@vivo.com; jaegeuk@kernel.org
抄送: linux-f2fs-devel@lists.sourceforge.net
主题: Re: [f2fs-dev] 答复: [RFC PATCH] f2fs: compress: remove unneeded read
when rewrite whole cluster

On 2021/5/28 10:49, Chao Yu wrote:
> 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) {

It will cause panic in f2fs_write_end() due to miss to assign fsdata with
NULL, updated as below:

---
  fs/f2fs/data.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index
2ea887a114c8..4e214ac87925 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3328,6 +3328,9 @@ static int f2fs_write_begin(struct file *file, struct
address_space *mapping,

  		*fsdata = NULL;

+		if (len == PAGE_SIZE)
+			goto repeat;
+
  		ret = f2fs_prepare_compress_overwrite(inode, pagep,
  							index, fsdata);
  		if (ret < 0) {
--
2.29.2

Thanks,

>    		int ret;
> 
>    		*fsdata = NULL;
> 




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