[f2fs-dev] 答复: [PATCH] f2fs: compress: avoid unnecessary check in f2fs_prepare_compress_overwrite

[<changfengnan@vivo.com>]

Thank you for the reminder, I hadn't thought about fallocate before.
I have done some tests and the results are as expected.
Here is my test method, create a compressed file, and use fallocate with keep size, when write data to expand area, f2fs_prepare_compress_overwrite
always return 0, the behavior is same as my patch , apply my patch can avoid those check.
Is there anything else I haven't thought of?

-----邮件原件-----
发件人: Gao Xiang <hsiangkao@redhat.com>
发送时间: 2021年4月26日 11:19
收件人: Fengnan Chang <changfengnan@vivo.com>
抄送: chao@kernel.org; jaegeuk@kernel.org;
linux-f2fs-devel@lists.sourceforge.net
主题: Re: [f2fs-dev] [PATCH] f2fs: compress: avoid unnecessary check in
f2fs_prepare_compress_overwrite

On Mon, Apr 26, 2021 at 10:11:53AM +0800, Fengnan Chang wrote:
> when write compressed file with O_TRUNC, there will be a lot of
> unnecessary check valid blocks in f2fs_prepare_compress_overwrite,
> especially when written in page size, remove it.
>
> Signed-off-by: Fengnan Chang <changfengnan@vivo.com>

Even though I didn't look into the whole thing, my reaction here is roughly
how to handle fallocate with keep size? Does it work as expected?

> ---
>  fs/f2fs/data.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index
> cf935474ffba..9c3b0849f35e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3270,6 +3270,7 @@ static int f2fs_write_begin(struct file *file,
> struct address_space *mapping,
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	struct page *page = NULL;
>  	pgoff_t index = ((unsigned long long) pos) >> PAGE_SHIFT;
> +	pgoff_t end = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  	bool need_balance = false, drop_atomic = false;
>  	block_t blkaddr = NULL_ADDR;
>  	int err = 0;
> @@ -3306,6 +3307,9 @@ static int f2fs_write_begin(struct file *file,
> struct address_space *mapping,
>
>  		*fsdata = NULL;
>
> +		if (index >= end)
> +			goto repeat;
> +
>  		ret = f2fs_prepare_compress_overwrite(inode, pagep,
>  							index, fsdata);
>  		if (ret < 0) {
> --
> 2.29.0









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