Hi Jaegeuk:
If there're existing clusters beyond i_size, may cause data corruption, but
will this happen in normal? maybe some error can cause this, if i_size is
error the data beyond size still can't handle properly. Is there normal
case can casue existing clusters beyond i_size?
Thanks.
-----邮件原件-----
发件人: Jaegeuk Kim <jaeg...@kernel.org>
发送时间: 2021年5月10日 23:44
收件人: Fengnan Chang <changfeng...@vivo.com>
抄送: c...@kernel.org; linux-f2fs-devel@lists.sourceforge.net
主题: Re: [PATCH v4] f2fs: compress: avoid unnecessary check in
f2fs_prepare_compress_overwrite
On 05/07, 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.
>
> This patch will not bring significant performance improvements, I test
> this on mobile phone, use androbench, the sequential write test case
> was open file with O_TRUNC, set write size to 4KB, performance
> improved about 2%-3%. If write size set to 32MB, performance improved
about 0.5%.
>
> Signed-off-by: Fengnan Chang <changfeng...@vivo.com>
> ---
> fs/f2fs/data.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index
> cf935474ffba..b9ec7b182f45 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3303,9 +3303,17 @@ static int f2fs_write_begin(struct file *file,
> struct address_space *mapping, #ifdef CONFIG_F2FS_FS_COMPRESSION
> if (f2fs_compressed_file(inode)) {
> int ret;
> + pgoff_t end = (i_size_read(inode) + PAGE_SIZE - 1) >>
PAGE_SHIFT;
>
> *fsdata = NULL;
>
> + /*
> + * when write pos is bigger than inode size
,f2fs_prepare_compress_overwrite
> + * always return 0, so check pos first to avoid this.
> + */
> + if (index >= end)
> + goto repeat;
What if there're existing clusters beyond i_size? Given performance impacts,
do we really need this?
> +
> ret = f2fs_prepare_compress_overwrite(inode, pagep,
> index, fsdata);
> if (ret < 0) {
> --
> 2.29.0
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