On 05/11, changfeng...@vivo.com wrote:
> 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?
We don't have a rule to sync between i_size and i_blocks.
>
> 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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