答复: [PATCH] exfat: fdatasync flag should be same like generic_write_sync()

[张政旭 (Zhengxu Zhang)]

> -----邮件原件-----
> 发件人: Yuezhang.Mo@xxxxxxxx <Yuezhang.Mo@xxxxxxxx>
> 发送时间: 2025年6月17日 11:32
> 收件人: 张政旭 (Zhengxu Zhang) <Zhengxu.Zhang@xxxxxxxxxx>; Cixi Geng
> <cixi.geng@xxxxxxxxx>; linkinjeon@xxxxxxxxxx; sj1557.seo@xxxxxxxxxxx
> 抄送: linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; 王皓 (Hao_hao
> Wang) <Hao_hao.Wang@xxxxxxxxxx>
> 主题: Re: [PATCH] exfat: fdatasync flag should be same like generic_write_sync()
> 
> 
> 
> > > > --- a/fs/exfat/file.c
> > > > +++ b/fs/exfat/file.c
> > > > @@ -625,7 +625,7 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb,
> > > > struct iov_iter *iter)
> > > >
> > > >        if (iocb_is_dsync(iocb) && iocb->ki_pos > pos) {
> > > >                 ssize_t err = vfs_fsync_range(file, pos, iocb->ki_pos - 1,
> > > > -                               iocb->ki_flags & IOCB_SYNC);
> > > > +                               (iocb->ki_flags & IOCB_SYNC) ? 0 : 1);
> > >
> > > How about calling generic_write_sync() instead of vfs_fsync_range(), like in
> > > generic_file_write_iter()?
> > The second arg of vfs_fsync_range "pos" maybe changed by valid_size (if pos >
> valid_size).
> > It can not replace by iocb->ki_pos - ret (ret by __generic_file_write_iter).
> > So current way maybe better.
> 
> Here we synchronize the areas written by exfat_extend_valid_size() and
> __generic_file_write_iter() if valid_size < pos.
> 
> The lengths of these two write areas are 'pos-valid_size' and 'ret'.
> We can use generic_write_sync() and pass it the sum of these two lengths.
> 
> Of course, regardless of whether valid_size < pos, exfat_file_write_iter() only
> needs to return the length written by __generic_file_write_iter().

I try the sum of 'pos-valid_size' and 'ret',like this:
        if (iocb->ki_pos > pos) {
                ssize_t err = generic_write_sync(iocb, pos + ret - valid_size);
                if (err < 0)
                        return err;
        }
The test crashed, that maybe io error. 
So I try a simple way that use iocb->ki_pos - pos. like this:
        if (iocb->ki_pos > pos) {
                ssize_t err = generic_write_sync(iocb, iocb->ki_pos - pos);
                if (err < 0)
                        return err;
        }
The test pass. pls check again.