linux-kernel - Re: [PATCH] exfat: fdatasync flag should be same like generic_write

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Message-ID:
 <PUZPR04MB6316B91DB1F5E14578C65C0A8173A@PUZPR04MB6316.apcprd04.prod.outlook.com>
Date: Tue, 17 Jun 2025 03:31:52 +0000
From: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To: 张政旭 (Zhengxu Zhang)
	<Zhengxu.Zhang@...soc.com>,
        Cixi Geng <cixi.geng@...ux.dev>,
        "linkinjeon@...nel.org" <linkinjeon@...nel.org>,
        "sj1557.seo@...sung.com"
	<sj1557.seo@...sung.com>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        王皓 (Hao_hao Wang) <Hao_hao.Wang@...soc.com>
Subject: 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().