linux-kernel - Re: [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write

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Date:   Thu, 7 Oct 2021 11:23:06 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Chengguang Xu <cgxu519@...ernel.net>
Cc:     Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org,
        overlayfs <linux-unionfs@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write_inode operation

On Thu, 23 Sept 2021 at 15:08, Chengguang Xu <cgxu519@...ernel.net> wrote:
>
> Implement overlayfs' ->write_inode to sync dirty data
> and redirty overlayfs' inode if necessary.
>
> Signed-off-by: Chengguang Xu <cgxu519@...ernel.net>
> ---
>  fs/overlayfs/super.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 2ab77adf7256..cddae3ca2fa5 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -412,12 +412,42 @@ static void ovl_evict_inode(struct inode *inode)
>         clear_inode(inode);
>  }
>
> +static int ovl_write_inode(struct inode *inode,
> +                          struct writeback_control *wbc)
> +{
> +       struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> +       struct inode *upper = ovl_inode_upper(inode);
> +       unsigned long iflag = 0;
> +       int ret = 0;
> +
> +       if (!upper)
> +               return 0;
> +
> +       if (!ovl_should_sync(ofs))
> +               return 0;
> +
> +       if (upper->i_sb->s_op->write_inode)
> +               ret = upper->i_sb->s_op->write_inode(inode, wbc);

Where is page writeback on upper inode triggered?

Thanks,
Miklos