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

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Message-ID: <CAJfpegt4jZpSCXGFk2ieqUXVm3m=ng7QtSzZp2bXVs07bfrbXg@mail.gmail.com>
Date:   Thu, 7 Oct 2021 15:34:19 +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 <linux-fsdevel@...r.kernel.org>,
        overlayfs <linux-unionfs@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v5 06/10] ovl: implement overlayfs' ->write_inode operation

On Thu, 7 Oct 2021 at 15:10, Chengguang Xu <cgxu519@...ernel.net> wrote:
>  > However that wasn't what I was asking about.  AFAICS ->write_inode()
>  > won't start write back for dirty pages.   Maybe I'm missing something,
>  > but there it looks as if nothing will actually trigger writeback for
>  > dirty pages in upper inode.
>  >
>
> Actually, page writeback on upper inode will be triggered by overlayfs ->writepages and
> overlayfs' ->writepages will be called by vfs writeback function (i.e writeback_sb_inodes).

Right.

But wouldn't it be simpler to do this from ->write_inode()?

I.e. call write_inode_now() as suggested by Jan.

Also could just call mark_inode_dirty() on the overlay inode
regardless of the dirty flags on the upper inode since it shouldn't
matter and results in simpler logic.

Thanks,
Miklos


>
> Thanks,
> Chengguang
>
>
>