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

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Message-ID: <17c5b3e4f2b.113dc38cd26071.2800661599712778589@mykernel.net>
Date:   Thu, 07 Oct 2021 22:53:02 +0800
From:   Chengguang Xu <cgxu519@...ernel.net>
To:     "Jan Kara" <jack@...e.cz>, "Miklos Szeredi" <miklos@...redi.hu>
Cc:     "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

 ---- 在 星期四, 2021-10-07 22:46:46 Jan Kara <jack@...e.cz> 撰写 ----
 > On Thu 07-10-21 15:34:19, Miklos Szeredi wrote:
 > > 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()?
 > 
 > You could but then you'd have to make sure you have I_DIRTY_SYNC always set
 > when I_DIRTY_PAGES is set on the upper inode so that your ->write_inode()
 > callback gets called. Overall I agree the logic would be probably simpler.
 > 

Hi Jan, Miklos

Thnaks for your suggestions. Let me have a try in next version.


Thanks,
Chengguang