linux-kernel - Re: [RFC PATCH V6 7/7] ovl: implement containerized syncfs for overlayfs

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Date:   Fri, 26 Nov 2021 13:03:26 +0800
From:   Chengguang Xu <cgxu519@...ernel.net>
To:     "Amir Goldstein" <amir73il@...il.com>
Cc:     "Miklos Szeredi" <miklos@...redi.hu>, "Jan Kara" <jack@...e.cz>,
        "overlayfs" <linux-unionfs@...r.kernel.org>,
        "linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "Chengguang Xu" <charliecgxu@...cent.com>
Subject: Re: [RFC PATCH V6 7/7] ovl: implement containerized syncfs for
 overlayfs

 ---- 在 星期一, 2021-11-22 15:40:59 Amir Goldstein <amir73il@...il.com> 撰写 ----
 > On Mon, Nov 22, 2021 at 5:01 AM Chengguang Xu <cgxu519@...ernel.net> wrote:
 > >
 > > From: Chengguang Xu <charliecgxu@...cent.com>
 > >
 > > Now overlayfs can only sync own dirty inodes during syncfs,
 > > so remove unnecessary sync_filesystem() on upper file system.
 > >
 > > Signed-off-by: Chengguang Xu <charliecgxu@...cent.com>
 > > ---
 > >  fs/overlayfs/super.c | 14 +++++---------
 > >  1 file changed, 5 insertions(+), 9 deletions(-)
 > >
 > > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
 > > index ccffcd96491d..213b795a6a86 100644
 > > --- a/fs/overlayfs/super.c
 > > +++ b/fs/overlayfs/super.c
 > > @@ -292,18 +292,14 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 > >         /*
 > >          * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
 > >          * All the super blocks will be iterated, including upper_sb.
 > > -        *
 > > -        * If this is a syncfs(2) call, then we do need to call
 > > -        * sync_filesystem() on upper_sb, but enough if we do it when being
 > > -        * called with wait == 1.
 > >          */
 > > -       if (!wait)
 > > -               return 0;
 > > -
 > >         upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 > > -
 > >         down_read(&upper_sb->s_umount);
 > > -       ret = sync_filesystem(upper_sb);
 > > +       if (wait)
 > > +               wait_sb_inodes(upper_sb);
 > > +       if (upper_sb->s_op->sync_fs)
 > > +               upper_sb->s_op->sync_fs(upper_sb, wait);
 > > +       ret = ovl_sync_upper_blockdev(upper_sb, wait);
 > 
 > I think it will be cleaner to use a helper ovl_sync_upper_filesystem()
 > with everything from  upper_sb = ... and a comment to explain that
 > this is a variant of __sync_filesystem() where all the dirty inodes write
 > have already been started.
 > 
 
I agree with you. 

Thanks,
Chengguang