linux-kernel - Re: [RFC PATCH V6 2/7] ovl: mark overlayfs inode dirty when it has upper

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Date:   Fri, 26 Nov 2021 15:32:59 +0100
From:   Jan Kara <jack@...e.cz>
To:     Chengguang Xu <cgxu519@...ernel.net>
Cc:     Jan Kara <jack@...e.cz>, miklos <miklos@...redi.hu>,
        amir73il <amir73il@...il.com>,
        linux-unionfs <linux-unionfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Chengguang Xu <charliecgxu@...cent.com>,
        ronyjin <ronyjin@...cent.com>
Subject: Re: [RFC PATCH V6 2/7] ovl: mark overlayfs inode dirty when it has
 upper

On Fri 26-11-21 21:06:10, Chengguang Xu wrote:
>  ---- 在 星期五, 2021-11-26 17:10:07 Jan Kara <jack@...e.cz> 撰写 ----
>  > On Mon 22-11-21 11:00:33, Chengguang Xu wrote:
>  > > From: Chengguang Xu <charliecgxu@...cent.com>
>  > > 
>  > > We simply mark overlayfs inode dirty when it has upper,
>  > > it's much simpler than mark dirtiness on modification.
>  > > 
>  > > Signed-off-by: Chengguang Xu <charliecgxu@...cent.com>
>  > > ---
>  > >  fs/overlayfs/inode.c | 4 +++-
>  > >  fs/overlayfs/util.c  | 1 +
>  > >  2 files changed, 4 insertions(+), 1 deletion(-)
>  > > 
>  > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
>  > > index 1f36158c7dbe..027ffc0a2539 100644
>  > > --- a/fs/overlayfs/inode.c
>  > > +++ b/fs/overlayfs/inode.c
>  > > @@ -778,8 +778,10 @@ void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
>  > >  {
>  > >      struct inode *realinode;
>  > >  
>  > > -    if (oip->upperdentry)
>  > > +    if (oip->upperdentry) {
>  > >          OVL_I(inode)->__upperdentry = oip->upperdentry;
>  > > +        mark_inode_dirty(inode);
>  > > +    }
>  > >      if (oip->lowerpath && oip->lowerpath->dentry)
>  > >          OVL_I(inode)->lower = igrab(d_inode(oip->lowerpath->dentry));
>  > >      if (oip->lowerdata)
>  > 
>  > Hum, does this get called only for inodes with upper inode existing? I
>  > suppose we do not need to track inodes that were not copied up because they
>  > cannot be dirty? I'm sorry, my knowledge of overlayfs is rather limited so
>  > I may be missing something basic.
>  > 
> 
> Well, as long as overly inode has upper it can be modified without copy-up,
> so we need to track all overlay inodes which have upper inode.

OK, and oip->upperdentry is set only if there's upper inode, now I
understand. Thanks for explanation and feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR