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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 7 Oct 2021 16:46:46 +0200
From:   Jan Kara <jack@...e.cz>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Chengguang Xu <cgxu519@...ernel.net>, 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 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.

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