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From: Amir Goldstein <amir73il@gmail.com>
To: Jan Kara <jack@suse.cz>
Cc: Chengguang Xu <cgxu519@mykernel.net>,
	Miklos Szeredi <miklos@szeredi.hu>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH v3 07/10] ovl: implement overlayfs' ->write_inode operation
Date: Tue, 10 Nov 2020 18:18:35 +0200
Message-ID: <CAOQ4uxgacry9pYVJeS6832G=MZVBCbamFvJULGPjk1aSBJbLxQ@mail.gmail.com> (raw)
In-Reply-To: <20201110134551.GA28132@quack2.suse.cz>

On Tue, Nov 10, 2020 at 3:45 PM Jan Kara <jack@suse.cz> wrote:
>
> On Sun 08-11-20 22:03:04, Chengguang Xu wrote:
> > +static int ovl_write_inode(struct inode *inode,
> > +                        struct writeback_control *wbc)
> > +{
> > +     struct ovl_fs *ofs = inode->i_sb->s_fs_info;
> > +     struct inode *upper = ovl_inode_upper(inode);
> > +     unsigned long iflag = 0;
> > +     int ret = 0;
> > +
> > +     if (!upper)
> > +             return 0;
> > +
> > +     if (!ovl_should_sync(ofs))
> > +             return 0;
> > +
> > +     if (upper->i_sb->s_op->write_inode)
> > +             ret = upper->i_sb->s_op->write_inode(inode, wbc);
> > +
> > +     iflag |= upper->i_state & I_DIRTY_ALL;
> > +
> > +     if (mapping_writably_mapped(upper->i_mapping) ||
> > +         mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK))
> > +             iflag |= I_DIRTY_PAGES;
> > +
> > +     if (iflag)
> > +             ovl_mark_inode_dirty(inode);
>
> I think you didn't incorporate feedback we were speaking about in the last
> version of the series. May comment in [1] still applies - you can miss
> inodes dirtied through mmap when you decide to clean the inode here. So
> IMHO you need something like:
>
>         if (inode_is_open_for_write(inode))
>                 ovl_mark_inode_dirty(inode);
>
> here to keep inode dirty while it is open for write (and not based on upper
> inode state which is unreliable).
>

Just to be clear, as long as the ovl inode is open for write, the upper inode
is also open for write via the realfile reference, but not the other
way around -
after open(); mmap(); close() of the overlay file, the ovl inode is not
open for write, but the upper inode is, because ovl_mmap() maps the
realfile and upper inode without taking any reference on the ovl file/inode.

Hence the check for mapping_writably_mapped(upper->i_mapping)
above.

Thanks,
Amir.

  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-08 14:02 [RFC PATCH v3 00/10] implement containerized syncfs for overlayfs Chengguang Xu
2020-11-08 14:02 ` [RFC PATCH v3 01/10] ovl: setup overlayfs' private bdi Chengguang Xu
2020-11-08 14:02 ` [RFC PATCH v3 02/10] ovl: introduce waiting list for syncfs Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 03/10] ovl: implement ->writepages operation Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 04/10] ovl: implement overlayfs' ->evict_inode operation Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 05/10] ovl: mark overlayfs' inode dirty on modification Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 06/10] ovl: mark overlayfs' inode dirty on shared mmap Chengguang Xu
2020-11-11 13:05   ` 回复:[RFC " Chengguang Xu
2020-11-11 15:20     ` [RFC " Amir Goldstein
2020-11-11 16:09       ` Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 07/10] ovl: implement overlayfs' ->write_inode operation Chengguang Xu
2020-11-10 13:45   ` Jan Kara
2020-11-10 15:12     ` Chengguang Xu
2020-11-11 10:54       ` Jan Kara
2020-11-10 16:18     ` Amir Goldstein [this message]
2020-11-08 14:03 ` [RFC PATCH v3 08/10] ovl: cache dirty overlayfs' inode Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 09/10] ovl: introduce helper of syncfs writeback inode waiting Chengguang Xu
2020-11-09  3:33   ` 回复:[RFC " Chengguang Xu
2020-11-09  7:07     ` [RFC " Amir Goldstein
2020-11-09  8:34       ` Chengguang Xu
2020-11-09 10:07         ` Amir Goldstein
2020-11-09 12:06           ` Chengguang Xu
2020-11-08 14:03 ` [RFC PATCH v3 10/10] ovl: implement containerized syncfs for overlayfs Chengguang Xu

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