---- 在 星期五, 2021-04-09 21:49:07 Miklos Szeredi <miklos@xxxxxxxxxx> 撰写 ----
> On Fri, Nov 13, 2020 at 7:57 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote:
> >
> > Implement overlayfs' ->write_inode to sync dirty data
> > and redirty overlayfs' inode if necessary.
> >
> > Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
> > ---
> > fs/overlayfs/super.c | 30 ++++++++++++++++++++++++++++++
> > 1 file changed, 30 insertions(+)
> >
> > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> > index 883172ac8a12..82e001b97f38 100644
> > --- a/fs/overlayfs/super.c
> > +++ b/fs/overlayfs/super.c
> > @@ -390,6 +390,35 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
> > return ret;
> > }
> >
> > +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);
> > +
> > + if (mapping_writably_mapped(upper->i_mapping) ||
> > + mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK))
> > + iflag |= I_DIRTY_PAGES;
> > +
> > + iflag |= upper->i_state & I_DIRTY_ALL;
>
> How is I_DIRTY_SYNC added/removed from the overlay inode?
>
generally, I_DIRTY_SYNC is added to overlay inode when the operation dirties
upper inode, I'll check all those places and call ovl_mark_inode_dirty() to do it.
After writeback if upper inode becomes clean status, we will remove I_DIRTY_SYNC
from overlay inode.
One exception is mmaped file, it will always keep I_DIRTY_SYNC until to be evicted.
Thanks,
Chengguang
