Re: [PATCH -next RFC 02/14] xen/blkback: use bdev api in xen_update_blkif_status()

Christoph Hellwig
2023-12-06T07:21:46Z

On Wed, Dec 06, 2023 at 02:56:05PM +0800, Yu Kuai wrote:
> > > - invalidate_inode_pages2(
> > > - blkif->vbd.bdev_handle->bdev->bd_inode->i_mapping);
> > > + invalidate_bdev(blkif->vbd.bdev_handle->bdev);
> >
> > blkbak is a bdev exported. I don't think it should ever call
> > invalidate_inode_pages2, through a wrapper or not.
>
> I'm not sure about this. I'm not familiar with xen/blkback, but I saw
> that xen-blkback will open a bdev from xen_vbd_create(), hence this
> looks like a dm/md for me, hence it sounds reasonable to sync +
> invalidate the opened bdev while initialization. Please kindly correct
> me if I'm wrong.

I guess we have enough precedence for this, so the switchover here
isn't wrong. But all this invalidating of the bdev cache seems to
be asking for trouble.