Subject: Re: [PATCH v36 2/5] virtio_balloon: replace oom notifier with shrinker
On 07/23/2018 10:13 PM, Michael S. Tsirkin wrote:
vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops; #endif + err = virtio_balloon_register_shrinker(vb); + if (err) + goto out_del_vqs; So we can get scans before device is ready. Leak will fail then. Why not register later after device is ready?Probably no. - it would be better not to set device ready when register_shrinker failed.That's very rare so I won't be too worried.
Just a little confused with the point here. "very rare" means it still could happen (even it's a corner case), and if that happens, we got something wrong functionally. So it will be a bug if we change like that, right?
Still couldn't understand the reason of changing shrinker_register after device_ready (the original oom notifier was registered before setting device ready too)? (I think the driver won't get shrinker_scan called if device isn't ready because of the reasons below)
- When the device isn't ready, ballooning won't happen, that is, vb->num_pages will be 0, which results in shrinker_count=0 and shrinker_scan won't be called.