On Thu 25-07-24 10:50:45, Barry Song wrote: > On Thu, Jul 25, 2024 at 12:27 AM Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Wed 24-07-24 20:55:40, Barry Song wrote: [...] > > > diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c > > > index 791d38d6284c..eff700e5f7a2 100644 > > > --- a/drivers/vdpa/vdpa_user/iova_domain.c > > > +++ b/drivers/vdpa/vdpa_user/iova_domain.c > > > @@ -287,28 +287,44 @@ void vduse_domain_remove_user_bounce_pages(struct vduse_iova_domain *domain) > > > { > > > struct vduse_bounce_map *map; > > > unsigned long i, count; > > > + struct page **pages = NULL; > > > > > > write_lock(&domain->bounce_lock); > > > if (!domain->user_bounce_pages) > > > goto out; > > > - > > > count = domain->bounce_size >> PAGE_SHIFT; > > > + write_unlock(&domain->bounce_lock); > > > + > > > + pages = kmalloc_array(count, sizeof(*pages), GFP_KERNEL | __GFP_NOFAIL); > > > + for (i = 0; i < count; i++) > > > + pages[i] = alloc_page(GFP_KERNEL | __GFP_NOFAIL); > > > > AFAICS vduse_domain_release calls this function with > > spin_lock(&domain->iotlb_lock) so dropping &domain->bounce_lock is not > > sufficient. > > yes. this is true: > > static int vduse_domain_release(struct inode *inode, struct file *file) > { > struct vduse_iova_domain *domain = file->private_data; > > spin_lock(&domain->iotlb_lock); > vduse_iotlb_del_range(domain, 0, ULLONG_MAX); > vduse_domain_remove_user_bounce_pages(domain); > vduse_domain_free_kernel_bounce_pages(domain); > spin_unlock(&domain->iotlb_lock); > put_iova_domain(&domain->stream_iovad); > put_iova_domain(&domain->consistent_iovad); > vhost_iotlb_free(domain->iotlb); > vfree(domain->bounce_maps); > kfree(domain); > > return 0; > } > > This is quite a pain. I admit I don't have knowledge of this driver, and I don't > think it's safe to release two locks and then reacquire them. The situation is > rather complex. Therefore, I would prefer if the VDPA maintainers could > take the lead in implementing a proper fix. Would it be possible to move all that work to a deferred context? -- Michal Hocko SUSE Labs