From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: [PATCH v1 07/11] virtio-mem: Allow to offline partially unplugged memory blocks Date: Mon, 2 Mar 2020 14:49:37 +0100 Message-ID: <20200302134941.315212-8-david@redhat.com> References: <20200302134941.315212-1-david@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: In-Reply-To: <20200302134941.315212-1-david@redhat.com> To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Michal Hocko , Andrew Morton , "Michael S . Tsirkin" , David Hildenbrand , Jason Wang , Oscar Salvador , Igor Mammedov , Dave Young , Dan Williams , Pavel Tatashin , Stefan Hajnoczi , Vlastimil Babka List-Id: virtualization@lists.linuxfoundation.org Dropping the reference count of PageOffline() pages allows offlining code to skip them. However, we also have to convert PG_reserved to another flag - let's use PG_dirty - so has_unmovable_pages() will properly handle them. PG_reserved pages get detected as unmovable right away. We need the flag to see if we are onlining pages the first time, or if we allocated them via alloc_contig_range(). Properly take care of offlining code also modifying the stats and special handling in case the driver gets unloaded. Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Oscar Salvador Cc: Michal Hocko Cc: Igor Mammedov Cc: Dave Young Cc: Andrew Morton Cc: Dan Williams Cc: Pavel Tatashin Cc: Stefan Hajnoczi Cc: Vlastimil Babka Signed-off-by: David Hildenbrand --- drivers/virtio/virtio_mem.c | 64 ++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 5b26d57be551..2916f8b970fa 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -570,6 +570,53 @@ static void virtio_mem_notify_online(struct virtio_m= em *vm, unsigned long mb_id, virtio_mem_retry(vm); } =20 +static void virtio_mem_notify_going_offline(struct virtio_mem *vm, + unsigned long mb_id) +{ + const unsigned long nr_pages =3D PFN_DOWN(vm->subblock_size); + unsigned long pfn; + int sb_id, i; + + for (sb_id =3D 0; sb_id < vm->nb_sb_per_mb; sb_id++) { + if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1)) + continue; + /* + * Drop our reference to the pages so the memory can get + * offlined and add the unplugged pages to the managed + * page counters (so offlining code can correctly subtract + * them again). + */ + pfn =3D PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) + + sb_id * vm->subblock_size); + adjust_managed_page_count(pfn_to_page(pfn), nr_pages); + for (i =3D 0; i < nr_pages; i++) + page_ref_dec(pfn_to_page(pfn + i)); + } +} + +static void virtio_mem_notify_cancel_offline(struct virtio_mem *vm, + unsigned long mb_id) +{ + const unsigned long nr_pages =3D PFN_DOWN(vm->subblock_size); + unsigned long pfn; + int sb_id, i; + + for (sb_id =3D 0; sb_id < vm->nb_sb_per_mb; sb_id++) { + if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1)) + continue; + /* + * Get the reference we dropped when going offline and + * subtract the unplugged pages from the managed page + * counters. + */ + pfn =3D PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) + + sb_id * vm->subblock_size); + adjust_managed_page_count(pfn_to_page(pfn), -nr_pages); + for (i =3D 0; i < nr_pages; i++) + page_ref_inc(pfn_to_page(pfn + i)); + } +} + /* * This callback will either be called synchronously from add_memory() o= r * asynchronously (e.g., triggered via user space). We have to be carefu= l @@ -616,6 +663,7 @@ static int virtio_mem_memory_notifier_cb(struct notif= ier_block *nb, break; } vm->hotplug_active =3D true; + virtio_mem_notify_going_offline(vm, mb_id); break; case MEM_GOING_ONLINE: mutex_lock(&vm->hotplug_mutex); @@ -640,6 +688,12 @@ static int virtio_mem_memory_notifier_cb(struct noti= fier_block *nb, mutex_unlock(&vm->hotplug_mutex); break; case MEM_CANCEL_OFFLINE: + if (!vm->hotplug_active) + break; + virtio_mem_notify_cancel_offline(vm, mb_id); + vm->hotplug_active =3D false; + mutex_unlock(&vm->hotplug_mutex); + break; case MEM_CANCEL_ONLINE: if (!vm->hotplug_active) break; @@ -666,8 +720,11 @@ static void virtio_mem_set_fake_offline(unsigned lon= g pfn, struct page *page =3D pfn_to_page(pfn); =20 __SetPageOffline(page); - if (!onlined) + if (!onlined) { SetPageDirty(page); + /* FIXME: remove after cleanups */ + ClearPageReserved(page); + } } } =20 @@ -1717,6 +1774,11 @@ static void virtio_mem_remove(struct virtio_device= *vdev) rc =3D virtio_mem_mb_remove(vm, mb_id); BUG_ON(rc); } + /* + * After we unregistered our callbacks, user space can no longer + * offline partially plugged online memory blocks. No need to worry + * about them. + */ =20 /* unregister callbacks */ unregister_virtio_mem_device(vm); --=20 2.24.1