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From: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
To: David Hildenbrand <david@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>,
	virtio-dev@lists.oasis-open.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Oscar Salvador <osalvador@suse.de>,
	Igor Mammedov <imammedo@redhat.com>,
	Dave Young <dyoung@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Pavel Tatashin <pasha.tatashin@soleen.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v2 08/10] virtio-mem: Offline and remove completely unplugged memory blocks
Date: Wed, 15 Apr 2020 09:42:08 +0200	[thread overview]
Message-ID: <CAM9Jb+iuZ4hzP1ik+RUib3Vi1ymc9y5++8_EX50=MCTBsC+1fQ@mail.gmail.com> (raw)
In-Reply-To: <20200311171422.10484-9-david@redhat.com>

> Let's offline+remove memory blocks once all subblocks are unplugged. We
> can use the new Linux MM interface for that. As no memory is in use
> anymore, this shouldn't take a long time and shouldn't fail. There might
> be corner cases where the offlining could still fail (especially, if
> another notifier NACKs the offlining request).
>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Dave Young <dyoung@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  drivers/virtio/virtio_mem.c | 47 +++++++++++++++++++++++++++++++++----
>  1 file changed, 43 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
> index 35f20232770c..aa322e7732a4 100644
> --- a/drivers/virtio/virtio_mem.c
> +++ b/drivers/virtio/virtio_mem.c
> @@ -443,6 +443,28 @@ static int virtio_mem_mb_remove(struct virtio_mem *vm, unsigned long mb_id)
>         return remove_memory(nid, addr, memory_block_size_bytes());
>  }
>
> +/*
> + * Try to offline and remove a memory block from Linux.
> + *
> + * Must not be called with the vm->hotplug_mutex held (possible deadlock with
> + * onlining code).
> + *
> + * Will not modify the state of the memory block.
> + */
> +static int virtio_mem_mb_offline_and_remove(struct virtio_mem *vm,
> +                                           unsigned long mb_id)
> +{
> +       const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id);
> +       int nid = vm->nid;
> +
> +       if (nid == NUMA_NO_NODE)
> +               nid = memory_add_physaddr_to_nid(addr);
> +
> +       dev_dbg(&vm->vdev->dev, "offlining and removing memory block: %lu\n",
> +               mb_id);
> +       return offline_and_remove_memory(nid, addr, memory_block_size_bytes());
> +}
> +
>  /*
>   * Trigger the workqueue so the device can perform its magic.
>   */
> @@ -535,7 +557,13 @@ static void virtio_mem_notify_offline(struct virtio_mem *vm,
>                 break;
>         }
>
> -       /* trigger the workqueue, maybe we can now unplug memory. */
> +       /*
> +        * Trigger the workqueue, maybe we can now unplug memory. Also,
> +        * when we offline and remove a memory block, this will re-trigger
> +        * us immediately - which is often nice because the removal of
> +        * the memory block (e.g., memmap) might have freed up memory
> +        * on other memory blocks we manage.
> +        */
>         virtio_mem_retry(vm);
>  }
>
> @@ -1282,7 +1310,8 @@ static int virtio_mem_mb_unplug_any_sb_offline(struct virtio_mem *vm,
>   * Unplug the desired number of plugged subblocks of an online memory block.
>   * Will skip subblock that are busy.
>   *
> - * Will modify the state of the memory block.
> + * Will modify the state of the memory block. Might temporarily drop the
> + * hotplug_mutex.
>   *
>   * Note: Can fail after some subblocks were successfully unplugged. Can
>   *       return 0 even if subblocks were busy and could not get unplugged.
> @@ -1338,9 +1367,19 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm,
>         }
>
>         /*
> -        * TODO: Once all subblocks of a memory block were unplugged, we want
> -        * to offline the memory block and remove it.
> +        * Once all subblocks of a memory block were unplugged, offline and
> +        * remove it. This will usually not fail, as no memory is in use
> +        * anymore - however some other notifiers might NACK the request.
>          */
> +       if (virtio_mem_mb_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
> +               mutex_unlock(&vm->hotplug_mutex);
> +               rc = virtio_mem_mb_offline_and_remove(vm, mb_id);
> +               mutex_lock(&vm->hotplug_mutex);
> +               if (!rc)
> +                       virtio_mem_mb_set_state(vm, mb_id,
> +                                               VIRTIO_MEM_MB_STATE_UNUSED);
> +       }
> +
>         return 0;
>  }
>

Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>

> --

  reply	other threads:[~2020-04-15  7:43 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 17:14 [PATCH v2 00/10] virtio-mem: paravirtualized memory David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 01/10] virtio-mem: Paravirtualized memory hotplug David Hildenbrand
2020-04-15  5:59   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 02/10] virtio-mem: Allow to specify an ACPI PXM as nid David Hildenbrand
2020-03-30 11:04   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 03/10] virtio-mem: Paravirtualized memory hotunplug part 1 David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 04/10] virtio-mem: Paravirtualized memory hotunplug part 2 David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 05/10] mm: Allow to offline unmovable PageOffline() pages via MEM_GOING_OFFLINE David Hildenbrand
2020-04-14 16:34   ` Michael S. Tsirkin
2020-04-15  0:32     ` Andrew Morton
2020-03-11 17:14 ` [PATCH v2 06/10] virtio-mem: Allow to offline partially unplugged memory blocks David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 07/10] mm/memory_hotplug: Introduce offline_and_remove_memory() David Hildenbrand
2020-03-11 17:19   ` David Hildenbrand
2020-04-14 16:35     ` Michael S. Tsirkin
2020-04-15  0:30       ` Andrew Morton
2020-04-15  7:35   ` Pankaj Gupta
2020-03-11 17:14 ` [PATCH v2 08/10] virtio-mem: Offline and remove completely unplugged memory blocks David Hildenbrand
2020-04-15  7:42   ` Pankaj Gupta [this message]
2020-03-11 17:14 ` [PATCH v2 09/10] virtio-mem: Better retry handling David Hildenbrand
2020-03-11 17:14 ` [PATCH v2 10/10] MAINTAINERS: Add myself as virtio-mem maintainer David Hildenbrand
2020-03-27 16:58 ` [PATCH v2 00/10] virtio-mem: paravirtualized memory Pankaj Gupta
2020-03-27 17:03   ` David Hildenbrand
2020-03-27 17:07     ` David Hildenbrand
2020-03-29 15:41     ` Pankaj Gupta
2020-03-30  8:42       ` David Hildenbrand
2020-03-29 12:42 ` Michael S. Tsirkin
2020-03-30  8:16   ` David Hildenbrand
2020-04-14  9:15   ` David Hildenbrand
2020-04-14 16:28     ` Michael S. Tsirkin
2020-04-14 18:39       ` David Hildenbrand

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