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virtio-mem: retry fake-offlining via alloc_contig_range() on ZONE_MOVABLE

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ZONE_MOVABLE is supposed to give some guarantees, yet,
alloc_contig_range() isn't prepared to properly deal with some racy
cases properly (e.g., temporary page pinning when exiting processed, PCP).

Retry 5 times for now. There is certainly room for improvement in the
future.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-11-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
David Hildenbrand 2020-11-12 14:37:56 +01:00 committed by Michael S. Tsirkin
parent 7a34c77dab
commit f2d799d591
1 changed files with 26 additions and 11 deletions
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37
drivers/virtio/virtio_mem.c
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@ -784,19 +784,34 @@ static void virtio_mem_fake_online(unsigned long pfn, unsigned long nr_pages)
*/
static int virtio_mem_fake_offline(unsigned long pfn, unsigned long nr_pages)
{
int rc;
const bool is_movable = zone_idx(page_zone(pfn_to_page(pfn))) ==
ZONE_MOVABLE;
int rc, retry_count;
rc = alloc_contig_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE,
GFP_KERNEL);
if (rc == -ENOMEM)
/* whoops, out of memory */
return rc;
if (rc)
return -EBUSY;
/*
* TODO: We want an alloc_contig_range() mode that tries to allocate
* harder (e.g., dealing with temporarily pinned pages, PCP), especially
* with ZONE_MOVABLE. So for now, retry a couple of times with
* ZONE_MOVABLE before giving up - because that zone is supposed to give
* some guarantees.
*/
for (retry_count = 0; retry_count < 5; retry_count++) {
rc = alloc_contig_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE,
GFP_KERNEL);
if (rc == -ENOMEM)
/* whoops, out of memory */
return rc;
else if (rc && !is_movable)
break;
else if (rc)
continue;
virtio_mem_set_fake_offline(pfn, nr_pages, true);
adjust_managed_page_count(pfn_to_page(pfn), -nr_pages);
return 0;
virtio_mem_set_fake_offline(pfn, nr_pages, true);
adjust_managed_page_count(pfn_to_page(pfn), -nr_pages);
return 0;
}
return -EBUSY;
}
/*