diff options
| author | David Hildenbrand <david@redhat.com> | 2022-03-22 14:43:20 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-22 15:57:06 -0700 |
| commit | b3d40a2b6d10c9d0424d2b398bf962fb6adad87e (patch) | |
| tree | d74622173508e2ccf0cf8f182356512493878024 /drivers/virtio | |
| parent | e16faf26780fc0c8dd693ea9ee8420a7706cb2f5 (diff) | |
mm: enforce pageblock_order < MAX_ORDER
Some places in the kernel don't really expect pageblock_order >=
MAX_ORDER, and it looks like this is only possible in corner cases:
1) CONFIG_DEFERRED_STRUCT_PAGE_INIT we'll end up freeing pageblock_order
pages via __free_pages_core(), which cannot possibly work.
2) find_zone_movable_pfns_for_nodes() will roundup the ZONE_MOVABLE
start PFN to MAX_ORDER_NR_PAGES. Consequently with a bigger
pageblock_order, we could have a single pageblock partially managed by
two zones.
3) compaction code runs into __fragmentation_index() with order
>= MAX_ORDER, when checking WARN_ON_ONCE(order >= MAX_ORDER). [1]
4) mm/page_reporting.c won't be reporting any pages with default
page_reporting_order == pageblock_order, as we'll be skipping the
reporting loop inside page_reporting_process_zone().
5) __rmqueue_fallback() will never be able to steal with
ALLOC_NOFRAGMENT.
pageblock_order >= MAX_ORDER is weird either way: it's a pure
optimization for making alloc_contig_range(), as used for allcoation of
gigantic pages, a little more reliable to succeed. However, if there is
demand for somewhat reliable allocation of gigantic pages, affected
setups should be using CMA or boottime allocations instead.
So let's make sure that pageblock_order < MAX_ORDER and simplify.
[1] https://lkml.kernel.org/r/87r189a2ks.fsf@linux.ibm.com
Link: https://lkml.kernel.org/r/20220214174132.219303-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: John Garry via iommu <iommu@lists.linux-foundation.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/virtio')
| -rw-r--r-- | drivers/virtio/virtio_mem.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 38becd8d578c..e7d6b679596d 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -2476,13 +2476,10 @@ static int virtio_mem_init_hotplug(struct virtio_mem *vm) VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD); /* - * We want subblocks to span at least MAX_ORDER_NR_PAGES and - * pageblock_nr_pages pages. This: - * - Is required for now for alloc_contig_range() to work reliably - - * it doesn't properly handle smaller granularity on ZONE_NORMAL. + * TODO: once alloc_contig_range() works reliably with pageblock + * granularity on ZONE_NORMAL, use pageblock_nr_pages instead. */ - sb_size = max_t(uint64_t, MAX_ORDER_NR_PAGES, - pageblock_nr_pages) * PAGE_SIZE; + sb_size = PAGE_SIZE * MAX_ORDER_NR_PAGES; sb_size = max_t(uint64_t, vm->device_block_size, sb_size); if (sb_size < memory_block_size_bytes() && !force_bbm) { |