From: Zi Yan <ziy@xxxxxxxxxx> Hi David, You suggested to make alloc_contig_range() deal with pageblock_order instead of MAX_ORDER - 1 and get rid of MAX_ORDER - 1 dependency in virtio_mem[1]. This patchset is my attempt to achieve that. Please take a look and let me know if I am doing it correctly or not. >From what my understanding, cma required alignment of max(MAX_ORDER - 1, pageblock_order), because when MIGRATE_CMA was introduced, __free_one_page() does not prevent merging two different pageblocks, when MAX_ORDER - 1 > pageblock_order. But current __free_one_page() implementation does prevent that. It should be OK to just align cma to pageblock_order. alloc_contig_range() relies on MIGRATE_CMA to get free pages, so it can use pageblock_order as alignment too. In terms of virtio_mem, if I understand correctly, it relies on alloc_contig_range() to obtain contiguous free pages and offlines them to reduce guest memory size. As the result of alloc_contig_range() alignment change, virtio_mem should be able to just align PFNs to pageblock_order. Thanks. [1] https://lore.kernel.org/linux-mm/28b57903-fae6-47ac-7e1b-a1dd41421349@xxxxxxxxxx/ Zi Yan (3): mm: cma: alloc_contig_range: use pageblock_order as the single alignment. drivers: virtio_mem: use pageblock size as the minimum virtio_mem size. arch: powerpc: adjust fadump alignment to be pageblock aligned. arch/powerpc/include/asm/fadump-internal.h | 4 +--- drivers/virtio/virtio_mem.c | 6 ++---- include/linux/mmzone.h | 5 +---- kernel/dma/contiguous.c | 2 +- mm/cma.c | 6 ++---- mm/page_alloc.c | 12 +++++------- 6 files changed, 12 insertions(+), 23 deletions(-) -- 2.33.0
