On 10.7.2020 10.00, Alex Shi wrote: > > 在 2020/7/10 下午1:28, Mika Penttilä 写道: >>> Thanks a lot for quick reply! >>> What I am confusing is the call chain: __iommu_dma_alloc_pages() >>> to split_huge_page(), in the func, splited page, >>> page = alloc_pages_node(nid, alloc_flags, order); >>> And if the pages were added into lru, they maybe reclaimed and lost, >>> that would be a panic bug. But in fact, this never happened for long time. >>> Also I put a BUG() at the line, it's nevre triggered in ltp, and run_vmtests >> In __iommu_dma_alloc_pages, after split_huge_page(), who is taking a >> reference on tail pages? Seems tail pages are freed and the function >> errornously returns them in pages[] array for use? >> > Why you say so? It looks like the tail page returned and be used > pages = __iommu_dma_alloc_pages() in iommu_dma_alloc_remap() > and still on node's lru. Is this right? > > thanks! IMHO they are new pages coming from alloc_pages_node() so they are not on lru. And split_huge_page() frees not pinned tail pages again to page allocator. Thanks, Mika
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