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The coordination between freeing of unused memory map, pfn_valid() and core mm assumptions about validity of the memory map in various ranges was not designed for complex layouts of the physical memory with a lot of holes all over the place. Kefen Wang reported crashes in move_freepages() on a system with the following memory layout [1]: node 0: [mem 0x0000000080a00000-0x00000000855fffff] node 0: [mem 0x0000000086a00000-0x0000000087dfffff] node 0: [mem 0x000000008bd00000-0x000000008c4fffff] node 0: [mem 0x000000008e300000-0x000000008ecfffff] node 0: [mem 0x0000000090d00000-0x00000000bfffffff] node 0: [mem 0x00000000cc000000-0x00000000dc9fffff] node 0: [mem 0x00000000de700000-0x00000000de9fffff] node 0: [mem 0x00000000e0800000-0x00000000e0bfffff] node 0: [mem 0x00000000f4b00000-0x00000000f6ffffff] node 0: [mem 0x00000000fda00000-0x00000000ffffefff] These crashes can be mitigated by enabling CONFIG_HOLES_IN_ZONE on ARM and essentially turning pfn_valid_within() to pfn_valid() instead of having it hardwired to 1 on that architecture, but this would require to keep CONFIG_HOLES_IN_ZONE solely for this purpose. A cleaner approach is to update ARM's implementation of pfn_valid() to take into accounting rounding of the freed memory map to pageblock boundaries and make sure it returns true for PFNs that have memory map entries even if there is no physical memory backing those PFNs. [1] https://lore.kernel.org/lkml/2a1592ad-bc9d-4664-fd19-f7448a37edc0@huawei.com -----BEGIN PGP SIGNATURE----- iQFHBAABCAAxFiEEeOVYVaWZL5900a/pOQOGJssO/ZEFAmDhzQQTHHJwcHRAbGlu dXguaWJtLmNvbQAKCRA5A4Ymyw79kXeUCACS0lssuKbaBxFk6OkEe0nbmbwN/n9z zKd2AWzw9xFxYZkLfOCmi5EPUMI0IeDYjOyZmnj8YDDd7wRLVxZ51LSdyFDZafXY j6SVYprSmwUjLkuajmqifY5DLbZYeGuI6WFvNVLljltHc0i/GIzx1Tld2yO/M0Jk NzHQ0/5nXmU74PvvY8LrWk+rRjTYqMuolHvbbl4nNId5e/FYEWNxEqNO5gq6aG5g +5t1BjyLf1NMp67uc5aLoLmr2ZwK8/UmZeSZ7i9z03gU/5B1srLluhoBsYBPVHFY hRNRKwWUDRUmqjJnu5/EzI+iQnj7t6zV1hyt+E5B1gb89vuSVcJNOPQt =wCcY -----END PGP SIGNATURE----- Merge tag 'memblock-v5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock Pull memblock updates from Mike Rapoport: "Fix arm crashes caused by holes in the memory map. The coordination between freeing of unused memory map, pfn_valid() and core mm assumptions about validity of the memory map in various ranges was not designed for complex layouts of the physical memory with a lot of holes all over the place. Kefen Wang reported crashes in move_freepages() on a system with the following memory layout [1]: node 0: [mem 0x0000000080a00000-0x00000000855fffff] node 0: [mem 0x0000000086a00000-0x0000000087dfffff] node 0: [mem 0x000000008bd00000-0x000000008c4fffff] node 0: [mem 0x000000008e300000-0x000000008ecfffff] node 0: [mem 0x0000000090d00000-0x00000000bfffffff] node 0: [mem 0x00000000cc000000-0x00000000dc9fffff] node 0: [mem 0x00000000de700000-0x00000000de9fffff] node 0: [mem 0x00000000e0800000-0x00000000e0bfffff] node 0: [mem 0x00000000f4b00000-0x00000000f6ffffff] node 0: [mem 0x00000000fda00000-0x00000000ffffefff] These crashes can be mitigated by enabling CONFIG_HOLES_IN_ZONE on ARM and essentially turning pfn_valid_within() to pfn_valid() instead of having it hardwired to 1 on that architecture, but this would require to keep CONFIG_HOLES_IN_ZONE solely for this purpose. A cleaner approach is to update ARM's implementation of pfn_valid() to take into accounting rounding of the freed memory map to pageblock boundaries and make sure it returns true for PFNs that have memory map entries even if there is no physical memory backing those PFNs" Link: https://lore.kernel.org/lkml/2a1592ad-bc9d-4664-fd19-f7448a37edc0@huawei.com [1] * tag 'memblock-v5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock: arm: extend pfn_valid to take into account freed memory map alignment memblock: ensure there is no overflow in memblock_overlaps_region() memblock: align freed memory map on pageblock boundaries with SPARSEMEM memblock: free_unused_memmap: use pageblock units instead of MAX_ORDER |
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