Changes since v2 [1]: 1/ Fixed a bug inserting multi-order entries into pgmap_radix. The insert index needs to be 'order' aligned. 2/ Fixed a __meminit section mismatch warning for section_activate() 3/ Forward ported to v4.10-rc4 [1]: https://lwn.net/Articles/708627/ --- The initial motivation for this change is persistent memory platforms that, unfortunately, align the pmem range on a boundary less than a full section (64M vs 128M), and may change the alignment from one boot to the next. A secondary motivation is the arrival of prospective ZONE_DEVICE users that want devm_memremap_pages() to map PCI-E device memory ranges to enable peer-to-peer DMA. There is a range of possible physical address alignments of PCI-E BARs that are less than 128M. Currently the libnvdimm core injects padding when 'pfn' (struct page mapping configuration) instances are created. However, not all users of devm_memremap_pages() have the opportunity to inject such padding. Users of the memmap=ss!nn kernel command line option can trigger the following failure with unaligned parameters like "memmap=0xfc000000!8G": WARNING: CPU: 0 PID: 558 at kernel/memremap.c:300 devm_memremap_pages attempted on mixed region [mem 0x200000000-0x2fbffffff flags 0x200] [..] Call Trace: [<ffffffff814c0393>] dump_stack+0x86/0xc3 [<ffffffff810b173b>] __warn+0xcb/0xf0 [<ffffffff810b17bf>] warn_slowpath_fmt+0x5f/0x80 [<ffffffff811eb105>] devm_memremap_pages+0x3b5/0x4c0 [<ffffffffa006f308>] __wrap_devm_memremap_pages+0x58/0x70 [nfit_test_iomap] [<ffffffffa00e231a>] pmem_attach_disk+0x19a/0x440 [nd_pmem] Without this change a user could inadvertently lose access to nvdimm namespaces after a configuration change. The act of adding, removing, or rearranging DIMMs in the platform could lead to the BIOS changing the base alignment of the namespace in an incompatible fashion. With this support we can accommodate a BIOS changing the namespace to any alignment provided it is >= SECTION_ACTIVE_SIZE. In other words, we are protecting against misalignment injected by the BIOS after the libnvdimm sub-system already recorded that the namespace does not need alignment padding. In that case the user would need to figure out how to undo the configuration change to regain access to their nvdimm capacity. --- The patches have received a build success notification from the 0day-kbuild robot across 142 configs and pass the latest libnvdimm/ndctl unit test suite. They merge cleanly on top of current -next (test merge with next-20170118). --- Dan Williams (12): mm: fix type width of section to/from pfn conversion macros mm, devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups mm: introduce struct mem_section_usage to track partial population of a section mm: introduce common definitions for the size and mask of a section mm: cleanup sparse_init_one_section() return value mm: track active portions of a section at boot mm: fix register_new_memory() zone type detection mm: convert kmalloc_section_memmap() to populate_section_memmap() mm: prepare for hot-{add,remove} of sub-section ranges mm: support section-unaligned ZONE_DEVICE memory ranges mm: enable section-unaligned devm_memremap_pages() libnvdimm, pfn, dax: stop padding pmem namespaces to section alignment arch/x86/mm/init_64.c | 15 + drivers/base/memory.c | 26 +- drivers/nvdimm/pfn_devs.c | 42 +--- include/linux/memory.h | 4 include/linux/memory_hotplug.h | 6 - include/linux/mm.h | 3 include/linux/mmzone.h | 30 ++- kernel/memremap.c | 74 ++++--- mm/Kconfig | 1 mm/memory_hotplug.c | 95 ++++---- mm/page_alloc.c | 6 - mm/sparse-vmemmap.c | 24 +- mm/sparse.c | 454 +++++++++++++++++++++++++++++----------- 13 files changed, 511 insertions(+), 269 deletions(-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>