| Message ID | 155552633539.2015392.2477781120122237934.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | mm: Sub-section memory hotplug support | expand |
On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@intel.com> wrote: > The memory hotplug section is an arbitrary / convenient unit for memory > hotplug. 'Section-size' units have bled into the user interface > ('memblock' sysfs) and can not be changed without breaking existing > userspace. The section-size constraint, while mostly benign for typical > memory hotplug, has and continues to wreak havoc with 'device-memory' > use cases, persistent memory (pmem) in particular. Recall that pmem uses > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a > 'struct page' memmap for pmem. However, it does not use the 'bottom > half' of memory hotplug, i.e. never marks pmem pages online and never > exposes the userspace memblock interface for pmem. This leaves an > opening to redress the section-size constraint. v6 and we're not showing any review activity. Who would be suitable people to help out here?
On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@intel.com> wrote: > > > The memory hotplug section is an arbitrary / convenient unit for memory > > hotplug. 'Section-size' units have bled into the user interface > > ('memblock' sysfs) and can not be changed without breaking existing > > userspace. The section-size constraint, while mostly benign for typical > > memory hotplug, has and continues to wreak havoc with 'device-memory' > > use cases, persistent memory (pmem) in particular. Recall that pmem uses > > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a > > 'struct page' memmap for pmem. However, it does not use the 'bottom > > half' of memory hotplug, i.e. never marks pmem pages online and never > > exposes the userspace memblock interface for pmem. This leaves an > > opening to redress the section-size constraint. > > v6 and we're not showing any review activity. Who would be suitable > people to help out here? There was quite a bit of review of the cover letter from Michal and David, but you're right the details not so much as of yet. I'd like to call out other people where I can reciprocate with some review of my own. Oscar's altmap work looks like a good candidate for that.
On Wed, Apr 17, 2019 at 3:59 PM Dan Williams <dan.j.williams@intel.com> wrote: > > On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > > > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@intel.com> wrote: > > > > > The memory hotplug section is an arbitrary / convenient unit for memory > > > hotplug. 'Section-size' units have bled into the user interface > > > ('memblock' sysfs) and can not be changed without breaking existing > > > userspace. The section-size constraint, while mostly benign for typical > > > memory hotplug, has and continues to wreak havoc with 'device-memory' > > > use cases, persistent memory (pmem) in particular. Recall that pmem uses > > > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a > > > 'struct page' memmap for pmem. However, it does not use the 'bottom > > > half' of memory hotplug, i.e. never marks pmem pages online and never > > > exposes the userspace memblock interface for pmem. This leaves an > > > opening to redress the section-size constraint. > > > > v6 and we're not showing any review activity. Who would be suitable > > people to help out here? > > There was quite a bit of review of the cover letter from Michal and > David, but you're right the details not so much as of yet. I'd like to > call out other people where I can reciprocate with some review of my > own. Oscar's altmap work looks like a good candidate for that. I'm also hoping Jeff can give a tested-by for the customer scenarios that fall over with the current implementation.
Dan Williams <dan.j.williams@intel.com> writes: >> On Wed, Apr 17, 2019 at 3:59 PM Dan Williams <dan.j.williams@intel.com> wrote: >> >> On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@linux-foundation.org> wrote: >> > >> > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@intel.com> wrote: >> > >> > > The memory hotplug section is an arbitrary / convenient unit for memory >> > > hotplug. 'Section-size' units have bled into the user interface >> > > ('memblock' sysfs) and can not be changed without breaking existing >> > > userspace. The section-size constraint, while mostly benign for typical >> > > memory hotplug, has and continues to wreak havoc with 'device-memory' >> > > use cases, persistent memory (pmem) in particular. Recall that pmem uses >> > > devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a >> > > 'struct page' memmap for pmem. However, it does not use the 'bottom >> > > half' of memory hotplug, i.e. never marks pmem pages online and never >> > > exposes the userspace memblock interface for pmem. This leaves an >> > > opening to redress the section-size constraint. >> > >> > v6 and we're not showing any review activity. Who would be suitable >> > people to help out here? >> >> There was quite a bit of review of the cover letter from Michal and >> David, but you're right the details not so much as of yet. I'd like to >> call out other people where I can reciprocate with some review of my >> own. Oscar's altmap work looks like a good candidate for that. > > I'm also hoping Jeff can give a tested-by for the customer scenarios > that fall over with the current implementation. Sure. I'll also have a look over the patches. -Jeff
On Thu, Apr 18, 2019 at 5:45 AM Jeff Moyer <jmoyer@redhat.com> wrote: [..] > >> > v6 and we're not showing any review activity. Who would be suitable > >> > people to help out here? > >> > >> There was quite a bit of review of the cover letter from Michal and > >> David, but you're right the details not so much as of yet. I'd like to > >> call out other people where I can reciprocate with some review of my > >> own. Oscar's altmap work looks like a good candidate for that. > > > > I'm also hoping Jeff can give a tested-by for the customer scenarios > > that fall over with the current implementation. > > Sure. I'll also have a look over the patches. Andrew, heads up it looks like there is a memory corruption bug in these patches as I've gotten a few reported of "bad page state" at boot. Please drop until I can track down the failure.
On Wed, 2019-04-17 at 15:59 -0700, Dan Williams wrote: > On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@linux-foundation. > org> wrote: > > > > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@int > > el.com> wrote: > > > > > The memory hotplug section is an arbitrary / convenient unit for > > > memory > > > hotplug. 'Section-size' units have bled into the user interface > > > ('memblock' sysfs) and can not be changed without breaking > > > existing > > > userspace. The section-size constraint, while mostly benign for > > > typical > > > memory hotplug, has and continues to wreak havoc with 'device- > > > memory' > > > use cases, persistent memory (pmem) in particular. Recall that > > > pmem uses > > > devm_memremap_pages(), and subsequently arch_add_memory(), to > > > allocate a > > > 'struct page' memmap for pmem. However, it does not use the > > > 'bottom > > > half' of memory hotplug, i.e. never marks pmem pages online and > > > never > > > exposes the userspace memblock interface for pmem. This leaves an > > > opening to redress the section-size constraint. > > > > v6 and we're not showing any review activity. Who would be > > suitable > > people to help out here? > > There was quite a bit of review of the cover letter from Michal and > David, but you're right the details not so much as of yet. I'd like > to > call out other people where I can reciprocate with some review of my > own. Oscar's altmap work looks like a good candidate for that. Thanks Dan for ccing me. I will take a look at the patches soon.
I am also taking a look at this work now. I will review and test it in the next couple of days. Pasha On Tue, Apr 23, 2019 at 9:17 AM Oscar Salvador <osalvador@suse.de> wrote: > > On Wed, 2019-04-17 at 15:59 -0700, Dan Williams wrote: > > On Wed, Apr 17, 2019 at 3:04 PM Andrew Morton <akpm@linux-foundation. > > org> wrote: > > > > > > On Wed, 17 Apr 2019 11:38:55 -0700 Dan Williams <dan.j.williams@int > > > el.com> wrote: > > > > > > > The memory hotplug section is an arbitrary / convenient unit for > > > > memory > > > > hotplug. 'Section-size' units have bled into the user interface > > > > ('memblock' sysfs) and can not be changed without breaking > > > > existing > > > > userspace. The section-size constraint, while mostly benign for > > > > typical > > > > memory hotplug, has and continues to wreak havoc with 'device- > > > > memory' > > > > use cases, persistent memory (pmem) in particular. Recall that > > > > pmem uses > > > > devm_memremap_pages(), and subsequently arch_add_memory(), to > > > > allocate a > > > > 'struct page' memmap for pmem. However, it does not use the > > > > 'bottom > > > > half' of memory hotplug, i.e. never marks pmem pages online and > > > > never > > > > exposes the userspace memblock interface for pmem. This leaves an > > > > opening to redress the section-size constraint. > > > > > > v6 and we're not showing any review activity. Who would be > > > suitable > > > people to help out here? > > > > There was quite a bit of review of the cover letter from Michal and > > David, but you're right the details not so much as of yet. I'd like > > to > > call out other people where I can reciprocate with some review of my > > own. Oscar's altmap work looks like a good candidate for that. > > Thanks Dan for ccing me. > I will take a look at the patches soon. > > -- > Oscar Salvador > SUSE L3
Hi Dan, How do you test these patches? Do you have any instructions? I see for example that check_hotplug_memory_range() still enforces memory_block_size_bytes() alignment. Also, after removing check_hotplug_memory_range(), I tried to online 16M aligned DAX memory, and got the following panic: # echo online > /sys/devices/system/memory/memory7/state [ 202.193132] WARNING: CPU: 2 PID: 351 at drivers/base/memory.c:207 memory_block_action+0x110/0x178 [ 202.193391] Modules linked in: [ 202.193698] CPU: 2 PID: 351 Comm: sh Not tainted 5.1.0-rc7_pt_devdax-00038-g865af4385544-dirty #9 [ 202.193909] Hardware name: linux,dummy-virt (DT) [ 202.194122] pstate: 60000005 (nZCv daif -PAN -UAO) [ 202.194243] pc : memory_block_action+0x110/0x178 [ 202.194404] lr : memory_block_action+0x90/0x178 [ 202.194506] sp : ffff000016763ca0 [ 202.194592] x29: ffff000016763ca0 x28: ffff80016fd29b80 [ 202.194724] x27: 0000000000000000 x26: 0000000000000000 [ 202.194838] x25: ffff000015546000 x24: 00000000001c0000 [ 202.194949] x23: 0000000000000000 x22: 0000000000040000 [ 202.195058] x21: 00000000001c0000 x20: 0000000000000008 [ 202.195168] x19: 0000000000000007 x18: 0000000000000000 [ 202.195281] x17: 0000000000000000 x16: 0000000000000000 [ 202.195393] x15: 0000000000000000 x14: 0000000000000000 [ 202.195505] x13: 0000000000000000 x12: 0000000000000000 [ 202.195614] x11: 0000000000000000 x10: 0000000000000000 [ 202.195744] x9 : 0000000000000000 x8 : 0000000180000000 [ 202.195858] x7 : 0000000000000018 x6 : ffff000015541930 [ 202.195966] x5 : ffff000015541930 x4 : 0000000000000001 [ 202.196074] x3 : 0000000000000001 x2 : 0000000000000000 [ 202.196185] x1 : 0000000000000070 x0 : 0000000000000000 [ 202.196366] Call trace: [ 202.196455] memory_block_action+0x110/0x178 [ 202.196589] memory_subsys_online+0x3c/0x80 [ 202.196681] device_online+0x6c/0x90 [ 202.196761] state_store+0x84/0x100 [ 202.196841] dev_attr_store+0x18/0x28 [ 202.196927] sysfs_kf_write+0x40/0x58 [ 202.197010] kernfs_fop_write+0xcc/0x1d8 [ 202.197099] __vfs_write+0x18/0x40 [ 202.197187] vfs_write+0xa4/0x1b0 [ 202.197295] ksys_write+0x64/0xd8 [ 202.197430] __arm64_sys_write+0x18/0x20 [ 202.197521] el0_svc_common.constprop.0+0x7c/0xe8 [ 202.197621] el0_svc_handler+0x28/0x78 [ 202.197706] el0_svc+0x8/0xc [ 202.197828] ---[ end trace 57719823dda6d21e ]--- Thank you, Pasha
On Thu, May 2, 2019 at 3:46 PM Pavel Tatashin <pasha.tatashin@soleen.com> wrote: > > Hi Dan, > > How do you test these patches? Do you have any instructions? Yes, I briefly mentioned this in the cover letter, but here is the test I am using: > > I see for example that check_hotplug_memory_range() still enforces > memory_block_size_bytes() alignment. > > Also, after removing check_hotplug_memory_range(), I tried to online > 16M aligned DAX memory, and got the following panic: Right, this functionality is currently strictly limited to the devm_memremap_pages() case where there are guarantees that the memory will never be onlined. This is due to the fact that the section size is entangled with the memblock api. That said I would have expected you to trigger the warning in subsection_check() before getting this far into the hotplug process. > > # echo online > /sys/devices/system/memory/memory7/state > [ 202.193132] WARNING: CPU: 2 PID: 351 at drivers/base/memory.c:207 > memory_block_action+0x110/0x178 > [ 202.193391] Modules linked in: > [ 202.193698] CPU: 2 PID: 351 Comm: sh Not tainted > 5.1.0-rc7_pt_devdax-00038-g865af4385544-dirty #9 > [ 202.193909] Hardware name: linux,dummy-virt (DT) > [ 202.194122] pstate: 60000005 (nZCv daif -PAN -UAO) > [ 202.194243] pc : memory_block_action+0x110/0x178 > [ 202.194404] lr : memory_block_action+0x90/0x178 > [ 202.194506] sp : ffff000016763ca0 > [ 202.194592] x29: ffff000016763ca0 x28: ffff80016fd29b80 > [ 202.194724] x27: 0000000000000000 x26: 0000000000000000 > [ 202.194838] x25: ffff000015546000 x24: 00000000001c0000 > [ 202.194949] x23: 0000000000000000 x22: 0000000000040000 > [ 202.195058] x21: 00000000001c0000 x20: 0000000000000008 > [ 202.195168] x19: 0000000000000007 x18: 0000000000000000 > [ 202.195281] x17: 0000000000000000 x16: 0000000000000000 > [ 202.195393] x15: 0000000000000000 x14: 0000000000000000 > [ 202.195505] x13: 0000000000000000 x12: 0000000000000000 > [ 202.195614] x11: 0000000000000000 x10: 0000000000000000 > [ 202.195744] x9 : 0000000000000000 x8 : 0000000180000000 > [ 202.195858] x7 : 0000000000000018 x6 : ffff000015541930 > [ 202.195966] x5 : ffff000015541930 x4 : 0000000000000001 > [ 202.196074] x3 : 0000000000000001 x2 : 0000000000000000 > [ 202.196185] x1 : 0000000000000070 x0 : 0000000000000000 > [ 202.196366] Call trace: > [ 202.196455] memory_block_action+0x110/0x178 > [ 202.196589] memory_subsys_online+0x3c/0x80 > [ 202.196681] device_online+0x6c/0x90 > [ 202.196761] state_store+0x84/0x100 > [ 202.196841] dev_attr_store+0x18/0x28 > [ 202.196927] sysfs_kf_write+0x40/0x58 > [ 202.197010] kernfs_fop_write+0xcc/0x1d8 > [ 202.197099] __vfs_write+0x18/0x40 > [ 202.197187] vfs_write+0xa4/0x1b0 > [ 202.197295] ksys_write+0x64/0xd8 > [ 202.197430] __arm64_sys_write+0x18/0x20 > [ 202.197521] el0_svc_common.constprop.0+0x7c/0xe8 > [ 202.197621] el0_svc_handler+0x28/0x78 > [ 202.197706] el0_svc+0x8/0xc > [ 202.197828] ---[ end trace 57719823dda6d21e ]--- > > Thank you, > Pasha
On Thu, May 2, 2019 at 4:20 PM Dan Williams <dan.j.williams@intel.com> wrote: > > On Thu, May 2, 2019 at 3:46 PM Pavel Tatashin <pasha.tatashin@soleen.com> wrote: > > > > Hi Dan, > > > > How do you test these patches? Do you have any instructions? > > Yes, I briefly mentioned this in the cover letter, but here is the > test I am using: Sorry, fumble fingered the 'send' button, here is that link: https://github.com/pmem/ndctl/blob/subsection-pending/test/sub-section.sh
On Thu, May 02, 2019 at 04:20:03PM -0700, Dan Williams wrote: > On Thu, May 2, 2019 at 3:46 PM Pavel Tatashin <pasha.tatashin@soleen.com> wrote: > > > > Hi Dan, > > > > How do you test these patches? Do you have any instructions? > > Yes, I briefly mentioned this in the cover letter, but here is the > test I am using: > > > > > I see for example that check_hotplug_memory_range() still enforces > > memory_block_size_bytes() alignment. > > > > Also, after removing check_hotplug_memory_range(), I tried to online > > 16M aligned DAX memory, and got the following panic: > > Right, this functionality is currently strictly limited to the > devm_memremap_pages() case where there are guarantees that the memory > will never be onlined. This is due to the fact that the section size > is entangled with the memblock api. That said I would have expected > you to trigger the warning in subsection_check() before getting this > far into the hotplug process. > > > > # echo online > /sys/devices/system/memory/memory7/state > > [ 202.193132] WARNING: CPU: 2 PID: 351 at drivers/base/memory.c:207 > > memory_block_action+0x110/0x178 > > [ 202.193391] Modules linked in: > > [ 202.193698] CPU: 2 PID: 351 Comm: sh Not tainted > > 5.1.0-rc7_pt_devdax-00038-g865af4385544-dirty #9 > > [ 202.193909] Hardware name: linux,dummy-virt (DT) > > [ 202.194122] pstate: 60000005 (nZCv daif -PAN -UAO) > > [ 202.194243] pc : memory_block_action+0x110/0x178 > > [ 202.194404] lr : memory_block_action+0x90/0x178 > > [ 202.194506] sp : ffff000016763ca0 > > [ 202.194592] x29: ffff000016763ca0 x28: ffff80016fd29b80 > > [ 202.194724] x27: 0000000000000000 x26: 0000000000000000 > > [ 202.194838] x25: ffff000015546000 x24: 00000000001c0000 > > [ 202.194949] x23: 0000000000000000 x22: 0000000000040000 > > [ 202.195058] x21: 00000000001c0000 x20: 0000000000000008 > > [ 202.195168] x19: 0000000000000007 x18: 0000000000000000 > > [ 202.195281] x17: 0000000000000000 x16: 0000000000000000 > > [ 202.195393] x15: 0000000000000000 x14: 0000000000000000 > > [ 202.195505] x13: 0000000000000000 x12: 0000000000000000 > > [ 202.195614] x11: 0000000000000000 x10: 0000000000000000 > > [ 202.195744] x9 : 0000000000000000 x8 : 0000000180000000 > > [ 202.195858] x7 : 0000000000000018 x6 : ffff000015541930 > > [ 202.195966] x5 : ffff000015541930 x4 : 0000000000000001 > > [ 202.196074] x3 : 0000000000000001 x2 : 0000000000000000 > > [ 202.196185] x1 : 0000000000000070 x0 : 0000000000000000 > > [ 202.196366] Call trace: > > [ 202.196455] memory_block_action+0x110/0x178 > > [ 202.196589] memory_subsys_online+0x3c/0x80 > > [ 202.196681] device_online+0x6c/0x90 > > [ 202.196761] state_store+0x84/0x100 > > [ 202.196841] dev_attr_store+0x18/0x28 > > [ 202.196927] sysfs_kf_write+0x40/0x58 > > [ 202.197010] kernfs_fop_write+0xcc/0x1d8 > > [ 202.197099] __vfs_write+0x18/0x40 > > [ 202.197187] vfs_write+0xa4/0x1b0 > > [ 202.197295] ksys_write+0x64/0xd8 > > [ 202.197430] __arm64_sys_write+0x18/0x20 > > [ 202.197521] el0_svc_common.constprop.0+0x7c/0xe8 > > [ 202.197621] el0_svc_handler+0x28/0x78 > > [ 202.197706] el0_svc+0x8/0xc > > [ 202.197828] ---[ end trace 57719823dda6d21e ]--- This warning relates to: for (; section_nr < section_nr_end; section_nr++) { if (WARN_ON_ONCE(!pfn_valid(pfn))) return false; from pages_correctly_probed(). AFAICS, this is orthogonal to subsection_check().
Changes since v5 [1]: - Rebase on next-20190416 and the new 'struct mhp_restrictions' infrastructure. - Extend mhp_restrictions to the 'remove' case so the sub-section policy can be clarified with respect to the memblock-api in a symmetric manner with the 'add' case. - Kill is_dev_zone() since cleanups have now made it moot [1]: https://lwn.net/Articles/783808/ --- The memory hotplug section is an arbitrary / convenient unit for memory hotplug. 'Section-size' units have bled into the user interface ('memblock' sysfs) and can not be changed without breaking existing userspace. The section-size constraint, while mostly benign for typical memory hotplug, has and continues to wreak havoc with 'device-memory' use cases, persistent memory (pmem) in particular. Recall that pmem uses devm_memremap_pages(), and subsequently arch_add_memory(), to allocate a 'struct page' memmap for pmem. However, it does not use the 'bottom half' of memory hotplug, i.e. never marks pmem pages online and never exposes the userspace memblock interface for pmem. This leaves an opening to redress the section-size constraint. To date, the libnvdimm subsystem has attempted to inject padding to satisfy the internal constraints of arch_add_memory(). Beyond complicating the code, leading to bugs [2], wasting memory, and limiting configuration flexibility, the padding hack is broken when the platform changes this physical memory alignment of pmem from one boot to the next. Device failure (intermittent or permanent) and physical reconfiguration are events that can cause the platform firmware to change the physical placement of pmem on a subsequent boot, and device failure is an everyday event in a data-center. It turns out that sections are only a hard requirement of the user-facing interface for memory hotplug and with a bit more infrastructure sub-section arch_add_memory() support can be added for kernel internal usages like devm_memremap_pages(). Here is an analysis of the current design assumptions in the current code and how they are addressed in the new implementation: Current design assumptions: - Sections that describe boot memory (early sections) are never unplugged / removed. - pfn_valid(), in the CONFIG_SPARSEMEM_VMEMMAP=y, case devolves to a valid_section() check - __add_pages() and helper routines assume all operations occur in PAGES_PER_SECTION units. - The memblock sysfs interface only comprehends full sections New design assumptions: - Sections are instrumented with a sub-section bitmask to track (on x86) individual 2MB sub-divisions of a 128MB section. - Partially populated early sections can be extended with additional sub-sections, and those sub-sections can be removed with arch_remove_memory(). With this in place we no longer lose usable memory capacity to padding. - pfn_valid() is updated to look deeper than valid_section() to also check the active-sub-section mask. This indication is in the same cacheline as the valid_section() so the performance impact is expected to be negligible. So far the lkp robot has not reported any regressions. - Outside of the core vmemmap population routines which are replaced, other helper routines like shrink_{zone,pgdat}_span() are updated to handle the smaller granularity. Core memory hotplug routines that deal with online memory are not touched. - The existing memblock sysfs user api guarantees / assumptions are not touched since this capability is limited to !online !memblock-sysfs-accessible sections. Meanwhile the issue reports continue to roll in from users that do not understand when and how the 128MB constraint will bite them. The current implementation relied on being able to support at least one misaligned namespace, but that immediately falls over on any moderately complex namespace creation attempt. Beyond the initial problem of 'System RAM' colliding with pmem, and the unsolvable problem of physical alignment changes, Linux is now being exposed to platforms that collide pmem ranges with other pmem ranges by default [3]. In short, devm_memremap_pages() has pushed the venerable section-size constraint past the breaking point, and the simplicity of section-aligned arch_add_memory() is no longer tenable. These patches are exposed to the kbuild robot on my libnvdimm-pending branch [4], and a preview of the unit test for this functionality is available on the 'subsection-pending' branch of ndctl [5]. [2]: https://lore.kernel.org/r/155000671719.348031.2347363160141119237.stgit@dwillia2-desk3.amr.corp.intel.com [3]: https://github.com/pmem/ndctl/issues/76 [4]: https://git.kernel.org/pub/scm/linux/kernel/git/djbw/nvdimm.git/log/?h=libnvdimm-pending [5]: https://github.com/pmem/ndctl/commit/7c59b4867e1c --- Dan Williams (12): mm/sparsemem: Introduce struct mem_section_usage mm/sparsemem: Introduce common definitions for the size and mask of a section mm/sparsemem: Add helpers track active portions of a section at boot mm/hotplug: Prepare shrink_{zone,pgdat}_span for sub-section removal mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap() mm/hotplug: Add mem-hotplug restrictions for remove_memory() mm: Kill is_dev_zone() helper mm/sparsemem: Prepare for sub-section ranges mm/sparsemem: Support sub-section hotplug mm/devm_memremap_pages: Enable sub-section remap libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields libnvdimm/pfn: Stop padding pmem namespaces to section alignment arch/ia64/mm/init.c | 4 arch/powerpc/mm/mem.c | 5 - arch/s390/mm/init.c | 2 arch/sh/mm/init.c | 4 arch/x86/mm/init_32.c | 4 arch/x86/mm/init_64.c | 9 + drivers/nvdimm/dax_devs.c | 2 drivers/nvdimm/pfn.h | 12 - drivers/nvdimm/pfn_devs.c | 93 +++------- include/linux/memory_hotplug.h | 12 + include/linux/mm.h | 4 include/linux/mmzone.h | 72 ++++++-- kernel/memremap.c | 70 +++----- mm/hmm.c | 2 mm/memory_hotplug.c | 148 +++++++++------- mm/page_alloc.c | 8 + mm/sparse-vmemmap.c | 21 ++ mm/sparse.c | 371 +++++++++++++++++++++++++++------------- 18 files changed, 503 insertions(+), 340 deletions(-)