linux/mm/sparse.c, branch v5.7

mm/sparse.c: move subsection_map related functions together

2020-04-07T17:43:40Z

No functional change. [bhe@redhat.com: move functions into CONFIG_MEMORY_HOTPLUG ifdeffery scope] Link: http://lkml.kernel.org/r/20200316045804.GC3486@MiWiFi-R3L-srv Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Cc: Michal Hocko Cc: David Hildenbrand Cc: Wei Yang Cc: Dan Williams Cc: Pankaj Gupta Cc: Stephen Rothwell Link: http://lkml.kernel.org/r/20200312124414.439-6-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/sparse.c: add note about only VMEMMAP supporting sub-section hotplug

2020-04-07T17:43:40Z

And tell check_pfn_span() gating the porper alignment and size of hot added memory region. And also move the code comments from inside section_deactivate() to being above it. The code comments are reasonable for the whole function, and the moving makes code cleaner. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Cc: Dan Williams Cc: Pankaj Gupta Cc: Wei Yang Link: http://lkml.kernel.org/r/20200312124414.439-5-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/sparse.c: only use subsection map in VMEMMAP case

2020-04-07T17:43:40Z

Currently, to support subsection aligned memory region adding for pmem, subsection map is added to track which subsection is present. However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the classic sparse, it's meaningless. Even worse, it may confuse people when checking code related to the classic sparse. About the classic sparse which doesn't support subsection hotplug, Dan said it's more because the effort and maintenance burden outweighs the benefit. Besides, the current 64 bit ARCHes all enable SPARSEMEM_VMEMMAP_ENABLE by default. Combining the above reasons, no need to provide subsection map and the relevant handling for the classic sparse. Let's remove them. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Cc: Dan Williams Cc: Michal Hocko Cc: Pankaj Gupta Cc: Wei Yang Link: http://lkml.kernel.org/r/20200312124414.439-4-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/sparse.c: introduce a new function clear_subsection_map()

2020-04-07T17:43:40Z

Factor out the code which clear subsection map of one memory region from section_deactivate() into clear_subsection_map(). And also add helper function is_subsection_map_empty() to check if the current subsection map is empty or not. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Acked-by: Pankaj Gupta Cc: Dan Williams Cc: Michal Hocko Cc: Wei Yang Link: http://lkml.kernel.org/r/20200312124414.439-3-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/sparse.c: introduce new function fill_subsection_map()

2020-04-07T17:43:40Z

Patch series "mm/hotplug: Only use subsection map for VMEMMAP", v4. Memory sub-section hotplug was added to fix the issue that nvdimm could be mapped at non-section aligned starting address. A subsection map is added into struct mem_section_usage to implement it. However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the classic sparse, subsection map is meaningless and confusing. About the classic sparse which doesn't support subsection hotplug, Dan said it's more because the effort and maintenance burden outweighs the benefit. Besides, the current 64 bit ARCHes all enable SPARSEMEM_VMEMMAP_ENABLE by default. This patch (of 5): Factor out the code that fills the subsection map from section_activate() into fill_subsection_map(), this makes section_activate() cleaner and easier to follow. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: Wei Yang Reviewed-by: David Hildenbrand Acked-by: Pankaj Gupta Cc: Dan Williams Cc: Michal Hocko Link: http://lkml.kernel.org/r/20200312124414.439-2-bhe@redhat.com Signed-off-by: Linus Torvalds

mm/sparse.c: allocate memmap preferring the given node

2020-04-02T16:35:30Z

When allocating memmap for hot added memory with the classic sparse, the specified 'nid' is ignored in populate_section_memmap(). While in allocating memmap for the classic sparse during boot, the node given by 'nid' is preferred. And VMEMMAP prefers the node of 'nid' in both boot stage and memory hot adding. So seems no reason to not respect the node of 'nid' for the classic sparse when hot adding memory. Use kvmalloc_node instead to use the passed in 'nid'. Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Reviewed-by: Wei Yang Acked-by: Michal Hocko Acked-by: Pankaj Gupta Link: http://lkml.kernel.org/r/20200316125625.GH3486@MiWiFi-R3L-srv Signed-off-by: Linus Torvalds

mm/sparse.c: use kvmalloc/kvfree to alloc/free memmap for the classic sparse

2020-04-02T16:35:30Z

This change makes populate_section_memmap()/depopulate_section_memmap much simpler. Suggested-by: Michal Hocko Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: David Hildenbrand Reviewed-by: Pankaj Gupta Reviewed-by: Matthew Wilcox (Oracle) Reviewed-by: Wei Yang Acked-by: Michal Hocko Link: http://lkml.kernel.org/r/20200316125450.GG3486@MiWiFi-R3L-srv Signed-off-by: Linus Torvalds

mm/sparsemem: get address to page struct instead of address to pfn

2020-04-02T16:35:30Z

memmap should be the address to page struct instead of address to pfn. As mentioned by David, if system memory and devmem sit within a section, the mismatch address would lead kdump to dump unexpected memory. Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is valid to get the page struct address at this point. Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") Signed-off-by: Wei Yang Signed-off-by: Andrew Morton Acked-by: David Hildenbrand Cc: Dan Williams Cc: Baoquan He Link: http://lkml.kernel.org/r/20200210005048.10437-1-richardw.yang@linux.intel.com Signed-off-by: Linus Torvalds

mm/sparse: fix kernel crash with pfn_section_valid check

2020-03-29T16:47:06Z

Fix the crash like this: BUG: Kernel NULL pointer dereference on read at 0x00000000 Faulting instruction address: 0xc000000000c3447c Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries CPU: 11 PID: 7519 Comm: lt-ndctl Not tainted 5.6.0-rc7-autotest #1 ... NIP [c000000000c3447c] vmemmap_populated+0x98/0xc0 LR [c000000000088354] vmemmap_free+0x144/0x320 Call Trace: section_deactivate+0x220/0x240 __remove_pages+0x118/0x170 arch_remove_memory+0x3c/0x150 memunmap_pages+0x1cc/0x2f0 devm_action_release+0x30/0x50 release_nodes+0x2f8/0x3e0 device_release_driver_internal+0x168/0x270 unbind_store+0x130/0x170 drv_attr_store+0x44/0x60 sysfs_kf_write+0x68/0x80 kernfs_fop_write+0x100/0x290 __vfs_write+0x3c/0x70 vfs_write+0xcc/0x240 ksys_write+0x7c/0x140 system_call+0x5c/0x68 The crash is due to NULL dereference at test_bit(idx, ms->usage->subsection_map); due to ms->usage = NULL in pfn_section_valid() With commit d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case") section_mem_map is set to NULL after depopulate_section_mem(). This was done so that pfn_page() can work correctly with kernel config that disables SPARSEMEM_VMEMMAP. With that config pfn_to_page does __section_mem_map_addr(__sec) + __pfn; where static inline struct page *__section_mem_map_addr(struct mem_section *section) { unsigned long map = section->section_mem_map; map &= SECTION_MAP_MASK; return (struct page *)map; } Now with SPASEMEM_VMEMAP enabled, mem_section->usage->subsection_map is used to check the pfn validity (pfn_valid()). Since section_deactivate release mem_section->usage if a section is fully deactivated, pfn_valid() check after a subsection_deactivate cause a kernel crash. static inline int pfn_valid(unsigned long pfn) { ... return early_section(ms) || pfn_section_valid(ms, pfn); } where static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) { int idx = subsection_map_index(pfn); return test_bit(idx, ms->usage->subsection_map); } Avoid this by clearing SECTION_HAS_MEM_MAP when mem_section->usage is freed. For architectures like ppc64 where large pages are used for vmmemap mapping (16MB), a specific vmemmap mapping can cover multiple sections. Hence before a vmemmap mapping page can be freed, the kernel needs to make sure there are no valid sections within that mapping. Clearing the section valid bit before depopulate_section_memap enables this. [aneesh.kumar@linux.ibm.com: add comment] Link: http://lkml.kernel.org/r/20200326133235.343616-1-aneesh.kumar@linux.ibm.comLink: http://lkml.kernel.org/r/20200325031914.107660-1-aneesh.kumar@linux.ibm.com Fixes: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case") Reported-by: Sachin Sant Signed-off-by: Aneesh Kumar K.V Signed-off-by: Andrew Morton Tested-by: Sachin Sant Reviewed-by: Baoquan He Reviewed-by: Wei Yang Acked-by: Michal Hocko Acked-by: Pankaj Gupta Cc: Michael Ellerman Cc: Dan Williams Cc: David Hildenbrand Cc: Oscar Salvador Cc: Mike Rapoport Cc: Signed-off-by: Linus Torvalds

mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case

2020-03-22T01:56:06Z

In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It causes a hot remove failure: kernel BUG at mm/page_alloc.c:4806! invalid opcode: 0000 [#1] SMP PTI CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G W 5.5.0-next-20200205+ #340 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 Workqueue: kacpi_hotplug acpi_hotplug_work_fn RIP: 0010:free_pages+0x85/0xa0 Call Trace: __remove_pages+0x99/0xc0 arch_remove_memory+0x23/0x4d try_remove_memory+0xc8/0x130 __remove_memory+0xa/0x11 acpi_memory_device_remove+0x72/0x100 acpi_bus_trim+0x55/0x90 acpi_device_hotplug+0x2eb/0x3d0 acpi_hotplug_work_fn+0x1a/0x30 process_one_work+0x1a7/0x370 worker_thread+0x30/0x380 kthread+0x112/0x130 ret_from_fork+0x35/0x40 Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it. [akpm@linux-foundation.org: remove unneeded initialization, per David] Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") Signed-off-by: Baoquan He Signed-off-by: Andrew Morton Reviewed-by: Pankaj Gupta Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Cc: Wei Yang Cc: Oscar Salvador Cc: Mike Rapoport Cc: Link: http://lkml.kernel.org/r/20200307084229.28251-2-bhe@redhat.com Signed-off-by: Linus Torvalds