From: "Aneesh Kumar K.V" aneesh.kumar@linux.ibm.com

[ Upstream commit 87a7ae75d7383afa998f57656d1d14e2a730cc47 ]

commit 4917f55b4ef9 ("mm/sparse-vmemmap: improve memory savings for compound devmaps") added support for using optimized vmmemap for devdax devices. But how vmemmap mappings are created are architecture specific. For example, powerpc with hash translation doesn't have vmemmap mappings in init_mm page table instead they are bolted table entries in the hardware page table

vmemmap_populate_compound_pages() used by vmemmap optimization code is not aware of these architecture-specific mapping. Hence allow architecture to opt for this feature. I selected architectures supporting HUGETLB_PAGE_OPTIMIZE_VMEMMAP option as also supporting this feature.

This patch fixes the below crash on ppc64.

BUG: Unable to handle kernel data access on write at 0xc00c000100400038 Faulting instruction address: 0xc000000001269d90 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 7 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc5-150500.34-default+ #2 5c90a668b6bbd142599890245c2fb5de19d7d28a Hardware name: IBM,9009-42G POWER9 (raw) 0x4e0202 0xf000005 of:IBM,FW950.40 (VL950_099) hv:phyp pSeries NIP: c000000001269d90 LR: c0000000004c57d4 CTR: 0000000000000000 REGS: c000000003632c30 TRAP: 0300 Not tainted (6.3.0-rc5-150500.34-default+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24842228 XER: 00000000 CFAR: c0000000004c57d0 DAR: c00c000100400038 DSISR: 42000000 IRQMASK: 0 .... NIP [c000000001269d90] __init_single_page.isra.74+0x14/0x4c LR [c0000000004c57d4] __init_zone_device_page+0x44/0xd0 Call Trace: [c000000003632ed0] [c000000003632f60] 0xc000000003632f60 (unreliable) [c000000003632f10] [c0000000004c5ca0] memmap_init_zone_device+0x170/0x250 [c000000003632fe0] [c0000000005575f8] memremap_pages+0x2c8/0x7f0 [c0000000036330c0] [c000000000557b5c] devm_memremap_pages+0x3c/0xa0 [c000000003633100] [c000000000d458a8] dev_dax_probe+0x108/0x3e0 [c0000000036331a0] [c000000000d41430] dax_bus_probe+0xb0/0x140 [c0000000036331d0] [c000000000cef27c] really_probe+0x19c/0x520 [c000000003633260] [c000000000cef6b4] __driver_probe_device+0xb4/0x230 [c0000000036332e0] [c000000000cef888] driver_probe_device+0x58/0x120 [c000000003633320] [c000000000cefa6c] __device_attach_driver+0x11c/0x1e0 [c0000000036333a0] [c000000000cebc58] bus_for_each_drv+0xa8/0x130 [c000000003633400] [c000000000ceefcc] __device_attach+0x15c/0x250 [c0000000036334a0] [c000000000ced458] bus_probe_device+0x108/0x110 [c0000000036334f0] [c000000000ce92dc] device_add+0x7fc/0xa10 [c0000000036335b0] [c000000000d447c8] devm_create_dev_dax+0x1d8/0x530 [c000000003633640] [c000000000d46b60] __dax_pmem_probe+0x200/0x270 [c0000000036337b0] [c000000000d46bf0] dax_pmem_probe+0x20/0x70 [c0000000036337d0] [c000000000d2279c] nvdimm_bus_probe+0xac/0x2b0 [c000000003633860] [c000000000cef27c] really_probe+0x19c/0x520 [c0000000036338f0] [c000000000cef6b4] __driver_probe_device+0xb4/0x230 [c000000003633970] [c000000000cef888] driver_probe_device+0x58/0x120 [c0000000036339b0] [c000000000cefd08] __driver_attach+0x1d8/0x240 [c000000003633a30] [c000000000cebb04] bus_for_each_dev+0xb4/0x130 [c000000003633a90] [c000000000cee564] driver_attach+0x34/0x50 [c000000003633ab0] [c000000000ced878] bus_add_driver+0x218/0x300 [c000000003633b40] [c000000000cf1144] driver_register+0xa4/0x1b0 [c000000003633bb0] [c000000000d21a0c] __nd_driver_register+0x5c/0x100 [c000000003633c10] [c00000000206a2e8] dax_pmem_init+0x34/0x48 [c000000003633c30] [c0000000000132d0] do_one_initcall+0x60/0x320 [c000000003633d00] [c0000000020051b0] kernel_init_freeable+0x360/0x400 [c000000003633de0] [c000000000013764] kernel_init+0x34/0x1d0 [c000000003633e50] [c00000000000de14] ret_from_kernel_thread+0x5c/0x64

The patch: 87a7ae75d738 ("mm/vmemmap/devdax: fix kernel crash when probing devdax devices") would apply cleanly on Linux 6.3.2 stable if all its dependencies were applied too: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c") 23baf831a32c ("mm, treewide: redefine MAX_ORDER sanely") 61883d3c3241 ("iommu: fix MAX_ORDER usage in __iommu_dma_alloc_pages()") 7a16d7c7619b ("mm/slub: fix MAX_ORDER usage in calculate_order()") 75558ad31548 ("sparc/mm: fix MAX_ORDER usage in tsb_grow()")

commit 87a7ae75d738 makes changes to 'mm/mm_init.c', of which the changed parts used to reside in 'mm/page_alloc.c', but were moved to 'mm/mm_init.c' by commit 9420f89db2dd. Hence, applying commit 9420f89db2dd atop the patch described below (if required in future) would create a conflict. commit 9420f89db2dd also included the changes made by commit 23baf831a32c to 'mm/page_alloc.c'. Hence, applying commit 23baf831a32c atop commit 9420f89db2dd or 87a7ae75d738 would also create a conflict.

Nevertheless, the patch below is an iteration of commit 87a7ae75d738 (changes made here in 'mm/init.c' were put in 'mm/page_alloc.c', where the code originally resided before commit 9420f89db2dd) and applies on Linux 6.3.2 stable."

Link: https://lkml.kernel.org/r/20230411142214.64464-1-aneesh.kumar@linux.ibm.com Fixes: 4917f55b4ef9 ("mm/sparse-vmemmap: improve memory savings for compound devmaps") Signed-off-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Reported-by: Tarun Sahu tsahu@linux.ibm.com Reviewed-by: Joao Martins joao.m.martins@oracle.com Cc: Muchun Song songmuchun@bytedance.com Cc: Dan Williams dan.j.williams@intel.com Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Piyush Sachdeva piyushs@linux.ibm.com (cherry picked from commit 87a7ae75d7383afa998f57656d1d14e2a730cc47) --- include/linux/mm.h | 16 ++++++++++++++++ mm/page_alloc.c | 10 ++++++---- mm/sparse-vmemmap.c | 3 +-- 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h index 1f79667824eb..ced82b9c18e5 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3425,6 +3425,22 @@ void vmemmap_populate_print_last(void); void vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap); #endif + +#ifdef CONFIG_ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, + struct dev_pagemap *pgmap) +{ + return is_power_of_2(sizeof(struct page)) && + pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap; +} +#else +static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, + struct dev_pagemap *pgmap) +{ + return false; +} +#endif + void register_page_bootmem_memmap(unsigned long section_nr, struct page *map, unsigned long nr_pages);

diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8e39705c7bdc..afcfb2a94e6e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6905,10 +6905,12 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, * of an altmap. See vmemmap_populate_compound_pages(). */ static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, - unsigned long nr_pages) + struct dev_pagemap *pgmap) { - return is_power_of_2(sizeof(struct page)) && - !altmap ? 2 * (PAGE_SIZE / sizeof(struct page)) : nr_pages; + if (!vmemmap_can_optimize(altmap, pgmap)) + return pgmap_vmemmap_nr(pgmap); + + return 2 * (PAGE_SIZE / sizeof(struct page)); }

static void __ref memmap_init_compound(struct page *head, @@ -6973,7 +6975,7 @@ void __ref memmap_init_zone_device(struct zone *zone, continue;

memmap_init_compound(page, pfn, zone_idx, nid, pgmap, - compound_nr_pages(altmap, pfns_per_compound)); + compound_nr_pages(altmap, pgmap)); }

pr_info("%s initialised %lu pages in %ums\n", __func__, diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index c5398a5960d0..10d73a0dfcec 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -458,8 +458,7 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn, !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) return NULL;

- if (is_power_of_2(sizeof(struct page)) && - pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap) + if (vmemmap_can_optimize(altmap, pgmap)) r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); else r = vmemmap_populate(start, end, nid, altmap);