devm_memremap_pages() records mapped ranges in pgmap_radix with an entry per section's worth of memory (128MB). The key for each of those entries is a section number. This leads to false positives when devm_memremap_pages() is passed a section-unaligned range as lookups in the misalignment fail to return NULL. We can close this hole by using the pfn as the key for entries in the tree. The number of entries required to describe a remapped range is reduced by leveraging multi-order entries. In practice this approach usually yields just one entry in the tree if the size and starting address are of the same power-of-2 alignment. Previously we always needed nr_entries = mapping_size / 128MB. Link: https://lists.01.org/pipermail/linux-nvdimm/2016-August/006666.html Reported-by: Toshi Kani <toshi.kani@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- kernel/memremap.c | 52 ++++++++++++++++++++++++++++++++++++++-------------- mm/Kconfig | 1 + 2 files changed, 39 insertions(+), 14 deletions(-) diff --git a/kernel/memremap.c b/kernel/memremap.c index 9ecedc28b928..e0a2de6a168b 100644 --- a/kernel/memremap.c +++ b/kernel/memremap.c @@ -194,18 +194,41 @@ void put_zone_device_page(struct page *page) } EXPORT_SYMBOL(put_zone_device_page); -static void pgmap_radix_release(struct resource *res) +static unsigned long order_at(struct resource *res, unsigned long pgoff) { - resource_size_t key, align_start, align_size, align_end; + unsigned long phys_pgoff = PHYS_PFN(res->start) + pgoff; + unsigned long nr_pages, mask; - align_start = res->start & ~(SECTION_SIZE - 1); - align_size = ALIGN(resource_size(res), SECTION_SIZE); - align_end = align_start + align_size - 1; + nr_pages = PHYS_PFN(resource_size(res)); + if (nr_pages == pgoff) + return ULONG_MAX; + + /* + * What is the largest aligned power-of-2 range available from + * this resource pgoff to the end of the resource range, + * considering the alignment of the current pgoff? + */ + mask = phys_pgoff | rounddown_pow_of_two(nr_pages - pgoff); + if (!mask) + return ULONG_MAX; + + return find_first_bit(&mask, BITS_PER_LONG); +} + +#define foreach_order_pgoff(res, order, pgoff) \ + for (pgoff = 0, order = order_at((res), pgoff); order < ULONG_MAX; \ + pgoff += 1UL << order, order = order_at((res), pgoff)) + +static void pgmap_radix_release(struct resource *res) +{ + unsigned long pgoff, order; mutex_lock(&pgmap_lock); - for (key = res->start; key <= res->end; key += SECTION_SIZE) - radix_tree_delete(&pgmap_radix, key >> PA_SECTION_SHIFT); + foreach_order_pgoff(res, order, pgoff) + radix_tree_delete(&pgmap_radix, PHYS_PFN(res->start) + pgoff); mutex_unlock(&pgmap_lock); + + synchronize_rcu(); } static unsigned long pfn_first(struct page_map *page_map) @@ -262,7 +285,7 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys) WARN_ON_ONCE(!rcu_read_lock_held()); - page_map = radix_tree_lookup(&pgmap_radix, phys >> PA_SECTION_SHIFT); + page_map = radix_tree_lookup(&pgmap_radix, PHYS_PFN(phys)); return page_map ? &page_map->pgmap : NULL; } @@ -284,12 +307,12 @@ struct dev_pagemap *find_dev_pagemap(resource_size_t phys) void *devm_memremap_pages(struct device *dev, struct resource *res, struct percpu_ref *ref, struct vmem_altmap *altmap) { - resource_size_t key, align_start, align_size, align_end; + resource_size_t align_start, align_size, align_end; + unsigned long pfn, pgoff, order; pgprot_t pgprot = PAGE_KERNEL; struct dev_pagemap *pgmap; struct page_map *page_map; int error, nid, is_ram; - unsigned long pfn; align_start = res->start & ~(SECTION_SIZE - 1); align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE) @@ -328,11 +351,12 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, mutex_lock(&pgmap_lock); error = 0; align_end = align_start + align_size - 1; - for (key = align_start; key <= align_end; key += SECTION_SIZE) { + + foreach_order_pgoff(res, order, pgoff) { struct dev_pagemap *dup; rcu_read_lock(); - dup = find_dev_pagemap(key); + dup = find_dev_pagemap(res->start + PFN_PHYS(pgoff)); rcu_read_unlock(); if (dup) { dev_err(dev, "%s: %pr collides with mapping for %s\n", @@ -340,8 +364,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, error = -EBUSY; break; } - error = radix_tree_insert(&pgmap_radix, key >> PA_SECTION_SHIFT, - page_map); + error = __radix_tree_insert(&pgmap_radix, + PHYS_PFN(res->start) + pgoff, order, page_map); if (error) { dev_err(dev, "%s: failed: %d\n", __func__, error); break; diff --git a/mm/Kconfig b/mm/Kconfig index 9b8fccb969dc..4aff67e042f1 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -690,6 +690,7 @@ config ZONE_DEVICE depends on MEMORY_HOTREMOVE depends on SPARSEMEM_VMEMMAP depends on X86_64 #arch_add_memory() comprehends device memory + select RADIX_TREE_MULTIORDER help Device memory hotplug support allows for establishing pmem, -- 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>