To prepare for supporting boot-time page size selection, refactor code to remove assumptions about PAGE_SIZE being compile-time constant. Code intended to be equivalent when compile-time page size is active. Refactor "struct vmap_block" to use a flexible array for used_mmap since VMAP_BBMAP_BITS is not a compile time constant for the boot-time page size case. Update various BUILD_BUG_ON() instances to check against appropriate page size limit. Re-define "union swap_header" so that it's no longer exactly page-sized. Instead define a flexible "magic" array with a define which tells the offset to where the magic signature begins. Consider page size limit in some CPP condditionals. Wrap global variables that are initialized with PAGE_SIZE derived values using DEFINE_GLOBAL_PAGE_SIZE_VAR() so their initialization can be deferred for boot-time page size builds. Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> --- ***NOTE*** Any confused maintainers may want to read the cover note here for context: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ drivers/mtd/mtdswap.c | 4 ++-- include/linux/mm.h | 2 +- include/linux/mm_types_task.h | 2 +- include/linux/mmzone.h | 3 ++- include/linux/slab.h | 7 ++++--- include/linux/swap.h | 17 ++++++++++++----- include/linux/swapops.h | 6 +++++- mm/memcontrol.c | 2 +- mm/memory.c | 4 ++-- mm/mmap.c | 2 +- mm/page-writeback.c | 2 +- mm/slub.c | 2 +- mm/sparse.c | 2 +- mm/swapfile.c | 2 +- mm/vmalloc.c | 7 ++++--- 15 files changed, 39 insertions(+), 25 deletions(-) diff --git a/drivers/mtd/mtdswap.c b/drivers/mtd/mtdswap.c index 680366616da24..7412a32708114 100644 --- a/drivers/mtd/mtdswap.c +++ b/drivers/mtd/mtdswap.c @@ -1062,13 +1062,13 @@ static int mtdswap_auto_header(struct mtdswap_dev *d, char *buf) { union swap_header *hd = (union swap_header *)(buf); - memset(buf, 0, PAGE_SIZE - 10); + memset(buf, 0, SWAP_HEADER_MAGIC); hd->info.version = 1; hd->info.last_page = d->mbd_dev->size - 1; hd->info.nr_badpages = 0; - memcpy(buf + PAGE_SIZE - 10, "SWAPSPACE2", 10); + memcpy(buf + SWAP_HEADER_MAGIC, "SWAPSPACE2", 10); return 0; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 09a840517c23a..49c2078354e6e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2927,7 +2927,7 @@ static inline spinlock_t *pte_lockptr(struct mm_struct *mm, pmd_t *pmd) static inline spinlock_t *ptep_lockptr(struct mm_struct *mm, pte_t *pte) { BUILD_BUG_ON(IS_ENABLED(CONFIG_HIGHPTE)); - BUILD_BUG_ON(MAX_PTRS_PER_PTE * sizeof(pte_t) > PAGE_SIZE); + BUILD_BUG_ON(MAX_PTRS_PER_PTE * sizeof(pte_t) > PAGE_SIZE_MAX); return ptlock_ptr(virt_to_ptdesc(pte)); } diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h index a2f6179b672b8..c356897d5f41c 100644 --- a/include/linux/mm_types_task.h +++ b/include/linux/mm_types_task.h @@ -37,7 +37,7 @@ struct page; struct page_frag { struct page *page; -#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536) +#if (BITS_PER_LONG > 32) || (PAGE_SIZE_MAX >= 65536) __u32 offset; __u32 size; #else diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 1dc6248feb832..cd58034b82c81 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1744,6 +1744,7 @@ static inline bool movable_only_nodes(nodemask_t *nodes) */ #define PA_SECTION_SHIFT (SECTION_SIZE_BITS) #define PFN_SECTION_SHIFT (SECTION_SIZE_BITS - PAGE_SHIFT) +#define PFN_SECTION_SHIFT_MIN (SECTION_SIZE_BITS - PAGE_SHIFT_MAX) #define NR_MEM_SECTIONS (1UL << SECTIONS_SHIFT) @@ -1753,7 +1754,7 @@ static inline bool movable_only_nodes(nodemask_t *nodes) #define SECTION_BLOCKFLAGS_BITS \ ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS) -#if (MAX_PAGE_ORDER + PAGE_SHIFT) > SECTION_SIZE_BITS +#if (MAX_PAGE_ORDER + PAGE_SHIFT_MAX) > SECTION_SIZE_BITS #error Allocator MAX_PAGE_ORDER exceeds SECTION_SIZE #endif diff --git a/include/linux/slab.h b/include/linux/slab.h index eb2bf46291576..11c6ff3a12579 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -347,7 +347,7 @@ static inline unsigned int arch_slab_minalign(void) */ #define __assume_kmalloc_alignment __assume_aligned(ARCH_KMALLOC_MINALIGN) #define __assume_slab_alignment __assume_aligned(ARCH_SLAB_MINALIGN) -#define __assume_page_alignment __assume_aligned(PAGE_SIZE) +#define __assume_page_alignment __assume_aligned(PAGE_SIZE_MIN) /* * Kmalloc array related definitions @@ -358,6 +358,7 @@ static inline unsigned int arch_slab_minalign(void) * (PAGE_SIZE*2). Larger requests are passed to the page allocator. */ #define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1) +#define KMALLOC_SHIFT_HIGH_MAX (PAGE_SHIFT_MAX + 1) #define KMALLOC_SHIFT_MAX (MAX_PAGE_ORDER + PAGE_SHIFT) #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 3 @@ -426,7 +427,7 @@ enum kmalloc_cache_type { NR_KMALLOC_TYPES }; -typedef struct kmem_cache * kmem_buckets[KMALLOC_SHIFT_HIGH + 1]; +typedef struct kmem_cache * kmem_buckets[KMALLOC_SHIFT_HIGH_MAX + 1]; extern kmem_buckets kmalloc_caches[NR_KMALLOC_TYPES]; @@ -524,7 +525,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size, /* Will never be reached. Needed because the compiler may complain */ return -1; } -static_assert(PAGE_SHIFT <= 20); +static_assert(PAGE_SHIFT_MAX <= 20); #define kmalloc_index(s) __kmalloc_index(s, true) #include <linux/alloc_tag.h> diff --git a/include/linux/swap.h b/include/linux/swap.h index ba7ea95d1c57a..e85df0332979f 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -132,10 +132,17 @@ static inline int current_is_kswapd(void) * bootbits... */ union swap_header { - struct { - char reserved[PAGE_SIZE - 10]; - char magic[10]; /* SWAP-SPACE or SWAPSPACE2 */ - } magic; + /* + * Exists conceptually, but since PAGE_SIZE may not be known at compile + * time, we must access through pointer arithmetic at run time. + * + * struct { + * char reserved[PAGE_SIZE - 10]; + * char magic[10]; SWAP-SPACE or SWAPSPACE2 + * } magic; + */ +#define SWAP_HEADER_MAGIC (PAGE_SIZE - 10) + char magic[1]; struct { char bootbits[1024]; /* Space for disklabel etc. */ __u32 version; @@ -201,7 +208,7 @@ struct swap_extent { * Max bad pages in the new format.. */ #define MAX_SWAP_BADPAGES \ - ((offsetof(union swap_header, magic.magic) - \ + ((SWAP_HEADER_MAGIC - \ offsetof(union swap_header, info.badpages)) / sizeof(int)) enum { diff --git a/include/linux/swapops.h b/include/linux/swapops.h index cb468e418ea11..890fe6a3e6702 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -34,10 +34,14 @@ */ #ifdef MAX_PHYSMEM_BITS #define SWP_PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT) +#define SWP_PFN_BITS_MAX (MAX_PHYSMEM_BITS - PAGE_SHIFT_MIN) #else /* MAX_PHYSMEM_BITS */ #define SWP_PFN_BITS min_t(int, \ sizeof(phys_addr_t) * 8 - PAGE_SHIFT, \ SWP_TYPE_SHIFT) +#define SWP_PFN_BITS_MAX min_t(int, \ + sizeof(phys_addr_t) * 8 - PAGE_SHIFT_MIN, \ + SWP_TYPE_SHIFT) #endif /* MAX_PHYSMEM_BITS */ #define SWP_PFN_MASK (BIT(SWP_PFN_BITS) - 1) @@ -519,7 +523,7 @@ static inline struct folio *pfn_swap_entry_folio(swp_entry_t entry) static inline bool is_pfn_swap_entry(swp_entry_t entry) { /* Make sure the swp offset can always store the needed fields */ - BUILD_BUG_ON(SWP_TYPE_SHIFT < SWP_PFN_BITS); + BUILD_BUG_ON(SWP_TYPE_SHIFT < SWP_PFN_BITS_MAX); return is_migration_entry(entry) || is_device_private_entry(entry) || is_device_exclusive_entry(entry) || is_hwpoison_entry(entry); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c5f9195f76c65..4b17bec566fbd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4881,7 +4881,7 @@ static int __init mem_cgroup_init(void) * to work fine, we should make sure that the overfill threshold can't * exceed S32_MAX / PAGE_SIZE. */ - BUILD_BUG_ON(MEMCG_CHARGE_BATCH > S32_MAX / PAGE_SIZE); + BUILD_BUG_ON(MEMCG_CHARGE_BATCH > S32_MAX / PAGE_SIZE_MIN); cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL, memcg_hotplug_cpu_dead); diff --git a/mm/memory.c b/mm/memory.c index ebfc9768f801a..14b5ef6870486 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4949,8 +4949,8 @@ vm_fault_t finish_fault(struct vm_fault *vmf) return ret; } -static unsigned long fault_around_pages __read_mostly = - 65536 >> PAGE_SHIFT; +static __DEFINE_GLOBAL_PAGE_SIZE_VAR(unsigned long, fault_around_pages, + __read_mostly, 65536 >> PAGE_SHIFT); #ifdef CONFIG_DEBUG_FS static int fault_around_bytes_get(void *data, u64 *val) diff --git a/mm/mmap.c b/mm/mmap.c index d0dfc85b209bb..d9642aba07ac4 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2279,7 +2279,7 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address) } /* enforced gap between the expanding stack and other mappings. */ -unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT; +DEFINE_GLOBAL_PAGE_SIZE_VAR(unsigned long, stack_guard_gap, 256UL<<PAGE_SHIFT); static int __init cmdline_parse_stack_guard_gap(char *p) { diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4430ac68e4c41..8fc9ac50749bd 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2292,7 +2292,7 @@ static int page_writeback_cpu_online(unsigned int cpu) #ifdef CONFIG_SYSCTL /* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */ -static const unsigned long dirty_bytes_min = 2 * PAGE_SIZE; +static DEFINE_GLOBAL_PAGE_SIZE_VAR_CONST(unsigned long, dirty_bytes_min, 2 * PAGE_SIZE); static struct ctl_table vm_page_writeback_sysctls[] = { { diff --git a/mm/slub.c b/mm/slub.c index a77f354f83251..82f6e98cf25bb 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -5001,7 +5001,7 @@ init_kmem_cache_node(struct kmem_cache_node *n) static inline int alloc_kmem_cache_cpus(struct kmem_cache *s) { BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE < - NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * + NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH_MAX * sizeof(struct kmem_cache_cpu)); /* diff --git a/mm/sparse.c b/mm/sparse.c index dc38539f85603..2491425930c4d 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -277,7 +277,7 @@ static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long p { unsigned long coded_mem_map = (unsigned long)(mem_map - (section_nr_to_pfn(pnum))); - BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT); + BUILD_BUG_ON(SECTION_MAP_LAST_BIT > PFN_SECTION_SHIFT_MIN); BUG_ON(coded_mem_map & ~SECTION_MAP_MASK); return coded_mem_map; } diff --git a/mm/swapfile.c b/mm/swapfile.c index 38bdc439651ac..6311a1cc7e46b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2931,7 +2931,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p, unsigned long swapfilepages; unsigned long last_page; - if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { + if (memcmp("SWAPSPACE2", &swap_header->magic[SWAP_HEADER_MAGIC], 10)) { pr_err("Unable to find swap-space signature\n"); return 0; } diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a0df1e2e155a8..b4fbba204603c 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2497,12 +2497,12 @@ struct vmap_block { spinlock_t lock; struct vmap_area *va; unsigned long free, dirty; - DECLARE_BITMAP(used_map, VMAP_BBMAP_BITS); unsigned long dirty_min, dirty_max; /*< dirty range */ struct list_head free_list; struct rcu_head rcu_head; struct list_head purge; unsigned int cpu; + unsigned long used_map[]; }; /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */ @@ -2600,11 +2600,12 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) unsigned long vb_idx; int node, err; void *vaddr; + size_t size; node = numa_node_id(); - vb = kmalloc_node(sizeof(struct vmap_block), - gfp_mask & GFP_RECLAIM_MASK, node); + size = struct_size(vb, used_map, BITS_TO_LONGS(VMAP_BBMAP_BITS)); + vb = kmalloc_node(size, gfp_mask & GFP_RECLAIM_MASK, node); if (unlikely(!vb)) return ERR_PTR(-ENOMEM); -- 2.43.0
