+ Matthew Wilcox This was a rather tricky series to get the recipients correct for and my script did not realize that "supporter" was a pseudonym for "maintainer" so you were missed off the original post. Appologies! More context in cover letter: https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@xxxxxxx/ On 14/10/2024 11:58, Ryan Roberts wrote: > 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); >
