diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 935ec5829be9..3628fb5b2a28 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -25,8 +25,8 @@ * * @remap_pte: called for each lowest-level entry (PTE). * @nr_walked: the number of walked pte. - * @reuse_page: the page which is reused for the tail vmemmap pages. - * @reuse_addr: the virtual address of the @reuse_page page. + * @vmemmap_head: the page to be installed as first in the vmemmap range + * @vmemmap_tail: the page to be installed as non-first in the vmemmap range * @vmemmap_pages: the list head of the vmemmap pages that can be freed * or is mapped from. * @flags: used to modify behavior in vmemmap page table walking @@ -35,11 +35,13 @@ struct vmemmap_remap_walk { void (*remap_pte)(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk); + unsigned long nr_walked; - struct page *reuse_page; - unsigned long reuse_addr; + struct page *vmemmap_head; + struct page *vmemmap_tail; struct list_head *vmemmap_pages; + /* Skip the TLB flush when we split the PMD */ #define VMEMMAP_SPLIT_NO_TLB_FLUSH BIT(0) /* Skip the TLB flush when we remap the PTE */ @@ -141,14 +143,7 @@ static int vmemmap_pte_entry(pte_t *pte, unsigned long addr, { struct vmemmap_remap_walk *vmemmap_walk = walk->private; - /* - * The reuse_page is found 'first' in page table walking before - * starting remapping. - */ - if (!vmemmap_walk->reuse_page) - vmemmap_walk->reuse_page = pte_page(ptep_get(pte)); - else - vmemmap_walk->remap_pte(pte, addr, vmemmap_walk); + vmemmap_walk->remap_pte(pte, addr, vmemmap_walk); vmemmap_walk->nr_walked++; return 0; @@ -208,18 +203,12 @@ static void free_vmemmap_page_list(struct list_head *list) static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk) { - /* - * Remap the tail pages as read-only to catch illegal write operation - * to the tail pages. - */ - pgprot_t pgprot = PAGE_KERNEL_RO; struct page *page = pte_page(ptep_get(pte)); pte_t entry; /* Remapping the head page requires r/w */ - if (unlikely(addr == walk->reuse_addr)) { - pgprot = PAGE_KERNEL; - list_del(&walk->reuse_page->lru); + if (unlikely(walk->nr_walked == 0 && walk->vmemmap_head)) { + list_del(&walk->vmemmap_head->lru); /* * Makes sure that preceding stores to the page contents from @@ -227,53 +216,50 @@ static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, * write. */ smp_wmb(); + + entry = mk_pte(walk->vmemmap_head, PAGE_KERNEL); + } else { + /* + * Remap the tail pages as read-only to catch illegal write + * operation to the tail pages. + */ + entry = mk_pte(walk->vmemmap_tail, PAGE_KERNEL_RO); } - entry = mk_pte(walk->reuse_page, pgprot); list_add(&page->lru, walk->vmemmap_pages); set_pte_at(&init_mm, addr, pte, entry); } -/* - * How many struct page structs need to be reset. When we reuse the head - * struct page, the special metadata (e.g. page->flags or page->mapping) - * cannot copy to the tail struct page structs. The invalid value will be - * checked in the free_tail_page_prepare(). In order to avoid the message - * of "corrupted mapping in tail page". We need to reset at least 4 (one - * head struct page struct and three tail struct page structs) struct page - * structs. - */ -#define NR_RESET_STRUCT_PAGE 4 - -static inline void reset_struct_pages(struct page *start) -{ - struct page *from = start + NR_RESET_STRUCT_PAGE; - - BUILD_BUG_ON(NR_RESET_STRUCT_PAGE * 2 > PAGE_SIZE / sizeof(struct page)); - memcpy(start, from, sizeof(*from) * NR_RESET_STRUCT_PAGE); -} - static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk) { - pgprot_t pgprot = PAGE_KERNEL; struct page *page; - void *to; - - BUG_ON(pte_page(ptep_get(pte)) != walk->reuse_page); + struct page *from, *to; page = list_first_entry(walk->vmemmap_pages, struct page, lru); list_del(&page->lru); + + /* + * Initialize tail pages in the newly allocated vmemmap page. + * + * There is folio-scope metadata that is encoded in the first few + * tail pages. + * + * Use the value last tail page in the page with the head page + * to initialize the rest of tail pages. + */ + from = compound_head((struct page *)addr) + + PAGE_SIZE / sizeof(struct page) - 1; to = page_to_virt(page); - copy_page(to, (void *)walk->reuse_addr); - reset_struct_pages(to); + for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++, to++) + *to = *from; /* * Makes sure that preceding stores to the page contents become visible * before the set_pte_at() write. */ smp_wmb(); - set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot)); + set_pte_at(&init_mm, addr, pte, mk_pte(page, PAGE_KERNEL)); } /** @@ -283,33 +269,28 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. - * @reuse: reuse address. - * * Return: %0 on success, negative error code otherwise. */ -static int vmemmap_remap_split(unsigned long start, unsigned long end, - unsigned long reuse) +static int vmemmap_remap_split(unsigned long start, unsigned long end) { struct vmemmap_remap_walk walk = { .remap_pte = NULL, .flags = VMEMMAP_SPLIT_NO_TLB_FLUSH, }; - /* See the comment in the vmemmap_remap_free(). */ - BUG_ON(start - reuse != PAGE_SIZE); - - return vmemmap_remap_range(reuse, end, &walk); + return vmemmap_remap_range(start, end, &walk); } /** * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end) - * to the page which @reuse is mapped to, then free vmemmap - * which the range are mapped to. + * to use @vmemmap_head/tail, then free vmemmap which + * the range are mapped to. * @start: start address of the vmemmap virtual address range that we want * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. - * @reuse: reuse address. + * @vmemmap_head: the page to be installed as first in the vmemmap range + * @vmemmap_tail: the page to be installed as non-first in the vmemmap range * @vmemmap_pages: list to deposit vmemmap pages to be freed. It is callers * responsibility to free pages. * @flags: modifications to vmemmap_remap_walk flags @@ -317,69 +298,38 @@ static int vmemmap_remap_split(unsigned long start, unsigned long end, * Return: %0 on success, negative error code otherwise. */ static int vmemmap_remap_free(unsigned long start, unsigned long end, - unsigned long reuse, + struct page *vmemmap_head, + struct page *vmemmap_tail, struct list_head *vmemmap_pages, unsigned long flags) { int ret; struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_remap_pte, - .reuse_addr = reuse, + .vmemmap_head = vmemmap_head, + .vmemmap_tail = vmemmap_tail, .vmemmap_pages = vmemmap_pages, .flags = flags, }; - int nid = page_to_nid((struct page *)reuse); - gfp_t gfp_mask = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN; + + ret = vmemmap_remap_range(start, end, &walk); + if (!ret || !walk.nr_walked) + return ret; + + end = start + walk.nr_walked * PAGE_SIZE; /* - * Allocate a new head vmemmap page to avoid breaking a contiguous - * block of struct page memory when freeing it back to page allocator - * in free_vmemmap_page_list(). This will allow the likely contiguous - * struct page backing memory to be kept contiguous and allowing for - * more allocations of hugepages. Fallback to the currently - * mapped head page in case should it fail to allocate. + * vmemmap_pages contains pages from the previous vmemmap_remap_range() + * call which failed. These are pages which were removed from + * the vmemmap. They will be restored in the following call. */ - walk.reuse_page = alloc_pages_node(nid, gfp_mask, 0); - if (walk.reuse_page) { - copy_page(page_to_virt(walk.reuse_page), - (void *)walk.reuse_addr); - list_add(&walk.reuse_page->lru, vmemmap_pages); - memmap_pages_add(1); - } + walk = (struct vmemmap_remap_walk) { + .remap_pte = vmemmap_restore_pte, + .vmemmap_pages = vmemmap_pages, + .flags = 0, + }; - /* - * In order to make remapping routine most efficient for the huge pages, - * the routine of vmemmap page table walking has the following rules - * (see more details from the vmemmap_pte_range()): - * - * - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE) - * should be continuous. - * - The @reuse address is part of the range [@reuse, @end) that we are - * walking which is passed to vmemmap_remap_range(). - * - The @reuse address is the first in the complete range. - * - * So we need to make sure that @start and @reuse meet the above rules. - */ - BUG_ON(start - reuse != PAGE_SIZE); - - ret = vmemmap_remap_range(reuse, end, &walk); - if (ret && walk.nr_walked) { - end = reuse + walk.nr_walked * PAGE_SIZE; - /* - * vmemmap_pages contains pages from the previous - * vmemmap_remap_range call which failed. These - * are pages which were removed from the vmemmap. - * They will be restored in the following call. - */ - walk = (struct vmemmap_remap_walk) { - .remap_pte = vmemmap_restore_pte, - .reuse_addr = reuse, - .vmemmap_pages = vmemmap_pages, - .flags = 0, - }; - - vmemmap_remap_range(reuse, end, &walk); - } + vmemmap_remap_range(start, end, &walk); return ret; } @@ -416,29 +366,24 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end, * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. - * @reuse: reuse address. * @flags: modifications to vmemmap_remap_walk flags * * Return: %0 on success, negative error code otherwise. */ static int vmemmap_remap_alloc(unsigned long start, unsigned long end, - unsigned long reuse, unsigned long flags) + unsigned long flags) { LIST_HEAD(vmemmap_pages); struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_restore_pte, - .reuse_addr = reuse, .vmemmap_pages = &vmemmap_pages, .flags = flags, }; - /* See the comment in the vmemmap_remap_free(). */ - BUG_ON(start - reuse != PAGE_SIZE); - if (alloc_vmemmap_page_list(start, end, &vmemmap_pages)) return -ENOMEM; - return vmemmap_remap_range(reuse, end, &walk); + return vmemmap_remap_range(start, end, &walk); } DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key); @@ -455,8 +400,7 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h, struct folio *folio, unsigned long flags) { int ret; - unsigned long vmemmap_start = (unsigned long)&folio->page, vmemmap_end; - unsigned long vmemmap_reuse; + unsigned long vmemmap_start, vmemmap_end; VM_WARN_ON_ONCE_FOLIO(!folio_test_hugetlb(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_ref_count(folio), folio); @@ -467,18 +411,18 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h, if (flags & VMEMMAP_SYNCHRONIZE_RCU) synchronize_rcu(); + vmemmap_start = (unsigned long)&folio->page; vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h); - vmemmap_reuse = vmemmap_start; + vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE; /* * The pages which the vmemmap virtual address range [@vmemmap_start, - * @vmemmap_end) are mapped to are freed to the buddy allocator, and - * the range is mapped to the page which @vmemmap_reuse is mapped to. + * @vmemmap_end) are mapped to are freed to the buddy allocator. * When a HugeTLB page is freed to the buddy allocator, previously * discarded vmemmap pages must be allocated and remapping. */ - ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse, flags); + ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, flags); if (!ret) { folio_clear_hugetlb_vmemmap_optimized(folio); static_branch_dec(&hugetlb_optimize_vmemmap_key); @@ -566,9 +510,9 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct list_head *vmemmap_pages, unsigned long flags) { - int ret = 0; - unsigned long vmemmap_start = (unsigned long)&folio->page, vmemmap_end; - unsigned long vmemmap_reuse; + unsigned long vmemmap_start, vmemmap_end; + struct page *vmemmap_head, *vmemmap_tail; + int nid, ret = 0; VM_WARN_ON_ONCE_FOLIO(!folio_test_hugetlb(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_ref_count(folio), folio); @@ -593,18 +537,30 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h, */ folio_set_hugetlb_vmemmap_optimized(folio); + nid = folio_nid(folio); + vmemmap_head = alloc_pages_node(nid, GFP_KERNEL, 0); + if (!vmemmap_head) { + ret = -ENOMEM; + goto out; + } + + copy_page(page_to_virt(vmemmap_head), folio); + list_add(&vmemmap_head->lru, vmemmap_pages); + memmap_pages_add(1); + + vmemmap_tail = vmemmap_head; + vmemmap_start = (unsigned long)&folio->page; vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h); - vmemmap_reuse = vmemmap_start; - vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE; /* - * Remap the vmemmap virtual address range [@vmemmap_start, @vmemmap_end) - * to the page which @vmemmap_reuse is mapped to. Add pages previously - * mapping the range to vmemmap_pages list so that they can be freed by - * the caller. + * Remap the vmemmap virtual address range [@vmemmap_start, @vmemmap_end). + * Add pages previously mapping the range to vmemmap_pages list so that + * they can be freed by the caller. */ - ret = vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse, + ret = vmemmap_remap_free(vmemmap_start, vmemmap_end, + vmemmap_head, vmemmap_tail, vmemmap_pages, flags); +out: if (ret) { static_branch_dec(&hugetlb_optimize_vmemmap_key); folio_clear_hugetlb_vmemmap_optimized(folio); @@ -633,21 +589,19 @@ void hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio) static int hugetlb_vmemmap_split_folio(const struct hstate *h, struct folio *folio) { - unsigned long vmemmap_start = (unsigned long)&folio->page, vmemmap_end; - unsigned long vmemmap_reuse; + unsigned long vmemmap_start, vmemmap_end; if (!vmemmap_should_optimize_folio(h, folio)) return 0; + vmemmap_start = (unsigned long)&folio->page; vmemmap_end = vmemmap_start + hugetlb_vmemmap_size(h); - vmemmap_reuse = vmemmap_start; - vmemmap_start += HUGETLB_VMEMMAP_RESERVE_SIZE; /* * Split PMDs on the vmemmap virtual address range [@vmemmap_start, * @vmemmap_end] */ - return vmemmap_remap_split(vmemmap_start, vmemmap_end, vmemmap_reuse); + return vmemmap_remap_split(vmemmap_start, vmemmap_end); } static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,