Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Lockless get_user_pages_fast for s390 |
| 3 | * |
| 4 | * Copyright IBM Corp. 2010 |
| 5 | * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> |
| 6 | */ |
| 7 | #include <linux/sched.h> |
| 8 | #include <linux/mm.h> |
| 9 | #include <linux/hugetlb.h> |
| 10 | #include <linux/vmstat.h> |
| 11 | #include <linux/pagemap.h> |
| 12 | #include <linux/rwsem.h> |
| 13 | #include <asm/pgtable.h> |
| 14 | |
| 15 | /* |
| 16 | * The performance critical leaf functions are made noinline otherwise gcc |
| 17 | * inlines everything into a single function which results in too much |
| 18 | * register pressure. |
| 19 | */ |
| 20 | static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, |
| 21 | unsigned long end, int write, struct page **pages, int *nr) |
| 22 | { |
Gerald Schaefer | fc897c9 | 2016-03-17 15:00:04 +0100 | [diff] [blame] | 23 | struct page *head, *page; |
Martin Schwidefsky | 25591b0 | 2010-11-10 10:05:51 +0100 | [diff] [blame] | 24 | unsigned long mask; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 25 | pte_t *ptep, pte; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 26 | |
Martin Schwidefsky | e509861 | 2013-07-23 20:57:57 +0200 | [diff] [blame] | 27 | mask = (write ? _PAGE_PROTECT : 0) | _PAGE_INVALID | _PAGE_SPECIAL; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 28 | |
| 29 | ptep = ((pte_t *) pmd_deref(pmd)) + pte_index(addr); |
| 30 | do { |
| 31 | pte = *ptep; |
| 32 | barrier(); |
Gerald Schaefer | ecf46ab | 2015-05-29 15:34:51 +0200 | [diff] [blame] | 33 | /* Similar to the PMD case, NUMA hinting must take slow path */ |
| 34 | if (pte_protnone(pte)) |
| 35 | return 0; |
Martin Schwidefsky | 25591b0 | 2010-11-10 10:05:51 +0100 | [diff] [blame] | 36 | if ((pte_val(pte) & mask) != 0) |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 37 | return 0; |
| 38 | VM_BUG_ON(!pfn_valid(pte_pfn(pte))); |
| 39 | page = pte_page(pte); |
Gerald Schaefer | fc897c9 | 2016-03-17 15:00:04 +0100 | [diff] [blame] | 40 | head = compound_head(page); |
| 41 | if (!page_cache_get_speculative(head)) |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 42 | return 0; |
| 43 | if (unlikely(pte_val(pte) != pte_val(*ptep))) { |
Gerald Schaefer | fc897c9 | 2016-03-17 15:00:04 +0100 | [diff] [blame] | 44 | put_page(head); |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 45 | return 0; |
| 46 | } |
Gerald Schaefer | fc897c9 | 2016-03-17 15:00:04 +0100 | [diff] [blame] | 47 | VM_BUG_ON_PAGE(compound_head(page) != head, page); |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 48 | pages[*nr] = page; |
| 49 | (*nr)++; |
| 50 | |
| 51 | } while (ptep++, addr += PAGE_SIZE, addr != end); |
| 52 | |
| 53 | return 1; |
| 54 | } |
| 55 | |
| 56 | static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, |
| 57 | unsigned long end, int write, struct page **pages, int *nr) |
| 58 | { |
Kirill A. Shutemov | ddc58f2 | 2016-01-15 16:52:56 -0800 | [diff] [blame] | 59 | struct page *head, *page; |
Gerald Schaefer | 22338c5 | 2017-09-18 16:51:51 +0200 | [diff] [blame] | 60 | unsigned long mask; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 61 | int refs; |
| 62 | |
Gerald Schaefer | 22338c5 | 2017-09-18 16:51:51 +0200 | [diff] [blame] | 63 | mask = (write ? _SEGMENT_ENTRY_PROTECT : 0) | _SEGMENT_ENTRY_INVALID; |
| 64 | if ((pmd_val(pmd) & mask) != 0) |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 65 | return 0; |
| 66 | VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT)); |
| 67 | |
| 68 | refs = 0; |
| 69 | head = pmd_page(pmd); |
| 70 | page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); |
| 71 | do { |
| 72 | VM_BUG_ON(compound_head(page) != head); |
| 73 | pages[*nr] = page; |
| 74 | (*nr)++; |
| 75 | page++; |
| 76 | refs++; |
| 77 | } while (addr += PAGE_SIZE, addr != end); |
| 78 | |
| 79 | if (!page_cache_add_speculative(head, refs)) { |
| 80 | *nr -= refs; |
| 81 | return 0; |
| 82 | } |
| 83 | |
| 84 | if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) { |
| 85 | *nr -= refs; |
| 86 | while (refs--) |
| 87 | put_page(head); |
Andrea Arcangeli | 0693bc9 | 2011-11-02 13:37:28 -0700 | [diff] [blame] | 88 | return 0; |
| 89 | } |
| 90 | |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 91 | return 1; |
| 92 | } |
| 93 | |
| 94 | |
| 95 | static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, |
| 96 | unsigned long end, int write, struct page **pages, int *nr) |
| 97 | { |
| 98 | unsigned long next; |
| 99 | pmd_t *pmdp, pmd; |
| 100 | |
| 101 | pmdp = (pmd_t *) pudp; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 102 | if ((pud_val(pud) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3) |
| 103 | pmdp = (pmd_t *) pud_deref(pud); |
| 104 | pmdp += pmd_index(addr); |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 105 | do { |
| 106 | pmd = *pmdp; |
| 107 | barrier(); |
| 108 | next = pmd_addr_end(addr, end); |
Kirill A. Shutemov | fecffad | 2016-01-15 16:53:24 -0800 | [diff] [blame] | 109 | if (pmd_none(pmd)) |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 110 | return 0; |
Gerald Schaefer | 156152f | 2012-10-25 17:24:12 +0200 | [diff] [blame] | 111 | if (unlikely(pmd_large(pmd))) { |
Gerald Schaefer | ecf46ab | 2015-05-29 15:34:51 +0200 | [diff] [blame] | 112 | /* |
| 113 | * NUMA hinting faults need to be handled in the GUP |
| 114 | * slowpath for accounting purposes and so that they |
| 115 | * can be serialised against THP migration. |
| 116 | */ |
| 117 | if (pmd_protnone(pmd)) |
| 118 | return 0; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 119 | if (!gup_huge_pmd(pmdp, pmd, addr, next, |
| 120 | write, pages, nr)) |
| 121 | return 0; |
| 122 | } else if (!gup_pte_range(pmdp, pmd, addr, next, |
| 123 | write, pages, nr)) |
| 124 | return 0; |
| 125 | } while (pmdp++, addr = next, addr != end); |
| 126 | |
| 127 | return 1; |
| 128 | } |
| 129 | |
Gerald Schaefer | d08de8e | 2016-07-04 14:47:01 +0200 | [diff] [blame] | 130 | static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr, |
| 131 | unsigned long end, int write, struct page **pages, int *nr) |
| 132 | { |
| 133 | struct page *head, *page; |
| 134 | unsigned long mask; |
| 135 | int refs; |
| 136 | |
| 137 | mask = (write ? _REGION_ENTRY_PROTECT : 0) | _REGION_ENTRY_INVALID; |
| 138 | if ((pud_val(pud) & mask) != 0) |
| 139 | return 0; |
| 140 | VM_BUG_ON(!pfn_valid(pud_pfn(pud))); |
| 141 | |
| 142 | refs = 0; |
| 143 | head = pud_page(pud); |
| 144 | page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); |
| 145 | do { |
| 146 | VM_BUG_ON_PAGE(compound_head(page) != head, page); |
| 147 | pages[*nr] = page; |
| 148 | (*nr)++; |
| 149 | page++; |
| 150 | refs++; |
| 151 | } while (addr += PAGE_SIZE, addr != end); |
| 152 | |
| 153 | if (!page_cache_add_speculative(head, refs)) { |
| 154 | *nr -= refs; |
| 155 | return 0; |
| 156 | } |
| 157 | |
| 158 | if (unlikely(pud_val(pud) != pud_val(*pudp))) { |
| 159 | *nr -= refs; |
| 160 | while (refs--) |
| 161 | put_page(head); |
| 162 | return 0; |
| 163 | } |
| 164 | |
| 165 | return 1; |
| 166 | } |
| 167 | |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 168 | static inline int gup_pud_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, |
| 169 | unsigned long end, int write, struct page **pages, int *nr) |
| 170 | { |
| 171 | unsigned long next; |
| 172 | pud_t *pudp, pud; |
| 173 | |
| 174 | pudp = (pud_t *) pgdp; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 175 | if ((pgd_val(pgd) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R2) |
| 176 | pudp = (pud_t *) pgd_deref(pgd); |
| 177 | pudp += pud_index(addr); |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 178 | do { |
| 179 | pud = *pudp; |
| 180 | barrier(); |
| 181 | next = pud_addr_end(addr, end); |
| 182 | if (pud_none(pud)) |
| 183 | return 0; |
Gerald Schaefer | d08de8e | 2016-07-04 14:47:01 +0200 | [diff] [blame] | 184 | if (unlikely(pud_large(pud))) { |
| 185 | if (!gup_huge_pud(pudp, pud, addr, next, write, pages, |
| 186 | nr)) |
| 187 | return 0; |
| 188 | } else if (!gup_pmd_range(pudp, pud, addr, next, write, pages, |
| 189 | nr)) |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 190 | return 0; |
| 191 | } while (pudp++, addr = next, addr != end); |
| 192 | |
| 193 | return 1; |
| 194 | } |
| 195 | |
Gerald Schaefer | 34cda99 | 2012-09-04 15:37:55 +0200 | [diff] [blame] | 196 | /* |
| 197 | * Like get_user_pages_fast() except its IRQ-safe in that it won't fall |
| 198 | * back to the regular GUP. |
| 199 | */ |
| 200 | int __get_user_pages_fast(unsigned long start, int nr_pages, int write, |
| 201 | struct page **pages) |
| 202 | { |
| 203 | struct mm_struct *mm = current->mm; |
| 204 | unsigned long addr, len, end; |
| 205 | unsigned long next, flags; |
| 206 | pgd_t *pgdp, pgd; |
| 207 | int nr = 0; |
| 208 | |
| 209 | start &= PAGE_MASK; |
| 210 | addr = start; |
| 211 | len = (unsigned long) nr_pages << PAGE_SHIFT; |
| 212 | end = start + len; |
Heiko Carstens | eb0bf92 | 2013-10-08 09:29:09 +0200 | [diff] [blame] | 213 | if ((end <= start) || (end > TASK_SIZE)) |
Gerald Schaefer | 34cda99 | 2012-09-04 15:37:55 +0200 | [diff] [blame] | 214 | return 0; |
Heiko Carstens | 01997bb | 2013-10-07 16:14:50 +0200 | [diff] [blame] | 215 | /* |
| 216 | * local_irq_save() doesn't prevent pagetable teardown, but does |
| 217 | * prevent the pagetables from being freed on s390. |
| 218 | * |
| 219 | * So long as we atomically load page table pointers versus teardown, |
| 220 | * we can follow the address down to the the page and take a ref on it. |
| 221 | */ |
Gerald Schaefer | 34cda99 | 2012-09-04 15:37:55 +0200 | [diff] [blame] | 222 | local_irq_save(flags); |
| 223 | pgdp = pgd_offset(mm, addr); |
| 224 | do { |
| 225 | pgd = *pgdp; |
| 226 | barrier(); |
| 227 | next = pgd_addr_end(addr, end); |
| 228 | if (pgd_none(pgd)) |
| 229 | break; |
| 230 | if (!gup_pud_range(pgdp, pgd, addr, next, write, pages, &nr)) |
| 231 | break; |
| 232 | } while (pgdp++, addr = next, addr != end); |
| 233 | local_irq_restore(flags); |
| 234 | |
| 235 | return nr; |
| 236 | } |
| 237 | |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 238 | /** |
| 239 | * get_user_pages_fast() - pin user pages in memory |
| 240 | * @start: starting user address |
| 241 | * @nr_pages: number of pages from start to pin |
| 242 | * @write: whether pages will be written to |
| 243 | * @pages: array that receives pointers to the pages pinned. |
| 244 | * Should be at least nr_pages long. |
| 245 | * |
| 246 | * Attempt to pin user pages in memory without taking mm->mmap_sem. |
| 247 | * If not successful, it will fall back to taking the lock and |
| 248 | * calling get_user_pages(). |
| 249 | * |
| 250 | * Returns number of pages pinned. This may be fewer than the number |
| 251 | * requested. If nr_pages is 0 or negative, returns 0. If no pages |
| 252 | * were pinned, returns -errno. |
| 253 | */ |
| 254 | int get_user_pages_fast(unsigned long start, int nr_pages, int write, |
| 255 | struct page **pages) |
| 256 | { |
Heiko Carstens | 01997bb | 2013-10-07 16:14:50 +0200 | [diff] [blame] | 257 | int nr, ret; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 258 | |
David Hildenbrand | 40612351 | 2015-10-15 10:47:18 +0200 | [diff] [blame] | 259 | might_sleep(); |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 260 | start &= PAGE_MASK; |
Heiko Carstens | 01997bb | 2013-10-07 16:14:50 +0200 | [diff] [blame] | 261 | nr = __get_user_pages_fast(start, nr_pages, write, pages); |
| 262 | if (nr == nr_pages) |
| 263 | return nr; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 264 | |
Heiko Carstens | 01997bb | 2013-10-07 16:14:50 +0200 | [diff] [blame] | 265 | /* Try to get the remaining pages with get_user_pages */ |
| 266 | start += nr << PAGE_SHIFT; |
| 267 | pages += nr; |
Lorenzo Stoakes | c164154 | 2016-10-13 01:20:13 +0100 | [diff] [blame] | 268 | ret = get_user_pages_unlocked(start, nr_pages - nr, pages, |
| 269 | write ? FOLL_WRITE : 0); |
Heiko Carstens | 01997bb | 2013-10-07 16:14:50 +0200 | [diff] [blame] | 270 | /* Have to be a bit careful with return values */ |
| 271 | if (nr > 0) |
| 272 | ret = (ret < 0) ? nr : ret + nr; |
| 273 | return ret; |
Martin Schwidefsky | 8021714 | 2010-10-25 16:10:11 +0200 | [diff] [blame] | 274 | } |