Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * mm/rmap.c - physical to virtual reverse mappings |
| 3 | * |
| 4 | * Copyright 2001, Rik van Riel <riel@conectiva.com.br> |
| 5 | * Released under the General Public License (GPL). |
| 6 | * |
| 7 | * Simple, low overhead reverse mapping scheme. |
| 8 | * Please try to keep this thing as modular as possible. |
| 9 | * |
| 10 | * Provides methods for unmapping each kind of mapped page: |
| 11 | * the anon methods track anonymous pages, and |
| 12 | * the file methods track pages belonging to an inode. |
| 13 | * |
| 14 | * Original design by Rik van Riel <riel@conectiva.com.br> 2001 |
| 15 | * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004 |
| 16 | * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004 |
| 17 | * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004 |
| 18 | */ |
| 19 | |
| 20 | /* |
| 21 | * Lock ordering in mm: |
| 22 | * |
Jes Sorensen | 1b1dcc1 | 2006-01-09 15:59:24 -0800 | [diff] [blame] | 23 | * inode->i_mutex (while writing or truncating, not reading or faulting) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 24 | * inode->i_alloc_sem |
| 25 | * |
| 26 | * When a page fault occurs in writing from user to file, down_read |
Jes Sorensen | 1b1dcc1 | 2006-01-09 15:59:24 -0800 | [diff] [blame] | 27 | * of mmap_sem nests within i_mutex; in sys_msync, i_mutex nests within |
| 28 | * down_read of mmap_sem; i_mutex and down_write of mmap_sem are never |
| 29 | * taken together; in truncation, i_mutex is taken outermost. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 30 | * |
| 31 | * mm->mmap_sem |
| 32 | * page->flags PG_locked (lock_page) |
| 33 | * mapping->i_mmap_lock |
| 34 | * anon_vma->lock |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 35 | * mm->page_table_lock or pte_lock |
Nick Piggin | 053837f | 2006-01-18 17:42:27 -0800 | [diff] [blame] | 36 | * zone->lru_lock (in mark_page_accessed, isolate_lru_page) |
Hugh Dickins | 5d337b9 | 2005-09-03 15:54:41 -0700 | [diff] [blame] | 37 | * swap_lock (in swap_duplicate, swap_info_get) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 38 | * mmlist_lock (in mmput, drain_mmlist and others) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 39 | * mapping->private_lock (in __set_page_dirty_buffers) |
| 40 | * inode_lock (in set_page_dirty's __mark_inode_dirty) |
| 41 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
| 42 | * mapping->tree_lock (widely used, in set_page_dirty, |
| 43 | * in arch-dependent flush_dcache_mmap_lock, |
| 44 | * within inode_lock in __sync_single_inode) |
| 45 | */ |
| 46 | |
| 47 | #include <linux/mm.h> |
| 48 | #include <linux/pagemap.h> |
| 49 | #include <linux/swap.h> |
| 50 | #include <linux/swapops.h> |
| 51 | #include <linux/slab.h> |
| 52 | #include <linux/init.h> |
| 53 | #include <linux/rmap.h> |
| 54 | #include <linux/rcupdate.h> |
Christoph Lameter | a48d07a | 2006-02-01 03:05:38 -0800 | [diff] [blame] | 55 | #include <linux/module.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 56 | |
| 57 | #include <asm/tlbflush.h> |
| 58 | |
Pekka Enberg | fcc234f | 2006-03-22 00:08:13 -0800 | [diff] [blame] | 59 | struct kmem_cache *anon_vma_cachep; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 60 | |
| 61 | static inline void validate_anon_vma(struct vm_area_struct *find_vma) |
| 62 | { |
Nick Piggin | b7ab795 | 2006-03-22 00:08:42 -0800 | [diff] [blame] | 63 | #ifdef CONFIG_DEBUG_VM |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 64 | struct anon_vma *anon_vma = find_vma->anon_vma; |
| 65 | struct vm_area_struct *vma; |
| 66 | unsigned int mapcount = 0; |
| 67 | int found = 0; |
| 68 | |
| 69 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { |
| 70 | mapcount++; |
| 71 | BUG_ON(mapcount > 100000); |
| 72 | if (vma == find_vma) |
| 73 | found = 1; |
| 74 | } |
| 75 | BUG_ON(!found); |
| 76 | #endif |
| 77 | } |
| 78 | |
| 79 | /* This must be called under the mmap_sem. */ |
| 80 | int anon_vma_prepare(struct vm_area_struct *vma) |
| 81 | { |
| 82 | struct anon_vma *anon_vma = vma->anon_vma; |
| 83 | |
| 84 | might_sleep(); |
| 85 | if (unlikely(!anon_vma)) { |
| 86 | struct mm_struct *mm = vma->vm_mm; |
| 87 | struct anon_vma *allocated, *locked; |
| 88 | |
| 89 | anon_vma = find_mergeable_anon_vma(vma); |
| 90 | if (anon_vma) { |
| 91 | allocated = NULL; |
| 92 | locked = anon_vma; |
| 93 | spin_lock(&locked->lock); |
| 94 | } else { |
| 95 | anon_vma = anon_vma_alloc(); |
| 96 | if (unlikely(!anon_vma)) |
| 97 | return -ENOMEM; |
| 98 | allocated = anon_vma; |
| 99 | locked = NULL; |
| 100 | } |
| 101 | |
| 102 | /* page_table_lock to protect against threads */ |
| 103 | spin_lock(&mm->page_table_lock); |
| 104 | if (likely(!vma->anon_vma)) { |
| 105 | vma->anon_vma = anon_vma; |
Christoph Lameter | 0697212 | 2006-06-23 02:03:35 -0700 | [diff] [blame] | 106 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 107 | allocated = NULL; |
| 108 | } |
| 109 | spin_unlock(&mm->page_table_lock); |
| 110 | |
| 111 | if (locked) |
| 112 | spin_unlock(&locked->lock); |
| 113 | if (unlikely(allocated)) |
| 114 | anon_vma_free(allocated); |
| 115 | } |
| 116 | return 0; |
| 117 | } |
| 118 | |
| 119 | void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next) |
| 120 | { |
| 121 | BUG_ON(vma->anon_vma != next->anon_vma); |
| 122 | list_del(&next->anon_vma_node); |
| 123 | } |
| 124 | |
| 125 | void __anon_vma_link(struct vm_area_struct *vma) |
| 126 | { |
| 127 | struct anon_vma *anon_vma = vma->anon_vma; |
| 128 | |
| 129 | if (anon_vma) { |
Christoph Lameter | 0697212 | 2006-06-23 02:03:35 -0700 | [diff] [blame] | 130 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 131 | validate_anon_vma(vma); |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | void anon_vma_link(struct vm_area_struct *vma) |
| 136 | { |
| 137 | struct anon_vma *anon_vma = vma->anon_vma; |
| 138 | |
| 139 | if (anon_vma) { |
| 140 | spin_lock(&anon_vma->lock); |
Christoph Lameter | 0697212 | 2006-06-23 02:03:35 -0700 | [diff] [blame] | 141 | list_add_tail(&vma->anon_vma_node, &anon_vma->head); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 142 | validate_anon_vma(vma); |
| 143 | spin_unlock(&anon_vma->lock); |
| 144 | } |
| 145 | } |
| 146 | |
| 147 | void anon_vma_unlink(struct vm_area_struct *vma) |
| 148 | { |
| 149 | struct anon_vma *anon_vma = vma->anon_vma; |
| 150 | int empty; |
| 151 | |
| 152 | if (!anon_vma) |
| 153 | return; |
| 154 | |
| 155 | spin_lock(&anon_vma->lock); |
| 156 | validate_anon_vma(vma); |
| 157 | list_del(&vma->anon_vma_node); |
| 158 | |
| 159 | /* We must garbage collect the anon_vma if it's empty */ |
| 160 | empty = list_empty(&anon_vma->head); |
| 161 | spin_unlock(&anon_vma->lock); |
| 162 | |
| 163 | if (empty) |
| 164 | anon_vma_free(anon_vma); |
| 165 | } |
| 166 | |
Pekka Enberg | fcc234f | 2006-03-22 00:08:13 -0800 | [diff] [blame] | 167 | static void anon_vma_ctor(void *data, struct kmem_cache *cachep, |
| 168 | unsigned long flags) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 169 | { |
| 170 | if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == |
| 171 | SLAB_CTOR_CONSTRUCTOR) { |
| 172 | struct anon_vma *anon_vma = data; |
| 173 | |
| 174 | spin_lock_init(&anon_vma->lock); |
| 175 | INIT_LIST_HEAD(&anon_vma->head); |
| 176 | } |
| 177 | } |
| 178 | |
| 179 | void __init anon_vma_init(void) |
| 180 | { |
| 181 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), |
| 182 | 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL); |
| 183 | } |
| 184 | |
| 185 | /* |
| 186 | * Getting a lock on a stable anon_vma from a page off the LRU is |
| 187 | * tricky: page_lock_anon_vma rely on RCU to guard against the races. |
| 188 | */ |
| 189 | static struct anon_vma *page_lock_anon_vma(struct page *page) |
| 190 | { |
| 191 | struct anon_vma *anon_vma = NULL; |
| 192 | unsigned long anon_mapping; |
| 193 | |
| 194 | rcu_read_lock(); |
| 195 | anon_mapping = (unsigned long) page->mapping; |
| 196 | if (!(anon_mapping & PAGE_MAPPING_ANON)) |
| 197 | goto out; |
| 198 | if (!page_mapped(page)) |
| 199 | goto out; |
| 200 | |
| 201 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| 202 | spin_lock(&anon_vma->lock); |
| 203 | out: |
| 204 | rcu_read_unlock(); |
| 205 | return anon_vma; |
| 206 | } |
| 207 | |
| 208 | /* |
| 209 | * At what user virtual address is page expected in vma? |
| 210 | */ |
| 211 | static inline unsigned long |
| 212 | vma_address(struct page *page, struct vm_area_struct *vma) |
| 213 | { |
| 214 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 215 | unsigned long address; |
| 216 | |
| 217 | address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
| 218 | if (unlikely(address < vma->vm_start || address >= vma->vm_end)) { |
| 219 | /* page should be within any vma from prio_tree_next */ |
| 220 | BUG_ON(!PageAnon(page)); |
| 221 | return -EFAULT; |
| 222 | } |
| 223 | return address; |
| 224 | } |
| 225 | |
| 226 | /* |
| 227 | * At what user virtual address is page expected in vma? checking that the |
Hugh Dickins | ee498ed | 2005-11-21 21:32:18 -0800 | [diff] [blame] | 228 | * page matches the vma: currently only used on anon pages, by unuse_vma; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 229 | */ |
| 230 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
| 231 | { |
| 232 | if (PageAnon(page)) { |
| 233 | if ((void *)vma->anon_vma != |
| 234 | (void *)page->mapping - PAGE_MAPPING_ANON) |
| 235 | return -EFAULT; |
| 236 | } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) { |
Hugh Dickins | ee498ed | 2005-11-21 21:32:18 -0800 | [diff] [blame] | 237 | if (!vma->vm_file || |
| 238 | vma->vm_file->f_mapping != page->mapping) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 239 | return -EFAULT; |
| 240 | } else |
| 241 | return -EFAULT; |
| 242 | return vma_address(page, vma); |
| 243 | } |
| 244 | |
| 245 | /* |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 246 | * Check that @page is mapped at @address into @mm. |
| 247 | * |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 248 | * On success returns with pte mapped and locked. |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 249 | */ |
Carsten Otte | ceffc07 | 2005-06-23 22:05:25 -0700 | [diff] [blame] | 250 | pte_t *page_check_address(struct page *page, struct mm_struct *mm, |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 251 | unsigned long address, spinlock_t **ptlp) |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 252 | { |
| 253 | pgd_t *pgd; |
| 254 | pud_t *pud; |
| 255 | pmd_t *pmd; |
| 256 | pte_t *pte; |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 257 | spinlock_t *ptl; |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 258 | |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 259 | pgd = pgd_offset(mm, address); |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 260 | if (!pgd_present(*pgd)) |
| 261 | return NULL; |
| 262 | |
| 263 | pud = pud_offset(pgd, address); |
| 264 | if (!pud_present(*pud)) |
| 265 | return NULL; |
| 266 | |
| 267 | pmd = pmd_offset(pud, address); |
| 268 | if (!pmd_present(*pmd)) |
| 269 | return NULL; |
| 270 | |
| 271 | pte = pte_offset_map(pmd, address); |
| 272 | /* Make a quick check before getting the lock */ |
| 273 | if (!pte_present(*pte)) { |
| 274 | pte_unmap(pte); |
| 275 | return NULL; |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 276 | } |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 277 | |
Hugh Dickins | 4c21e2f | 2005-10-29 18:16:40 -0700 | [diff] [blame] | 278 | ptl = pte_lockptr(mm, pmd); |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 279 | spin_lock(ptl); |
| 280 | if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { |
| 281 | *ptlp = ptl; |
| 282 | return pte; |
| 283 | } |
| 284 | pte_unmap_unlock(pte, ptl); |
| 285 | return NULL; |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 286 | } |
| 287 | |
| 288 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 289 | * Subfunctions of page_referenced: page_referenced_one called |
| 290 | * repeatedly from either page_referenced_anon or page_referenced_file. |
| 291 | */ |
| 292 | static int page_referenced_one(struct page *page, |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 293 | struct vm_area_struct *vma, unsigned int *mapcount) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 294 | { |
| 295 | struct mm_struct *mm = vma->vm_mm; |
| 296 | unsigned long address; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 297 | pte_t *pte; |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 298 | spinlock_t *ptl; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 299 | int referenced = 0; |
| 300 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 301 | address = vma_address(page, vma); |
| 302 | if (address == -EFAULT) |
| 303 | goto out; |
| 304 | |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 305 | pte = page_check_address(page, mm, address, &ptl); |
| 306 | if (!pte) |
| 307 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 308 | |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 309 | if (ptep_clear_flush_young(vma, address, pte)) |
| 310 | referenced++; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 311 | |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 312 | /* Pretend the page is referenced if the task has the |
| 313 | swap token and is in the middle of a page fault. */ |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 314 | if (mm != current->mm && has_swap_token(mm) && |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 315 | rwsem_is_locked(&mm->mmap_sem)) |
| 316 | referenced++; |
| 317 | |
| 318 | (*mapcount)--; |
| 319 | pte_unmap_unlock(pte, ptl); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 320 | out: |
| 321 | return referenced; |
| 322 | } |
| 323 | |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 324 | static int page_referenced_anon(struct page *page) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 325 | { |
| 326 | unsigned int mapcount; |
| 327 | struct anon_vma *anon_vma; |
| 328 | struct vm_area_struct *vma; |
| 329 | int referenced = 0; |
| 330 | |
| 331 | anon_vma = page_lock_anon_vma(page); |
| 332 | if (!anon_vma) |
| 333 | return referenced; |
| 334 | |
| 335 | mapcount = page_mapcount(page); |
| 336 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 337 | referenced += page_referenced_one(page, vma, &mapcount); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 338 | if (!mapcount) |
| 339 | break; |
| 340 | } |
| 341 | spin_unlock(&anon_vma->lock); |
| 342 | return referenced; |
| 343 | } |
| 344 | |
| 345 | /** |
| 346 | * page_referenced_file - referenced check for object-based rmap |
| 347 | * @page: the page we're checking references on. |
| 348 | * |
| 349 | * For an object-based mapped page, find all the places it is mapped and |
| 350 | * check/clear the referenced flag. This is done by following the page->mapping |
| 351 | * pointer, then walking the chain of vmas it holds. It returns the number |
| 352 | * of references it found. |
| 353 | * |
| 354 | * This function is only called from page_referenced for object-based pages. |
| 355 | */ |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 356 | static int page_referenced_file(struct page *page) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 357 | { |
| 358 | unsigned int mapcount; |
| 359 | struct address_space *mapping = page->mapping; |
| 360 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 361 | struct vm_area_struct *vma; |
| 362 | struct prio_tree_iter iter; |
| 363 | int referenced = 0; |
| 364 | |
| 365 | /* |
| 366 | * The caller's checks on page->mapping and !PageAnon have made |
| 367 | * sure that this is a file page: the check for page->mapping |
| 368 | * excludes the case just before it gets set on an anon page. |
| 369 | */ |
| 370 | BUG_ON(PageAnon(page)); |
| 371 | |
| 372 | /* |
| 373 | * The page lock not only makes sure that page->mapping cannot |
| 374 | * suddenly be NULLified by truncation, it makes sure that the |
| 375 | * structure at mapping cannot be freed and reused yet, |
| 376 | * so we can safely take mapping->i_mmap_lock. |
| 377 | */ |
| 378 | BUG_ON(!PageLocked(page)); |
| 379 | |
| 380 | spin_lock(&mapping->i_mmap_lock); |
| 381 | |
| 382 | /* |
| 383 | * i_mmap_lock does not stabilize mapcount at all, but mapcount |
| 384 | * is more likely to be accurate if we note it after spinning. |
| 385 | */ |
| 386 | mapcount = page_mapcount(page); |
| 387 | |
| 388 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
| 389 | if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE)) |
| 390 | == (VM_LOCKED|VM_MAYSHARE)) { |
| 391 | referenced++; |
| 392 | break; |
| 393 | } |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 394 | referenced += page_referenced_one(page, vma, &mapcount); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 395 | if (!mapcount) |
| 396 | break; |
| 397 | } |
| 398 | |
| 399 | spin_unlock(&mapping->i_mmap_lock); |
| 400 | return referenced; |
| 401 | } |
| 402 | |
| 403 | /** |
| 404 | * page_referenced - test if the page was referenced |
| 405 | * @page: the page to test |
| 406 | * @is_locked: caller holds lock on the page |
| 407 | * |
| 408 | * Quick test_and_clear_referenced for all mappings to a page, |
| 409 | * returns the number of ptes which referenced the page. |
| 410 | */ |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 411 | int page_referenced(struct page *page, int is_locked) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 412 | { |
| 413 | int referenced = 0; |
| 414 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 415 | if (page_test_and_clear_young(page)) |
| 416 | referenced++; |
| 417 | |
| 418 | if (TestClearPageReferenced(page)) |
| 419 | referenced++; |
| 420 | |
| 421 | if (page_mapped(page) && page->mapping) { |
| 422 | if (PageAnon(page)) |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 423 | referenced += page_referenced_anon(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 424 | else if (is_locked) |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 425 | referenced += page_referenced_file(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 426 | else if (TestSetPageLocked(page)) |
| 427 | referenced++; |
| 428 | else { |
| 429 | if (page->mapping) |
Rik van Riel | f7b7fd8 | 2005-11-28 13:44:07 -0800 | [diff] [blame] | 430 | referenced += page_referenced_file(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 431 | unlock_page(page); |
| 432 | } |
| 433 | } |
| 434 | return referenced; |
| 435 | } |
| 436 | |
| 437 | /** |
Nick Piggin | 9617d95 | 2006-01-06 00:11:12 -0800 | [diff] [blame] | 438 | * page_set_anon_rmap - setup new anonymous rmap |
| 439 | * @page: the page to add the mapping to |
| 440 | * @vma: the vm area in which the mapping is added |
| 441 | * @address: the user virtual address mapped |
| 442 | */ |
| 443 | static void __page_set_anon_rmap(struct page *page, |
| 444 | struct vm_area_struct *vma, unsigned long address) |
| 445 | { |
| 446 | struct anon_vma *anon_vma = vma->anon_vma; |
| 447 | |
| 448 | BUG_ON(!anon_vma); |
| 449 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| 450 | page->mapping = (struct address_space *) anon_vma; |
| 451 | |
| 452 | page->index = linear_page_index(vma, address); |
| 453 | |
Nick Piggin | a74609f | 2006-01-06 00:11:20 -0800 | [diff] [blame] | 454 | /* |
| 455 | * nr_mapped state can be updated without turning off |
| 456 | * interrupts because it is not modified via interrupt. |
| 457 | */ |
Christoph Lameter | 65ba55f | 2006-06-30 01:55:34 -0700 | [diff] [blame^] | 458 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
Nick Piggin | 9617d95 | 2006-01-06 00:11:12 -0800 | [diff] [blame] | 459 | } |
| 460 | |
| 461 | /** |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 462 | * page_add_anon_rmap - add pte mapping to an anonymous page |
| 463 | * @page: the page to add the mapping to |
| 464 | * @vma: the vm area in which the mapping is added |
| 465 | * @address: the user virtual address mapped |
| 466 | * |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 467 | * The caller needs to hold the pte lock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 468 | */ |
| 469 | void page_add_anon_rmap(struct page *page, |
| 470 | struct vm_area_struct *vma, unsigned long address) |
| 471 | { |
Nick Piggin | 9617d95 | 2006-01-06 00:11:12 -0800 | [diff] [blame] | 472 | if (atomic_inc_and_test(&page->_mapcount)) |
| 473 | __page_set_anon_rmap(page, vma, address); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 474 | /* else checking page index and mapping is racy */ |
| 475 | } |
| 476 | |
Nick Piggin | 9617d95 | 2006-01-06 00:11:12 -0800 | [diff] [blame] | 477 | /* |
| 478 | * page_add_new_anon_rmap - add pte mapping to a new anonymous page |
| 479 | * @page: the page to add the mapping to |
| 480 | * @vma: the vm area in which the mapping is added |
| 481 | * @address: the user virtual address mapped |
| 482 | * |
| 483 | * Same as page_add_anon_rmap but must only be called on *new* pages. |
| 484 | * This means the inc-and-test can be bypassed. |
| 485 | */ |
| 486 | void page_add_new_anon_rmap(struct page *page, |
| 487 | struct vm_area_struct *vma, unsigned long address) |
| 488 | { |
| 489 | atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */ |
| 490 | __page_set_anon_rmap(page, vma, address); |
| 491 | } |
| 492 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 493 | /** |
| 494 | * page_add_file_rmap - add pte mapping to a file page |
| 495 | * @page: the page to add the mapping to |
| 496 | * |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 497 | * The caller needs to hold the pte lock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 498 | */ |
| 499 | void page_add_file_rmap(struct page *page) |
| 500 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 501 | if (atomic_inc_and_test(&page->_mapcount)) |
Christoph Lameter | 65ba55f | 2006-06-30 01:55:34 -0700 | [diff] [blame^] | 502 | __inc_zone_page_state(page, NR_FILE_MAPPED); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 503 | } |
| 504 | |
| 505 | /** |
| 506 | * page_remove_rmap - take down pte mapping from a page |
| 507 | * @page: page to remove mapping from |
| 508 | * |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 509 | * The caller needs to hold the pte lock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 510 | */ |
| 511 | void page_remove_rmap(struct page *page) |
| 512 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 513 | if (atomic_add_negative(-1, &page->_mapcount)) { |
Nick Piggin | b7ab795 | 2006-03-22 00:08:42 -0800 | [diff] [blame] | 514 | #ifdef CONFIG_DEBUG_VM |
| 515 | if (unlikely(page_mapcount(page) < 0)) { |
Dave Jones | ef2bf0d | 2006-01-08 01:01:00 -0800 | [diff] [blame] | 516 | printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page)); |
| 517 | printk (KERN_EMERG " page->flags = %lx\n", page->flags); |
| 518 | printk (KERN_EMERG " page->count = %x\n", page_count(page)); |
| 519 | printk (KERN_EMERG " page->mapping = %p\n", page->mapping); |
| 520 | } |
Nick Piggin | b7ab795 | 2006-03-22 00:08:42 -0800 | [diff] [blame] | 521 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 522 | BUG_ON(page_mapcount(page) < 0); |
| 523 | /* |
| 524 | * It would be tidy to reset the PageAnon mapping here, |
| 525 | * but that might overwrite a racing page_add_anon_rmap |
| 526 | * which increments mapcount after us but sets mapping |
| 527 | * before us: so leave the reset to free_hot_cold_page, |
| 528 | * and remember that it's only reliable while mapped. |
| 529 | * Leaving it set also helps swapoff to reinstate ptes |
| 530 | * faster for those pages still in swapcache. |
| 531 | */ |
| 532 | if (page_test_and_clear_dirty(page)) |
| 533 | set_page_dirty(page); |
Christoph Lameter | 65ba55f | 2006-06-30 01:55:34 -0700 | [diff] [blame^] | 534 | __dec_zone_page_state(page, NR_FILE_MAPPED); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 535 | } |
| 536 | } |
| 537 | |
| 538 | /* |
| 539 | * Subfunctions of try_to_unmap: try_to_unmap_one called |
| 540 | * repeatedly from either try_to_unmap_anon or try_to_unmap_file. |
| 541 | */ |
Christoph Lameter | a48d07a | 2006-02-01 03:05:38 -0800 | [diff] [blame] | 542 | static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 543 | int migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 544 | { |
| 545 | struct mm_struct *mm = vma->vm_mm; |
| 546 | unsigned long address; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 547 | pte_t *pte; |
| 548 | pte_t pteval; |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 549 | spinlock_t *ptl; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 550 | int ret = SWAP_AGAIN; |
| 551 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 552 | address = vma_address(page, vma); |
| 553 | if (address == -EFAULT) |
| 554 | goto out; |
| 555 | |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 556 | pte = page_check_address(page, mm, address, &ptl); |
| 557 | if (!pte) |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 558 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 559 | |
| 560 | /* |
| 561 | * If the page is mlock()d, we cannot swap it out. |
| 562 | * If it's recently referenced (perhaps page_referenced |
| 563 | * skipped over this mm) then we should reactivate it. |
| 564 | */ |
Christoph Lameter | e6a1530 | 2006-06-25 05:46:49 -0700 | [diff] [blame] | 565 | if (!migration && ((vma->vm_flags & VM_LOCKED) || |
| 566 | (ptep_clear_flush_young(vma, address, pte)))) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 567 | ret = SWAP_FAIL; |
| 568 | goto out_unmap; |
| 569 | } |
| 570 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 571 | /* Nuke the page table entry. */ |
| 572 | flush_cache_page(vma, address, page_to_pfn(page)); |
| 573 | pteval = ptep_clear_flush(vma, address, pte); |
| 574 | |
| 575 | /* Move the dirty bit to the physical page now the pte is gone. */ |
| 576 | if (pte_dirty(pteval)) |
| 577 | set_page_dirty(page); |
| 578 | |
Hugh Dickins | 365e9c87 | 2005-10-29 18:16:18 -0700 | [diff] [blame] | 579 | /* Update high watermark before we lower rss */ |
| 580 | update_hiwater_rss(mm); |
| 581 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 582 | if (PageAnon(page)) { |
Hugh Dickins | 4c21e2f | 2005-10-29 18:16:40 -0700 | [diff] [blame] | 583 | swp_entry_t entry = { .val = page_private(page) }; |
Christoph Lameter | 0697212 | 2006-06-23 02:03:35 -0700 | [diff] [blame] | 584 | |
| 585 | if (PageSwapCache(page)) { |
| 586 | /* |
| 587 | * Store the swap location in the pte. |
| 588 | * See handle_pte_fault() ... |
| 589 | */ |
| 590 | swap_duplicate(entry); |
| 591 | if (list_empty(&mm->mmlist)) { |
| 592 | spin_lock(&mmlist_lock); |
| 593 | if (list_empty(&mm->mmlist)) |
| 594 | list_add(&mm->mmlist, &init_mm.mmlist); |
| 595 | spin_unlock(&mmlist_lock); |
| 596 | } |
Christoph Lameter | 442c913 | 2006-06-23 02:03:38 -0700 | [diff] [blame] | 597 | dec_mm_counter(mm, anon_rss); |
Christoph Lameter | 04e62a2 | 2006-06-23 02:03:38 -0700 | [diff] [blame] | 598 | #ifdef CONFIG_MIGRATION |
Christoph Lameter | 0697212 | 2006-06-23 02:03:35 -0700 | [diff] [blame] | 599 | } else { |
| 600 | /* |
| 601 | * Store the pfn of the page in a special migration |
| 602 | * pte. do_swap_page() will wait until the migration |
| 603 | * pte is removed and then restart fault handling. |
| 604 | */ |
| 605 | BUG_ON(!migration); |
| 606 | entry = make_migration_entry(page, pte_write(pteval)); |
Christoph Lameter | 04e62a2 | 2006-06-23 02:03:38 -0700 | [diff] [blame] | 607 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 608 | } |
| 609 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
| 610 | BUG_ON(pte_file(*pte)); |
Hugh Dickins | 4294621 | 2005-10-29 18:16:05 -0700 | [diff] [blame] | 611 | } else |
Christoph Lameter | 04e62a2 | 2006-06-23 02:03:38 -0700 | [diff] [blame] | 612 | #ifdef CONFIG_MIGRATION |
| 613 | if (migration) { |
| 614 | /* Establish migration entry for a file page */ |
| 615 | swp_entry_t entry; |
| 616 | entry = make_migration_entry(page, pte_write(pteval)); |
| 617 | set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
| 618 | } else |
| 619 | #endif |
Hugh Dickins | 4294621 | 2005-10-29 18:16:05 -0700 | [diff] [blame] | 620 | dec_mm_counter(mm, file_rss); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 621 | |
Christoph Lameter | 04e62a2 | 2006-06-23 02:03:38 -0700 | [diff] [blame] | 622 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 623 | page_remove_rmap(page); |
| 624 | page_cache_release(page); |
| 625 | |
| 626 | out_unmap: |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 627 | pte_unmap_unlock(pte, ptl); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 628 | out: |
| 629 | return ret; |
| 630 | } |
| 631 | |
| 632 | /* |
| 633 | * objrmap doesn't work for nonlinear VMAs because the assumption that |
| 634 | * offset-into-file correlates with offset-into-virtual-addresses does not hold. |
| 635 | * Consequently, given a particular page and its ->index, we cannot locate the |
| 636 | * ptes which are mapping that page without an exhaustive linear search. |
| 637 | * |
| 638 | * So what this code does is a mini "virtual scan" of each nonlinear VMA which |
| 639 | * maps the file to which the target page belongs. The ->vm_private_data field |
| 640 | * holds the current cursor into that scan. Successive searches will circulate |
| 641 | * around the vma's virtual address space. |
| 642 | * |
| 643 | * So as more replacement pressure is applied to the pages in a nonlinear VMA, |
| 644 | * more scanning pressure is placed against them as well. Eventually pages |
| 645 | * will become fully unmapped and are eligible for eviction. |
| 646 | * |
| 647 | * For very sparsely populated VMAs this is a little inefficient - chances are |
| 648 | * there there won't be many ptes located within the scan cluster. In this case |
| 649 | * maybe we could scan further - to the end of the pte page, perhaps. |
| 650 | */ |
| 651 | #define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) |
| 652 | #define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) |
| 653 | |
| 654 | static void try_to_unmap_cluster(unsigned long cursor, |
| 655 | unsigned int *mapcount, struct vm_area_struct *vma) |
| 656 | { |
| 657 | struct mm_struct *mm = vma->vm_mm; |
| 658 | pgd_t *pgd; |
| 659 | pud_t *pud; |
| 660 | pmd_t *pmd; |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 661 | pte_t *pte; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 662 | pte_t pteval; |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 663 | spinlock_t *ptl; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 664 | struct page *page; |
| 665 | unsigned long address; |
| 666 | unsigned long end; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 667 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 668 | address = (vma->vm_start + cursor) & CLUSTER_MASK; |
| 669 | end = address + CLUSTER_SIZE; |
| 670 | if (address < vma->vm_start) |
| 671 | address = vma->vm_start; |
| 672 | if (end > vma->vm_end) |
| 673 | end = vma->vm_end; |
| 674 | |
| 675 | pgd = pgd_offset(mm, address); |
| 676 | if (!pgd_present(*pgd)) |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 677 | return; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 678 | |
| 679 | pud = pud_offset(pgd, address); |
| 680 | if (!pud_present(*pud)) |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 681 | return; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 682 | |
| 683 | pmd = pmd_offset(pud, address); |
| 684 | if (!pmd_present(*pmd)) |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 685 | return; |
| 686 | |
| 687 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 688 | |
Hugh Dickins | 365e9c87 | 2005-10-29 18:16:18 -0700 | [diff] [blame] | 689 | /* Update high watermark before we lower rss */ |
| 690 | update_hiwater_rss(mm); |
| 691 | |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 692 | for (; address < end; pte++, address += PAGE_SIZE) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 693 | if (!pte_present(*pte)) |
| 694 | continue; |
Linus Torvalds | 6aab341 | 2005-11-28 14:34:23 -0800 | [diff] [blame] | 695 | page = vm_normal_page(vma, address, *pte); |
| 696 | BUG_ON(!page || PageAnon(page)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 697 | |
| 698 | if (ptep_clear_flush_young(vma, address, pte)) |
| 699 | continue; |
| 700 | |
| 701 | /* Nuke the page table entry. */ |
Ben Collins | eca3513 | 2005-11-29 11:45:26 -0800 | [diff] [blame] | 702 | flush_cache_page(vma, address, pte_pfn(*pte)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 703 | pteval = ptep_clear_flush(vma, address, pte); |
| 704 | |
| 705 | /* If nonlinear, store the file page offset in the pte. */ |
| 706 | if (page->index != linear_page_index(vma, address)) |
| 707 | set_pte_at(mm, address, pte, pgoff_to_pte(page->index)); |
| 708 | |
| 709 | /* Move the dirty bit to the physical page now the pte is gone. */ |
| 710 | if (pte_dirty(pteval)) |
| 711 | set_page_dirty(page); |
| 712 | |
| 713 | page_remove_rmap(page); |
| 714 | page_cache_release(page); |
Hugh Dickins | 4294621 | 2005-10-29 18:16:05 -0700 | [diff] [blame] | 715 | dec_mm_counter(mm, file_rss); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 716 | (*mapcount)--; |
| 717 | } |
Hugh Dickins | c071880 | 2005-10-29 18:16:31 -0700 | [diff] [blame] | 718 | pte_unmap_unlock(pte - 1, ptl); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 719 | } |
| 720 | |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 721 | static int try_to_unmap_anon(struct page *page, int migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 722 | { |
| 723 | struct anon_vma *anon_vma; |
| 724 | struct vm_area_struct *vma; |
| 725 | int ret = SWAP_AGAIN; |
| 726 | |
| 727 | anon_vma = page_lock_anon_vma(page); |
| 728 | if (!anon_vma) |
| 729 | return ret; |
| 730 | |
| 731 | list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 732 | ret = try_to_unmap_one(page, vma, migration); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 733 | if (ret == SWAP_FAIL || !page_mapped(page)) |
| 734 | break; |
| 735 | } |
| 736 | spin_unlock(&anon_vma->lock); |
| 737 | return ret; |
| 738 | } |
| 739 | |
| 740 | /** |
| 741 | * try_to_unmap_file - unmap file page using the object-based rmap method |
| 742 | * @page: the page to unmap |
| 743 | * |
| 744 | * Find all the mappings of a page using the mapping pointer and the vma chains |
| 745 | * contained in the address_space struct it points to. |
| 746 | * |
| 747 | * This function is only called from try_to_unmap for object-based pages. |
| 748 | */ |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 749 | static int try_to_unmap_file(struct page *page, int migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 750 | { |
| 751 | struct address_space *mapping = page->mapping; |
| 752 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); |
| 753 | struct vm_area_struct *vma; |
| 754 | struct prio_tree_iter iter; |
| 755 | int ret = SWAP_AGAIN; |
| 756 | unsigned long cursor; |
| 757 | unsigned long max_nl_cursor = 0; |
| 758 | unsigned long max_nl_size = 0; |
| 759 | unsigned int mapcount; |
| 760 | |
| 761 | spin_lock(&mapping->i_mmap_lock); |
| 762 | vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 763 | ret = try_to_unmap_one(page, vma, migration); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 764 | if (ret == SWAP_FAIL || !page_mapped(page)) |
| 765 | goto out; |
| 766 | } |
| 767 | |
| 768 | if (list_empty(&mapping->i_mmap_nonlinear)) |
| 769 | goto out; |
| 770 | |
| 771 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
| 772 | shared.vm_set.list) { |
Christoph Lameter | e6a1530 | 2006-06-25 05:46:49 -0700 | [diff] [blame] | 773 | if ((vma->vm_flags & VM_LOCKED) && !migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 774 | continue; |
| 775 | cursor = (unsigned long) vma->vm_private_data; |
| 776 | if (cursor > max_nl_cursor) |
| 777 | max_nl_cursor = cursor; |
| 778 | cursor = vma->vm_end - vma->vm_start; |
| 779 | if (cursor > max_nl_size) |
| 780 | max_nl_size = cursor; |
| 781 | } |
| 782 | |
| 783 | if (max_nl_size == 0) { /* any nonlinears locked or reserved */ |
| 784 | ret = SWAP_FAIL; |
| 785 | goto out; |
| 786 | } |
| 787 | |
| 788 | /* |
| 789 | * We don't try to search for this page in the nonlinear vmas, |
| 790 | * and page_referenced wouldn't have found it anyway. Instead |
| 791 | * just walk the nonlinear vmas trying to age and unmap some. |
| 792 | * The mapcount of the page we came in with is irrelevant, |
| 793 | * but even so use it as a guide to how hard we should try? |
| 794 | */ |
| 795 | mapcount = page_mapcount(page); |
| 796 | if (!mapcount) |
| 797 | goto out; |
| 798 | cond_resched_lock(&mapping->i_mmap_lock); |
| 799 | |
| 800 | max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK; |
| 801 | if (max_nl_cursor == 0) |
| 802 | max_nl_cursor = CLUSTER_SIZE; |
| 803 | |
| 804 | do { |
| 805 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, |
| 806 | shared.vm_set.list) { |
Christoph Lameter | e6a1530 | 2006-06-25 05:46:49 -0700 | [diff] [blame] | 807 | if ((vma->vm_flags & VM_LOCKED) && !migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 808 | continue; |
| 809 | cursor = (unsigned long) vma->vm_private_data; |
Hugh Dickins | 839b968 | 2005-09-03 15:54:43 -0700 | [diff] [blame] | 810 | while ( cursor < max_nl_cursor && |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 811 | cursor < vma->vm_end - vma->vm_start) { |
| 812 | try_to_unmap_cluster(cursor, &mapcount, vma); |
| 813 | cursor += CLUSTER_SIZE; |
| 814 | vma->vm_private_data = (void *) cursor; |
| 815 | if ((int)mapcount <= 0) |
| 816 | goto out; |
| 817 | } |
| 818 | vma->vm_private_data = (void *) max_nl_cursor; |
| 819 | } |
| 820 | cond_resched_lock(&mapping->i_mmap_lock); |
| 821 | max_nl_cursor += CLUSTER_SIZE; |
| 822 | } while (max_nl_cursor <= max_nl_size); |
| 823 | |
| 824 | /* |
| 825 | * Don't loop forever (perhaps all the remaining pages are |
| 826 | * in locked vmas). Reset cursor on all unreserved nonlinear |
| 827 | * vmas, now forgetting on which ones it had fallen behind. |
| 828 | */ |
Hugh Dickins | 101d2be | 2005-11-21 21:32:16 -0800 | [diff] [blame] | 829 | list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) |
| 830 | vma->vm_private_data = NULL; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 831 | out: |
| 832 | spin_unlock(&mapping->i_mmap_lock); |
| 833 | return ret; |
| 834 | } |
| 835 | |
| 836 | /** |
| 837 | * try_to_unmap - try to remove all page table mappings to a page |
| 838 | * @page: the page to get unmapped |
| 839 | * |
| 840 | * Tries to remove all the page table entries which are mapping this |
| 841 | * page, used in the pageout path. Caller must hold the page lock. |
| 842 | * Return values are: |
| 843 | * |
| 844 | * SWAP_SUCCESS - we succeeded in removing all mappings |
| 845 | * SWAP_AGAIN - we missed a mapping, try again later |
| 846 | * SWAP_FAIL - the page is unswappable |
| 847 | */ |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 848 | int try_to_unmap(struct page *page, int migration) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 849 | { |
| 850 | int ret; |
| 851 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 852 | BUG_ON(!PageLocked(page)); |
| 853 | |
| 854 | if (PageAnon(page)) |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 855 | ret = try_to_unmap_anon(page, migration); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 856 | else |
Christoph Lameter | 7352349 | 2006-06-23 02:03:27 -0700 | [diff] [blame] | 857 | ret = try_to_unmap_file(page, migration); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 858 | |
| 859 | if (!page_mapped(page)) |
| 860 | ret = SWAP_SUCCESS; |
| 861 | return ret; |
| 862 | } |
Nikita Danilov | 81b4082 | 2005-05-01 08:58:36 -0700 | [diff] [blame] | 863 | |