shmem.c revision 38f38657444d15e1a8574eae80ed3de9f501737a
1/* 2 * Resizable virtual memory filesystem for Linux. 3 * 4 * Copyright (C) 2000 Linus Torvalds. 5 * 2000 Transmeta Corp. 6 * 2000-2001 Christoph Rohland 7 * 2000-2001 SAP AG 8 * 2002 Red Hat Inc. 9 * Copyright (C) 2002-2011 Hugh Dickins. 10 * Copyright (C) 2011 Google Inc. 11 * Copyright (C) 2002-2005 VERITAS Software Corporation. 12 * Copyright (C) 2004 Andi Kleen, SuSE Labs 13 * 14 * Extended attribute support for tmpfs: 15 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net> 16 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com> 17 * 18 * tiny-shmem: 19 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com> 20 * 21 * This file is released under the GPL. 22 */ 23 24#include <linux/fs.h> 25#include <linux/init.h> 26#include <linux/vfs.h> 27#include <linux/mount.h> 28#include <linux/pagemap.h> 29#include <linux/file.h> 30#include <linux/mm.h> 31#include <linux/export.h> 32#include <linux/swap.h> 33 34static struct vfsmount *shm_mnt; 35 36#ifdef CONFIG_SHMEM 37/* 38 * This virtual memory filesystem is heavily based on the ramfs. It 39 * extends ramfs by the ability to use swap and honor resource limits 40 * which makes it a completely usable filesystem. 41 */ 42 43#include <linux/xattr.h> 44#include <linux/exportfs.h> 45#include <linux/posix_acl.h> 46#include <linux/generic_acl.h> 47#include <linux/mman.h> 48#include <linux/string.h> 49#include <linux/slab.h> 50#include <linux/backing-dev.h> 51#include <linux/shmem_fs.h> 52#include <linux/writeback.h> 53#include <linux/blkdev.h> 54#include <linux/pagevec.h> 55#include <linux/percpu_counter.h> 56#include <linux/falloc.h> 57#include <linux/splice.h> 58#include <linux/security.h> 59#include <linux/swapops.h> 60#include <linux/mempolicy.h> 61#include <linux/namei.h> 62#include <linux/ctype.h> 63#include <linux/migrate.h> 64#include <linux/highmem.h> 65#include <linux/seq_file.h> 66#include <linux/magic.h> 67 68#include <asm/uaccess.h> 69#include <asm/pgtable.h> 70 71#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512) 72#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT) 73 74/* Pretend that each entry is of this size in directory's i_size */ 75#define BOGO_DIRENT_SIZE 20 76 77/* Symlink up to this size is kmalloc'ed instead of using a swappable page */ 78#define SHORT_SYMLINK_LEN 128 79 80/* 81 * shmem_fallocate and shmem_writepage communicate via inode->i_private 82 * (with i_mutex making sure that it has only one user at a time): 83 * we would prefer not to enlarge the shmem inode just for that. 84 */ 85struct shmem_falloc { 86 pgoff_t start; /* start of range currently being fallocated */ 87 pgoff_t next; /* the next page offset to be fallocated */ 88 pgoff_t nr_falloced; /* how many new pages have been fallocated */ 89 pgoff_t nr_unswapped; /* how often writepage refused to swap out */ 90}; 91 92/* Flag allocation requirements to shmem_getpage */ 93enum sgp_type { 94 SGP_READ, /* don't exceed i_size, don't allocate page */ 95 SGP_CACHE, /* don't exceed i_size, may allocate page */ 96 SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */ 97 SGP_WRITE, /* may exceed i_size, may allocate !Uptodate page */ 98 SGP_FALLOC, /* like SGP_WRITE, but make existing page Uptodate */ 99}; 100 101#ifdef CONFIG_TMPFS 102static unsigned long shmem_default_max_blocks(void) 103{ 104 return totalram_pages / 2; 105} 106 107static unsigned long shmem_default_max_inodes(void) 108{ 109 return min(totalram_pages - totalhigh_pages, totalram_pages / 2); 110} 111#endif 112 113static bool shmem_should_replace_page(struct page *page, gfp_t gfp); 114static int shmem_replace_page(struct page **pagep, gfp_t gfp, 115 struct shmem_inode_info *info, pgoff_t index); 116static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 117 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type); 118 119static inline int shmem_getpage(struct inode *inode, pgoff_t index, 120 struct page **pagep, enum sgp_type sgp, int *fault_type) 121{ 122 return shmem_getpage_gfp(inode, index, pagep, sgp, 123 mapping_gfp_mask(inode->i_mapping), fault_type); 124} 125 126static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb) 127{ 128 return sb->s_fs_info; 129} 130 131/* 132 * shmem_file_setup pre-accounts the whole fixed size of a VM object, 133 * for shared memory and for shared anonymous (/dev/zero) mappings 134 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1), 135 * consistent with the pre-accounting of private mappings ... 136 */ 137static inline int shmem_acct_size(unsigned long flags, loff_t size) 138{ 139 return (flags & VM_NORESERVE) ? 140 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size)); 141} 142 143static inline void shmem_unacct_size(unsigned long flags, loff_t size) 144{ 145 if (!(flags & VM_NORESERVE)) 146 vm_unacct_memory(VM_ACCT(size)); 147} 148 149/* 150 * ... whereas tmpfs objects are accounted incrementally as 151 * pages are allocated, in order to allow huge sparse files. 152 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM, 153 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM. 154 */ 155static inline int shmem_acct_block(unsigned long flags) 156{ 157 return (flags & VM_NORESERVE) ? 158 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0; 159} 160 161static inline void shmem_unacct_blocks(unsigned long flags, long pages) 162{ 163 if (flags & VM_NORESERVE) 164 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE)); 165} 166 167static const struct super_operations shmem_ops; 168static const struct address_space_operations shmem_aops; 169static const struct file_operations shmem_file_operations; 170static const struct inode_operations shmem_inode_operations; 171static const struct inode_operations shmem_dir_inode_operations; 172static const struct inode_operations shmem_special_inode_operations; 173static const struct vm_operations_struct shmem_vm_ops; 174 175static struct backing_dev_info shmem_backing_dev_info __read_mostly = { 176 .ra_pages = 0, /* No readahead */ 177 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, 178}; 179 180static LIST_HEAD(shmem_swaplist); 181static DEFINE_MUTEX(shmem_swaplist_mutex); 182 183static int shmem_reserve_inode(struct super_block *sb) 184{ 185 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 186 if (sbinfo->max_inodes) { 187 spin_lock(&sbinfo->stat_lock); 188 if (!sbinfo->free_inodes) { 189 spin_unlock(&sbinfo->stat_lock); 190 return -ENOSPC; 191 } 192 sbinfo->free_inodes--; 193 spin_unlock(&sbinfo->stat_lock); 194 } 195 return 0; 196} 197 198static void shmem_free_inode(struct super_block *sb) 199{ 200 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 201 if (sbinfo->max_inodes) { 202 spin_lock(&sbinfo->stat_lock); 203 sbinfo->free_inodes++; 204 spin_unlock(&sbinfo->stat_lock); 205 } 206} 207 208/** 209 * shmem_recalc_inode - recalculate the block usage of an inode 210 * @inode: inode to recalc 211 * 212 * We have to calculate the free blocks since the mm can drop 213 * undirtied hole pages behind our back. 214 * 215 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped 216 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped) 217 * 218 * It has to be called with the spinlock held. 219 */ 220static void shmem_recalc_inode(struct inode *inode) 221{ 222 struct shmem_inode_info *info = SHMEM_I(inode); 223 long freed; 224 225 freed = info->alloced - info->swapped - inode->i_mapping->nrpages; 226 if (freed > 0) { 227 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); 228 if (sbinfo->max_blocks) 229 percpu_counter_add(&sbinfo->used_blocks, -freed); 230 info->alloced -= freed; 231 inode->i_blocks -= freed * BLOCKS_PER_PAGE; 232 shmem_unacct_blocks(info->flags, freed); 233 } 234} 235 236/* 237 * Replace item expected in radix tree by a new item, while holding tree lock. 238 */ 239static int shmem_radix_tree_replace(struct address_space *mapping, 240 pgoff_t index, void *expected, void *replacement) 241{ 242 void **pslot; 243 void *item = NULL; 244 245 VM_BUG_ON(!expected); 246 pslot = radix_tree_lookup_slot(&mapping->page_tree, index); 247 if (pslot) 248 item = radix_tree_deref_slot_protected(pslot, 249 &mapping->tree_lock); 250 if (item != expected) 251 return -ENOENT; 252 if (replacement) 253 radix_tree_replace_slot(pslot, replacement); 254 else 255 radix_tree_delete(&mapping->page_tree, index); 256 return 0; 257} 258 259/* 260 * Sometimes, before we decide whether to proceed or to fail, we must check 261 * that an entry was not already brought back from swap by a racing thread. 262 * 263 * Checking page is not enough: by the time a SwapCache page is locked, it 264 * might be reused, and again be SwapCache, using the same swap as before. 265 */ 266static bool shmem_confirm_swap(struct address_space *mapping, 267 pgoff_t index, swp_entry_t swap) 268{ 269 void *item; 270 271 rcu_read_lock(); 272 item = radix_tree_lookup(&mapping->page_tree, index); 273 rcu_read_unlock(); 274 return item == swp_to_radix_entry(swap); 275} 276 277/* 278 * Like add_to_page_cache_locked, but error if expected item has gone. 279 */ 280static int shmem_add_to_page_cache(struct page *page, 281 struct address_space *mapping, 282 pgoff_t index, gfp_t gfp, void *expected) 283{ 284 int error; 285 286 VM_BUG_ON(!PageLocked(page)); 287 VM_BUG_ON(!PageSwapBacked(page)); 288 289 page_cache_get(page); 290 page->mapping = mapping; 291 page->index = index; 292 293 spin_lock_irq(&mapping->tree_lock); 294 if (!expected) 295 error = radix_tree_insert(&mapping->page_tree, index, page); 296 else 297 error = shmem_radix_tree_replace(mapping, index, expected, 298 page); 299 if (!error) { 300 mapping->nrpages++; 301 __inc_zone_page_state(page, NR_FILE_PAGES); 302 __inc_zone_page_state(page, NR_SHMEM); 303 spin_unlock_irq(&mapping->tree_lock); 304 } else { 305 page->mapping = NULL; 306 spin_unlock_irq(&mapping->tree_lock); 307 page_cache_release(page); 308 } 309 return error; 310} 311 312/* 313 * Like delete_from_page_cache, but substitutes swap for page. 314 */ 315static void shmem_delete_from_page_cache(struct page *page, void *radswap) 316{ 317 struct address_space *mapping = page->mapping; 318 int error; 319 320 spin_lock_irq(&mapping->tree_lock); 321 error = shmem_radix_tree_replace(mapping, page->index, page, radswap); 322 page->mapping = NULL; 323 mapping->nrpages--; 324 __dec_zone_page_state(page, NR_FILE_PAGES); 325 __dec_zone_page_state(page, NR_SHMEM); 326 spin_unlock_irq(&mapping->tree_lock); 327 page_cache_release(page); 328 BUG_ON(error); 329} 330 331/* 332 * Like find_get_pages, but collecting swap entries as well as pages. 333 */ 334static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping, 335 pgoff_t start, unsigned int nr_pages, 336 struct page **pages, pgoff_t *indices) 337{ 338 unsigned int i; 339 unsigned int ret; 340 unsigned int nr_found; 341 342 rcu_read_lock(); 343restart: 344 nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, 345 (void ***)pages, indices, start, nr_pages); 346 ret = 0; 347 for (i = 0; i < nr_found; i++) { 348 struct page *page; 349repeat: 350 page = radix_tree_deref_slot((void **)pages[i]); 351 if (unlikely(!page)) 352 continue; 353 if (radix_tree_exception(page)) { 354 if (radix_tree_deref_retry(page)) 355 goto restart; 356 /* 357 * Otherwise, we must be storing a swap entry 358 * here as an exceptional entry: so return it 359 * without attempting to raise page count. 360 */ 361 goto export; 362 } 363 if (!page_cache_get_speculative(page)) 364 goto repeat; 365 366 /* Has the page moved? */ 367 if (unlikely(page != *((void **)pages[i]))) { 368 page_cache_release(page); 369 goto repeat; 370 } 371export: 372 indices[ret] = indices[i]; 373 pages[ret] = page; 374 ret++; 375 } 376 if (unlikely(!ret && nr_found)) 377 goto restart; 378 rcu_read_unlock(); 379 return ret; 380} 381 382/* 383 * Remove swap entry from radix tree, free the swap and its page cache. 384 */ 385static int shmem_free_swap(struct address_space *mapping, 386 pgoff_t index, void *radswap) 387{ 388 int error; 389 390 spin_lock_irq(&mapping->tree_lock); 391 error = shmem_radix_tree_replace(mapping, index, radswap, NULL); 392 spin_unlock_irq(&mapping->tree_lock); 393 if (!error) 394 free_swap_and_cache(radix_to_swp_entry(radswap)); 395 return error; 396} 397 398/* 399 * Pagevec may contain swap entries, so shuffle up pages before releasing. 400 */ 401static void shmem_deswap_pagevec(struct pagevec *pvec) 402{ 403 int i, j; 404 405 for (i = 0, j = 0; i < pagevec_count(pvec); i++) { 406 struct page *page = pvec->pages[i]; 407 if (!radix_tree_exceptional_entry(page)) 408 pvec->pages[j++] = page; 409 } 410 pvec->nr = j; 411} 412 413/* 414 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists. 415 */ 416void shmem_unlock_mapping(struct address_space *mapping) 417{ 418 struct pagevec pvec; 419 pgoff_t indices[PAGEVEC_SIZE]; 420 pgoff_t index = 0; 421 422 pagevec_init(&pvec, 0); 423 /* 424 * Minor point, but we might as well stop if someone else SHM_LOCKs it. 425 */ 426 while (!mapping_unevictable(mapping)) { 427 /* 428 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it 429 * has finished, if it hits a row of PAGEVEC_SIZE swap entries. 430 */ 431 pvec.nr = shmem_find_get_pages_and_swap(mapping, index, 432 PAGEVEC_SIZE, pvec.pages, indices); 433 if (!pvec.nr) 434 break; 435 index = indices[pvec.nr - 1] + 1; 436 shmem_deswap_pagevec(&pvec); 437 check_move_unevictable_pages(pvec.pages, pvec.nr); 438 pagevec_release(&pvec); 439 cond_resched(); 440 } 441} 442 443/* 444 * Remove range of pages and swap entries from radix tree, and free them. 445 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate. 446 */ 447static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, 448 bool unfalloc) 449{ 450 struct address_space *mapping = inode->i_mapping; 451 struct shmem_inode_info *info = SHMEM_I(inode); 452 pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 453 pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT; 454 unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1); 455 unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1); 456 struct pagevec pvec; 457 pgoff_t indices[PAGEVEC_SIZE]; 458 long nr_swaps_freed = 0; 459 pgoff_t index; 460 int i; 461 462 if (lend == -1) 463 end = -1; /* unsigned, so actually very big */ 464 465 pagevec_init(&pvec, 0); 466 index = start; 467 while (index < end) { 468 pvec.nr = shmem_find_get_pages_and_swap(mapping, index, 469 min(end - index, (pgoff_t)PAGEVEC_SIZE), 470 pvec.pages, indices); 471 if (!pvec.nr) 472 break; 473 mem_cgroup_uncharge_start(); 474 for (i = 0; i < pagevec_count(&pvec); i++) { 475 struct page *page = pvec.pages[i]; 476 477 index = indices[i]; 478 if (index >= end) 479 break; 480 481 if (radix_tree_exceptional_entry(page)) { 482 if (unfalloc) 483 continue; 484 nr_swaps_freed += !shmem_free_swap(mapping, 485 index, page); 486 continue; 487 } 488 489 if (!trylock_page(page)) 490 continue; 491 if (!unfalloc || !PageUptodate(page)) { 492 if (page->mapping == mapping) { 493 VM_BUG_ON(PageWriteback(page)); 494 truncate_inode_page(mapping, page); 495 } 496 } 497 unlock_page(page); 498 } 499 shmem_deswap_pagevec(&pvec); 500 pagevec_release(&pvec); 501 mem_cgroup_uncharge_end(); 502 cond_resched(); 503 index++; 504 } 505 506 if (partial_start) { 507 struct page *page = NULL; 508 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL); 509 if (page) { 510 unsigned int top = PAGE_CACHE_SIZE; 511 if (start > end) { 512 top = partial_end; 513 partial_end = 0; 514 } 515 zero_user_segment(page, partial_start, top); 516 set_page_dirty(page); 517 unlock_page(page); 518 page_cache_release(page); 519 } 520 } 521 if (partial_end) { 522 struct page *page = NULL; 523 shmem_getpage(inode, end, &page, SGP_READ, NULL); 524 if (page) { 525 zero_user_segment(page, 0, partial_end); 526 set_page_dirty(page); 527 unlock_page(page); 528 page_cache_release(page); 529 } 530 } 531 if (start >= end) 532 return; 533 534 index = start; 535 for ( ; ; ) { 536 cond_resched(); 537 pvec.nr = shmem_find_get_pages_and_swap(mapping, index, 538 min(end - index, (pgoff_t)PAGEVEC_SIZE), 539 pvec.pages, indices); 540 if (!pvec.nr) { 541 if (index == start || unfalloc) 542 break; 543 index = start; 544 continue; 545 } 546 if ((index == start || unfalloc) && indices[0] >= end) { 547 shmem_deswap_pagevec(&pvec); 548 pagevec_release(&pvec); 549 break; 550 } 551 mem_cgroup_uncharge_start(); 552 for (i = 0; i < pagevec_count(&pvec); i++) { 553 struct page *page = pvec.pages[i]; 554 555 index = indices[i]; 556 if (index >= end) 557 break; 558 559 if (radix_tree_exceptional_entry(page)) { 560 if (unfalloc) 561 continue; 562 nr_swaps_freed += !shmem_free_swap(mapping, 563 index, page); 564 continue; 565 } 566 567 lock_page(page); 568 if (!unfalloc || !PageUptodate(page)) { 569 if (page->mapping == mapping) { 570 VM_BUG_ON(PageWriteback(page)); 571 truncate_inode_page(mapping, page); 572 } 573 } 574 unlock_page(page); 575 } 576 shmem_deswap_pagevec(&pvec); 577 pagevec_release(&pvec); 578 mem_cgroup_uncharge_end(); 579 index++; 580 } 581 582 spin_lock(&info->lock); 583 info->swapped -= nr_swaps_freed; 584 shmem_recalc_inode(inode); 585 spin_unlock(&info->lock); 586} 587 588void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 589{ 590 shmem_undo_range(inode, lstart, lend, false); 591 inode->i_ctime = inode->i_mtime = CURRENT_TIME; 592} 593EXPORT_SYMBOL_GPL(shmem_truncate_range); 594 595static int shmem_setattr(struct dentry *dentry, struct iattr *attr) 596{ 597 struct inode *inode = dentry->d_inode; 598 int error; 599 600 error = inode_change_ok(inode, attr); 601 if (error) 602 return error; 603 604 if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) { 605 loff_t oldsize = inode->i_size; 606 loff_t newsize = attr->ia_size; 607 608 if (newsize != oldsize) { 609 i_size_write(inode, newsize); 610 inode->i_ctime = inode->i_mtime = CURRENT_TIME; 611 } 612 if (newsize < oldsize) { 613 loff_t holebegin = round_up(newsize, PAGE_SIZE); 614 unmap_mapping_range(inode->i_mapping, holebegin, 0, 1); 615 shmem_truncate_range(inode, newsize, (loff_t)-1); 616 /* unmap again to remove racily COWed private pages */ 617 unmap_mapping_range(inode->i_mapping, holebegin, 0, 1); 618 } 619 } 620 621 setattr_copy(inode, attr); 622#ifdef CONFIG_TMPFS_POSIX_ACL 623 if (attr->ia_valid & ATTR_MODE) 624 error = generic_acl_chmod(inode); 625#endif 626 return error; 627} 628 629static void shmem_evict_inode(struct inode *inode) 630{ 631 struct shmem_inode_info *info = SHMEM_I(inode); 632 633 if (inode->i_mapping->a_ops == &shmem_aops) { 634 shmem_unacct_size(info->flags, inode->i_size); 635 inode->i_size = 0; 636 shmem_truncate_range(inode, 0, (loff_t)-1); 637 if (!list_empty(&info->swaplist)) { 638 mutex_lock(&shmem_swaplist_mutex); 639 list_del_init(&info->swaplist); 640 mutex_unlock(&shmem_swaplist_mutex); 641 } 642 } else 643 kfree(info->symlink); 644 645 simple_xattrs_free(&info->xattrs); 646 BUG_ON(inode->i_blocks); 647 shmem_free_inode(inode->i_sb); 648 clear_inode(inode); 649} 650 651/* 652 * If swap found in inode, free it and move page from swapcache to filecache. 653 */ 654static int shmem_unuse_inode(struct shmem_inode_info *info, 655 swp_entry_t swap, struct page **pagep) 656{ 657 struct address_space *mapping = info->vfs_inode.i_mapping; 658 void *radswap; 659 pgoff_t index; 660 gfp_t gfp; 661 int error = 0; 662 663 radswap = swp_to_radix_entry(swap); 664 index = radix_tree_locate_item(&mapping->page_tree, radswap); 665 if (index == -1) 666 return 0; 667 668 /* 669 * Move _head_ to start search for next from here. 670 * But be careful: shmem_evict_inode checks list_empty without taking 671 * mutex, and there's an instant in list_move_tail when info->swaplist 672 * would appear empty, if it were the only one on shmem_swaplist. 673 */ 674 if (shmem_swaplist.next != &info->swaplist) 675 list_move_tail(&shmem_swaplist, &info->swaplist); 676 677 gfp = mapping_gfp_mask(mapping); 678 if (shmem_should_replace_page(*pagep, gfp)) { 679 mutex_unlock(&shmem_swaplist_mutex); 680 error = shmem_replace_page(pagep, gfp, info, index); 681 mutex_lock(&shmem_swaplist_mutex); 682 /* 683 * We needed to drop mutex to make that restrictive page 684 * allocation, but the inode might have been freed while we 685 * dropped it: although a racing shmem_evict_inode() cannot 686 * complete without emptying the radix_tree, our page lock 687 * on this swapcache page is not enough to prevent that - 688 * free_swap_and_cache() of our swap entry will only 689 * trylock_page(), removing swap from radix_tree whatever. 690 * 691 * We must not proceed to shmem_add_to_page_cache() if the 692 * inode has been freed, but of course we cannot rely on 693 * inode or mapping or info to check that. However, we can 694 * safely check if our swap entry is still in use (and here 695 * it can't have got reused for another page): if it's still 696 * in use, then the inode cannot have been freed yet, and we 697 * can safely proceed (if it's no longer in use, that tells 698 * nothing about the inode, but we don't need to unuse swap). 699 */ 700 if (!page_swapcount(*pagep)) 701 error = -ENOENT; 702 } 703 704 /* 705 * We rely on shmem_swaplist_mutex, not only to protect the swaplist, 706 * but also to hold up shmem_evict_inode(): so inode cannot be freed 707 * beneath us (pagelock doesn't help until the page is in pagecache). 708 */ 709 if (!error) 710 error = shmem_add_to_page_cache(*pagep, mapping, index, 711 GFP_NOWAIT, radswap); 712 if (error != -ENOMEM) { 713 /* 714 * Truncation and eviction use free_swap_and_cache(), which 715 * only does trylock page: if we raced, best clean up here. 716 */ 717 delete_from_swap_cache(*pagep); 718 set_page_dirty(*pagep); 719 if (!error) { 720 spin_lock(&info->lock); 721 info->swapped--; 722 spin_unlock(&info->lock); 723 swap_free(swap); 724 } 725 error = 1; /* not an error, but entry was found */ 726 } 727 return error; 728} 729 730/* 731 * Search through swapped inodes to find and replace swap by page. 732 */ 733int shmem_unuse(swp_entry_t swap, struct page *page) 734{ 735 struct list_head *this, *next; 736 struct shmem_inode_info *info; 737 int found = 0; 738 int error = 0; 739 740 /* 741 * There's a faint possibility that swap page was replaced before 742 * caller locked it: caller will come back later with the right page. 743 */ 744 if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val)) 745 goto out; 746 747 /* 748 * Charge page using GFP_KERNEL while we can wait, before taking 749 * the shmem_swaplist_mutex which might hold up shmem_writepage(). 750 * Charged back to the user (not to caller) when swap account is used. 751 */ 752 error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL); 753 if (error) 754 goto out; 755 /* No radix_tree_preload: swap entry keeps a place for page in tree */ 756 757 mutex_lock(&shmem_swaplist_mutex); 758 list_for_each_safe(this, next, &shmem_swaplist) { 759 info = list_entry(this, struct shmem_inode_info, swaplist); 760 if (info->swapped) 761 found = shmem_unuse_inode(info, swap, &page); 762 else 763 list_del_init(&info->swaplist); 764 cond_resched(); 765 if (found) 766 break; 767 } 768 mutex_unlock(&shmem_swaplist_mutex); 769 770 if (found < 0) 771 error = found; 772out: 773 unlock_page(page); 774 page_cache_release(page); 775 return error; 776} 777 778/* 779 * Move the page from the page cache to the swap cache. 780 */ 781static int shmem_writepage(struct page *page, struct writeback_control *wbc) 782{ 783 struct shmem_inode_info *info; 784 struct address_space *mapping; 785 struct inode *inode; 786 swp_entry_t swap; 787 pgoff_t index; 788 789 BUG_ON(!PageLocked(page)); 790 mapping = page->mapping; 791 index = page->index; 792 inode = mapping->host; 793 info = SHMEM_I(inode); 794 if (info->flags & VM_LOCKED) 795 goto redirty; 796 if (!total_swap_pages) 797 goto redirty; 798 799 /* 800 * shmem_backing_dev_info's capabilities prevent regular writeback or 801 * sync from ever calling shmem_writepage; but a stacking filesystem 802 * might use ->writepage of its underlying filesystem, in which case 803 * tmpfs should write out to swap only in response to memory pressure, 804 * and not for the writeback threads or sync. 805 */ 806 if (!wbc->for_reclaim) { 807 WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ 808 goto redirty; 809 } 810 811 /* 812 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC 813 * value into swapfile.c, the only way we can correctly account for a 814 * fallocated page arriving here is now to initialize it and write it. 815 * 816 * That's okay for a page already fallocated earlier, but if we have 817 * not yet completed the fallocation, then (a) we want to keep track 818 * of this page in case we have to undo it, and (b) it may not be a 819 * good idea to continue anyway, once we're pushing into swap. So 820 * reactivate the page, and let shmem_fallocate() quit when too many. 821 */ 822 if (!PageUptodate(page)) { 823 if (inode->i_private) { 824 struct shmem_falloc *shmem_falloc; 825 spin_lock(&inode->i_lock); 826 shmem_falloc = inode->i_private; 827 if (shmem_falloc && 828 index >= shmem_falloc->start && 829 index < shmem_falloc->next) 830 shmem_falloc->nr_unswapped++; 831 else 832 shmem_falloc = NULL; 833 spin_unlock(&inode->i_lock); 834 if (shmem_falloc) 835 goto redirty; 836 } 837 clear_highpage(page); 838 flush_dcache_page(page); 839 SetPageUptodate(page); 840 } 841 842 swap = get_swap_page(); 843 if (!swap.val) 844 goto redirty; 845 846 /* 847 * Add inode to shmem_unuse()'s list of swapped-out inodes, 848 * if it's not already there. Do it now before the page is 849 * moved to swap cache, when its pagelock no longer protects 850 * the inode from eviction. But don't unlock the mutex until 851 * we've incremented swapped, because shmem_unuse_inode() will 852 * prune a !swapped inode from the swaplist under this mutex. 853 */ 854 mutex_lock(&shmem_swaplist_mutex); 855 if (list_empty(&info->swaplist)) 856 list_add_tail(&info->swaplist, &shmem_swaplist); 857 858 if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) { 859 swap_shmem_alloc(swap); 860 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap)); 861 862 spin_lock(&info->lock); 863 info->swapped++; 864 shmem_recalc_inode(inode); 865 spin_unlock(&info->lock); 866 867 mutex_unlock(&shmem_swaplist_mutex); 868 BUG_ON(page_mapped(page)); 869 swap_writepage(page, wbc); 870 return 0; 871 } 872 873 mutex_unlock(&shmem_swaplist_mutex); 874 swapcache_free(swap, NULL); 875redirty: 876 set_page_dirty(page); 877 if (wbc->for_reclaim) 878 return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */ 879 unlock_page(page); 880 return 0; 881} 882 883#ifdef CONFIG_NUMA 884#ifdef CONFIG_TMPFS 885static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) 886{ 887 char buffer[64]; 888 889 if (!mpol || mpol->mode == MPOL_DEFAULT) 890 return; /* show nothing */ 891 892 mpol_to_str(buffer, sizeof(buffer), mpol, 1); 893 894 seq_printf(seq, ",mpol=%s", buffer); 895} 896 897static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) 898{ 899 struct mempolicy *mpol = NULL; 900 if (sbinfo->mpol) { 901 spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */ 902 mpol = sbinfo->mpol; 903 mpol_get(mpol); 904 spin_unlock(&sbinfo->stat_lock); 905 } 906 return mpol; 907} 908#endif /* CONFIG_TMPFS */ 909 910static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, 911 struct shmem_inode_info *info, pgoff_t index) 912{ 913 struct mempolicy mpol, *spol; 914 struct vm_area_struct pvma; 915 916 spol = mpol_cond_copy(&mpol, 917 mpol_shared_policy_lookup(&info->policy, index)); 918 919 /* Create a pseudo vma that just contains the policy */ 920 pvma.vm_start = 0; 921 /* Bias interleave by inode number to distribute better across nodes */ 922 pvma.vm_pgoff = index + info->vfs_inode.i_ino; 923 pvma.vm_ops = NULL; 924 pvma.vm_policy = spol; 925 return swapin_readahead(swap, gfp, &pvma, 0); 926} 927 928static struct page *shmem_alloc_page(gfp_t gfp, 929 struct shmem_inode_info *info, pgoff_t index) 930{ 931 struct vm_area_struct pvma; 932 933 /* Create a pseudo vma that just contains the policy */ 934 pvma.vm_start = 0; 935 /* Bias interleave by inode number to distribute better across nodes */ 936 pvma.vm_pgoff = index + info->vfs_inode.i_ino; 937 pvma.vm_ops = NULL; 938 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); 939 940 /* 941 * alloc_page_vma() will drop the shared policy reference 942 */ 943 return alloc_page_vma(gfp, &pvma, 0); 944} 945#else /* !CONFIG_NUMA */ 946#ifdef CONFIG_TMPFS 947static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) 948{ 949} 950#endif /* CONFIG_TMPFS */ 951 952static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, 953 struct shmem_inode_info *info, pgoff_t index) 954{ 955 return swapin_readahead(swap, gfp, NULL, 0); 956} 957 958static inline struct page *shmem_alloc_page(gfp_t gfp, 959 struct shmem_inode_info *info, pgoff_t index) 960{ 961 return alloc_page(gfp); 962} 963#endif /* CONFIG_NUMA */ 964 965#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS) 966static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) 967{ 968 return NULL; 969} 970#endif 971 972/* 973 * When a page is moved from swapcache to shmem filecache (either by the 974 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of 975 * shmem_unuse_inode()), it may have been read in earlier from swap, in 976 * ignorance of the mapping it belongs to. If that mapping has special 977 * constraints (like the gma500 GEM driver, which requires RAM below 4GB), 978 * we may need to copy to a suitable page before moving to filecache. 979 * 980 * In a future release, this may well be extended to respect cpuset and 981 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page(); 982 * but for now it is a simple matter of zone. 983 */ 984static bool shmem_should_replace_page(struct page *page, gfp_t gfp) 985{ 986 return page_zonenum(page) > gfp_zone(gfp); 987} 988 989static int shmem_replace_page(struct page **pagep, gfp_t gfp, 990 struct shmem_inode_info *info, pgoff_t index) 991{ 992 struct page *oldpage, *newpage; 993 struct address_space *swap_mapping; 994 pgoff_t swap_index; 995 int error; 996 997 oldpage = *pagep; 998 swap_index = page_private(oldpage); 999 swap_mapping = page_mapping(oldpage); 1000 1001 /* 1002 * We have arrived here because our zones are constrained, so don't 1003 * limit chance of success by further cpuset and node constraints. 1004 */ 1005 gfp &= ~GFP_CONSTRAINT_MASK; 1006 newpage = shmem_alloc_page(gfp, info, index); 1007 if (!newpage) 1008 return -ENOMEM; 1009 1010 page_cache_get(newpage); 1011 copy_highpage(newpage, oldpage); 1012 flush_dcache_page(newpage); 1013 1014 __set_page_locked(newpage); 1015 SetPageUptodate(newpage); 1016 SetPageSwapBacked(newpage); 1017 set_page_private(newpage, swap_index); 1018 SetPageSwapCache(newpage); 1019 1020 /* 1021 * Our caller will very soon move newpage out of swapcache, but it's 1022 * a nice clean interface for us to replace oldpage by newpage there. 1023 */ 1024 spin_lock_irq(&swap_mapping->tree_lock); 1025 error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage, 1026 newpage); 1027 if (!error) { 1028 __inc_zone_page_state(newpage, NR_FILE_PAGES); 1029 __dec_zone_page_state(oldpage, NR_FILE_PAGES); 1030 } 1031 spin_unlock_irq(&swap_mapping->tree_lock); 1032 1033 if (unlikely(error)) { 1034 /* 1035 * Is this possible? I think not, now that our callers check 1036 * both PageSwapCache and page_private after getting page lock; 1037 * but be defensive. Reverse old to newpage for clear and free. 1038 */ 1039 oldpage = newpage; 1040 } else { 1041 mem_cgroup_replace_page_cache(oldpage, newpage); 1042 lru_cache_add_anon(newpage); 1043 *pagep = newpage; 1044 } 1045 1046 ClearPageSwapCache(oldpage); 1047 set_page_private(oldpage, 0); 1048 1049 unlock_page(oldpage); 1050 page_cache_release(oldpage); 1051 page_cache_release(oldpage); 1052 return error; 1053} 1054 1055/* 1056 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate 1057 * 1058 * If we allocate a new one we do not mark it dirty. That's up to the 1059 * vm. If we swap it in we mark it dirty since we also free the swap 1060 * entry since a page cannot live in both the swap and page cache 1061 */ 1062static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 1063 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type) 1064{ 1065 struct address_space *mapping = inode->i_mapping; 1066 struct shmem_inode_info *info; 1067 struct shmem_sb_info *sbinfo; 1068 struct page *page; 1069 swp_entry_t swap; 1070 int error; 1071 int once = 0; 1072 int alloced = 0; 1073 1074 if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT)) 1075 return -EFBIG; 1076repeat: 1077 swap.val = 0; 1078 page = find_lock_page(mapping, index); 1079 if (radix_tree_exceptional_entry(page)) { 1080 swap = radix_to_swp_entry(page); 1081 page = NULL; 1082 } 1083 1084 if (sgp != SGP_WRITE && sgp != SGP_FALLOC && 1085 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) { 1086 error = -EINVAL; 1087 goto failed; 1088 } 1089 1090 /* fallocated page? */ 1091 if (page && !PageUptodate(page)) { 1092 if (sgp != SGP_READ) 1093 goto clear; 1094 unlock_page(page); 1095 page_cache_release(page); 1096 page = NULL; 1097 } 1098 if (page || (sgp == SGP_READ && !swap.val)) { 1099 *pagep = page; 1100 return 0; 1101 } 1102 1103 /* 1104 * Fast cache lookup did not find it: 1105 * bring it back from swap or allocate. 1106 */ 1107 info = SHMEM_I(inode); 1108 sbinfo = SHMEM_SB(inode->i_sb); 1109 1110 if (swap.val) { 1111 /* Look it up and read it in.. */ 1112 page = lookup_swap_cache(swap); 1113 if (!page) { 1114 /* here we actually do the io */ 1115 if (fault_type) 1116 *fault_type |= VM_FAULT_MAJOR; 1117 page = shmem_swapin(swap, gfp, info, index); 1118 if (!page) { 1119 error = -ENOMEM; 1120 goto failed; 1121 } 1122 } 1123 1124 /* We have to do this with page locked to prevent races */ 1125 lock_page(page); 1126 if (!PageSwapCache(page) || page_private(page) != swap.val || 1127 !shmem_confirm_swap(mapping, index, swap)) { 1128 error = -EEXIST; /* try again */ 1129 goto unlock; 1130 } 1131 if (!PageUptodate(page)) { 1132 error = -EIO; 1133 goto failed; 1134 } 1135 wait_on_page_writeback(page); 1136 1137 if (shmem_should_replace_page(page, gfp)) { 1138 error = shmem_replace_page(&page, gfp, info, index); 1139 if (error) 1140 goto failed; 1141 } 1142 1143 error = mem_cgroup_cache_charge(page, current->mm, 1144 gfp & GFP_RECLAIM_MASK); 1145 if (!error) { 1146 error = shmem_add_to_page_cache(page, mapping, index, 1147 gfp, swp_to_radix_entry(swap)); 1148 /* We already confirmed swap, and make no allocation */ 1149 VM_BUG_ON(error); 1150 } 1151 if (error) 1152 goto failed; 1153 1154 spin_lock(&info->lock); 1155 info->swapped--; 1156 shmem_recalc_inode(inode); 1157 spin_unlock(&info->lock); 1158 1159 delete_from_swap_cache(page); 1160 set_page_dirty(page); 1161 swap_free(swap); 1162 1163 } else { 1164 if (shmem_acct_block(info->flags)) { 1165 error = -ENOSPC; 1166 goto failed; 1167 } 1168 if (sbinfo->max_blocks) { 1169 if (percpu_counter_compare(&sbinfo->used_blocks, 1170 sbinfo->max_blocks) >= 0) { 1171 error = -ENOSPC; 1172 goto unacct; 1173 } 1174 percpu_counter_inc(&sbinfo->used_blocks); 1175 } 1176 1177 page = shmem_alloc_page(gfp, info, index); 1178 if (!page) { 1179 error = -ENOMEM; 1180 goto decused; 1181 } 1182 1183 SetPageSwapBacked(page); 1184 __set_page_locked(page); 1185 error = mem_cgroup_cache_charge(page, current->mm, 1186 gfp & GFP_RECLAIM_MASK); 1187 if (error) 1188 goto decused; 1189 error = radix_tree_preload(gfp & GFP_RECLAIM_MASK); 1190 if (!error) { 1191 error = shmem_add_to_page_cache(page, mapping, index, 1192 gfp, NULL); 1193 radix_tree_preload_end(); 1194 } 1195 if (error) { 1196 mem_cgroup_uncharge_cache_page(page); 1197 goto decused; 1198 } 1199 lru_cache_add_anon(page); 1200 1201 spin_lock(&info->lock); 1202 info->alloced++; 1203 inode->i_blocks += BLOCKS_PER_PAGE; 1204 shmem_recalc_inode(inode); 1205 spin_unlock(&info->lock); 1206 alloced = true; 1207 1208 /* 1209 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page. 1210 */ 1211 if (sgp == SGP_FALLOC) 1212 sgp = SGP_WRITE; 1213clear: 1214 /* 1215 * Let SGP_WRITE caller clear ends if write does not fill page; 1216 * but SGP_FALLOC on a page fallocated earlier must initialize 1217 * it now, lest undo on failure cancel our earlier guarantee. 1218 */ 1219 if (sgp != SGP_WRITE) { 1220 clear_highpage(page); 1221 flush_dcache_page(page); 1222 SetPageUptodate(page); 1223 } 1224 if (sgp == SGP_DIRTY) 1225 set_page_dirty(page); 1226 } 1227 1228 /* Perhaps the file has been truncated since we checked */ 1229 if (sgp != SGP_WRITE && sgp != SGP_FALLOC && 1230 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) { 1231 error = -EINVAL; 1232 if (alloced) 1233 goto trunc; 1234 else 1235 goto failed; 1236 } 1237 *pagep = page; 1238 return 0; 1239 1240 /* 1241 * Error recovery. 1242 */ 1243trunc: 1244 info = SHMEM_I(inode); 1245 ClearPageDirty(page); 1246 delete_from_page_cache(page); 1247 spin_lock(&info->lock); 1248 info->alloced--; 1249 inode->i_blocks -= BLOCKS_PER_PAGE; 1250 spin_unlock(&info->lock); 1251decused: 1252 sbinfo = SHMEM_SB(inode->i_sb); 1253 if (sbinfo->max_blocks) 1254 percpu_counter_add(&sbinfo->used_blocks, -1); 1255unacct: 1256 shmem_unacct_blocks(info->flags, 1); 1257failed: 1258 if (swap.val && error != -EINVAL && 1259 !shmem_confirm_swap(mapping, index, swap)) 1260 error = -EEXIST; 1261unlock: 1262 if (page) { 1263 unlock_page(page); 1264 page_cache_release(page); 1265 } 1266 if (error == -ENOSPC && !once++) { 1267 info = SHMEM_I(inode); 1268 spin_lock(&info->lock); 1269 shmem_recalc_inode(inode); 1270 spin_unlock(&info->lock); 1271 goto repeat; 1272 } 1273 if (error == -EEXIST) /* from above or from radix_tree_insert */ 1274 goto repeat; 1275 return error; 1276} 1277 1278static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1279{ 1280 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 1281 int error; 1282 int ret = VM_FAULT_LOCKED; 1283 1284 error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret); 1285 if (error) 1286 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS); 1287 1288 if (ret & VM_FAULT_MAJOR) { 1289 count_vm_event(PGMAJFAULT); 1290 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 1291 } 1292 return ret; 1293} 1294 1295#ifdef CONFIG_NUMA 1296static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol) 1297{ 1298 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 1299 return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol); 1300} 1301 1302static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma, 1303 unsigned long addr) 1304{ 1305 struct inode *inode = vma->vm_file->f_path.dentry->d_inode; 1306 pgoff_t index; 1307 1308 index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 1309 return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index); 1310} 1311#endif 1312 1313int shmem_lock(struct file *file, int lock, struct user_struct *user) 1314{ 1315 struct inode *inode = file->f_path.dentry->d_inode; 1316 struct shmem_inode_info *info = SHMEM_I(inode); 1317 int retval = -ENOMEM; 1318 1319 spin_lock(&info->lock); 1320 if (lock && !(info->flags & VM_LOCKED)) { 1321 if (!user_shm_lock(inode->i_size, user)) 1322 goto out_nomem; 1323 info->flags |= VM_LOCKED; 1324 mapping_set_unevictable(file->f_mapping); 1325 } 1326 if (!lock && (info->flags & VM_LOCKED) && user) { 1327 user_shm_unlock(inode->i_size, user); 1328 info->flags &= ~VM_LOCKED; 1329 mapping_clear_unevictable(file->f_mapping); 1330 } 1331 retval = 0; 1332 1333out_nomem: 1334 spin_unlock(&info->lock); 1335 return retval; 1336} 1337 1338static int shmem_mmap(struct file *file, struct vm_area_struct *vma) 1339{ 1340 file_accessed(file); 1341 vma->vm_ops = &shmem_vm_ops; 1342 vma->vm_flags |= VM_CAN_NONLINEAR; 1343 return 0; 1344} 1345 1346static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir, 1347 umode_t mode, dev_t dev, unsigned long flags) 1348{ 1349 struct inode *inode; 1350 struct shmem_inode_info *info; 1351 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 1352 1353 if (shmem_reserve_inode(sb)) 1354 return NULL; 1355 1356 inode = new_inode(sb); 1357 if (inode) { 1358 inode->i_ino = get_next_ino(); 1359 inode_init_owner(inode, dir, mode); 1360 inode->i_blocks = 0; 1361 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info; 1362 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 1363 inode->i_generation = get_seconds(); 1364 info = SHMEM_I(inode); 1365 memset(info, 0, (char *)inode - (char *)info); 1366 spin_lock_init(&info->lock); 1367 info->flags = flags & VM_NORESERVE; 1368 INIT_LIST_HEAD(&info->swaplist); 1369 simple_xattrs_init(&info->xattrs); 1370 cache_no_acl(inode); 1371 1372 switch (mode & S_IFMT) { 1373 default: 1374 inode->i_op = &shmem_special_inode_operations; 1375 init_special_inode(inode, mode, dev); 1376 break; 1377 case S_IFREG: 1378 inode->i_mapping->a_ops = &shmem_aops; 1379 inode->i_op = &shmem_inode_operations; 1380 inode->i_fop = &shmem_file_operations; 1381 mpol_shared_policy_init(&info->policy, 1382 shmem_get_sbmpol(sbinfo)); 1383 break; 1384 case S_IFDIR: 1385 inc_nlink(inode); 1386 /* Some things misbehave if size == 0 on a directory */ 1387 inode->i_size = 2 * BOGO_DIRENT_SIZE; 1388 inode->i_op = &shmem_dir_inode_operations; 1389 inode->i_fop = &simple_dir_operations; 1390 break; 1391 case S_IFLNK: 1392 /* 1393 * Must not load anything in the rbtree, 1394 * mpol_free_shared_policy will not be called. 1395 */ 1396 mpol_shared_policy_init(&info->policy, NULL); 1397 break; 1398 } 1399 } else 1400 shmem_free_inode(sb); 1401 return inode; 1402} 1403 1404#ifdef CONFIG_TMPFS 1405static const struct inode_operations shmem_symlink_inode_operations; 1406static const struct inode_operations shmem_short_symlink_operations; 1407 1408#ifdef CONFIG_TMPFS_XATTR 1409static int shmem_initxattrs(struct inode *, const struct xattr *, void *); 1410#else 1411#define shmem_initxattrs NULL 1412#endif 1413 1414static int 1415shmem_write_begin(struct file *file, struct address_space *mapping, 1416 loff_t pos, unsigned len, unsigned flags, 1417 struct page **pagep, void **fsdata) 1418{ 1419 struct inode *inode = mapping->host; 1420 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 1421 return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL); 1422} 1423 1424static int 1425shmem_write_end(struct file *file, struct address_space *mapping, 1426 loff_t pos, unsigned len, unsigned copied, 1427 struct page *page, void *fsdata) 1428{ 1429 struct inode *inode = mapping->host; 1430 1431 if (pos + copied > inode->i_size) 1432 i_size_write(inode, pos + copied); 1433 1434 if (!PageUptodate(page)) { 1435 if (copied < PAGE_CACHE_SIZE) { 1436 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 1437 zero_user_segments(page, 0, from, 1438 from + copied, PAGE_CACHE_SIZE); 1439 } 1440 SetPageUptodate(page); 1441 } 1442 set_page_dirty(page); 1443 unlock_page(page); 1444 page_cache_release(page); 1445 1446 return copied; 1447} 1448 1449static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor) 1450{ 1451 struct inode *inode = filp->f_path.dentry->d_inode; 1452 struct address_space *mapping = inode->i_mapping; 1453 pgoff_t index; 1454 unsigned long offset; 1455 enum sgp_type sgp = SGP_READ; 1456 1457 /* 1458 * Might this read be for a stacking filesystem? Then when reading 1459 * holes of a sparse file, we actually need to allocate those pages, 1460 * and even mark them dirty, so it cannot exceed the max_blocks limit. 1461 */ 1462 if (segment_eq(get_fs(), KERNEL_DS)) 1463 sgp = SGP_DIRTY; 1464 1465 index = *ppos >> PAGE_CACHE_SHIFT; 1466 offset = *ppos & ~PAGE_CACHE_MASK; 1467 1468 for (;;) { 1469 struct page *page = NULL; 1470 pgoff_t end_index; 1471 unsigned long nr, ret; 1472 loff_t i_size = i_size_read(inode); 1473 1474 end_index = i_size >> PAGE_CACHE_SHIFT; 1475 if (index > end_index) 1476 break; 1477 if (index == end_index) { 1478 nr = i_size & ~PAGE_CACHE_MASK; 1479 if (nr <= offset) 1480 break; 1481 } 1482 1483 desc->error = shmem_getpage(inode, index, &page, sgp, NULL); 1484 if (desc->error) { 1485 if (desc->error == -EINVAL) 1486 desc->error = 0; 1487 break; 1488 } 1489 if (page) 1490 unlock_page(page); 1491 1492 /* 1493 * We must evaluate after, since reads (unlike writes) 1494 * are called without i_mutex protection against truncate 1495 */ 1496 nr = PAGE_CACHE_SIZE; 1497 i_size = i_size_read(inode); 1498 end_index = i_size >> PAGE_CACHE_SHIFT; 1499 if (index == end_index) { 1500 nr = i_size & ~PAGE_CACHE_MASK; 1501 if (nr <= offset) { 1502 if (page) 1503 page_cache_release(page); 1504 break; 1505 } 1506 } 1507 nr -= offset; 1508 1509 if (page) { 1510 /* 1511 * If users can be writing to this page using arbitrary 1512 * virtual addresses, take care about potential aliasing 1513 * before reading the page on the kernel side. 1514 */ 1515 if (mapping_writably_mapped(mapping)) 1516 flush_dcache_page(page); 1517 /* 1518 * Mark the page accessed if we read the beginning. 1519 */ 1520 if (!offset) 1521 mark_page_accessed(page); 1522 } else { 1523 page = ZERO_PAGE(0); 1524 page_cache_get(page); 1525 } 1526 1527 /* 1528 * Ok, we have the page, and it's up-to-date, so 1529 * now we can copy it to user space... 1530 * 1531 * The actor routine returns how many bytes were actually used.. 1532 * NOTE! This may not be the same as how much of a user buffer 1533 * we filled up (we may be padding etc), so we can only update 1534 * "pos" here (the actor routine has to update the user buffer 1535 * pointers and the remaining count). 1536 */ 1537 ret = actor(desc, page, offset, nr); 1538 offset += ret; 1539 index += offset >> PAGE_CACHE_SHIFT; 1540 offset &= ~PAGE_CACHE_MASK; 1541 1542 page_cache_release(page); 1543 if (ret != nr || !desc->count) 1544 break; 1545 1546 cond_resched(); 1547 } 1548 1549 *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset; 1550 file_accessed(filp); 1551} 1552 1553static ssize_t shmem_file_aio_read(struct kiocb *iocb, 1554 const struct iovec *iov, unsigned long nr_segs, loff_t pos) 1555{ 1556 struct file *filp = iocb->ki_filp; 1557 ssize_t retval; 1558 unsigned long seg; 1559 size_t count; 1560 loff_t *ppos = &iocb->ki_pos; 1561 1562 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE); 1563 if (retval) 1564 return retval; 1565 1566 for (seg = 0; seg < nr_segs; seg++) { 1567 read_descriptor_t desc; 1568 1569 desc.written = 0; 1570 desc.arg.buf = iov[seg].iov_base; 1571 desc.count = iov[seg].iov_len; 1572 if (desc.count == 0) 1573 continue; 1574 desc.error = 0; 1575 do_shmem_file_read(filp, ppos, &desc, file_read_actor); 1576 retval += desc.written; 1577 if (desc.error) { 1578 retval = retval ?: desc.error; 1579 break; 1580 } 1581 if (desc.count > 0) 1582 break; 1583 } 1584 return retval; 1585} 1586 1587static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 1588 struct pipe_inode_info *pipe, size_t len, 1589 unsigned int flags) 1590{ 1591 struct address_space *mapping = in->f_mapping; 1592 struct inode *inode = mapping->host; 1593 unsigned int loff, nr_pages, req_pages; 1594 struct page *pages[PIPE_DEF_BUFFERS]; 1595 struct partial_page partial[PIPE_DEF_BUFFERS]; 1596 struct page *page; 1597 pgoff_t index, end_index; 1598 loff_t isize, left; 1599 int error, page_nr; 1600 struct splice_pipe_desc spd = { 1601 .pages = pages, 1602 .partial = partial, 1603 .nr_pages_max = PIPE_DEF_BUFFERS, 1604 .flags = flags, 1605 .ops = &page_cache_pipe_buf_ops, 1606 .spd_release = spd_release_page, 1607 }; 1608 1609 isize = i_size_read(inode); 1610 if (unlikely(*ppos >= isize)) 1611 return 0; 1612 1613 left = isize - *ppos; 1614 if (unlikely(left < len)) 1615 len = left; 1616 1617 if (splice_grow_spd(pipe, &spd)) 1618 return -ENOMEM; 1619 1620 index = *ppos >> PAGE_CACHE_SHIFT; 1621 loff = *ppos & ~PAGE_CACHE_MASK; 1622 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1623 nr_pages = min(req_pages, pipe->buffers); 1624 1625 spd.nr_pages = find_get_pages_contig(mapping, index, 1626 nr_pages, spd.pages); 1627 index += spd.nr_pages; 1628 error = 0; 1629 1630 while (spd.nr_pages < nr_pages) { 1631 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL); 1632 if (error) 1633 break; 1634 unlock_page(page); 1635 spd.pages[spd.nr_pages++] = page; 1636 index++; 1637 } 1638 1639 index = *ppos >> PAGE_CACHE_SHIFT; 1640 nr_pages = spd.nr_pages; 1641 spd.nr_pages = 0; 1642 1643 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 1644 unsigned int this_len; 1645 1646 if (!len) 1647 break; 1648 1649 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 1650 page = spd.pages[page_nr]; 1651 1652 if (!PageUptodate(page) || page->mapping != mapping) { 1653 error = shmem_getpage(inode, index, &page, 1654 SGP_CACHE, NULL); 1655 if (error) 1656 break; 1657 unlock_page(page); 1658 page_cache_release(spd.pages[page_nr]); 1659 spd.pages[page_nr] = page; 1660 } 1661 1662 isize = i_size_read(inode); 1663 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1664 if (unlikely(!isize || index > end_index)) 1665 break; 1666 1667 if (end_index == index) { 1668 unsigned int plen; 1669 1670 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1671 if (plen <= loff) 1672 break; 1673 1674 this_len = min(this_len, plen - loff); 1675 len = this_len; 1676 } 1677 1678 spd.partial[page_nr].offset = loff; 1679 spd.partial[page_nr].len = this_len; 1680 len -= this_len; 1681 loff = 0; 1682 spd.nr_pages++; 1683 index++; 1684 } 1685 1686 while (page_nr < nr_pages) 1687 page_cache_release(spd.pages[page_nr++]); 1688 1689 if (spd.nr_pages) 1690 error = splice_to_pipe(pipe, &spd); 1691 1692 splice_shrink_spd(&spd); 1693 1694 if (error > 0) { 1695 *ppos += error; 1696 file_accessed(in); 1697 } 1698 return error; 1699} 1700 1701static long shmem_fallocate(struct file *file, int mode, loff_t offset, 1702 loff_t len) 1703{ 1704 struct inode *inode = file->f_path.dentry->d_inode; 1705 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); 1706 struct shmem_falloc shmem_falloc; 1707 pgoff_t start, index, end; 1708 int error; 1709 1710 mutex_lock(&inode->i_mutex); 1711 1712 if (mode & FALLOC_FL_PUNCH_HOLE) { 1713 struct address_space *mapping = file->f_mapping; 1714 loff_t unmap_start = round_up(offset, PAGE_SIZE); 1715 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1; 1716 1717 if ((u64)unmap_end > (u64)unmap_start) 1718 unmap_mapping_range(mapping, unmap_start, 1719 1 + unmap_end - unmap_start, 0); 1720 shmem_truncate_range(inode, offset, offset + len - 1); 1721 /* No need to unmap again: hole-punching leaves COWed pages */ 1722 error = 0; 1723 goto out; 1724 } 1725 1726 /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */ 1727 error = inode_newsize_ok(inode, offset + len); 1728 if (error) 1729 goto out; 1730 1731 start = offset >> PAGE_CACHE_SHIFT; 1732 end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1733 /* Try to avoid a swapstorm if len is impossible to satisfy */ 1734 if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) { 1735 error = -ENOSPC; 1736 goto out; 1737 } 1738 1739 shmem_falloc.start = start; 1740 shmem_falloc.next = start; 1741 shmem_falloc.nr_falloced = 0; 1742 shmem_falloc.nr_unswapped = 0; 1743 spin_lock(&inode->i_lock); 1744 inode->i_private = &shmem_falloc; 1745 spin_unlock(&inode->i_lock); 1746 1747 for (index = start; index < end; index++) { 1748 struct page *page; 1749 1750 /* 1751 * Good, the fallocate(2) manpage permits EINTR: we may have 1752 * been interrupted because we are using up too much memory. 1753 */ 1754 if (signal_pending(current)) 1755 error = -EINTR; 1756 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced) 1757 error = -ENOMEM; 1758 else 1759 error = shmem_getpage(inode, index, &page, SGP_FALLOC, 1760 NULL); 1761 if (error) { 1762 /* Remove the !PageUptodate pages we added */ 1763 shmem_undo_range(inode, 1764 (loff_t)start << PAGE_CACHE_SHIFT, 1765 (loff_t)index << PAGE_CACHE_SHIFT, true); 1766 goto undone; 1767 } 1768 1769 /* 1770 * Inform shmem_writepage() how far we have reached. 1771 * No need for lock or barrier: we have the page lock. 1772 */ 1773 shmem_falloc.next++; 1774 if (!PageUptodate(page)) 1775 shmem_falloc.nr_falloced++; 1776 1777 /* 1778 * If !PageUptodate, leave it that way so that freeable pages 1779 * can be recognized if we need to rollback on error later. 1780 * But set_page_dirty so that memory pressure will swap rather 1781 * than free the pages we are allocating (and SGP_CACHE pages 1782 * might still be clean: we now need to mark those dirty too). 1783 */ 1784 set_page_dirty(page); 1785 unlock_page(page); 1786 page_cache_release(page); 1787 cond_resched(); 1788 } 1789 1790 if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size) 1791 i_size_write(inode, offset + len); 1792 inode->i_ctime = CURRENT_TIME; 1793undone: 1794 spin_lock(&inode->i_lock); 1795 inode->i_private = NULL; 1796 spin_unlock(&inode->i_lock); 1797out: 1798 mutex_unlock(&inode->i_mutex); 1799 return error; 1800} 1801 1802static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf) 1803{ 1804 struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb); 1805 1806 buf->f_type = TMPFS_MAGIC; 1807 buf->f_bsize = PAGE_CACHE_SIZE; 1808 buf->f_namelen = NAME_MAX; 1809 if (sbinfo->max_blocks) { 1810 buf->f_blocks = sbinfo->max_blocks; 1811 buf->f_bavail = 1812 buf->f_bfree = sbinfo->max_blocks - 1813 percpu_counter_sum(&sbinfo->used_blocks); 1814 } 1815 if (sbinfo->max_inodes) { 1816 buf->f_files = sbinfo->max_inodes; 1817 buf->f_ffree = sbinfo->free_inodes; 1818 } 1819 /* else leave those fields 0 like simple_statfs */ 1820 return 0; 1821} 1822 1823/* 1824 * File creation. Allocate an inode, and we're done.. 1825 */ 1826static int 1827shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 1828{ 1829 struct inode *inode; 1830 int error = -ENOSPC; 1831 1832 inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE); 1833 if (inode) { 1834 error = security_inode_init_security(inode, dir, 1835 &dentry->d_name, 1836 shmem_initxattrs, NULL); 1837 if (error) { 1838 if (error != -EOPNOTSUPP) { 1839 iput(inode); 1840 return error; 1841 } 1842 } 1843#ifdef CONFIG_TMPFS_POSIX_ACL 1844 error = generic_acl_init(inode, dir); 1845 if (error) { 1846 iput(inode); 1847 return error; 1848 } 1849#else 1850 error = 0; 1851#endif 1852 dir->i_size += BOGO_DIRENT_SIZE; 1853 dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1854 d_instantiate(dentry, inode); 1855 dget(dentry); /* Extra count - pin the dentry in core */ 1856 } 1857 return error; 1858} 1859 1860static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 1861{ 1862 int error; 1863 1864 if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0))) 1865 return error; 1866 inc_nlink(dir); 1867 return 0; 1868} 1869 1870static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode, 1871 bool excl) 1872{ 1873 return shmem_mknod(dir, dentry, mode | S_IFREG, 0); 1874} 1875 1876/* 1877 * Link a file.. 1878 */ 1879static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) 1880{ 1881 struct inode *inode = old_dentry->d_inode; 1882 int ret; 1883 1884 /* 1885 * No ordinary (disk based) filesystem counts links as inodes; 1886 * but each new link needs a new dentry, pinning lowmem, and 1887 * tmpfs dentries cannot be pruned until they are unlinked. 1888 */ 1889 ret = shmem_reserve_inode(inode->i_sb); 1890 if (ret) 1891 goto out; 1892 1893 dir->i_size += BOGO_DIRENT_SIZE; 1894 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1895 inc_nlink(inode); 1896 ihold(inode); /* New dentry reference */ 1897 dget(dentry); /* Extra pinning count for the created dentry */ 1898 d_instantiate(dentry, inode); 1899out: 1900 return ret; 1901} 1902 1903static int shmem_unlink(struct inode *dir, struct dentry *dentry) 1904{ 1905 struct inode *inode = dentry->d_inode; 1906 1907 if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) 1908 shmem_free_inode(inode->i_sb); 1909 1910 dir->i_size -= BOGO_DIRENT_SIZE; 1911 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1912 drop_nlink(inode); 1913 dput(dentry); /* Undo the count from "create" - this does all the work */ 1914 return 0; 1915} 1916 1917static int shmem_rmdir(struct inode *dir, struct dentry *dentry) 1918{ 1919 if (!simple_empty(dentry)) 1920 return -ENOTEMPTY; 1921 1922 drop_nlink(dentry->d_inode); 1923 drop_nlink(dir); 1924 return shmem_unlink(dir, dentry); 1925} 1926 1927/* 1928 * The VFS layer already does all the dentry stuff for rename, 1929 * we just have to decrement the usage count for the target if 1930 * it exists so that the VFS layer correctly free's it when it 1931 * gets overwritten. 1932 */ 1933static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) 1934{ 1935 struct inode *inode = old_dentry->d_inode; 1936 int they_are_dirs = S_ISDIR(inode->i_mode); 1937 1938 if (!simple_empty(new_dentry)) 1939 return -ENOTEMPTY; 1940 1941 if (new_dentry->d_inode) { 1942 (void) shmem_unlink(new_dir, new_dentry); 1943 if (they_are_dirs) 1944 drop_nlink(old_dir); 1945 } else if (they_are_dirs) { 1946 drop_nlink(old_dir); 1947 inc_nlink(new_dir); 1948 } 1949 1950 old_dir->i_size -= BOGO_DIRENT_SIZE; 1951 new_dir->i_size += BOGO_DIRENT_SIZE; 1952 old_dir->i_ctime = old_dir->i_mtime = 1953 new_dir->i_ctime = new_dir->i_mtime = 1954 inode->i_ctime = CURRENT_TIME; 1955 return 0; 1956} 1957 1958static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname) 1959{ 1960 int error; 1961 int len; 1962 struct inode *inode; 1963 struct page *page; 1964 char *kaddr; 1965 struct shmem_inode_info *info; 1966 1967 len = strlen(symname) + 1; 1968 if (len > PAGE_CACHE_SIZE) 1969 return -ENAMETOOLONG; 1970 1971 inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE); 1972 if (!inode) 1973 return -ENOSPC; 1974 1975 error = security_inode_init_security(inode, dir, &dentry->d_name, 1976 shmem_initxattrs, NULL); 1977 if (error) { 1978 if (error != -EOPNOTSUPP) { 1979 iput(inode); 1980 return error; 1981 } 1982 error = 0; 1983 } 1984 1985 info = SHMEM_I(inode); 1986 inode->i_size = len-1; 1987 if (len <= SHORT_SYMLINK_LEN) { 1988 info->symlink = kmemdup(symname, len, GFP_KERNEL); 1989 if (!info->symlink) { 1990 iput(inode); 1991 return -ENOMEM; 1992 } 1993 inode->i_op = &shmem_short_symlink_operations; 1994 } else { 1995 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL); 1996 if (error) { 1997 iput(inode); 1998 return error; 1999 } 2000 inode->i_mapping->a_ops = &shmem_aops; 2001 inode->i_op = &shmem_symlink_inode_operations; 2002 kaddr = kmap_atomic(page); 2003 memcpy(kaddr, symname, len); 2004 kunmap_atomic(kaddr); 2005 SetPageUptodate(page); 2006 set_page_dirty(page); 2007 unlock_page(page); 2008 page_cache_release(page); 2009 } 2010 dir->i_size += BOGO_DIRENT_SIZE; 2011 dir->i_ctime = dir->i_mtime = CURRENT_TIME; 2012 d_instantiate(dentry, inode); 2013 dget(dentry); 2014 return 0; 2015} 2016 2017static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd) 2018{ 2019 nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink); 2020 return NULL; 2021} 2022 2023static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd) 2024{ 2025 struct page *page = NULL; 2026 int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL); 2027 nd_set_link(nd, error ? ERR_PTR(error) : kmap(page)); 2028 if (page) 2029 unlock_page(page); 2030 return page; 2031} 2032 2033static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) 2034{ 2035 if (!IS_ERR(nd_get_link(nd))) { 2036 struct page *page = cookie; 2037 kunmap(page); 2038 mark_page_accessed(page); 2039 page_cache_release(page); 2040 } 2041} 2042 2043#ifdef CONFIG_TMPFS_XATTR 2044/* 2045 * Superblocks without xattr inode operations may get some security.* xattr 2046 * support from the LSM "for free". As soon as we have any other xattrs 2047 * like ACLs, we also need to implement the security.* handlers at 2048 * filesystem level, though. 2049 */ 2050 2051/* 2052 * Callback for security_inode_init_security() for acquiring xattrs. 2053 */ 2054static int shmem_initxattrs(struct inode *inode, 2055 const struct xattr *xattr_array, 2056 void *fs_info) 2057{ 2058 struct shmem_inode_info *info = SHMEM_I(inode); 2059 const struct xattr *xattr; 2060 struct simple_xattr *new_xattr; 2061 size_t len; 2062 2063 for (xattr = xattr_array; xattr->name != NULL; xattr++) { 2064 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len); 2065 if (!new_xattr) 2066 return -ENOMEM; 2067 2068 len = strlen(xattr->name) + 1; 2069 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len, 2070 GFP_KERNEL); 2071 if (!new_xattr->name) { 2072 kfree(new_xattr); 2073 return -ENOMEM; 2074 } 2075 2076 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX, 2077 XATTR_SECURITY_PREFIX_LEN); 2078 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN, 2079 xattr->name, len); 2080 2081 simple_xattr_list_add(&info->xattrs, new_xattr); 2082 } 2083 2084 return 0; 2085} 2086 2087static const struct xattr_handler *shmem_xattr_handlers[] = { 2088#ifdef CONFIG_TMPFS_POSIX_ACL 2089 &generic_acl_access_handler, 2090 &generic_acl_default_handler, 2091#endif 2092 NULL 2093}; 2094 2095static int shmem_xattr_validate(const char *name) 2096{ 2097 struct { const char *prefix; size_t len; } arr[] = { 2098 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN }, 2099 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN } 2100 }; 2101 int i; 2102 2103 for (i = 0; i < ARRAY_SIZE(arr); i++) { 2104 size_t preflen = arr[i].len; 2105 if (strncmp(name, arr[i].prefix, preflen) == 0) { 2106 if (!name[preflen]) 2107 return -EINVAL; 2108 return 0; 2109 } 2110 } 2111 return -EOPNOTSUPP; 2112} 2113 2114static ssize_t shmem_getxattr(struct dentry *dentry, const char *name, 2115 void *buffer, size_t size) 2116{ 2117 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2118 int err; 2119 2120 /* 2121 * If this is a request for a synthetic attribute in the system.* 2122 * namespace use the generic infrastructure to resolve a handler 2123 * for it via sb->s_xattr. 2124 */ 2125 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2126 return generic_getxattr(dentry, name, buffer, size); 2127 2128 err = shmem_xattr_validate(name); 2129 if (err) 2130 return err; 2131 2132 return simple_xattr_get(&info->xattrs, name, buffer, size); 2133} 2134 2135static int shmem_setxattr(struct dentry *dentry, const char *name, 2136 const void *value, size_t size, int flags) 2137{ 2138 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2139 int err; 2140 2141 /* 2142 * If this is a request for a synthetic attribute in the system.* 2143 * namespace use the generic infrastructure to resolve a handler 2144 * for it via sb->s_xattr. 2145 */ 2146 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2147 return generic_setxattr(dentry, name, value, size, flags); 2148 2149 err = shmem_xattr_validate(name); 2150 if (err) 2151 return err; 2152 2153 return simple_xattr_set(&info->xattrs, name, value, size, flags); 2154} 2155 2156static int shmem_removexattr(struct dentry *dentry, const char *name) 2157{ 2158 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2159 int err; 2160 2161 /* 2162 * If this is a request for a synthetic attribute in the system.* 2163 * namespace use the generic infrastructure to resolve a handler 2164 * for it via sb->s_xattr. 2165 */ 2166 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2167 return generic_removexattr(dentry, name); 2168 2169 err = shmem_xattr_validate(name); 2170 if (err) 2171 return err; 2172 2173 return simple_xattr_remove(&info->xattrs, name); 2174} 2175 2176static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size) 2177{ 2178 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2179 return simple_xattr_list(&info->xattrs, buffer, size); 2180} 2181#endif /* CONFIG_TMPFS_XATTR */ 2182 2183static const struct inode_operations shmem_short_symlink_operations = { 2184 .readlink = generic_readlink, 2185 .follow_link = shmem_follow_short_symlink, 2186#ifdef CONFIG_TMPFS_XATTR 2187 .setxattr = shmem_setxattr, 2188 .getxattr = shmem_getxattr, 2189 .listxattr = shmem_listxattr, 2190 .removexattr = shmem_removexattr, 2191#endif 2192}; 2193 2194static const struct inode_operations shmem_symlink_inode_operations = { 2195 .readlink = generic_readlink, 2196 .follow_link = shmem_follow_link, 2197 .put_link = shmem_put_link, 2198#ifdef CONFIG_TMPFS_XATTR 2199 .setxattr = shmem_setxattr, 2200 .getxattr = shmem_getxattr, 2201 .listxattr = shmem_listxattr, 2202 .removexattr = shmem_removexattr, 2203#endif 2204}; 2205 2206static struct dentry *shmem_get_parent(struct dentry *child) 2207{ 2208 return ERR_PTR(-ESTALE); 2209} 2210 2211static int shmem_match(struct inode *ino, void *vfh) 2212{ 2213 __u32 *fh = vfh; 2214 __u64 inum = fh[2]; 2215 inum = (inum << 32) | fh[1]; 2216 return ino->i_ino == inum && fh[0] == ino->i_generation; 2217} 2218 2219static struct dentry *shmem_fh_to_dentry(struct super_block *sb, 2220 struct fid *fid, int fh_len, int fh_type) 2221{ 2222 struct inode *inode; 2223 struct dentry *dentry = NULL; 2224 u64 inum = fid->raw[2]; 2225 inum = (inum << 32) | fid->raw[1]; 2226 2227 if (fh_len < 3) 2228 return NULL; 2229 2230 inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]), 2231 shmem_match, fid->raw); 2232 if (inode) { 2233 dentry = d_find_alias(inode); 2234 iput(inode); 2235 } 2236 2237 return dentry; 2238} 2239 2240static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len, 2241 struct inode *parent) 2242{ 2243 if (*len < 3) { 2244 *len = 3; 2245 return 255; 2246 } 2247 2248 if (inode_unhashed(inode)) { 2249 /* Unfortunately insert_inode_hash is not idempotent, 2250 * so as we hash inodes here rather than at creation 2251 * time, we need a lock to ensure we only try 2252 * to do it once 2253 */ 2254 static DEFINE_SPINLOCK(lock); 2255 spin_lock(&lock); 2256 if (inode_unhashed(inode)) 2257 __insert_inode_hash(inode, 2258 inode->i_ino + inode->i_generation); 2259 spin_unlock(&lock); 2260 } 2261 2262 fh[0] = inode->i_generation; 2263 fh[1] = inode->i_ino; 2264 fh[2] = ((__u64)inode->i_ino) >> 32; 2265 2266 *len = 3; 2267 return 1; 2268} 2269 2270static const struct export_operations shmem_export_ops = { 2271 .get_parent = shmem_get_parent, 2272 .encode_fh = shmem_encode_fh, 2273 .fh_to_dentry = shmem_fh_to_dentry, 2274}; 2275 2276static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo, 2277 bool remount) 2278{ 2279 char *this_char, *value, *rest; 2280 uid_t uid; 2281 gid_t gid; 2282 2283 while (options != NULL) { 2284 this_char = options; 2285 for (;;) { 2286 /* 2287 * NUL-terminate this option: unfortunately, 2288 * mount options form a comma-separated list, 2289 * but mpol's nodelist may also contain commas. 2290 */ 2291 options = strchr(options, ','); 2292 if (options == NULL) 2293 break; 2294 options++; 2295 if (!isdigit(*options)) { 2296 options[-1] = '\0'; 2297 break; 2298 } 2299 } 2300 if (!*this_char) 2301 continue; 2302 if ((value = strchr(this_char,'=')) != NULL) { 2303 *value++ = 0; 2304 } else { 2305 printk(KERN_ERR 2306 "tmpfs: No value for mount option '%s'\n", 2307 this_char); 2308 return 1; 2309 } 2310 2311 if (!strcmp(this_char,"size")) { 2312 unsigned long long size; 2313 size = memparse(value,&rest); 2314 if (*rest == '%') { 2315 size <<= PAGE_SHIFT; 2316 size *= totalram_pages; 2317 do_div(size, 100); 2318 rest++; 2319 } 2320 if (*rest) 2321 goto bad_val; 2322 sbinfo->max_blocks = 2323 DIV_ROUND_UP(size, PAGE_CACHE_SIZE); 2324 } else if (!strcmp(this_char,"nr_blocks")) { 2325 sbinfo->max_blocks = memparse(value, &rest); 2326 if (*rest) 2327 goto bad_val; 2328 } else if (!strcmp(this_char,"nr_inodes")) { 2329 sbinfo->max_inodes = memparse(value, &rest); 2330 if (*rest) 2331 goto bad_val; 2332 } else if (!strcmp(this_char,"mode")) { 2333 if (remount) 2334 continue; 2335 sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777; 2336 if (*rest) 2337 goto bad_val; 2338 } else if (!strcmp(this_char,"uid")) { 2339 if (remount) 2340 continue; 2341 uid = simple_strtoul(value, &rest, 0); 2342 if (*rest) 2343 goto bad_val; 2344 sbinfo->uid = make_kuid(current_user_ns(), uid); 2345 if (!uid_valid(sbinfo->uid)) 2346 goto bad_val; 2347 } else if (!strcmp(this_char,"gid")) { 2348 if (remount) 2349 continue; 2350 gid = simple_strtoul(value, &rest, 0); 2351 if (*rest) 2352 goto bad_val; 2353 sbinfo->gid = make_kgid(current_user_ns(), gid); 2354 if (!gid_valid(sbinfo->gid)) 2355 goto bad_val; 2356 } else if (!strcmp(this_char,"mpol")) { 2357 if (mpol_parse_str(value, &sbinfo->mpol, 1)) 2358 goto bad_val; 2359 } else { 2360 printk(KERN_ERR "tmpfs: Bad mount option %s\n", 2361 this_char); 2362 return 1; 2363 } 2364 } 2365 return 0; 2366 2367bad_val: 2368 printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n", 2369 value, this_char); 2370 return 1; 2371 2372} 2373 2374static int shmem_remount_fs(struct super_block *sb, int *flags, char *data) 2375{ 2376 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 2377 struct shmem_sb_info config = *sbinfo; 2378 unsigned long inodes; 2379 int error = -EINVAL; 2380 2381 if (shmem_parse_options(data, &config, true)) 2382 return error; 2383 2384 spin_lock(&sbinfo->stat_lock); 2385 inodes = sbinfo->max_inodes - sbinfo->free_inodes; 2386 if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0) 2387 goto out; 2388 if (config.max_inodes < inodes) 2389 goto out; 2390 /* 2391 * Those tests disallow limited->unlimited while any are in use; 2392 * but we must separately disallow unlimited->limited, because 2393 * in that case we have no record of how much is already in use. 2394 */ 2395 if (config.max_blocks && !sbinfo->max_blocks) 2396 goto out; 2397 if (config.max_inodes && !sbinfo->max_inodes) 2398 goto out; 2399 2400 error = 0; 2401 sbinfo->max_blocks = config.max_blocks; 2402 sbinfo->max_inodes = config.max_inodes; 2403 sbinfo->free_inodes = config.max_inodes - inodes; 2404 2405 mpol_put(sbinfo->mpol); 2406 sbinfo->mpol = config.mpol; /* transfers initial ref */ 2407out: 2408 spin_unlock(&sbinfo->stat_lock); 2409 return error; 2410} 2411 2412static int shmem_show_options(struct seq_file *seq, struct dentry *root) 2413{ 2414 struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb); 2415 2416 if (sbinfo->max_blocks != shmem_default_max_blocks()) 2417 seq_printf(seq, ",size=%luk", 2418 sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10)); 2419 if (sbinfo->max_inodes != shmem_default_max_inodes()) 2420 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes); 2421 if (sbinfo->mode != (S_IRWXUGO | S_ISVTX)) 2422 seq_printf(seq, ",mode=%03ho", sbinfo->mode); 2423 if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID)) 2424 seq_printf(seq, ",uid=%u", 2425 from_kuid_munged(&init_user_ns, sbinfo->uid)); 2426 if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID)) 2427 seq_printf(seq, ",gid=%u", 2428 from_kgid_munged(&init_user_ns, sbinfo->gid)); 2429 shmem_show_mpol(seq, sbinfo->mpol); 2430 return 0; 2431} 2432#endif /* CONFIG_TMPFS */ 2433 2434static void shmem_put_super(struct super_block *sb) 2435{ 2436 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 2437 2438 percpu_counter_destroy(&sbinfo->used_blocks); 2439 kfree(sbinfo); 2440 sb->s_fs_info = NULL; 2441} 2442 2443int shmem_fill_super(struct super_block *sb, void *data, int silent) 2444{ 2445 struct inode *inode; 2446 struct shmem_sb_info *sbinfo; 2447 int err = -ENOMEM; 2448 2449 /* Round up to L1_CACHE_BYTES to resist false sharing */ 2450 sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info), 2451 L1_CACHE_BYTES), GFP_KERNEL); 2452 if (!sbinfo) 2453 return -ENOMEM; 2454 2455 sbinfo->mode = S_IRWXUGO | S_ISVTX; 2456 sbinfo->uid = current_fsuid(); 2457 sbinfo->gid = current_fsgid(); 2458 sb->s_fs_info = sbinfo; 2459 2460#ifdef CONFIG_TMPFS 2461 /* 2462 * Per default we only allow half of the physical ram per 2463 * tmpfs instance, limiting inodes to one per page of lowmem; 2464 * but the internal instance is left unlimited. 2465 */ 2466 if (!(sb->s_flags & MS_NOUSER)) { 2467 sbinfo->max_blocks = shmem_default_max_blocks(); 2468 sbinfo->max_inodes = shmem_default_max_inodes(); 2469 if (shmem_parse_options(data, sbinfo, false)) { 2470 err = -EINVAL; 2471 goto failed; 2472 } 2473 } 2474 sb->s_export_op = &shmem_export_ops; 2475 sb->s_flags |= MS_NOSEC; 2476#else 2477 sb->s_flags |= MS_NOUSER; 2478#endif 2479 2480 spin_lock_init(&sbinfo->stat_lock); 2481 if (percpu_counter_init(&sbinfo->used_blocks, 0)) 2482 goto failed; 2483 sbinfo->free_inodes = sbinfo->max_inodes; 2484 2485 sb->s_maxbytes = MAX_LFS_FILESIZE; 2486 sb->s_blocksize = PAGE_CACHE_SIZE; 2487 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 2488 sb->s_magic = TMPFS_MAGIC; 2489 sb->s_op = &shmem_ops; 2490 sb->s_time_gran = 1; 2491#ifdef CONFIG_TMPFS_XATTR 2492 sb->s_xattr = shmem_xattr_handlers; 2493#endif 2494#ifdef CONFIG_TMPFS_POSIX_ACL 2495 sb->s_flags |= MS_POSIXACL; 2496#endif 2497 2498 inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE); 2499 if (!inode) 2500 goto failed; 2501 inode->i_uid = sbinfo->uid; 2502 inode->i_gid = sbinfo->gid; 2503 sb->s_root = d_make_root(inode); 2504 if (!sb->s_root) 2505 goto failed; 2506 return 0; 2507 2508failed: 2509 shmem_put_super(sb); 2510 return err; 2511} 2512 2513static struct kmem_cache *shmem_inode_cachep; 2514 2515static struct inode *shmem_alloc_inode(struct super_block *sb) 2516{ 2517 struct shmem_inode_info *info; 2518 info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL); 2519 if (!info) 2520 return NULL; 2521 return &info->vfs_inode; 2522} 2523 2524static void shmem_destroy_callback(struct rcu_head *head) 2525{ 2526 struct inode *inode = container_of(head, struct inode, i_rcu); 2527 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode)); 2528} 2529 2530static void shmem_destroy_inode(struct inode *inode) 2531{ 2532 if (S_ISREG(inode->i_mode)) 2533 mpol_free_shared_policy(&SHMEM_I(inode)->policy); 2534 call_rcu(&inode->i_rcu, shmem_destroy_callback); 2535} 2536 2537static void shmem_init_inode(void *foo) 2538{ 2539 struct shmem_inode_info *info = foo; 2540 inode_init_once(&info->vfs_inode); 2541} 2542 2543static int shmem_init_inodecache(void) 2544{ 2545 shmem_inode_cachep = kmem_cache_create("shmem_inode_cache", 2546 sizeof(struct shmem_inode_info), 2547 0, SLAB_PANIC, shmem_init_inode); 2548 return 0; 2549} 2550 2551static void shmem_destroy_inodecache(void) 2552{ 2553 kmem_cache_destroy(shmem_inode_cachep); 2554} 2555 2556static const struct address_space_operations shmem_aops = { 2557 .writepage = shmem_writepage, 2558 .set_page_dirty = __set_page_dirty_no_writeback, 2559#ifdef CONFIG_TMPFS 2560 .write_begin = shmem_write_begin, 2561 .write_end = shmem_write_end, 2562#endif 2563 .migratepage = migrate_page, 2564 .error_remove_page = generic_error_remove_page, 2565}; 2566 2567static const struct file_operations shmem_file_operations = { 2568 .mmap = shmem_mmap, 2569#ifdef CONFIG_TMPFS 2570 .llseek = generic_file_llseek, 2571 .read = do_sync_read, 2572 .write = do_sync_write, 2573 .aio_read = shmem_file_aio_read, 2574 .aio_write = generic_file_aio_write, 2575 .fsync = noop_fsync, 2576 .splice_read = shmem_file_splice_read, 2577 .splice_write = generic_file_splice_write, 2578 .fallocate = shmem_fallocate, 2579#endif 2580}; 2581 2582static const struct inode_operations shmem_inode_operations = { 2583 .setattr = shmem_setattr, 2584#ifdef CONFIG_TMPFS_XATTR 2585 .setxattr = shmem_setxattr, 2586 .getxattr = shmem_getxattr, 2587 .listxattr = shmem_listxattr, 2588 .removexattr = shmem_removexattr, 2589#endif 2590}; 2591 2592static const struct inode_operations shmem_dir_inode_operations = { 2593#ifdef CONFIG_TMPFS 2594 .create = shmem_create, 2595 .lookup = simple_lookup, 2596 .link = shmem_link, 2597 .unlink = shmem_unlink, 2598 .symlink = shmem_symlink, 2599 .mkdir = shmem_mkdir, 2600 .rmdir = shmem_rmdir, 2601 .mknod = shmem_mknod, 2602 .rename = shmem_rename, 2603#endif 2604#ifdef CONFIG_TMPFS_XATTR 2605 .setxattr = shmem_setxattr, 2606 .getxattr = shmem_getxattr, 2607 .listxattr = shmem_listxattr, 2608 .removexattr = shmem_removexattr, 2609#endif 2610#ifdef CONFIG_TMPFS_POSIX_ACL 2611 .setattr = shmem_setattr, 2612#endif 2613}; 2614 2615static const struct inode_operations shmem_special_inode_operations = { 2616#ifdef CONFIG_TMPFS_XATTR 2617 .setxattr = shmem_setxattr, 2618 .getxattr = shmem_getxattr, 2619 .listxattr = shmem_listxattr, 2620 .removexattr = shmem_removexattr, 2621#endif 2622#ifdef CONFIG_TMPFS_POSIX_ACL 2623 .setattr = shmem_setattr, 2624#endif 2625}; 2626 2627static const struct super_operations shmem_ops = { 2628 .alloc_inode = shmem_alloc_inode, 2629 .destroy_inode = shmem_destroy_inode, 2630#ifdef CONFIG_TMPFS 2631 .statfs = shmem_statfs, 2632 .remount_fs = shmem_remount_fs, 2633 .show_options = shmem_show_options, 2634#endif 2635 .evict_inode = shmem_evict_inode, 2636 .drop_inode = generic_delete_inode, 2637 .put_super = shmem_put_super, 2638}; 2639 2640static const struct vm_operations_struct shmem_vm_ops = { 2641 .fault = shmem_fault, 2642#ifdef CONFIG_NUMA 2643 .set_policy = shmem_set_policy, 2644 .get_policy = shmem_get_policy, 2645#endif 2646}; 2647 2648static struct dentry *shmem_mount(struct file_system_type *fs_type, 2649 int flags, const char *dev_name, void *data) 2650{ 2651 return mount_nodev(fs_type, flags, data, shmem_fill_super); 2652} 2653 2654static struct file_system_type shmem_fs_type = { 2655 .owner = THIS_MODULE, 2656 .name = "tmpfs", 2657 .mount = shmem_mount, 2658 .kill_sb = kill_litter_super, 2659}; 2660 2661int __init shmem_init(void) 2662{ 2663 int error; 2664 2665 error = bdi_init(&shmem_backing_dev_info); 2666 if (error) 2667 goto out4; 2668 2669 error = shmem_init_inodecache(); 2670 if (error) 2671 goto out3; 2672 2673 error = register_filesystem(&shmem_fs_type); 2674 if (error) { 2675 printk(KERN_ERR "Could not register tmpfs\n"); 2676 goto out2; 2677 } 2678 2679 shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER, 2680 shmem_fs_type.name, NULL); 2681 if (IS_ERR(shm_mnt)) { 2682 error = PTR_ERR(shm_mnt); 2683 printk(KERN_ERR "Could not kern_mount tmpfs\n"); 2684 goto out1; 2685 } 2686 return 0; 2687 2688out1: 2689 unregister_filesystem(&shmem_fs_type); 2690out2: 2691 shmem_destroy_inodecache(); 2692out3: 2693 bdi_destroy(&shmem_backing_dev_info); 2694out4: 2695 shm_mnt = ERR_PTR(error); 2696 return error; 2697} 2698 2699#else /* !CONFIG_SHMEM */ 2700 2701/* 2702 * tiny-shmem: simple shmemfs and tmpfs using ramfs code 2703 * 2704 * This is intended for small system where the benefits of the full 2705 * shmem code (swap-backed and resource-limited) are outweighed by 2706 * their complexity. On systems without swap this code should be 2707 * effectively equivalent, but much lighter weight. 2708 */ 2709 2710#include <linux/ramfs.h> 2711 2712static struct file_system_type shmem_fs_type = { 2713 .name = "tmpfs", 2714 .mount = ramfs_mount, 2715 .kill_sb = kill_litter_super, 2716}; 2717 2718int __init shmem_init(void) 2719{ 2720 BUG_ON(register_filesystem(&shmem_fs_type) != 0); 2721 2722 shm_mnt = kern_mount(&shmem_fs_type); 2723 BUG_ON(IS_ERR(shm_mnt)); 2724 2725 return 0; 2726} 2727 2728int shmem_unuse(swp_entry_t swap, struct page *page) 2729{ 2730 return 0; 2731} 2732 2733int shmem_lock(struct file *file, int lock, struct user_struct *user) 2734{ 2735 return 0; 2736} 2737 2738void shmem_unlock_mapping(struct address_space *mapping) 2739{ 2740} 2741 2742void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 2743{ 2744 truncate_inode_pages_range(inode->i_mapping, lstart, lend); 2745} 2746EXPORT_SYMBOL_GPL(shmem_truncate_range); 2747 2748#define shmem_vm_ops generic_file_vm_ops 2749#define shmem_file_operations ramfs_file_operations 2750#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev) 2751#define shmem_acct_size(flags, size) 0 2752#define shmem_unacct_size(flags, size) do {} while (0) 2753 2754#endif /* CONFIG_SHMEM */ 2755 2756/* common code */ 2757 2758/** 2759 * shmem_file_setup - get an unlinked file living in tmpfs 2760 * @name: name for dentry (to be seen in /proc/<pid>/maps 2761 * @size: size to be set for the file 2762 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size 2763 */ 2764struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags) 2765{ 2766 int error; 2767 struct file *file; 2768 struct inode *inode; 2769 struct path path; 2770 struct dentry *root; 2771 struct qstr this; 2772 2773 if (IS_ERR(shm_mnt)) 2774 return (void *)shm_mnt; 2775 2776 if (size < 0 || size > MAX_LFS_FILESIZE) 2777 return ERR_PTR(-EINVAL); 2778 2779 if (shmem_acct_size(flags, size)) 2780 return ERR_PTR(-ENOMEM); 2781 2782 error = -ENOMEM; 2783 this.name = name; 2784 this.len = strlen(name); 2785 this.hash = 0; /* will go */ 2786 root = shm_mnt->mnt_root; 2787 path.dentry = d_alloc(root, &this); 2788 if (!path.dentry) 2789 goto put_memory; 2790 path.mnt = mntget(shm_mnt); 2791 2792 error = -ENOSPC; 2793 inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags); 2794 if (!inode) 2795 goto put_dentry; 2796 2797 d_instantiate(path.dentry, inode); 2798 inode->i_size = size; 2799 clear_nlink(inode); /* It is unlinked */ 2800#ifndef CONFIG_MMU 2801 error = ramfs_nommu_expand_for_mapping(inode, size); 2802 if (error) 2803 goto put_dentry; 2804#endif 2805 2806 error = -ENFILE; 2807 file = alloc_file(&path, FMODE_WRITE | FMODE_READ, 2808 &shmem_file_operations); 2809 if (!file) 2810 goto put_dentry; 2811 2812 return file; 2813 2814put_dentry: 2815 path_put(&path); 2816put_memory: 2817 shmem_unacct_size(flags, size); 2818 return ERR_PTR(error); 2819} 2820EXPORT_SYMBOL_GPL(shmem_file_setup); 2821 2822/** 2823 * shmem_zero_setup - setup a shared anonymous mapping 2824 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff 2825 */ 2826int shmem_zero_setup(struct vm_area_struct *vma) 2827{ 2828 struct file *file; 2829 loff_t size = vma->vm_end - vma->vm_start; 2830 2831 file = shmem_file_setup("dev/zero", size, vma->vm_flags); 2832 if (IS_ERR(file)) 2833 return PTR_ERR(file); 2834 2835 if (vma->vm_file) 2836 fput(vma->vm_file); 2837 vma->vm_file = file; 2838 vma->vm_ops = &shmem_vm_ops; 2839 vma->vm_flags |= VM_CAN_NONLINEAR; 2840 return 0; 2841} 2842 2843/** 2844 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags. 2845 * @mapping: the page's address_space 2846 * @index: the page index 2847 * @gfp: the page allocator flags to use if allocating 2848 * 2849 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)", 2850 * with any new page allocations done using the specified allocation flags. 2851 * But read_cache_page_gfp() uses the ->readpage() method: which does not 2852 * suit tmpfs, since it may have pages in swapcache, and needs to find those 2853 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support. 2854 * 2855 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in 2856 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily. 2857 */ 2858struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, 2859 pgoff_t index, gfp_t gfp) 2860{ 2861#ifdef CONFIG_SHMEM 2862 struct inode *inode = mapping->host; 2863 struct page *page; 2864 int error; 2865 2866 BUG_ON(mapping->a_ops != &shmem_aops); 2867 error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL); 2868 if (error) 2869 page = ERR_PTR(error); 2870 else 2871 unlock_page(page); 2872 return page; 2873#else 2874 /* 2875 * The tiny !SHMEM case uses ramfs without swap 2876 */ 2877 return read_cache_page_gfp(mapping, index, gfp); 2878#endif 2879} 2880EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp); 2881