shmem.c revision f6cb85d00e1eb2fc3bf27ffcd0acc9d519512bb0
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/ramfs.h> 29#include <linux/pagemap.h> 30#include <linux/file.h> 31#include <linux/mm.h> 32#include <linux/export.h> 33#include <linux/swap.h> 34#include <linux/aio.h> 35 36static struct vfsmount *shm_mnt; 37 38#ifdef CONFIG_SHMEM 39/* 40 * This virtual memory filesystem is heavily based on the ramfs. It 41 * extends ramfs by the ability to use swap and honor resource limits 42 * which makes it a completely usable filesystem. 43 */ 44 45#include <linux/xattr.h> 46#include <linux/exportfs.h> 47#include <linux/posix_acl.h> 48#include <linux/posix_acl_xattr.h> 49#include <linux/mman.h> 50#include <linux/string.h> 51#include <linux/slab.h> 52#include <linux/backing-dev.h> 53#include <linux/shmem_fs.h> 54#include <linux/writeback.h> 55#include <linux/blkdev.h> 56#include <linux/pagevec.h> 57#include <linux/percpu_counter.h> 58#include <linux/falloc.h> 59#include <linux/splice.h> 60#include <linux/security.h> 61#include <linux/swapops.h> 62#include <linux/mempolicy.h> 63#include <linux/namei.h> 64#include <linux/ctype.h> 65#include <linux/migrate.h> 66#include <linux/highmem.h> 67#include <linux/seq_file.h> 68#include <linux/magic.h> 69 70#include <asm/uaccess.h> 71#include <asm/pgtable.h> 72 73#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512) 74#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT) 75 76/* Pretend that each entry is of this size in directory's i_size */ 77#define BOGO_DIRENT_SIZE 20 78 79/* Symlink up to this size is kmalloc'ed instead of using a swappable page */ 80#define SHORT_SYMLINK_LEN 128 81 82/* 83 * shmem_fallocate and shmem_writepage communicate via inode->i_private 84 * (with i_mutex making sure that it has only one user at a time): 85 * we would prefer not to enlarge the shmem inode just for that. 86 */ 87struct shmem_falloc { 88 pgoff_t start; /* start of range currently being fallocated */ 89 pgoff_t next; /* the next page offset to be fallocated */ 90 pgoff_t nr_falloced; /* how many new pages have been fallocated */ 91 pgoff_t nr_unswapped; /* how often writepage refused to swap out */ 92}; 93 94/* Flag allocation requirements to shmem_getpage */ 95enum sgp_type { 96 SGP_READ, /* don't exceed i_size, don't allocate page */ 97 SGP_CACHE, /* don't exceed i_size, may allocate page */ 98 SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */ 99 SGP_WRITE, /* may exceed i_size, may allocate !Uptodate page */ 100 SGP_FALLOC, /* like SGP_WRITE, but make existing page Uptodate */ 101}; 102 103#ifdef CONFIG_TMPFS 104static unsigned long shmem_default_max_blocks(void) 105{ 106 return totalram_pages / 2; 107} 108 109static unsigned long shmem_default_max_inodes(void) 110{ 111 return min(totalram_pages - totalhigh_pages, totalram_pages / 2); 112} 113#endif 114 115static bool shmem_should_replace_page(struct page *page, gfp_t gfp); 116static int shmem_replace_page(struct page **pagep, gfp_t gfp, 117 struct shmem_inode_info *info, pgoff_t index); 118static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 119 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type); 120 121static inline int shmem_getpage(struct inode *inode, pgoff_t index, 122 struct page **pagep, enum sgp_type sgp, int *fault_type) 123{ 124 return shmem_getpage_gfp(inode, index, pagep, sgp, 125 mapping_gfp_mask(inode->i_mapping), fault_type); 126} 127 128static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb) 129{ 130 return sb->s_fs_info; 131} 132 133/* 134 * shmem_file_setup pre-accounts the whole fixed size of a VM object, 135 * for shared memory and for shared anonymous (/dev/zero) mappings 136 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1), 137 * consistent with the pre-accounting of private mappings ... 138 */ 139static inline int shmem_acct_size(unsigned long flags, loff_t size) 140{ 141 return (flags & VM_NORESERVE) ? 142 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size)); 143} 144 145static inline void shmem_unacct_size(unsigned long flags, loff_t size) 146{ 147 if (!(flags & VM_NORESERVE)) 148 vm_unacct_memory(VM_ACCT(size)); 149} 150 151/* 152 * ... whereas tmpfs objects are accounted incrementally as 153 * pages are allocated, in order to allow huge sparse files. 154 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM, 155 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM. 156 */ 157static inline int shmem_acct_block(unsigned long flags) 158{ 159 return (flags & VM_NORESERVE) ? 160 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0; 161} 162 163static inline void shmem_unacct_blocks(unsigned long flags, long pages) 164{ 165 if (flags & VM_NORESERVE) 166 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE)); 167} 168 169static const struct super_operations shmem_ops; 170static const struct address_space_operations shmem_aops; 171static const struct file_operations shmem_file_operations; 172static const struct inode_operations shmem_inode_operations; 173static const struct inode_operations shmem_dir_inode_operations; 174static const struct inode_operations shmem_special_inode_operations; 175static const struct vm_operations_struct shmem_vm_ops; 176 177static struct backing_dev_info shmem_backing_dev_info __read_mostly = { 178 .ra_pages = 0, /* No readahead */ 179 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, 180}; 181 182static LIST_HEAD(shmem_swaplist); 183static DEFINE_MUTEX(shmem_swaplist_mutex); 184 185static int shmem_reserve_inode(struct super_block *sb) 186{ 187 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 188 if (sbinfo->max_inodes) { 189 spin_lock(&sbinfo->stat_lock); 190 if (!sbinfo->free_inodes) { 191 spin_unlock(&sbinfo->stat_lock); 192 return -ENOSPC; 193 } 194 sbinfo->free_inodes--; 195 spin_unlock(&sbinfo->stat_lock); 196 } 197 return 0; 198} 199 200static void shmem_free_inode(struct super_block *sb) 201{ 202 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 203 if (sbinfo->max_inodes) { 204 spin_lock(&sbinfo->stat_lock); 205 sbinfo->free_inodes++; 206 spin_unlock(&sbinfo->stat_lock); 207 } 208} 209 210/** 211 * shmem_recalc_inode - recalculate the block usage of an inode 212 * @inode: inode to recalc 213 * 214 * We have to calculate the free blocks since the mm can drop 215 * undirtied hole pages behind our back. 216 * 217 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped 218 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped) 219 * 220 * It has to be called with the spinlock held. 221 */ 222static void shmem_recalc_inode(struct inode *inode) 223{ 224 struct shmem_inode_info *info = SHMEM_I(inode); 225 long freed; 226 227 freed = info->alloced - info->swapped - inode->i_mapping->nrpages; 228 if (freed > 0) { 229 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); 230 if (sbinfo->max_blocks) 231 percpu_counter_add(&sbinfo->used_blocks, -freed); 232 info->alloced -= freed; 233 inode->i_blocks -= freed * BLOCKS_PER_PAGE; 234 shmem_unacct_blocks(info->flags, freed); 235 } 236} 237 238/* 239 * Replace item expected in radix tree by a new item, while holding tree lock. 240 */ 241static int shmem_radix_tree_replace(struct address_space *mapping, 242 pgoff_t index, void *expected, void *replacement) 243{ 244 void **pslot; 245 void *item; 246 247 VM_BUG_ON(!expected); 248 VM_BUG_ON(!replacement); 249 pslot = radix_tree_lookup_slot(&mapping->page_tree, index); 250 if (!pslot) 251 return -ENOENT; 252 item = radix_tree_deref_slot_protected(pslot, &mapping->tree_lock); 253 if (item != expected) 254 return -ENOENT; 255 radix_tree_replace_slot(pslot, replacement); 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_PAGE(!PageLocked(page), page); 287 VM_BUG_ON_PAGE(!PageSwapBacked(page), 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 * Remove swap entry from radix tree, free the swap and its page cache. 333 */ 334static int shmem_free_swap(struct address_space *mapping, 335 pgoff_t index, void *radswap) 336{ 337 void *old; 338 339 spin_lock_irq(&mapping->tree_lock); 340 old = radix_tree_delete_item(&mapping->page_tree, index, radswap); 341 spin_unlock_irq(&mapping->tree_lock); 342 if (old != radswap) 343 return -ENOENT; 344 free_swap_and_cache(radix_to_swp_entry(radswap)); 345 return 0; 346} 347 348/* 349 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists. 350 */ 351void shmem_unlock_mapping(struct address_space *mapping) 352{ 353 struct pagevec pvec; 354 pgoff_t indices[PAGEVEC_SIZE]; 355 pgoff_t index = 0; 356 357 pagevec_init(&pvec, 0); 358 /* 359 * Minor point, but we might as well stop if someone else SHM_LOCKs it. 360 */ 361 while (!mapping_unevictable(mapping)) { 362 /* 363 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it 364 * has finished, if it hits a row of PAGEVEC_SIZE swap entries. 365 */ 366 pvec.nr = find_get_entries(mapping, index, 367 PAGEVEC_SIZE, pvec.pages, indices); 368 if (!pvec.nr) 369 break; 370 index = indices[pvec.nr - 1] + 1; 371 pagevec_remove_exceptionals(&pvec); 372 check_move_unevictable_pages(pvec.pages, pvec.nr); 373 pagevec_release(&pvec); 374 cond_resched(); 375 } 376} 377 378/* 379 * Remove range of pages and swap entries from radix tree, and free them. 380 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate. 381 */ 382static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, 383 bool unfalloc) 384{ 385 struct address_space *mapping = inode->i_mapping; 386 struct shmem_inode_info *info = SHMEM_I(inode); 387 pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 388 pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT; 389 unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1); 390 unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1); 391 struct pagevec pvec; 392 pgoff_t indices[PAGEVEC_SIZE]; 393 long nr_swaps_freed = 0; 394 pgoff_t index; 395 int i; 396 397 if (lend == -1) 398 end = -1; /* unsigned, so actually very big */ 399 400 pagevec_init(&pvec, 0); 401 index = start; 402 while (index < end) { 403 pvec.nr = find_get_entries(mapping, index, 404 min(end - index, (pgoff_t)PAGEVEC_SIZE), 405 pvec.pages, indices); 406 if (!pvec.nr) 407 break; 408 mem_cgroup_uncharge_start(); 409 for (i = 0; i < pagevec_count(&pvec); i++) { 410 struct page *page = pvec.pages[i]; 411 412 index = indices[i]; 413 if (index >= end) 414 break; 415 416 if (radix_tree_exceptional_entry(page)) { 417 if (unfalloc) 418 continue; 419 nr_swaps_freed += !shmem_free_swap(mapping, 420 index, page); 421 continue; 422 } 423 424 if (!trylock_page(page)) 425 continue; 426 if (!unfalloc || !PageUptodate(page)) { 427 if (page->mapping == mapping) { 428 VM_BUG_ON_PAGE(PageWriteback(page), page); 429 truncate_inode_page(mapping, page); 430 } 431 } 432 unlock_page(page); 433 } 434 pagevec_remove_exceptionals(&pvec); 435 pagevec_release(&pvec); 436 mem_cgroup_uncharge_end(); 437 cond_resched(); 438 index++; 439 } 440 441 if (partial_start) { 442 struct page *page = NULL; 443 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL); 444 if (page) { 445 unsigned int top = PAGE_CACHE_SIZE; 446 if (start > end) { 447 top = partial_end; 448 partial_end = 0; 449 } 450 zero_user_segment(page, partial_start, top); 451 set_page_dirty(page); 452 unlock_page(page); 453 page_cache_release(page); 454 } 455 } 456 if (partial_end) { 457 struct page *page = NULL; 458 shmem_getpage(inode, end, &page, SGP_READ, NULL); 459 if (page) { 460 zero_user_segment(page, 0, partial_end); 461 set_page_dirty(page); 462 unlock_page(page); 463 page_cache_release(page); 464 } 465 } 466 if (start >= end) 467 return; 468 469 index = start; 470 for ( ; ; ) { 471 cond_resched(); 472 473 pvec.nr = find_get_entries(mapping, index, 474 min(end - index, (pgoff_t)PAGEVEC_SIZE), 475 pvec.pages, indices); 476 if (!pvec.nr) { 477 if (index == start || unfalloc) 478 break; 479 index = start; 480 continue; 481 } 482 if ((index == start || unfalloc) && indices[0] >= end) { 483 pagevec_remove_exceptionals(&pvec); 484 pagevec_release(&pvec); 485 break; 486 } 487 mem_cgroup_uncharge_start(); 488 for (i = 0; i < pagevec_count(&pvec); i++) { 489 struct page *page = pvec.pages[i]; 490 491 index = indices[i]; 492 if (index >= end) 493 break; 494 495 if (radix_tree_exceptional_entry(page)) { 496 if (unfalloc) 497 continue; 498 nr_swaps_freed += !shmem_free_swap(mapping, 499 index, page); 500 continue; 501 } 502 503 lock_page(page); 504 if (!unfalloc || !PageUptodate(page)) { 505 if (page->mapping == mapping) { 506 VM_BUG_ON_PAGE(PageWriteback(page), page); 507 truncate_inode_page(mapping, page); 508 } 509 } 510 unlock_page(page); 511 } 512 pagevec_remove_exceptionals(&pvec); 513 pagevec_release(&pvec); 514 mem_cgroup_uncharge_end(); 515 index++; 516 } 517 518 spin_lock(&info->lock); 519 info->swapped -= nr_swaps_freed; 520 shmem_recalc_inode(inode); 521 spin_unlock(&info->lock); 522} 523 524void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 525{ 526 shmem_undo_range(inode, lstart, lend, false); 527 inode->i_ctime = inode->i_mtime = CURRENT_TIME; 528} 529EXPORT_SYMBOL_GPL(shmem_truncate_range); 530 531static int shmem_setattr(struct dentry *dentry, struct iattr *attr) 532{ 533 struct inode *inode = dentry->d_inode; 534 int error; 535 536 error = inode_change_ok(inode, attr); 537 if (error) 538 return error; 539 540 if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) { 541 loff_t oldsize = inode->i_size; 542 loff_t newsize = attr->ia_size; 543 544 if (newsize != oldsize) { 545 i_size_write(inode, newsize); 546 inode->i_ctime = inode->i_mtime = CURRENT_TIME; 547 } 548 if (newsize < oldsize) { 549 loff_t holebegin = round_up(newsize, PAGE_SIZE); 550 unmap_mapping_range(inode->i_mapping, holebegin, 0, 1); 551 shmem_truncate_range(inode, newsize, (loff_t)-1); 552 /* unmap again to remove racily COWed private pages */ 553 unmap_mapping_range(inode->i_mapping, holebegin, 0, 1); 554 } 555 } 556 557 setattr_copy(inode, attr); 558 if (attr->ia_valid & ATTR_MODE) 559 error = posix_acl_chmod(inode, inode->i_mode); 560 return error; 561} 562 563static void shmem_evict_inode(struct inode *inode) 564{ 565 struct shmem_inode_info *info = SHMEM_I(inode); 566 567 if (inode->i_mapping->a_ops == &shmem_aops) { 568 shmem_unacct_size(info->flags, inode->i_size); 569 inode->i_size = 0; 570 shmem_truncate_range(inode, 0, (loff_t)-1); 571 if (!list_empty(&info->swaplist)) { 572 mutex_lock(&shmem_swaplist_mutex); 573 list_del_init(&info->swaplist); 574 mutex_unlock(&shmem_swaplist_mutex); 575 } 576 } else 577 kfree(info->symlink); 578 579 simple_xattrs_free(&info->xattrs); 580 WARN_ON(inode->i_blocks); 581 shmem_free_inode(inode->i_sb); 582 clear_inode(inode); 583} 584 585/* 586 * If swap found in inode, free it and move page from swapcache to filecache. 587 */ 588static int shmem_unuse_inode(struct shmem_inode_info *info, 589 swp_entry_t swap, struct page **pagep) 590{ 591 struct address_space *mapping = info->vfs_inode.i_mapping; 592 void *radswap; 593 pgoff_t index; 594 gfp_t gfp; 595 int error = 0; 596 597 radswap = swp_to_radix_entry(swap); 598 index = radix_tree_locate_item(&mapping->page_tree, radswap); 599 if (index == -1) 600 return 0; 601 602 /* 603 * Move _head_ to start search for next from here. 604 * But be careful: shmem_evict_inode checks list_empty without taking 605 * mutex, and there's an instant in list_move_tail when info->swaplist 606 * would appear empty, if it were the only one on shmem_swaplist. 607 */ 608 if (shmem_swaplist.next != &info->swaplist) 609 list_move_tail(&shmem_swaplist, &info->swaplist); 610 611 gfp = mapping_gfp_mask(mapping); 612 if (shmem_should_replace_page(*pagep, gfp)) { 613 mutex_unlock(&shmem_swaplist_mutex); 614 error = shmem_replace_page(pagep, gfp, info, index); 615 mutex_lock(&shmem_swaplist_mutex); 616 /* 617 * We needed to drop mutex to make that restrictive page 618 * allocation, but the inode might have been freed while we 619 * dropped it: although a racing shmem_evict_inode() cannot 620 * complete without emptying the radix_tree, our page lock 621 * on this swapcache page is not enough to prevent that - 622 * free_swap_and_cache() of our swap entry will only 623 * trylock_page(), removing swap from radix_tree whatever. 624 * 625 * We must not proceed to shmem_add_to_page_cache() if the 626 * inode has been freed, but of course we cannot rely on 627 * inode or mapping or info to check that. However, we can 628 * safely check if our swap entry is still in use (and here 629 * it can't have got reused for another page): if it's still 630 * in use, then the inode cannot have been freed yet, and we 631 * can safely proceed (if it's no longer in use, that tells 632 * nothing about the inode, but we don't need to unuse swap). 633 */ 634 if (!page_swapcount(*pagep)) 635 error = -ENOENT; 636 } 637 638 /* 639 * We rely on shmem_swaplist_mutex, not only to protect the swaplist, 640 * but also to hold up shmem_evict_inode(): so inode cannot be freed 641 * beneath us (pagelock doesn't help until the page is in pagecache). 642 */ 643 if (!error) 644 error = shmem_add_to_page_cache(*pagep, mapping, index, 645 GFP_NOWAIT, radswap); 646 if (error != -ENOMEM) { 647 /* 648 * Truncation and eviction use free_swap_and_cache(), which 649 * only does trylock page: if we raced, best clean up here. 650 */ 651 delete_from_swap_cache(*pagep); 652 set_page_dirty(*pagep); 653 if (!error) { 654 spin_lock(&info->lock); 655 info->swapped--; 656 spin_unlock(&info->lock); 657 swap_free(swap); 658 } 659 error = 1; /* not an error, but entry was found */ 660 } 661 return error; 662} 663 664/* 665 * Search through swapped inodes to find and replace swap by page. 666 */ 667int shmem_unuse(swp_entry_t swap, struct page *page) 668{ 669 struct list_head *this, *next; 670 struct shmem_inode_info *info; 671 int found = 0; 672 int error = 0; 673 674 /* 675 * There's a faint possibility that swap page was replaced before 676 * caller locked it: caller will come back later with the right page. 677 */ 678 if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val)) 679 goto out; 680 681 /* 682 * Charge page using GFP_KERNEL while we can wait, before taking 683 * the shmem_swaplist_mutex which might hold up shmem_writepage(). 684 * Charged back to the user (not to caller) when swap account is used. 685 */ 686 error = mem_cgroup_charge_file(page, current->mm, GFP_KERNEL); 687 if (error) 688 goto out; 689 /* No radix_tree_preload: swap entry keeps a place for page in tree */ 690 691 mutex_lock(&shmem_swaplist_mutex); 692 list_for_each_safe(this, next, &shmem_swaplist) { 693 info = list_entry(this, struct shmem_inode_info, swaplist); 694 if (info->swapped) 695 found = shmem_unuse_inode(info, swap, &page); 696 else 697 list_del_init(&info->swaplist); 698 cond_resched(); 699 if (found) 700 break; 701 } 702 mutex_unlock(&shmem_swaplist_mutex); 703 704 if (found < 0) 705 error = found; 706out: 707 unlock_page(page); 708 page_cache_release(page); 709 return error; 710} 711 712/* 713 * Move the page from the page cache to the swap cache. 714 */ 715static int shmem_writepage(struct page *page, struct writeback_control *wbc) 716{ 717 struct shmem_inode_info *info; 718 struct address_space *mapping; 719 struct inode *inode; 720 swp_entry_t swap; 721 pgoff_t index; 722 723 BUG_ON(!PageLocked(page)); 724 mapping = page->mapping; 725 index = page->index; 726 inode = mapping->host; 727 info = SHMEM_I(inode); 728 if (info->flags & VM_LOCKED) 729 goto redirty; 730 if (!total_swap_pages) 731 goto redirty; 732 733 /* 734 * shmem_backing_dev_info's capabilities prevent regular writeback or 735 * sync from ever calling shmem_writepage; but a stacking filesystem 736 * might use ->writepage of its underlying filesystem, in which case 737 * tmpfs should write out to swap only in response to memory pressure, 738 * and not for the writeback threads or sync. 739 */ 740 if (!wbc->for_reclaim) { 741 WARN_ON_ONCE(1); /* Still happens? Tell us about it! */ 742 goto redirty; 743 } 744 745 /* 746 * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC 747 * value into swapfile.c, the only way we can correctly account for a 748 * fallocated page arriving here is now to initialize it and write it. 749 * 750 * That's okay for a page already fallocated earlier, but if we have 751 * not yet completed the fallocation, then (a) we want to keep track 752 * of this page in case we have to undo it, and (b) it may not be a 753 * good idea to continue anyway, once we're pushing into swap. So 754 * reactivate the page, and let shmem_fallocate() quit when too many. 755 */ 756 if (!PageUptodate(page)) { 757 if (inode->i_private) { 758 struct shmem_falloc *shmem_falloc; 759 spin_lock(&inode->i_lock); 760 shmem_falloc = inode->i_private; 761 if (shmem_falloc && 762 index >= shmem_falloc->start && 763 index < shmem_falloc->next) 764 shmem_falloc->nr_unswapped++; 765 else 766 shmem_falloc = NULL; 767 spin_unlock(&inode->i_lock); 768 if (shmem_falloc) 769 goto redirty; 770 } 771 clear_highpage(page); 772 flush_dcache_page(page); 773 SetPageUptodate(page); 774 } 775 776 swap = get_swap_page(); 777 if (!swap.val) 778 goto redirty; 779 780 /* 781 * Add inode to shmem_unuse()'s list of swapped-out inodes, 782 * if it's not already there. Do it now before the page is 783 * moved to swap cache, when its pagelock no longer protects 784 * the inode from eviction. But don't unlock the mutex until 785 * we've incremented swapped, because shmem_unuse_inode() will 786 * prune a !swapped inode from the swaplist under this mutex. 787 */ 788 mutex_lock(&shmem_swaplist_mutex); 789 if (list_empty(&info->swaplist)) 790 list_add_tail(&info->swaplist, &shmem_swaplist); 791 792 if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) { 793 swap_shmem_alloc(swap); 794 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap)); 795 796 spin_lock(&info->lock); 797 info->swapped++; 798 shmem_recalc_inode(inode); 799 spin_unlock(&info->lock); 800 801 mutex_unlock(&shmem_swaplist_mutex); 802 BUG_ON(page_mapped(page)); 803 swap_writepage(page, wbc); 804 return 0; 805 } 806 807 mutex_unlock(&shmem_swaplist_mutex); 808 swapcache_free(swap, NULL); 809redirty: 810 set_page_dirty(page); 811 if (wbc->for_reclaim) 812 return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */ 813 unlock_page(page); 814 return 0; 815} 816 817#ifdef CONFIG_NUMA 818#ifdef CONFIG_TMPFS 819static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) 820{ 821 char buffer[64]; 822 823 if (!mpol || mpol->mode == MPOL_DEFAULT) 824 return; /* show nothing */ 825 826 mpol_to_str(buffer, sizeof(buffer), mpol); 827 828 seq_printf(seq, ",mpol=%s", buffer); 829} 830 831static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) 832{ 833 struct mempolicy *mpol = NULL; 834 if (sbinfo->mpol) { 835 spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */ 836 mpol = sbinfo->mpol; 837 mpol_get(mpol); 838 spin_unlock(&sbinfo->stat_lock); 839 } 840 return mpol; 841} 842#endif /* CONFIG_TMPFS */ 843 844static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, 845 struct shmem_inode_info *info, pgoff_t index) 846{ 847 struct vm_area_struct pvma; 848 struct page *page; 849 850 /* Create a pseudo vma that just contains the policy */ 851 pvma.vm_start = 0; 852 /* Bias interleave by inode number to distribute better across nodes */ 853 pvma.vm_pgoff = index + info->vfs_inode.i_ino; 854 pvma.vm_ops = NULL; 855 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); 856 857 page = swapin_readahead(swap, gfp, &pvma, 0); 858 859 /* Drop reference taken by mpol_shared_policy_lookup() */ 860 mpol_cond_put(pvma.vm_policy); 861 862 return page; 863} 864 865static struct page *shmem_alloc_page(gfp_t gfp, 866 struct shmem_inode_info *info, pgoff_t index) 867{ 868 struct vm_area_struct pvma; 869 struct page *page; 870 871 /* Create a pseudo vma that just contains the policy */ 872 pvma.vm_start = 0; 873 /* Bias interleave by inode number to distribute better across nodes */ 874 pvma.vm_pgoff = index + info->vfs_inode.i_ino; 875 pvma.vm_ops = NULL; 876 pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); 877 878 page = alloc_page_vma(gfp, &pvma, 0); 879 880 /* Drop reference taken by mpol_shared_policy_lookup() */ 881 mpol_cond_put(pvma.vm_policy); 882 883 return page; 884} 885#else /* !CONFIG_NUMA */ 886#ifdef CONFIG_TMPFS 887static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol) 888{ 889} 890#endif /* CONFIG_TMPFS */ 891 892static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, 893 struct shmem_inode_info *info, pgoff_t index) 894{ 895 return swapin_readahead(swap, gfp, NULL, 0); 896} 897 898static inline struct page *shmem_alloc_page(gfp_t gfp, 899 struct shmem_inode_info *info, pgoff_t index) 900{ 901 return alloc_page(gfp); 902} 903#endif /* CONFIG_NUMA */ 904 905#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS) 906static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) 907{ 908 return NULL; 909} 910#endif 911 912/* 913 * When a page is moved from swapcache to shmem filecache (either by the 914 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of 915 * shmem_unuse_inode()), it may have been read in earlier from swap, in 916 * ignorance of the mapping it belongs to. If that mapping has special 917 * constraints (like the gma500 GEM driver, which requires RAM below 4GB), 918 * we may need to copy to a suitable page before moving to filecache. 919 * 920 * In a future release, this may well be extended to respect cpuset and 921 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page(); 922 * but for now it is a simple matter of zone. 923 */ 924static bool shmem_should_replace_page(struct page *page, gfp_t gfp) 925{ 926 return page_zonenum(page) > gfp_zone(gfp); 927} 928 929static int shmem_replace_page(struct page **pagep, gfp_t gfp, 930 struct shmem_inode_info *info, pgoff_t index) 931{ 932 struct page *oldpage, *newpage; 933 struct address_space *swap_mapping; 934 pgoff_t swap_index; 935 int error; 936 937 oldpage = *pagep; 938 swap_index = page_private(oldpage); 939 swap_mapping = page_mapping(oldpage); 940 941 /* 942 * We have arrived here because our zones are constrained, so don't 943 * limit chance of success by further cpuset and node constraints. 944 */ 945 gfp &= ~GFP_CONSTRAINT_MASK; 946 newpage = shmem_alloc_page(gfp, info, index); 947 if (!newpage) 948 return -ENOMEM; 949 950 page_cache_get(newpage); 951 copy_highpage(newpage, oldpage); 952 flush_dcache_page(newpage); 953 954 __set_page_locked(newpage); 955 SetPageUptodate(newpage); 956 SetPageSwapBacked(newpage); 957 set_page_private(newpage, swap_index); 958 SetPageSwapCache(newpage); 959 960 /* 961 * Our caller will very soon move newpage out of swapcache, but it's 962 * a nice clean interface for us to replace oldpage by newpage there. 963 */ 964 spin_lock_irq(&swap_mapping->tree_lock); 965 error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage, 966 newpage); 967 if (!error) { 968 __inc_zone_page_state(newpage, NR_FILE_PAGES); 969 __dec_zone_page_state(oldpage, NR_FILE_PAGES); 970 } 971 spin_unlock_irq(&swap_mapping->tree_lock); 972 973 if (unlikely(error)) { 974 /* 975 * Is this possible? I think not, now that our callers check 976 * both PageSwapCache and page_private after getting page lock; 977 * but be defensive. Reverse old to newpage for clear and free. 978 */ 979 oldpage = newpage; 980 } else { 981 mem_cgroup_replace_page_cache(oldpage, newpage); 982 lru_cache_add_anon(newpage); 983 *pagep = newpage; 984 } 985 986 ClearPageSwapCache(oldpage); 987 set_page_private(oldpage, 0); 988 989 unlock_page(oldpage); 990 page_cache_release(oldpage); 991 page_cache_release(oldpage); 992 return error; 993} 994 995/* 996 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate 997 * 998 * If we allocate a new one we do not mark it dirty. That's up to the 999 * vm. If we swap it in we mark it dirty since we also free the swap 1000 * entry since a page cannot live in both the swap and page cache 1001 */ 1002static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, 1003 struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type) 1004{ 1005 struct address_space *mapping = inode->i_mapping; 1006 struct shmem_inode_info *info; 1007 struct shmem_sb_info *sbinfo; 1008 struct page *page; 1009 swp_entry_t swap; 1010 int error; 1011 int once = 0; 1012 int alloced = 0; 1013 1014 if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT)) 1015 return -EFBIG; 1016repeat: 1017 swap.val = 0; 1018 page = find_lock_entry(mapping, index); 1019 if (radix_tree_exceptional_entry(page)) { 1020 swap = radix_to_swp_entry(page); 1021 page = NULL; 1022 } 1023 1024 if (sgp != SGP_WRITE && sgp != SGP_FALLOC && 1025 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) { 1026 error = -EINVAL; 1027 goto failed; 1028 } 1029 1030 /* fallocated page? */ 1031 if (page && !PageUptodate(page)) { 1032 if (sgp != SGP_READ) 1033 goto clear; 1034 unlock_page(page); 1035 page_cache_release(page); 1036 page = NULL; 1037 } 1038 if (page || (sgp == SGP_READ && !swap.val)) { 1039 *pagep = page; 1040 return 0; 1041 } 1042 1043 /* 1044 * Fast cache lookup did not find it: 1045 * bring it back from swap or allocate. 1046 */ 1047 info = SHMEM_I(inode); 1048 sbinfo = SHMEM_SB(inode->i_sb); 1049 1050 if (swap.val) { 1051 /* Look it up and read it in.. */ 1052 page = lookup_swap_cache(swap); 1053 if (!page) { 1054 /* here we actually do the io */ 1055 if (fault_type) 1056 *fault_type |= VM_FAULT_MAJOR; 1057 page = shmem_swapin(swap, gfp, info, index); 1058 if (!page) { 1059 error = -ENOMEM; 1060 goto failed; 1061 } 1062 } 1063 1064 /* We have to do this with page locked to prevent races */ 1065 lock_page(page); 1066 if (!PageSwapCache(page) || page_private(page) != swap.val || 1067 !shmem_confirm_swap(mapping, index, swap)) { 1068 error = -EEXIST; /* try again */ 1069 goto unlock; 1070 } 1071 if (!PageUptodate(page)) { 1072 error = -EIO; 1073 goto failed; 1074 } 1075 wait_on_page_writeback(page); 1076 1077 if (shmem_should_replace_page(page, gfp)) { 1078 error = shmem_replace_page(&page, gfp, info, index); 1079 if (error) 1080 goto failed; 1081 } 1082 1083 error = mem_cgroup_charge_file(page, current->mm, 1084 gfp & GFP_RECLAIM_MASK); 1085 if (!error) { 1086 error = shmem_add_to_page_cache(page, mapping, index, 1087 gfp, swp_to_radix_entry(swap)); 1088 /* 1089 * We already confirmed swap under page lock, and make 1090 * no memory allocation here, so usually no possibility 1091 * of error; but free_swap_and_cache() only trylocks a 1092 * page, so it is just possible that the entry has been 1093 * truncated or holepunched since swap was confirmed. 1094 * shmem_undo_range() will have done some of the 1095 * unaccounting, now delete_from_swap_cache() will do 1096 * the rest (including mem_cgroup_uncharge_swapcache). 1097 * Reset swap.val? No, leave it so "failed" goes back to 1098 * "repeat": reading a hole and writing should succeed. 1099 */ 1100 if (error) 1101 delete_from_swap_cache(page); 1102 } 1103 if (error) 1104 goto failed; 1105 1106 spin_lock(&info->lock); 1107 info->swapped--; 1108 shmem_recalc_inode(inode); 1109 spin_unlock(&info->lock); 1110 1111 delete_from_swap_cache(page); 1112 set_page_dirty(page); 1113 swap_free(swap); 1114 1115 } else { 1116 if (shmem_acct_block(info->flags)) { 1117 error = -ENOSPC; 1118 goto failed; 1119 } 1120 if (sbinfo->max_blocks) { 1121 if (percpu_counter_compare(&sbinfo->used_blocks, 1122 sbinfo->max_blocks) >= 0) { 1123 error = -ENOSPC; 1124 goto unacct; 1125 } 1126 percpu_counter_inc(&sbinfo->used_blocks); 1127 } 1128 1129 page = shmem_alloc_page(gfp, info, index); 1130 if (!page) { 1131 error = -ENOMEM; 1132 goto decused; 1133 } 1134 1135 SetPageSwapBacked(page); 1136 __set_page_locked(page); 1137 error = mem_cgroup_charge_file(page, current->mm, 1138 gfp & GFP_RECLAIM_MASK); 1139 if (error) 1140 goto decused; 1141 error = radix_tree_maybe_preload(gfp & GFP_RECLAIM_MASK); 1142 if (!error) { 1143 error = shmem_add_to_page_cache(page, mapping, index, 1144 gfp, NULL); 1145 radix_tree_preload_end(); 1146 } 1147 if (error) { 1148 mem_cgroup_uncharge_cache_page(page); 1149 goto decused; 1150 } 1151 lru_cache_add_anon(page); 1152 1153 spin_lock(&info->lock); 1154 info->alloced++; 1155 inode->i_blocks += BLOCKS_PER_PAGE; 1156 shmem_recalc_inode(inode); 1157 spin_unlock(&info->lock); 1158 alloced = true; 1159 1160 /* 1161 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page. 1162 */ 1163 if (sgp == SGP_FALLOC) 1164 sgp = SGP_WRITE; 1165clear: 1166 /* 1167 * Let SGP_WRITE caller clear ends if write does not fill page; 1168 * but SGP_FALLOC on a page fallocated earlier must initialize 1169 * it now, lest undo on failure cancel our earlier guarantee. 1170 */ 1171 if (sgp != SGP_WRITE) { 1172 clear_highpage(page); 1173 flush_dcache_page(page); 1174 SetPageUptodate(page); 1175 } 1176 if (sgp == SGP_DIRTY) 1177 set_page_dirty(page); 1178 } 1179 1180 /* Perhaps the file has been truncated since we checked */ 1181 if (sgp != SGP_WRITE && sgp != SGP_FALLOC && 1182 ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) { 1183 error = -EINVAL; 1184 if (alloced) 1185 goto trunc; 1186 else 1187 goto failed; 1188 } 1189 *pagep = page; 1190 return 0; 1191 1192 /* 1193 * Error recovery. 1194 */ 1195trunc: 1196 info = SHMEM_I(inode); 1197 ClearPageDirty(page); 1198 delete_from_page_cache(page); 1199 spin_lock(&info->lock); 1200 info->alloced--; 1201 inode->i_blocks -= BLOCKS_PER_PAGE; 1202 spin_unlock(&info->lock); 1203decused: 1204 sbinfo = SHMEM_SB(inode->i_sb); 1205 if (sbinfo->max_blocks) 1206 percpu_counter_add(&sbinfo->used_blocks, -1); 1207unacct: 1208 shmem_unacct_blocks(info->flags, 1); 1209failed: 1210 if (swap.val && error != -EINVAL && 1211 !shmem_confirm_swap(mapping, index, swap)) 1212 error = -EEXIST; 1213unlock: 1214 if (page) { 1215 unlock_page(page); 1216 page_cache_release(page); 1217 } 1218 if (error == -ENOSPC && !once++) { 1219 info = SHMEM_I(inode); 1220 spin_lock(&info->lock); 1221 shmem_recalc_inode(inode); 1222 spin_unlock(&info->lock); 1223 goto repeat; 1224 } 1225 if (error == -EEXIST) /* from above or from radix_tree_insert */ 1226 goto repeat; 1227 return error; 1228} 1229 1230static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) 1231{ 1232 struct inode *inode = file_inode(vma->vm_file); 1233 int error; 1234 int ret = VM_FAULT_LOCKED; 1235 1236 error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret); 1237 if (error) 1238 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS); 1239 1240 if (ret & VM_FAULT_MAJOR) { 1241 count_vm_event(PGMAJFAULT); 1242 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); 1243 } 1244 return ret; 1245} 1246 1247#ifdef CONFIG_NUMA 1248static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol) 1249{ 1250 struct inode *inode = file_inode(vma->vm_file); 1251 return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol); 1252} 1253 1254static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma, 1255 unsigned long addr) 1256{ 1257 struct inode *inode = file_inode(vma->vm_file); 1258 pgoff_t index; 1259 1260 index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; 1261 return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index); 1262} 1263#endif 1264 1265int shmem_lock(struct file *file, int lock, struct user_struct *user) 1266{ 1267 struct inode *inode = file_inode(file); 1268 struct shmem_inode_info *info = SHMEM_I(inode); 1269 int retval = -ENOMEM; 1270 1271 spin_lock(&info->lock); 1272 if (lock && !(info->flags & VM_LOCKED)) { 1273 if (!user_shm_lock(inode->i_size, user)) 1274 goto out_nomem; 1275 info->flags |= VM_LOCKED; 1276 mapping_set_unevictable(file->f_mapping); 1277 } 1278 if (!lock && (info->flags & VM_LOCKED) && user) { 1279 user_shm_unlock(inode->i_size, user); 1280 info->flags &= ~VM_LOCKED; 1281 mapping_clear_unevictable(file->f_mapping); 1282 } 1283 retval = 0; 1284 1285out_nomem: 1286 spin_unlock(&info->lock); 1287 return retval; 1288} 1289 1290static int shmem_mmap(struct file *file, struct vm_area_struct *vma) 1291{ 1292 file_accessed(file); 1293 vma->vm_ops = &shmem_vm_ops; 1294 return 0; 1295} 1296 1297static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir, 1298 umode_t mode, dev_t dev, unsigned long flags) 1299{ 1300 struct inode *inode; 1301 struct shmem_inode_info *info; 1302 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 1303 1304 if (shmem_reserve_inode(sb)) 1305 return NULL; 1306 1307 inode = new_inode(sb); 1308 if (inode) { 1309 inode->i_ino = get_next_ino(); 1310 inode_init_owner(inode, dir, mode); 1311 inode->i_blocks = 0; 1312 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info; 1313 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 1314 inode->i_generation = get_seconds(); 1315 info = SHMEM_I(inode); 1316 memset(info, 0, (char *)inode - (char *)info); 1317 spin_lock_init(&info->lock); 1318 info->flags = flags & VM_NORESERVE; 1319 INIT_LIST_HEAD(&info->swaplist); 1320 simple_xattrs_init(&info->xattrs); 1321 cache_no_acl(inode); 1322 1323 switch (mode & S_IFMT) { 1324 default: 1325 inode->i_op = &shmem_special_inode_operations; 1326 init_special_inode(inode, mode, dev); 1327 break; 1328 case S_IFREG: 1329 inode->i_mapping->a_ops = &shmem_aops; 1330 inode->i_op = &shmem_inode_operations; 1331 inode->i_fop = &shmem_file_operations; 1332 mpol_shared_policy_init(&info->policy, 1333 shmem_get_sbmpol(sbinfo)); 1334 break; 1335 case S_IFDIR: 1336 inc_nlink(inode); 1337 /* Some things misbehave if size == 0 on a directory */ 1338 inode->i_size = 2 * BOGO_DIRENT_SIZE; 1339 inode->i_op = &shmem_dir_inode_operations; 1340 inode->i_fop = &simple_dir_operations; 1341 break; 1342 case S_IFLNK: 1343 /* 1344 * Must not load anything in the rbtree, 1345 * mpol_free_shared_policy will not be called. 1346 */ 1347 mpol_shared_policy_init(&info->policy, NULL); 1348 break; 1349 } 1350 } else 1351 shmem_free_inode(sb); 1352 return inode; 1353} 1354 1355bool shmem_mapping(struct address_space *mapping) 1356{ 1357 return mapping->backing_dev_info == &shmem_backing_dev_info; 1358} 1359 1360#ifdef CONFIG_TMPFS 1361static const struct inode_operations shmem_symlink_inode_operations; 1362static const struct inode_operations shmem_short_symlink_operations; 1363 1364#ifdef CONFIG_TMPFS_XATTR 1365static int shmem_initxattrs(struct inode *, const struct xattr *, void *); 1366#else 1367#define shmem_initxattrs NULL 1368#endif 1369 1370static int 1371shmem_write_begin(struct file *file, struct address_space *mapping, 1372 loff_t pos, unsigned len, unsigned flags, 1373 struct page **pagep, void **fsdata) 1374{ 1375 struct inode *inode = mapping->host; 1376 pgoff_t index = pos >> PAGE_CACHE_SHIFT; 1377 return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL); 1378} 1379 1380static int 1381shmem_write_end(struct file *file, struct address_space *mapping, 1382 loff_t pos, unsigned len, unsigned copied, 1383 struct page *page, void *fsdata) 1384{ 1385 struct inode *inode = mapping->host; 1386 1387 if (pos + copied > inode->i_size) 1388 i_size_write(inode, pos + copied); 1389 1390 if (!PageUptodate(page)) { 1391 if (copied < PAGE_CACHE_SIZE) { 1392 unsigned from = pos & (PAGE_CACHE_SIZE - 1); 1393 zero_user_segments(page, 0, from, 1394 from + copied, PAGE_CACHE_SIZE); 1395 } 1396 SetPageUptodate(page); 1397 } 1398 set_page_dirty(page); 1399 unlock_page(page); 1400 page_cache_release(page); 1401 1402 return copied; 1403} 1404 1405static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) 1406{ 1407 struct file *file = iocb->ki_filp; 1408 struct inode *inode = file_inode(file); 1409 struct address_space *mapping = inode->i_mapping; 1410 pgoff_t index; 1411 unsigned long offset; 1412 enum sgp_type sgp = SGP_READ; 1413 int error = 0; 1414 ssize_t retval = 0; 1415 loff_t *ppos = &iocb->ki_pos; 1416 1417 /* 1418 * Might this read be for a stacking filesystem? Then when reading 1419 * holes of a sparse file, we actually need to allocate those pages, 1420 * and even mark them dirty, so it cannot exceed the max_blocks limit. 1421 */ 1422 if (segment_eq(get_fs(), KERNEL_DS)) 1423 sgp = SGP_DIRTY; 1424 1425 index = *ppos >> PAGE_CACHE_SHIFT; 1426 offset = *ppos & ~PAGE_CACHE_MASK; 1427 1428 for (;;) { 1429 struct page *page = NULL; 1430 pgoff_t end_index; 1431 unsigned long nr, ret; 1432 loff_t i_size = i_size_read(inode); 1433 1434 end_index = i_size >> PAGE_CACHE_SHIFT; 1435 if (index > end_index) 1436 break; 1437 if (index == end_index) { 1438 nr = i_size & ~PAGE_CACHE_MASK; 1439 if (nr <= offset) 1440 break; 1441 } 1442 1443 error = shmem_getpage(inode, index, &page, sgp, NULL); 1444 if (error) { 1445 if (error == -EINVAL) 1446 error = 0; 1447 break; 1448 } 1449 if (page) 1450 unlock_page(page); 1451 1452 /* 1453 * We must evaluate after, since reads (unlike writes) 1454 * are called without i_mutex protection against truncate 1455 */ 1456 nr = PAGE_CACHE_SIZE; 1457 i_size = i_size_read(inode); 1458 end_index = i_size >> PAGE_CACHE_SHIFT; 1459 if (index == end_index) { 1460 nr = i_size & ~PAGE_CACHE_MASK; 1461 if (nr <= offset) { 1462 if (page) 1463 page_cache_release(page); 1464 break; 1465 } 1466 } 1467 nr -= offset; 1468 1469 if (page) { 1470 /* 1471 * If users can be writing to this page using arbitrary 1472 * virtual addresses, take care about potential aliasing 1473 * before reading the page on the kernel side. 1474 */ 1475 if (mapping_writably_mapped(mapping)) 1476 flush_dcache_page(page); 1477 /* 1478 * Mark the page accessed if we read the beginning. 1479 */ 1480 if (!offset) 1481 mark_page_accessed(page); 1482 } else { 1483 page = ZERO_PAGE(0); 1484 page_cache_get(page); 1485 } 1486 1487 /* 1488 * Ok, we have the page, and it's up-to-date, so 1489 * now we can copy it to user space... 1490 */ 1491 ret = copy_page_to_iter(page, offset, nr, to); 1492 retval += ret; 1493 offset += ret; 1494 index += offset >> PAGE_CACHE_SHIFT; 1495 offset &= ~PAGE_CACHE_MASK; 1496 1497 page_cache_release(page); 1498 if (!iov_iter_count(to)) 1499 break; 1500 if (ret < nr) { 1501 error = -EFAULT; 1502 break; 1503 } 1504 cond_resched(); 1505 } 1506 1507 *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset; 1508 file_accessed(file); 1509 return retval ? retval : error; 1510} 1511 1512static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 1513 struct pipe_inode_info *pipe, size_t len, 1514 unsigned int flags) 1515{ 1516 struct address_space *mapping = in->f_mapping; 1517 struct inode *inode = mapping->host; 1518 unsigned int loff, nr_pages, req_pages; 1519 struct page *pages[PIPE_DEF_BUFFERS]; 1520 struct partial_page partial[PIPE_DEF_BUFFERS]; 1521 struct page *page; 1522 pgoff_t index, end_index; 1523 loff_t isize, left; 1524 int error, page_nr; 1525 struct splice_pipe_desc spd = { 1526 .pages = pages, 1527 .partial = partial, 1528 .nr_pages_max = PIPE_DEF_BUFFERS, 1529 .flags = flags, 1530 .ops = &page_cache_pipe_buf_ops, 1531 .spd_release = spd_release_page, 1532 }; 1533 1534 isize = i_size_read(inode); 1535 if (unlikely(*ppos >= isize)) 1536 return 0; 1537 1538 left = isize - *ppos; 1539 if (unlikely(left < len)) 1540 len = left; 1541 1542 if (splice_grow_spd(pipe, &spd)) 1543 return -ENOMEM; 1544 1545 index = *ppos >> PAGE_CACHE_SHIFT; 1546 loff = *ppos & ~PAGE_CACHE_MASK; 1547 req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1548 nr_pages = min(req_pages, spd.nr_pages_max); 1549 1550 spd.nr_pages = find_get_pages_contig(mapping, index, 1551 nr_pages, spd.pages); 1552 index += spd.nr_pages; 1553 error = 0; 1554 1555 while (spd.nr_pages < nr_pages) { 1556 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL); 1557 if (error) 1558 break; 1559 unlock_page(page); 1560 spd.pages[spd.nr_pages++] = page; 1561 index++; 1562 } 1563 1564 index = *ppos >> PAGE_CACHE_SHIFT; 1565 nr_pages = spd.nr_pages; 1566 spd.nr_pages = 0; 1567 1568 for (page_nr = 0; page_nr < nr_pages; page_nr++) { 1569 unsigned int this_len; 1570 1571 if (!len) 1572 break; 1573 1574 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff); 1575 page = spd.pages[page_nr]; 1576 1577 if (!PageUptodate(page) || page->mapping != mapping) { 1578 error = shmem_getpage(inode, index, &page, 1579 SGP_CACHE, NULL); 1580 if (error) 1581 break; 1582 unlock_page(page); 1583 page_cache_release(spd.pages[page_nr]); 1584 spd.pages[page_nr] = page; 1585 } 1586 1587 isize = i_size_read(inode); 1588 end_index = (isize - 1) >> PAGE_CACHE_SHIFT; 1589 if (unlikely(!isize || index > end_index)) 1590 break; 1591 1592 if (end_index == index) { 1593 unsigned int plen; 1594 1595 plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1; 1596 if (plen <= loff) 1597 break; 1598 1599 this_len = min(this_len, plen - loff); 1600 len = this_len; 1601 } 1602 1603 spd.partial[page_nr].offset = loff; 1604 spd.partial[page_nr].len = this_len; 1605 len -= this_len; 1606 loff = 0; 1607 spd.nr_pages++; 1608 index++; 1609 } 1610 1611 while (page_nr < nr_pages) 1612 page_cache_release(spd.pages[page_nr++]); 1613 1614 if (spd.nr_pages) 1615 error = splice_to_pipe(pipe, &spd); 1616 1617 splice_shrink_spd(&spd); 1618 1619 if (error > 0) { 1620 *ppos += error; 1621 file_accessed(in); 1622 } 1623 return error; 1624} 1625 1626/* 1627 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree. 1628 */ 1629static pgoff_t shmem_seek_hole_data(struct address_space *mapping, 1630 pgoff_t index, pgoff_t end, int whence) 1631{ 1632 struct page *page; 1633 struct pagevec pvec; 1634 pgoff_t indices[PAGEVEC_SIZE]; 1635 bool done = false; 1636 int i; 1637 1638 pagevec_init(&pvec, 0); 1639 pvec.nr = 1; /* start small: we may be there already */ 1640 while (!done) { 1641 pvec.nr = find_get_entries(mapping, index, 1642 pvec.nr, pvec.pages, indices); 1643 if (!pvec.nr) { 1644 if (whence == SEEK_DATA) 1645 index = end; 1646 break; 1647 } 1648 for (i = 0; i < pvec.nr; i++, index++) { 1649 if (index < indices[i]) { 1650 if (whence == SEEK_HOLE) { 1651 done = true; 1652 break; 1653 } 1654 index = indices[i]; 1655 } 1656 page = pvec.pages[i]; 1657 if (page && !radix_tree_exceptional_entry(page)) { 1658 if (!PageUptodate(page)) 1659 page = NULL; 1660 } 1661 if (index >= end || 1662 (page && whence == SEEK_DATA) || 1663 (!page && whence == SEEK_HOLE)) { 1664 done = true; 1665 break; 1666 } 1667 } 1668 pagevec_remove_exceptionals(&pvec); 1669 pagevec_release(&pvec); 1670 pvec.nr = PAGEVEC_SIZE; 1671 cond_resched(); 1672 } 1673 return index; 1674} 1675 1676static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence) 1677{ 1678 struct address_space *mapping = file->f_mapping; 1679 struct inode *inode = mapping->host; 1680 pgoff_t start, end; 1681 loff_t new_offset; 1682 1683 if (whence != SEEK_DATA && whence != SEEK_HOLE) 1684 return generic_file_llseek_size(file, offset, whence, 1685 MAX_LFS_FILESIZE, i_size_read(inode)); 1686 mutex_lock(&inode->i_mutex); 1687 /* We're holding i_mutex so we can access i_size directly */ 1688 1689 if (offset < 0) 1690 offset = -EINVAL; 1691 else if (offset >= inode->i_size) 1692 offset = -ENXIO; 1693 else { 1694 start = offset >> PAGE_CACHE_SHIFT; 1695 end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1696 new_offset = shmem_seek_hole_data(mapping, start, end, whence); 1697 new_offset <<= PAGE_CACHE_SHIFT; 1698 if (new_offset > offset) { 1699 if (new_offset < inode->i_size) 1700 offset = new_offset; 1701 else if (whence == SEEK_DATA) 1702 offset = -ENXIO; 1703 else 1704 offset = inode->i_size; 1705 } 1706 } 1707 1708 if (offset >= 0) 1709 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE); 1710 mutex_unlock(&inode->i_mutex); 1711 return offset; 1712} 1713 1714static long shmem_fallocate(struct file *file, int mode, loff_t offset, 1715 loff_t len) 1716{ 1717 struct inode *inode = file_inode(file); 1718 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); 1719 struct shmem_falloc shmem_falloc; 1720 pgoff_t start, index, end; 1721 int error; 1722 1723 mutex_lock(&inode->i_mutex); 1724 1725 if (mode & FALLOC_FL_PUNCH_HOLE) { 1726 struct address_space *mapping = file->f_mapping; 1727 loff_t unmap_start = round_up(offset, PAGE_SIZE); 1728 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1; 1729 1730 if ((u64)unmap_end > (u64)unmap_start) 1731 unmap_mapping_range(mapping, unmap_start, 1732 1 + unmap_end - unmap_start, 0); 1733 shmem_truncate_range(inode, offset, offset + len - 1); 1734 /* No need to unmap again: hole-punching leaves COWed pages */ 1735 error = 0; 1736 goto out; 1737 } 1738 1739 /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */ 1740 error = inode_newsize_ok(inode, offset + len); 1741 if (error) 1742 goto out; 1743 1744 start = offset >> PAGE_CACHE_SHIFT; 1745 end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 1746 /* Try to avoid a swapstorm if len is impossible to satisfy */ 1747 if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) { 1748 error = -ENOSPC; 1749 goto out; 1750 } 1751 1752 shmem_falloc.start = start; 1753 shmem_falloc.next = start; 1754 shmem_falloc.nr_falloced = 0; 1755 shmem_falloc.nr_unswapped = 0; 1756 spin_lock(&inode->i_lock); 1757 inode->i_private = &shmem_falloc; 1758 spin_unlock(&inode->i_lock); 1759 1760 for (index = start; index < end; index++) { 1761 struct page *page; 1762 1763 /* 1764 * Good, the fallocate(2) manpage permits EINTR: we may have 1765 * been interrupted because we are using up too much memory. 1766 */ 1767 if (signal_pending(current)) 1768 error = -EINTR; 1769 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced) 1770 error = -ENOMEM; 1771 else 1772 error = shmem_getpage(inode, index, &page, SGP_FALLOC, 1773 NULL); 1774 if (error) { 1775 /* Remove the !PageUptodate pages we added */ 1776 shmem_undo_range(inode, 1777 (loff_t)start << PAGE_CACHE_SHIFT, 1778 (loff_t)index << PAGE_CACHE_SHIFT, true); 1779 goto undone; 1780 } 1781 1782 /* 1783 * Inform shmem_writepage() how far we have reached. 1784 * No need for lock or barrier: we have the page lock. 1785 */ 1786 shmem_falloc.next++; 1787 if (!PageUptodate(page)) 1788 shmem_falloc.nr_falloced++; 1789 1790 /* 1791 * If !PageUptodate, leave it that way so that freeable pages 1792 * can be recognized if we need to rollback on error later. 1793 * But set_page_dirty so that memory pressure will swap rather 1794 * than free the pages we are allocating (and SGP_CACHE pages 1795 * might still be clean: we now need to mark those dirty too). 1796 */ 1797 set_page_dirty(page); 1798 unlock_page(page); 1799 page_cache_release(page); 1800 cond_resched(); 1801 } 1802 1803 if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size) 1804 i_size_write(inode, offset + len); 1805 inode->i_ctime = CURRENT_TIME; 1806undone: 1807 spin_lock(&inode->i_lock); 1808 inode->i_private = NULL; 1809 spin_unlock(&inode->i_lock); 1810out: 1811 mutex_unlock(&inode->i_mutex); 1812 return error; 1813} 1814 1815static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf) 1816{ 1817 struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb); 1818 1819 buf->f_type = TMPFS_MAGIC; 1820 buf->f_bsize = PAGE_CACHE_SIZE; 1821 buf->f_namelen = NAME_MAX; 1822 if (sbinfo->max_blocks) { 1823 buf->f_blocks = sbinfo->max_blocks; 1824 buf->f_bavail = 1825 buf->f_bfree = sbinfo->max_blocks - 1826 percpu_counter_sum(&sbinfo->used_blocks); 1827 } 1828 if (sbinfo->max_inodes) { 1829 buf->f_files = sbinfo->max_inodes; 1830 buf->f_ffree = sbinfo->free_inodes; 1831 } 1832 /* else leave those fields 0 like simple_statfs */ 1833 return 0; 1834} 1835 1836/* 1837 * File creation. Allocate an inode, and we're done.. 1838 */ 1839static int 1840shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) 1841{ 1842 struct inode *inode; 1843 int error = -ENOSPC; 1844 1845 inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE); 1846 if (inode) { 1847 error = simple_acl_create(dir, inode); 1848 if (error) 1849 goto out_iput; 1850 error = security_inode_init_security(inode, dir, 1851 &dentry->d_name, 1852 shmem_initxattrs, NULL); 1853 if (error && error != -EOPNOTSUPP) 1854 goto out_iput; 1855 1856 error = 0; 1857 dir->i_size += BOGO_DIRENT_SIZE; 1858 dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1859 d_instantiate(dentry, inode); 1860 dget(dentry); /* Extra count - pin the dentry in core */ 1861 } 1862 return error; 1863out_iput: 1864 iput(inode); 1865 return error; 1866} 1867 1868static int 1869shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode) 1870{ 1871 struct inode *inode; 1872 int error = -ENOSPC; 1873 1874 inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE); 1875 if (inode) { 1876 error = security_inode_init_security(inode, dir, 1877 NULL, 1878 shmem_initxattrs, NULL); 1879 if (error && error != -EOPNOTSUPP) 1880 goto out_iput; 1881 error = simple_acl_create(dir, inode); 1882 if (error) 1883 goto out_iput; 1884 d_tmpfile(dentry, inode); 1885 } 1886 return error; 1887out_iput: 1888 iput(inode); 1889 return error; 1890} 1891 1892static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 1893{ 1894 int error; 1895 1896 if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0))) 1897 return error; 1898 inc_nlink(dir); 1899 return 0; 1900} 1901 1902static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode, 1903 bool excl) 1904{ 1905 return shmem_mknod(dir, dentry, mode | S_IFREG, 0); 1906} 1907 1908/* 1909 * Link a file.. 1910 */ 1911static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) 1912{ 1913 struct inode *inode = old_dentry->d_inode; 1914 int ret; 1915 1916 /* 1917 * No ordinary (disk based) filesystem counts links as inodes; 1918 * but each new link needs a new dentry, pinning lowmem, and 1919 * tmpfs dentries cannot be pruned until they are unlinked. 1920 */ 1921 ret = shmem_reserve_inode(inode->i_sb); 1922 if (ret) 1923 goto out; 1924 1925 dir->i_size += BOGO_DIRENT_SIZE; 1926 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1927 inc_nlink(inode); 1928 ihold(inode); /* New dentry reference */ 1929 dget(dentry); /* Extra pinning count for the created dentry */ 1930 d_instantiate(dentry, inode); 1931out: 1932 return ret; 1933} 1934 1935static int shmem_unlink(struct inode *dir, struct dentry *dentry) 1936{ 1937 struct inode *inode = dentry->d_inode; 1938 1939 if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) 1940 shmem_free_inode(inode->i_sb); 1941 1942 dir->i_size -= BOGO_DIRENT_SIZE; 1943 inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; 1944 drop_nlink(inode); 1945 dput(dentry); /* Undo the count from "create" - this does all the work */ 1946 return 0; 1947} 1948 1949static int shmem_rmdir(struct inode *dir, struct dentry *dentry) 1950{ 1951 if (!simple_empty(dentry)) 1952 return -ENOTEMPTY; 1953 1954 drop_nlink(dentry->d_inode); 1955 drop_nlink(dir); 1956 return shmem_unlink(dir, dentry); 1957} 1958 1959/* 1960 * The VFS layer already does all the dentry stuff for rename, 1961 * we just have to decrement the usage count for the target if 1962 * it exists so that the VFS layer correctly free's it when it 1963 * gets overwritten. 1964 */ 1965static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) 1966{ 1967 struct inode *inode = old_dentry->d_inode; 1968 int they_are_dirs = S_ISDIR(inode->i_mode); 1969 1970 if (!simple_empty(new_dentry)) 1971 return -ENOTEMPTY; 1972 1973 if (new_dentry->d_inode) { 1974 (void) shmem_unlink(new_dir, new_dentry); 1975 if (they_are_dirs) 1976 drop_nlink(old_dir); 1977 } else if (they_are_dirs) { 1978 drop_nlink(old_dir); 1979 inc_nlink(new_dir); 1980 } 1981 1982 old_dir->i_size -= BOGO_DIRENT_SIZE; 1983 new_dir->i_size += BOGO_DIRENT_SIZE; 1984 old_dir->i_ctime = old_dir->i_mtime = 1985 new_dir->i_ctime = new_dir->i_mtime = 1986 inode->i_ctime = CURRENT_TIME; 1987 return 0; 1988} 1989 1990static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname) 1991{ 1992 int error; 1993 int len; 1994 struct inode *inode; 1995 struct page *page; 1996 char *kaddr; 1997 struct shmem_inode_info *info; 1998 1999 len = strlen(symname) + 1; 2000 if (len > PAGE_CACHE_SIZE) 2001 return -ENAMETOOLONG; 2002 2003 inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE); 2004 if (!inode) 2005 return -ENOSPC; 2006 2007 error = security_inode_init_security(inode, dir, &dentry->d_name, 2008 shmem_initxattrs, NULL); 2009 if (error) { 2010 if (error != -EOPNOTSUPP) { 2011 iput(inode); 2012 return error; 2013 } 2014 error = 0; 2015 } 2016 2017 info = SHMEM_I(inode); 2018 inode->i_size = len-1; 2019 if (len <= SHORT_SYMLINK_LEN) { 2020 info->symlink = kmemdup(symname, len, GFP_KERNEL); 2021 if (!info->symlink) { 2022 iput(inode); 2023 return -ENOMEM; 2024 } 2025 inode->i_op = &shmem_short_symlink_operations; 2026 } else { 2027 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL); 2028 if (error) { 2029 iput(inode); 2030 return error; 2031 } 2032 inode->i_mapping->a_ops = &shmem_aops; 2033 inode->i_op = &shmem_symlink_inode_operations; 2034 kaddr = kmap_atomic(page); 2035 memcpy(kaddr, symname, len); 2036 kunmap_atomic(kaddr); 2037 SetPageUptodate(page); 2038 set_page_dirty(page); 2039 unlock_page(page); 2040 page_cache_release(page); 2041 } 2042 dir->i_size += BOGO_DIRENT_SIZE; 2043 dir->i_ctime = dir->i_mtime = CURRENT_TIME; 2044 d_instantiate(dentry, inode); 2045 dget(dentry); 2046 return 0; 2047} 2048 2049static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd) 2050{ 2051 nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink); 2052 return NULL; 2053} 2054 2055static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd) 2056{ 2057 struct page *page = NULL; 2058 int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL); 2059 nd_set_link(nd, error ? ERR_PTR(error) : kmap(page)); 2060 if (page) 2061 unlock_page(page); 2062 return page; 2063} 2064 2065static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) 2066{ 2067 if (!IS_ERR(nd_get_link(nd))) { 2068 struct page *page = cookie; 2069 kunmap(page); 2070 mark_page_accessed(page); 2071 page_cache_release(page); 2072 } 2073} 2074 2075#ifdef CONFIG_TMPFS_XATTR 2076/* 2077 * Superblocks without xattr inode operations may get some security.* xattr 2078 * support from the LSM "for free". As soon as we have any other xattrs 2079 * like ACLs, we also need to implement the security.* handlers at 2080 * filesystem level, though. 2081 */ 2082 2083/* 2084 * Callback for security_inode_init_security() for acquiring xattrs. 2085 */ 2086static int shmem_initxattrs(struct inode *inode, 2087 const struct xattr *xattr_array, 2088 void *fs_info) 2089{ 2090 struct shmem_inode_info *info = SHMEM_I(inode); 2091 const struct xattr *xattr; 2092 struct simple_xattr *new_xattr; 2093 size_t len; 2094 2095 for (xattr = xattr_array; xattr->name != NULL; xattr++) { 2096 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len); 2097 if (!new_xattr) 2098 return -ENOMEM; 2099 2100 len = strlen(xattr->name) + 1; 2101 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len, 2102 GFP_KERNEL); 2103 if (!new_xattr->name) { 2104 kfree(new_xattr); 2105 return -ENOMEM; 2106 } 2107 2108 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX, 2109 XATTR_SECURITY_PREFIX_LEN); 2110 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN, 2111 xattr->name, len); 2112 2113 simple_xattr_list_add(&info->xattrs, new_xattr); 2114 } 2115 2116 return 0; 2117} 2118 2119static const struct xattr_handler *shmem_xattr_handlers[] = { 2120#ifdef CONFIG_TMPFS_POSIX_ACL 2121 &posix_acl_access_xattr_handler, 2122 &posix_acl_default_xattr_handler, 2123#endif 2124 NULL 2125}; 2126 2127static int shmem_xattr_validate(const char *name) 2128{ 2129 struct { const char *prefix; size_t len; } arr[] = { 2130 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN }, 2131 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN } 2132 }; 2133 int i; 2134 2135 for (i = 0; i < ARRAY_SIZE(arr); i++) { 2136 size_t preflen = arr[i].len; 2137 if (strncmp(name, arr[i].prefix, preflen) == 0) { 2138 if (!name[preflen]) 2139 return -EINVAL; 2140 return 0; 2141 } 2142 } 2143 return -EOPNOTSUPP; 2144} 2145 2146static ssize_t shmem_getxattr(struct dentry *dentry, const char *name, 2147 void *buffer, size_t size) 2148{ 2149 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2150 int err; 2151 2152 /* 2153 * If this is a request for a synthetic attribute in the system.* 2154 * namespace use the generic infrastructure to resolve a handler 2155 * for it via sb->s_xattr. 2156 */ 2157 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2158 return generic_getxattr(dentry, name, buffer, size); 2159 2160 err = shmem_xattr_validate(name); 2161 if (err) 2162 return err; 2163 2164 return simple_xattr_get(&info->xattrs, name, buffer, size); 2165} 2166 2167static int shmem_setxattr(struct dentry *dentry, const char *name, 2168 const void *value, size_t size, int flags) 2169{ 2170 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2171 int err; 2172 2173 /* 2174 * If this is a request for a synthetic attribute in the system.* 2175 * namespace use the generic infrastructure to resolve a handler 2176 * for it via sb->s_xattr. 2177 */ 2178 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2179 return generic_setxattr(dentry, name, value, size, flags); 2180 2181 err = shmem_xattr_validate(name); 2182 if (err) 2183 return err; 2184 2185 return simple_xattr_set(&info->xattrs, name, value, size, flags); 2186} 2187 2188static int shmem_removexattr(struct dentry *dentry, const char *name) 2189{ 2190 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2191 int err; 2192 2193 /* 2194 * If this is a request for a synthetic attribute in the system.* 2195 * namespace use the generic infrastructure to resolve a handler 2196 * for it via sb->s_xattr. 2197 */ 2198 if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) 2199 return generic_removexattr(dentry, name); 2200 2201 err = shmem_xattr_validate(name); 2202 if (err) 2203 return err; 2204 2205 return simple_xattr_remove(&info->xattrs, name); 2206} 2207 2208static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size) 2209{ 2210 struct shmem_inode_info *info = SHMEM_I(dentry->d_inode); 2211 return simple_xattr_list(&info->xattrs, buffer, size); 2212} 2213#endif /* CONFIG_TMPFS_XATTR */ 2214 2215static const struct inode_operations shmem_short_symlink_operations = { 2216 .readlink = generic_readlink, 2217 .follow_link = shmem_follow_short_symlink, 2218#ifdef CONFIG_TMPFS_XATTR 2219 .setxattr = shmem_setxattr, 2220 .getxattr = shmem_getxattr, 2221 .listxattr = shmem_listxattr, 2222 .removexattr = shmem_removexattr, 2223#endif 2224}; 2225 2226static const struct inode_operations shmem_symlink_inode_operations = { 2227 .readlink = generic_readlink, 2228 .follow_link = shmem_follow_link, 2229 .put_link = shmem_put_link, 2230#ifdef CONFIG_TMPFS_XATTR 2231 .setxattr = shmem_setxattr, 2232 .getxattr = shmem_getxattr, 2233 .listxattr = shmem_listxattr, 2234 .removexattr = shmem_removexattr, 2235#endif 2236}; 2237 2238static struct dentry *shmem_get_parent(struct dentry *child) 2239{ 2240 return ERR_PTR(-ESTALE); 2241} 2242 2243static int shmem_match(struct inode *ino, void *vfh) 2244{ 2245 __u32 *fh = vfh; 2246 __u64 inum = fh[2]; 2247 inum = (inum << 32) | fh[1]; 2248 return ino->i_ino == inum && fh[0] == ino->i_generation; 2249} 2250 2251static struct dentry *shmem_fh_to_dentry(struct super_block *sb, 2252 struct fid *fid, int fh_len, int fh_type) 2253{ 2254 struct inode *inode; 2255 struct dentry *dentry = NULL; 2256 u64 inum; 2257 2258 if (fh_len < 3) 2259 return NULL; 2260 2261 inum = fid->raw[2]; 2262 inum = (inum << 32) | fid->raw[1]; 2263 2264 inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]), 2265 shmem_match, fid->raw); 2266 if (inode) { 2267 dentry = d_find_alias(inode); 2268 iput(inode); 2269 } 2270 2271 return dentry; 2272} 2273 2274static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len, 2275 struct inode *parent) 2276{ 2277 if (*len < 3) { 2278 *len = 3; 2279 return FILEID_INVALID; 2280 } 2281 2282 if (inode_unhashed(inode)) { 2283 /* Unfortunately insert_inode_hash is not idempotent, 2284 * so as we hash inodes here rather than at creation 2285 * time, we need a lock to ensure we only try 2286 * to do it once 2287 */ 2288 static DEFINE_SPINLOCK(lock); 2289 spin_lock(&lock); 2290 if (inode_unhashed(inode)) 2291 __insert_inode_hash(inode, 2292 inode->i_ino + inode->i_generation); 2293 spin_unlock(&lock); 2294 } 2295 2296 fh[0] = inode->i_generation; 2297 fh[1] = inode->i_ino; 2298 fh[2] = ((__u64)inode->i_ino) >> 32; 2299 2300 *len = 3; 2301 return 1; 2302} 2303 2304static const struct export_operations shmem_export_ops = { 2305 .get_parent = shmem_get_parent, 2306 .encode_fh = shmem_encode_fh, 2307 .fh_to_dentry = shmem_fh_to_dentry, 2308}; 2309 2310static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo, 2311 bool remount) 2312{ 2313 char *this_char, *value, *rest; 2314 struct mempolicy *mpol = NULL; 2315 uid_t uid; 2316 gid_t gid; 2317 2318 while (options != NULL) { 2319 this_char = options; 2320 for (;;) { 2321 /* 2322 * NUL-terminate this option: unfortunately, 2323 * mount options form a comma-separated list, 2324 * but mpol's nodelist may also contain commas. 2325 */ 2326 options = strchr(options, ','); 2327 if (options == NULL) 2328 break; 2329 options++; 2330 if (!isdigit(*options)) { 2331 options[-1] = '\0'; 2332 break; 2333 } 2334 } 2335 if (!*this_char) 2336 continue; 2337 if ((value = strchr(this_char,'=')) != NULL) { 2338 *value++ = 0; 2339 } else { 2340 printk(KERN_ERR 2341 "tmpfs: No value for mount option '%s'\n", 2342 this_char); 2343 goto error; 2344 } 2345 2346 if (!strcmp(this_char,"size")) { 2347 unsigned long long size; 2348 size = memparse(value,&rest); 2349 if (*rest == '%') { 2350 size <<= PAGE_SHIFT; 2351 size *= totalram_pages; 2352 do_div(size, 100); 2353 rest++; 2354 } 2355 if (*rest) 2356 goto bad_val; 2357 sbinfo->max_blocks = 2358 DIV_ROUND_UP(size, PAGE_CACHE_SIZE); 2359 } else if (!strcmp(this_char,"nr_blocks")) { 2360 sbinfo->max_blocks = memparse(value, &rest); 2361 if (*rest) 2362 goto bad_val; 2363 } else if (!strcmp(this_char,"nr_inodes")) { 2364 sbinfo->max_inodes = memparse(value, &rest); 2365 if (*rest) 2366 goto bad_val; 2367 } else if (!strcmp(this_char,"mode")) { 2368 if (remount) 2369 continue; 2370 sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777; 2371 if (*rest) 2372 goto bad_val; 2373 } else if (!strcmp(this_char,"uid")) { 2374 if (remount) 2375 continue; 2376 uid = simple_strtoul(value, &rest, 0); 2377 if (*rest) 2378 goto bad_val; 2379 sbinfo->uid = make_kuid(current_user_ns(), uid); 2380 if (!uid_valid(sbinfo->uid)) 2381 goto bad_val; 2382 } else if (!strcmp(this_char,"gid")) { 2383 if (remount) 2384 continue; 2385 gid = simple_strtoul(value, &rest, 0); 2386 if (*rest) 2387 goto bad_val; 2388 sbinfo->gid = make_kgid(current_user_ns(), gid); 2389 if (!gid_valid(sbinfo->gid)) 2390 goto bad_val; 2391 } else if (!strcmp(this_char,"mpol")) { 2392 mpol_put(mpol); 2393 mpol = NULL; 2394 if (mpol_parse_str(value, &mpol)) 2395 goto bad_val; 2396 } else { 2397 printk(KERN_ERR "tmpfs: Bad mount option %s\n", 2398 this_char); 2399 goto error; 2400 } 2401 } 2402 sbinfo->mpol = mpol; 2403 return 0; 2404 2405bad_val: 2406 printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n", 2407 value, this_char); 2408error: 2409 mpol_put(mpol); 2410 return 1; 2411 2412} 2413 2414static int shmem_remount_fs(struct super_block *sb, int *flags, char *data) 2415{ 2416 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 2417 struct shmem_sb_info config = *sbinfo; 2418 unsigned long inodes; 2419 int error = -EINVAL; 2420 2421 config.mpol = NULL; 2422 if (shmem_parse_options(data, &config, true)) 2423 return error; 2424 2425 spin_lock(&sbinfo->stat_lock); 2426 inodes = sbinfo->max_inodes - sbinfo->free_inodes; 2427 if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0) 2428 goto out; 2429 if (config.max_inodes < inodes) 2430 goto out; 2431 /* 2432 * Those tests disallow limited->unlimited while any are in use; 2433 * but we must separately disallow unlimited->limited, because 2434 * in that case we have no record of how much is already in use. 2435 */ 2436 if (config.max_blocks && !sbinfo->max_blocks) 2437 goto out; 2438 if (config.max_inodes && !sbinfo->max_inodes) 2439 goto out; 2440 2441 error = 0; 2442 sbinfo->max_blocks = config.max_blocks; 2443 sbinfo->max_inodes = config.max_inodes; 2444 sbinfo->free_inodes = config.max_inodes - inodes; 2445 2446 /* 2447 * Preserve previous mempolicy unless mpol remount option was specified. 2448 */ 2449 if (config.mpol) { 2450 mpol_put(sbinfo->mpol); 2451 sbinfo->mpol = config.mpol; /* transfers initial ref */ 2452 } 2453out: 2454 spin_unlock(&sbinfo->stat_lock); 2455 return error; 2456} 2457 2458static int shmem_show_options(struct seq_file *seq, struct dentry *root) 2459{ 2460 struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb); 2461 2462 if (sbinfo->max_blocks != shmem_default_max_blocks()) 2463 seq_printf(seq, ",size=%luk", 2464 sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10)); 2465 if (sbinfo->max_inodes != shmem_default_max_inodes()) 2466 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes); 2467 if (sbinfo->mode != (S_IRWXUGO | S_ISVTX)) 2468 seq_printf(seq, ",mode=%03ho", sbinfo->mode); 2469 if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID)) 2470 seq_printf(seq, ",uid=%u", 2471 from_kuid_munged(&init_user_ns, sbinfo->uid)); 2472 if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID)) 2473 seq_printf(seq, ",gid=%u", 2474 from_kgid_munged(&init_user_ns, sbinfo->gid)); 2475 shmem_show_mpol(seq, sbinfo->mpol); 2476 return 0; 2477} 2478#endif /* CONFIG_TMPFS */ 2479 2480static void shmem_put_super(struct super_block *sb) 2481{ 2482 struct shmem_sb_info *sbinfo = SHMEM_SB(sb); 2483 2484 percpu_counter_destroy(&sbinfo->used_blocks); 2485 mpol_put(sbinfo->mpol); 2486 kfree(sbinfo); 2487 sb->s_fs_info = NULL; 2488} 2489 2490int shmem_fill_super(struct super_block *sb, void *data, int silent) 2491{ 2492 struct inode *inode; 2493 struct shmem_sb_info *sbinfo; 2494 int err = -ENOMEM; 2495 2496 /* Round up to L1_CACHE_BYTES to resist false sharing */ 2497 sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info), 2498 L1_CACHE_BYTES), GFP_KERNEL); 2499 if (!sbinfo) 2500 return -ENOMEM; 2501 2502 sbinfo->mode = S_IRWXUGO | S_ISVTX; 2503 sbinfo->uid = current_fsuid(); 2504 sbinfo->gid = current_fsgid(); 2505 sb->s_fs_info = sbinfo; 2506 2507#ifdef CONFIG_TMPFS 2508 /* 2509 * Per default we only allow half of the physical ram per 2510 * tmpfs instance, limiting inodes to one per page of lowmem; 2511 * but the internal instance is left unlimited. 2512 */ 2513 if (!(sb->s_flags & MS_KERNMOUNT)) { 2514 sbinfo->max_blocks = shmem_default_max_blocks(); 2515 sbinfo->max_inodes = shmem_default_max_inodes(); 2516 if (shmem_parse_options(data, sbinfo, false)) { 2517 err = -EINVAL; 2518 goto failed; 2519 } 2520 } else { 2521 sb->s_flags |= MS_NOUSER; 2522 } 2523 sb->s_export_op = &shmem_export_ops; 2524 sb->s_flags |= MS_NOSEC; 2525#else 2526 sb->s_flags |= MS_NOUSER; 2527#endif 2528 2529 spin_lock_init(&sbinfo->stat_lock); 2530 if (percpu_counter_init(&sbinfo->used_blocks, 0)) 2531 goto failed; 2532 sbinfo->free_inodes = sbinfo->max_inodes; 2533 2534 sb->s_maxbytes = MAX_LFS_FILESIZE; 2535 sb->s_blocksize = PAGE_CACHE_SIZE; 2536 sb->s_blocksize_bits = PAGE_CACHE_SHIFT; 2537 sb->s_magic = TMPFS_MAGIC; 2538 sb->s_op = &shmem_ops; 2539 sb->s_time_gran = 1; 2540#ifdef CONFIG_TMPFS_XATTR 2541 sb->s_xattr = shmem_xattr_handlers; 2542#endif 2543#ifdef CONFIG_TMPFS_POSIX_ACL 2544 sb->s_flags |= MS_POSIXACL; 2545#endif 2546 2547 inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE); 2548 if (!inode) 2549 goto failed; 2550 inode->i_uid = sbinfo->uid; 2551 inode->i_gid = sbinfo->gid; 2552 sb->s_root = d_make_root(inode); 2553 if (!sb->s_root) 2554 goto failed; 2555 return 0; 2556 2557failed: 2558 shmem_put_super(sb); 2559 return err; 2560} 2561 2562static struct kmem_cache *shmem_inode_cachep; 2563 2564static struct inode *shmem_alloc_inode(struct super_block *sb) 2565{ 2566 struct shmem_inode_info *info; 2567 info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL); 2568 if (!info) 2569 return NULL; 2570 return &info->vfs_inode; 2571} 2572 2573static void shmem_destroy_callback(struct rcu_head *head) 2574{ 2575 struct inode *inode = container_of(head, struct inode, i_rcu); 2576 kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode)); 2577} 2578 2579static void shmem_destroy_inode(struct inode *inode) 2580{ 2581 if (S_ISREG(inode->i_mode)) 2582 mpol_free_shared_policy(&SHMEM_I(inode)->policy); 2583 call_rcu(&inode->i_rcu, shmem_destroy_callback); 2584} 2585 2586static void shmem_init_inode(void *foo) 2587{ 2588 struct shmem_inode_info *info = foo; 2589 inode_init_once(&info->vfs_inode); 2590} 2591 2592static int shmem_init_inodecache(void) 2593{ 2594 shmem_inode_cachep = kmem_cache_create("shmem_inode_cache", 2595 sizeof(struct shmem_inode_info), 2596 0, SLAB_PANIC, shmem_init_inode); 2597 return 0; 2598} 2599 2600static void shmem_destroy_inodecache(void) 2601{ 2602 kmem_cache_destroy(shmem_inode_cachep); 2603} 2604 2605static const struct address_space_operations shmem_aops = { 2606 .writepage = shmem_writepage, 2607 .set_page_dirty = __set_page_dirty_no_writeback, 2608#ifdef CONFIG_TMPFS 2609 .write_begin = shmem_write_begin, 2610 .write_end = shmem_write_end, 2611#endif 2612 .migratepage = migrate_page, 2613 .error_remove_page = generic_error_remove_page, 2614}; 2615 2616static const struct file_operations shmem_file_operations = { 2617 .mmap = shmem_mmap, 2618#ifdef CONFIG_TMPFS 2619 .llseek = shmem_file_llseek, 2620 .read = new_sync_read, 2621 .write = new_sync_write, 2622 .read_iter = shmem_file_read_iter, 2623 .write_iter = generic_file_write_iter, 2624 .fsync = noop_fsync, 2625 .splice_read = shmem_file_splice_read, 2626 .splice_write = iter_file_splice_write, 2627 .fallocate = shmem_fallocate, 2628#endif 2629}; 2630 2631static const struct inode_operations shmem_inode_operations = { 2632 .setattr = shmem_setattr, 2633#ifdef CONFIG_TMPFS_XATTR 2634 .setxattr = shmem_setxattr, 2635 .getxattr = shmem_getxattr, 2636 .listxattr = shmem_listxattr, 2637 .removexattr = shmem_removexattr, 2638 .set_acl = simple_set_acl, 2639#endif 2640}; 2641 2642static const struct inode_operations shmem_dir_inode_operations = { 2643#ifdef CONFIG_TMPFS 2644 .create = shmem_create, 2645 .lookup = simple_lookup, 2646 .link = shmem_link, 2647 .unlink = shmem_unlink, 2648 .symlink = shmem_symlink, 2649 .mkdir = shmem_mkdir, 2650 .rmdir = shmem_rmdir, 2651 .mknod = shmem_mknod, 2652 .rename = shmem_rename, 2653 .tmpfile = shmem_tmpfile, 2654#endif 2655#ifdef CONFIG_TMPFS_XATTR 2656 .setxattr = shmem_setxattr, 2657 .getxattr = shmem_getxattr, 2658 .listxattr = shmem_listxattr, 2659 .removexattr = shmem_removexattr, 2660#endif 2661#ifdef CONFIG_TMPFS_POSIX_ACL 2662 .setattr = shmem_setattr, 2663 .set_acl = simple_set_acl, 2664#endif 2665}; 2666 2667static const struct inode_operations shmem_special_inode_operations = { 2668#ifdef CONFIG_TMPFS_XATTR 2669 .setxattr = shmem_setxattr, 2670 .getxattr = shmem_getxattr, 2671 .listxattr = shmem_listxattr, 2672 .removexattr = shmem_removexattr, 2673#endif 2674#ifdef CONFIG_TMPFS_POSIX_ACL 2675 .setattr = shmem_setattr, 2676 .set_acl = simple_set_acl, 2677#endif 2678}; 2679 2680static const struct super_operations shmem_ops = { 2681 .alloc_inode = shmem_alloc_inode, 2682 .destroy_inode = shmem_destroy_inode, 2683#ifdef CONFIG_TMPFS 2684 .statfs = shmem_statfs, 2685 .remount_fs = shmem_remount_fs, 2686 .show_options = shmem_show_options, 2687#endif 2688 .evict_inode = shmem_evict_inode, 2689 .drop_inode = generic_delete_inode, 2690 .put_super = shmem_put_super, 2691}; 2692 2693static const struct vm_operations_struct shmem_vm_ops = { 2694 .fault = shmem_fault, 2695 .map_pages = filemap_map_pages, 2696#ifdef CONFIG_NUMA 2697 .set_policy = shmem_set_policy, 2698 .get_policy = shmem_get_policy, 2699#endif 2700 .remap_pages = generic_file_remap_pages, 2701}; 2702 2703static struct dentry *shmem_mount(struct file_system_type *fs_type, 2704 int flags, const char *dev_name, void *data) 2705{ 2706 return mount_nodev(fs_type, flags, data, shmem_fill_super); 2707} 2708 2709static struct file_system_type shmem_fs_type = { 2710 .owner = THIS_MODULE, 2711 .name = "tmpfs", 2712 .mount = shmem_mount, 2713 .kill_sb = kill_litter_super, 2714 .fs_flags = FS_USERNS_MOUNT, 2715}; 2716 2717int __init shmem_init(void) 2718{ 2719 int error; 2720 2721 /* If rootfs called this, don't re-init */ 2722 if (shmem_inode_cachep) 2723 return 0; 2724 2725 error = bdi_init(&shmem_backing_dev_info); 2726 if (error) 2727 goto out4; 2728 2729 error = shmem_init_inodecache(); 2730 if (error) 2731 goto out3; 2732 2733 error = register_filesystem(&shmem_fs_type); 2734 if (error) { 2735 printk(KERN_ERR "Could not register tmpfs\n"); 2736 goto out2; 2737 } 2738 2739 shm_mnt = kern_mount(&shmem_fs_type); 2740 if (IS_ERR(shm_mnt)) { 2741 error = PTR_ERR(shm_mnt); 2742 printk(KERN_ERR "Could not kern_mount tmpfs\n"); 2743 goto out1; 2744 } 2745 return 0; 2746 2747out1: 2748 unregister_filesystem(&shmem_fs_type); 2749out2: 2750 shmem_destroy_inodecache(); 2751out3: 2752 bdi_destroy(&shmem_backing_dev_info); 2753out4: 2754 shm_mnt = ERR_PTR(error); 2755 return error; 2756} 2757 2758#else /* !CONFIG_SHMEM */ 2759 2760/* 2761 * tiny-shmem: simple shmemfs and tmpfs using ramfs code 2762 * 2763 * This is intended for small system where the benefits of the full 2764 * shmem code (swap-backed and resource-limited) are outweighed by 2765 * their complexity. On systems without swap this code should be 2766 * effectively equivalent, but much lighter weight. 2767 */ 2768 2769static struct file_system_type shmem_fs_type = { 2770 .name = "tmpfs", 2771 .mount = ramfs_mount, 2772 .kill_sb = kill_litter_super, 2773 .fs_flags = FS_USERNS_MOUNT, 2774}; 2775 2776int __init shmem_init(void) 2777{ 2778 BUG_ON(register_filesystem(&shmem_fs_type) != 0); 2779 2780 shm_mnt = kern_mount(&shmem_fs_type); 2781 BUG_ON(IS_ERR(shm_mnt)); 2782 2783 return 0; 2784} 2785 2786int shmem_unuse(swp_entry_t swap, struct page *page) 2787{ 2788 return 0; 2789} 2790 2791int shmem_lock(struct file *file, int lock, struct user_struct *user) 2792{ 2793 return 0; 2794} 2795 2796void shmem_unlock_mapping(struct address_space *mapping) 2797{ 2798} 2799 2800void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 2801{ 2802 truncate_inode_pages_range(inode->i_mapping, lstart, lend); 2803} 2804EXPORT_SYMBOL_GPL(shmem_truncate_range); 2805 2806#define shmem_vm_ops generic_file_vm_ops 2807#define shmem_file_operations ramfs_file_operations 2808#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev) 2809#define shmem_acct_size(flags, size) 0 2810#define shmem_unacct_size(flags, size) do {} while (0) 2811 2812#endif /* CONFIG_SHMEM */ 2813 2814/* common code */ 2815 2816static struct dentry_operations anon_ops = { 2817 .d_dname = simple_dname 2818}; 2819 2820static struct file *__shmem_file_setup(const char *name, loff_t size, 2821 unsigned long flags, unsigned int i_flags) 2822{ 2823 struct file *res; 2824 struct inode *inode; 2825 struct path path; 2826 struct super_block *sb; 2827 struct qstr this; 2828 2829 if (IS_ERR(shm_mnt)) 2830 return ERR_CAST(shm_mnt); 2831 2832 if (size < 0 || size > MAX_LFS_FILESIZE) 2833 return ERR_PTR(-EINVAL); 2834 2835 if (shmem_acct_size(flags, size)) 2836 return ERR_PTR(-ENOMEM); 2837 2838 res = ERR_PTR(-ENOMEM); 2839 this.name = name; 2840 this.len = strlen(name); 2841 this.hash = 0; /* will go */ 2842 sb = shm_mnt->mnt_sb; 2843 path.dentry = d_alloc_pseudo(sb, &this); 2844 if (!path.dentry) 2845 goto put_memory; 2846 d_set_d_op(path.dentry, &anon_ops); 2847 path.mnt = mntget(shm_mnt); 2848 2849 res = ERR_PTR(-ENOSPC); 2850 inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags); 2851 if (!inode) 2852 goto put_dentry; 2853 2854 inode->i_flags |= i_flags; 2855 d_instantiate(path.dentry, inode); 2856 inode->i_size = size; 2857 clear_nlink(inode); /* It is unlinked */ 2858 res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size)); 2859 if (IS_ERR(res)) 2860 goto put_dentry; 2861 2862 res = alloc_file(&path, FMODE_WRITE | FMODE_READ, 2863 &shmem_file_operations); 2864 if (IS_ERR(res)) 2865 goto put_dentry; 2866 2867 return res; 2868 2869put_dentry: 2870 path_put(&path); 2871put_memory: 2872 shmem_unacct_size(flags, size); 2873 return res; 2874} 2875 2876/** 2877 * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be 2878 * kernel internal. There will be NO LSM permission checks against the 2879 * underlying inode. So users of this interface must do LSM checks at a 2880 * higher layer. The one user is the big_key implementation. LSM checks 2881 * are provided at the key level rather than the inode level. 2882 * @name: name for dentry (to be seen in /proc/<pid>/maps 2883 * @size: size to be set for the file 2884 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size 2885 */ 2886struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags) 2887{ 2888 return __shmem_file_setup(name, size, flags, S_PRIVATE); 2889} 2890 2891/** 2892 * shmem_file_setup - get an unlinked file living in tmpfs 2893 * @name: name for dentry (to be seen in /proc/<pid>/maps 2894 * @size: size to be set for the file 2895 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size 2896 */ 2897struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags) 2898{ 2899 return __shmem_file_setup(name, size, flags, 0); 2900} 2901EXPORT_SYMBOL_GPL(shmem_file_setup); 2902 2903/** 2904 * shmem_zero_setup - setup a shared anonymous mapping 2905 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff 2906 */ 2907int shmem_zero_setup(struct vm_area_struct *vma) 2908{ 2909 struct file *file; 2910 loff_t size = vma->vm_end - vma->vm_start; 2911 2912 file = shmem_file_setup("dev/zero", size, vma->vm_flags); 2913 if (IS_ERR(file)) 2914 return PTR_ERR(file); 2915 2916 if (vma->vm_file) 2917 fput(vma->vm_file); 2918 vma->vm_file = file; 2919 vma->vm_ops = &shmem_vm_ops; 2920 return 0; 2921} 2922 2923/** 2924 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags. 2925 * @mapping: the page's address_space 2926 * @index: the page index 2927 * @gfp: the page allocator flags to use if allocating 2928 * 2929 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)", 2930 * with any new page allocations done using the specified allocation flags. 2931 * But read_cache_page_gfp() uses the ->readpage() method: which does not 2932 * suit tmpfs, since it may have pages in swapcache, and needs to find those 2933 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support. 2934 * 2935 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in 2936 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily. 2937 */ 2938struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, 2939 pgoff_t index, gfp_t gfp) 2940{ 2941#ifdef CONFIG_SHMEM 2942 struct inode *inode = mapping->host; 2943 struct page *page; 2944 int error; 2945 2946 BUG_ON(mapping->a_ops != &shmem_aops); 2947 error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL); 2948 if (error) 2949 page = ERR_PTR(error); 2950 else 2951 unlock_page(page); 2952 return page; 2953#else 2954 /* 2955 * The tiny !SHMEM case uses ramfs without swap 2956 */ 2957 return read_cache_page_gfp(mapping, index, gfp); 2958#endif 2959} 2960EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp); 2961