shmem.c 71.8 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8
/*
 * Resizable virtual memory filesystem for Linux.
 *
 * Copyright (C) 2000 Linus Torvalds.
 *		 2000 Transmeta Corp.
 *		 2000-2001 Christoph Rohland
 *		 2000-2001 SAP AG
 *		 2002 Red Hat Inc.
9 10
 * Copyright (C) 2002-2005 Hugh Dickins.
 * Copyright (C) 2002-2005 VERITAS Software Corporation.
Linus Torvalds's avatar
Linus Torvalds committed
11 12 13 14 15 16
 * Copyright (C) 2004 Andi Kleen, SuSE Labs
 *
 * Extended attribute support for tmpfs:
 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 *
17 18 19
 * tiny-shmem:
 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
 *
Linus Torvalds's avatar
Linus Torvalds committed
20 21 22
 * This file is released under the GPL.
 */

23 24 25 26
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/vfs.h>
#include <linux/mount.h>
Hugh Dickins's avatar
Hugh Dickins committed
27
#include <linux/pagemap.h>
28 29 30
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/module.h>
31
#include <linux/percpu_counter.h>
32 33 34 35 36
#include <linux/swap.h>

static struct vfsmount *shm_mnt;

#ifdef CONFIG_SHMEM
Linus Torvalds's avatar
Linus Torvalds committed
37 38 39 40 41 42
/*
 * This virtual memory filesystem is heavily based on the ramfs. It
 * extends ramfs by the ability to use swap and honor resource limits
 * which makes it a completely usable filesystem.
 */

43
#include <linux/xattr.h>
44
#include <linux/exportfs.h>
45
#include <linux/posix_acl.h>
46
#include <linux/generic_acl.h>
Linus Torvalds's avatar
Linus Torvalds committed
47 48 49 50 51 52 53 54 55 56 57
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/shmem_fs.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/swapops.h>
#include <linux/mempolicy.h>
#include <linux/namei.h>
58
#include <linux/ctype.h>
59
#include <linux/migrate.h>
60
#include <linux/highmem.h>
61
#include <linux/seq_file.h>
Mimi Zohar's avatar
Mimi Zohar committed
62
#include <linux/magic.h>
63

Linus Torvalds's avatar
Linus Torvalds committed
64 65 66 67
#include <asm/uaccess.h>
#include <asm/div64.h>
#include <asm/pgtable.h>

Hugh Dickins's avatar
Hugh Dickins committed
68 69 70 71 72 73 74 75 76 77 78 79
/*
 * The maximum size of a shmem/tmpfs file is limited by the maximum size of
 * its triple-indirect swap vector - see illustration at shmem_swp_entry().
 *
 * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
 * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
 * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
 * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
 *
 * We use / and * instead of shifts in the definitions below, so that the swap
 * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
 */
Linus Torvalds's avatar
Linus Torvalds committed
80
#define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
Yuri Tikhonov's avatar
Yuri Tikhonov committed
81
#define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
Linus Torvalds's avatar
Linus Torvalds committed
82

Hugh Dickins's avatar
Hugh Dickins committed
83 84
#define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
#define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
Linus Torvalds's avatar
Linus Torvalds committed
85

Hugh Dickins's avatar
Hugh Dickins committed
86 87 88 89
#define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
#define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))

#define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
Linus Torvalds's avatar
Linus Torvalds committed
90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
#define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)

/* info->flags needs VM_flags to handle pagein/truncate races efficiently */
#define SHMEM_PAGEIN	 VM_READ
#define SHMEM_TRUNCATE	 VM_WRITE

/* Definition to limit shmem_truncate's steps between cond_rescheds */
#define LATENCY_LIMIT	 64

/* Pretend that each entry is of this size in directory's i_size */
#define BOGO_DIRENT_SIZE 20

/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
enum sgp_type {
	SGP_READ,	/* don't exceed i_size, don't allocate page */
	SGP_CACHE,	/* don't exceed i_size, may allocate page */
106
	SGP_DIRTY,	/* like SGP_CACHE, but set new page dirty */
Linus Torvalds's avatar
Linus Torvalds committed
107 108 109
	SGP_WRITE,	/* may exceed i_size, may allocate page */
};

Andrew Morton's avatar
Andrew Morton committed
110
#ifdef CONFIG_TMPFS
111 112 113 114 115 116 117 118 119
static unsigned long shmem_default_max_blocks(void)
{
	return totalram_pages / 2;
}

static unsigned long shmem_default_max_inodes(void)
{
	return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
}
Andrew Morton's avatar
Andrew Morton committed
120
#endif
121

Linus Torvalds's avatar
Linus Torvalds committed
122 123 124
static int shmem_getpage(struct inode *inode, unsigned long idx,
			 struct page **pagep, enum sgp_type sgp, int *type);

Al Viro's avatar
Al Viro committed
125
static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
Linus Torvalds's avatar
Linus Torvalds committed
126 127 128 129 130
{
	/*
	 * The above definition of ENTRIES_PER_PAGE, and the use of
	 * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
	 * might be reconsidered if it ever diverges from PAGE_SIZE.
131
	 *
132
	 * Mobility flags are masked out as swap vectors cannot move
Linus Torvalds's avatar
Linus Torvalds committed
133
	 */
134
	return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
135
				PAGE_CACHE_SHIFT-PAGE_SHIFT);
Linus Torvalds's avatar
Linus Torvalds committed
136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187
}

static inline void shmem_dir_free(struct page *page)
{
	__free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
}

static struct page **shmem_dir_map(struct page *page)
{
	return (struct page **)kmap_atomic(page, KM_USER0);
}

static inline void shmem_dir_unmap(struct page **dir)
{
	kunmap_atomic(dir, KM_USER0);
}

static swp_entry_t *shmem_swp_map(struct page *page)
{
	return (swp_entry_t *)kmap_atomic(page, KM_USER1);
}

static inline void shmem_swp_balance_unmap(void)
{
	/*
	 * When passing a pointer to an i_direct entry, to code which
	 * also handles indirect entries and so will shmem_swp_unmap,
	 * we must arrange for the preempt count to remain in balance.
	 * What kmap_atomic of a lowmem page does depends on config
	 * and architecture, so pretend to kmap_atomic some lowmem page.
	 */
	(void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
}

static inline void shmem_swp_unmap(swp_entry_t *entry)
{
	kunmap_atomic(entry, KM_USER1);
}

static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

/*
 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 * for shared memory and for shared anonymous (/dev/zero) mappings
 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 * consistent with the pre-accounting of private mappings ...
 */
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
188 189
	return (flags & VM_NORESERVE) ?
		0 : security_vm_enough_memory_kern(VM_ACCT(size));
Linus Torvalds's avatar
Linus Torvalds committed
190 191 192 193
}

static inline void shmem_unacct_size(unsigned long flags, loff_t size)
{
194
	if (!(flags & VM_NORESERVE))
Linus Torvalds's avatar
Linus Torvalds committed
195 196 197 198 199 200 201 202 203 204 205
		vm_unacct_memory(VM_ACCT(size));
}

/*
 * ... whereas tmpfs objects are accounted incrementally as
 * pages are allocated, in order to allow huge sparse files.
 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 */
static inline int shmem_acct_block(unsigned long flags)
{
206 207
	return (flags & VM_NORESERVE) ?
		security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
Linus Torvalds's avatar
Linus Torvalds committed
208 209 210 211
}

static inline void shmem_unacct_blocks(unsigned long flags, long pages)
{
212
	if (flags & VM_NORESERVE)
Linus Torvalds's avatar
Linus Torvalds committed
213 214 215
		vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
}

216
static const struct super_operations shmem_ops;
217
static const struct address_space_operations shmem_aops;
218
static const struct file_operations shmem_file_operations;
219 220 221
static const struct inode_operations shmem_inode_operations;
static const struct inode_operations shmem_dir_inode_operations;
static const struct inode_operations shmem_special_inode_operations;
222
static const struct vm_operations_struct shmem_vm_ops;
Linus Torvalds's avatar
Linus Torvalds committed
223

224
static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
Linus Torvalds's avatar
Linus Torvalds committed
225
	.ra_pages	= 0,	/* No readahead */
226
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
Linus Torvalds's avatar
Linus Torvalds committed
227 228 229
};

static LIST_HEAD(shmem_swaplist);
230
static DEFINE_MUTEX(shmem_swaplist_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
231 232 233 234

static void shmem_free_blocks(struct inode *inode, long pages)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
235
	if (sbinfo->max_blocks) {
236 237
		percpu_counter_add(&sbinfo->used_blocks, -pages);
		spin_lock(&inode->i_lock);
Linus Torvalds's avatar
Linus Torvalds committed
238
		inode->i_blocks -= pages*BLOCKS_PER_PAGE;
239
		spin_unlock(&inode->i_lock);
Linus Torvalds's avatar
Linus Torvalds committed
240 241 242
	}
}

243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267
static int shmem_reserve_inode(struct super_block *sb)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
	if (sbinfo->max_inodes) {
		spin_lock(&sbinfo->stat_lock);
		if (!sbinfo->free_inodes) {
			spin_unlock(&sbinfo->stat_lock);
			return -ENOSPC;
		}
		sbinfo->free_inodes--;
		spin_unlock(&sbinfo->stat_lock);
	}
	return 0;
}

static void shmem_free_inode(struct super_block *sb)
{
	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
	if (sbinfo->max_inodes) {
		spin_lock(&sbinfo->stat_lock);
		sbinfo->free_inodes++;
		spin_unlock(&sbinfo->stat_lock);
	}
}

268
/**
Linus Torvalds's avatar
Linus Torvalds committed
269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292
 * shmem_recalc_inode - recalculate the size of an inode
 * @inode: inode to recalc
 *
 * We have to calculate the free blocks since the mm can drop
 * undirtied hole pages behind our back.
 *
 * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 *
 * It has to be called with the spinlock held.
 */
static void shmem_recalc_inode(struct inode *inode)
{
	struct shmem_inode_info *info = SHMEM_I(inode);
	long freed;

	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
	if (freed > 0) {
		info->alloced -= freed;
		shmem_unacct_blocks(info->flags, freed);
		shmem_free_blocks(inode, freed);
	}
}

293
/**
Linus Torvalds's avatar
Linus Torvalds committed
294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389
 * shmem_swp_entry - find the swap vector position in the info structure
 * @info:  info structure for the inode
 * @index: index of the page to find
 * @page:  optional page to add to the structure. Has to be preset to
 *         all zeros
 *
 * If there is no space allocated yet it will return NULL when
 * page is NULL, else it will use the page for the needed block,
 * setting it to NULL on return to indicate that it has been used.
 *
 * The swap vector is organized the following way:
 *
 * There are SHMEM_NR_DIRECT entries directly stored in the
 * shmem_inode_info structure. So small files do not need an addional
 * allocation.
 *
 * For pages with index > SHMEM_NR_DIRECT there is the pointer
 * i_indirect which points to a page which holds in the first half
 * doubly indirect blocks, in the second half triple indirect blocks:
 *
 * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 * following layout (for SHMEM_NR_DIRECT == 16):
 *
 * i_indirect -> dir --> 16-19
 * 	      |	     +-> 20-23
 * 	      |
 * 	      +-->dir2 --> 24-27
 * 	      |	       +-> 28-31
 * 	      |	       +-> 32-35
 * 	      |	       +-> 36-39
 * 	      |
 * 	      +-->dir3 --> 40-43
 * 	       	       +-> 44-47
 * 	      	       +-> 48-51
 * 	      	       +-> 52-55
 */
static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
{
	unsigned long offset;
	struct page **dir;
	struct page *subdir;

	if (index < SHMEM_NR_DIRECT) {
		shmem_swp_balance_unmap();
		return info->i_direct+index;
	}
	if (!info->i_indirect) {
		if (page) {
			info->i_indirect = *page;
			*page = NULL;
		}
		return NULL;			/* need another page */
	}

	index -= SHMEM_NR_DIRECT;
	offset = index % ENTRIES_PER_PAGE;
	index /= ENTRIES_PER_PAGE;
	dir = shmem_dir_map(info->i_indirect);

	if (index >= ENTRIES_PER_PAGE/2) {
		index -= ENTRIES_PER_PAGE/2;
		dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
		index %= ENTRIES_PER_PAGE;
		subdir = *dir;
		if (!subdir) {
			if (page) {
				*dir = *page;
				*page = NULL;
			}
			shmem_dir_unmap(dir);
			return NULL;		/* need another page */
		}
		shmem_dir_unmap(dir);
		dir = shmem_dir_map(subdir);
	}

	dir += index;
	subdir = *dir;
	if (!subdir) {
		if (!page || !(subdir = *page)) {
			shmem_dir_unmap(dir);
			return NULL;		/* need a page */
		}
		*dir = subdir;
		*page = NULL;
	}
	shmem_dir_unmap(dir);
	return shmem_swp_map(subdir) + offset;
}

static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
{
	long incdec = value? 1: -1;

	entry->val = value;
	info->swapped += incdec;
390 391 392 393
	if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
		struct page *page = kmap_atomic_to_page(entry);
		set_page_private(page, page_private(page) + incdec);
	}
Linus Torvalds's avatar
Linus Torvalds committed
394 395
}

396
/**
Linus Torvalds's avatar
Linus Torvalds committed
397 398 399 400
 * shmem_swp_alloc - get the position of the swap entry for the page.
 * @info:	info structure for the inode
 * @index:	index of the page to find
 * @sgp:	check and recheck i_size? skip allocation?
401 402
 *
 * If the entry does not exist, allocate it.
Linus Torvalds's avatar
Linus Torvalds committed
403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418
 */
static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
{
	struct inode *inode = &info->vfs_inode;
	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
	struct page *page = NULL;
	swp_entry_t *entry;

	if (sgp != SGP_WRITE &&
	    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
		return ERR_PTR(-EINVAL);

	while (!(entry = shmem_swp_entry(info, index, &page))) {
		if (sgp == SGP_READ)
			return shmem_swp_map(ZERO_PAGE(0));
		/*
419
		 * Test used_blocks against 1 less max_blocks, since we have 1 data
Linus Torvalds's avatar
Linus Torvalds committed
420 421 422
		 * page (and perhaps indirect index pages) yet to allocate:
		 * a waste to allocate index if we cannot allocate data.
		 */
423
		if (sbinfo->max_blocks) {
424
			if (percpu_counter_compare(&sbinfo->used_blocks, (sbinfo->max_blocks - 1)) > 0)
Linus Torvalds's avatar
Linus Torvalds committed
425
				return ERR_PTR(-ENOSPC);
426 427
			percpu_counter_inc(&sbinfo->used_blocks);
			spin_lock(&inode->i_lock);
Linus Torvalds's avatar
Linus Torvalds committed
428
			inode->i_blocks += BLOCKS_PER_PAGE;
429
			spin_unlock(&inode->i_lock);
Linus Torvalds's avatar
Linus Torvalds committed
430 431 432
		}

		spin_unlock(&info->lock);
433
		page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
Linus Torvalds's avatar
Linus Torvalds committed
434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457
		spin_lock(&info->lock);

		if (!page) {
			shmem_free_blocks(inode, 1);
			return ERR_PTR(-ENOMEM);
		}
		if (sgp != SGP_WRITE &&
		    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
			entry = ERR_PTR(-EINVAL);
			break;
		}
		if (info->next_index <= index)
			info->next_index = index + 1;
	}
	if (page) {
		/* another task gave its page, or truncated the file */
		shmem_free_blocks(inode, 1);
		shmem_dir_free(page);
	}
	if (info->next_index <= index && !IS_ERR(entry))
		info->next_index = index + 1;
	return entry;
}

458
/**
Linus Torvalds's avatar
Linus Torvalds committed
459
 * shmem_free_swp - free some swap entries in a directory
460 461 462
 * @dir:        pointer to the directory
 * @edir:       pointer after last entry of the directory
 * @punch_lock: pointer to spinlock when needed for the holepunch case
Linus Torvalds's avatar
Linus Torvalds committed
463
 */
464 465
static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
						spinlock_t *punch_lock)
Linus Torvalds's avatar
Linus Torvalds committed
466
{
467
	spinlock_t *punch_unlock = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
468 469 470 471 472
	swp_entry_t *ptr;
	int freed = 0;

	for (ptr = dir; ptr < edir; ptr++) {
		if (ptr->val) {
473 474 475 476 477 478 479
			if (unlikely(punch_lock)) {
				punch_unlock = punch_lock;
				punch_lock = NULL;
				spin_lock(punch_unlock);
				if (!ptr->val)
					continue;
			}
Linus Torvalds's avatar
Linus Torvalds committed
480 481 482 483 484
			free_swap_and_cache(*ptr);
			*ptr = (swp_entry_t){0};
			freed++;
		}
	}
485 486
	if (punch_unlock)
		spin_unlock(punch_unlock);
Linus Torvalds's avatar
Linus Torvalds committed
487 488 489
	return freed;
}

490 491
static int shmem_map_and_free_swp(struct page *subdir, int offset,
		int limit, struct page ***dir, spinlock_t *punch_lock)
Linus Torvalds's avatar
Linus Torvalds committed
492 493 494 495 496 497 498 499 500
{
	swp_entry_t *ptr;
	int freed = 0;

	ptr = shmem_swp_map(subdir);
	for (; offset < limit; offset += LATENCY_LIMIT) {
		int size = limit - offset;
		if (size > LATENCY_LIMIT)
			size = LATENCY_LIMIT;
501 502
		freed += shmem_free_swp(ptr+offset, ptr+offset+size,
							punch_lock);
Linus Torvalds's avatar
Linus Torvalds committed
503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533
		if (need_resched()) {
			shmem_swp_unmap(ptr);
			if (*dir) {
				shmem_dir_unmap(*dir);
				*dir = NULL;
			}
			cond_resched();
			ptr = shmem_swp_map(subdir);
		}
	}
	shmem_swp_unmap(ptr);
	return freed;
}

static void shmem_free_pages(struct list_head *next)
{
	struct page *page;
	int freed = 0;

	do {
		page = container_of(next, struct page, lru);
		next = next->next;
		shmem_dir_free(page);
		freed++;
		if (freed >= LATENCY_LIMIT) {
			cond_resched();
			freed = 0;
		}
	} while (next);
}

534
static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
Linus Torvalds's avatar
Linus Torvalds committed
535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551
{
	struct shmem_inode_info *info = SHMEM_I(inode);
	unsigned long idx;
	unsigned long size;
	unsigned long limit;
	unsigned long stage;
	unsigned long diroff;
	struct page **dir;
	struct page *topdir;
	struct page *middir;
	struct page *subdir;
	swp_entry_t *ptr;
	LIST_HEAD(pages_to_free);
	long nr_pages_to_free = 0;
	long nr_swaps_freed = 0;
	int offset;
	int freed;
552
	int punch_hole;
553 554
	spinlock_t *needs_lock;
	spinlock_t *punch_lock;
555
	unsigned long upper_limit;
Linus Torvalds's avatar
Linus Torvalds committed
556 557

	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
558
	idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
Linus Torvalds's avatar
Linus Torvalds committed
559 560 561 562 563
	if (idx >= info->next_index)
		return;

	spin_lock(&info->lock);
	info->flags |= SHMEM_TRUNCATE;
564 565
	if (likely(end == (loff_t) -1)) {
		limit = info->next_index;
566
		upper_limit = SHMEM_MAX_INDEX;
567
		info->next_index = idx;
568
		needs_lock = NULL;
569
		punch_hole = 0;
570
	} else {
571 572 573 574 575 576 577 578
		if (end + 1 >= inode->i_size) {	/* we may free a little more */
			limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
							PAGE_CACHE_SHIFT;
			upper_limit = SHMEM_MAX_INDEX;
		} else {
			limit = (end + 1) >> PAGE_CACHE_SHIFT;
			upper_limit = limit;
		}
579
		needs_lock = &info->lock;
580 581 582
		punch_hole = 1;
	}

Linus Torvalds's avatar
Linus Torvalds committed
583
	topdir = info->i_indirect;
584
	if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
Linus Torvalds's avatar
Linus Torvalds committed
585 586 587 588 589 590 591 592 593 594 595
		info->i_indirect = NULL;
		nr_pages_to_free++;
		list_add(&topdir->lru, &pages_to_free);
	}
	spin_unlock(&info->lock);

	if (info->swapped && idx < SHMEM_NR_DIRECT) {
		ptr = info->i_direct;
		size = limit;
		if (size > SHMEM_NR_DIRECT)
			size = SHMEM_NR_DIRECT;
596
		nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
Linus Torvalds's avatar
Linus Torvalds committed
597
	}
598 599 600 601 602

	/*
	 * If there are no indirect blocks or we are punching a hole
	 * below indirect blocks, nothing to be done.
	 */
603
	if (!topdir || limit <= SHMEM_NR_DIRECT)
Linus Torvalds's avatar
Linus Torvalds committed
604 605
		goto done2;

606 607 608 609 610 611 612 613 614 615 616 617 618
	/*
	 * The truncation case has already dropped info->lock, and we're safe
	 * because i_size and next_index have already been lowered, preventing
	 * access beyond.  But in the punch_hole case, we still need to take
	 * the lock when updating the swap directory, because there might be
	 * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
	 * shmem_writepage.  However, whenever we find we can remove a whole
	 * directory page (not at the misaligned start or end of the range),
	 * we first NULLify its pointer in the level above, and then have no
	 * need to take the lock when updating its contents: needs_lock and
	 * punch_lock (either pointing to info->lock or NULL) manage this.
	 */

619
	upper_limit -= SHMEM_NR_DIRECT;
Linus Torvalds's avatar
Linus Torvalds committed
620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638
	limit -= SHMEM_NR_DIRECT;
	idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
	offset = idx % ENTRIES_PER_PAGE;
	idx -= offset;

	dir = shmem_dir_map(topdir);
	stage = ENTRIES_PER_PAGEPAGE/2;
	if (idx < ENTRIES_PER_PAGEPAGE/2) {
		middir = topdir;
		diroff = idx/ENTRIES_PER_PAGE;
	} else {
		dir += ENTRIES_PER_PAGE/2;
		dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
		while (stage <= idx)
			stage += ENTRIES_PER_PAGEPAGE;
		middir = *dir;
		if (*dir) {
			diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
				ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
639
			if (!diroff && !offset && upper_limit >= stage) {
640 641 642 643 644 645 646
				if (needs_lock) {
					spin_lock(needs_lock);
					*dir = NULL;
					spin_unlock(needs_lock);
					needs_lock = NULL;
				} else
					*dir = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671
				nr_pages_to_free++;
				list_add(&middir->lru, &pages_to_free);
			}
			shmem_dir_unmap(dir);
			dir = shmem_dir_map(middir);
		} else {
			diroff = 0;
			offset = 0;
			idx = stage;
		}
	}

	for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
		if (unlikely(idx == stage)) {
			shmem_dir_unmap(dir);
			dir = shmem_dir_map(topdir) +
			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
			while (!*dir) {
				dir++;
				idx += ENTRIES_PER_PAGEPAGE;
				if (idx >= limit)
					goto done1;
			}
			stage = idx + ENTRIES_PER_PAGEPAGE;
			middir = *dir;
672 673
			if (punch_hole)
				needs_lock = &info->lock;
674
			if (upper_limit >= stage) {
675 676 677 678 679 680 681
				if (needs_lock) {
					spin_lock(needs_lock);
					*dir = NULL;
					spin_unlock(needs_lock);
					needs_lock = NULL;
				} else
					*dir = NULL;
682 683 684
				nr_pages_to_free++;
				list_add(&middir->lru, &pages_to_free);
			}
Linus Torvalds's avatar
Linus Torvalds committed
685 686 687 688 689
			shmem_dir_unmap(dir);
			cond_resched();
			dir = shmem_dir_map(middir);
			diroff = 0;
		}
690
		punch_lock = needs_lock;
Linus Torvalds's avatar
Linus Torvalds committed
691
		subdir = dir[diroff];
692 693 694 695 696 697 698 699 700 701 702 703
		if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
			if (needs_lock) {
				spin_lock(needs_lock);
				dir[diroff] = NULL;
				spin_unlock(needs_lock);
				punch_lock = NULL;
			} else
				dir[diroff] = NULL;
			nr_pages_to_free++;
			list_add(&subdir->lru, &pages_to_free);
		}
		if (subdir && page_private(subdir) /* has swap entries */) {
Linus Torvalds's avatar
Linus Torvalds committed
704 705 706 707
			size = limit - idx;
			if (size > ENTRIES_PER_PAGE)
				size = ENTRIES_PER_PAGE;
			freed = shmem_map_and_free_swp(subdir,
708
					offset, size, &dir, punch_lock);
Linus Torvalds's avatar
Linus Torvalds committed
709 710 711
			if (!dir)
				dir = shmem_dir_map(middir);
			nr_swaps_freed += freed;
712
			if (offset || punch_lock) {
Linus Torvalds's avatar
Linus Torvalds committed
713
				spin_lock(&info->lock);
714 715
				set_page_private(subdir,
					page_private(subdir) - freed);
Linus Torvalds's avatar
Linus Torvalds committed
716
				spin_unlock(&info->lock);
717 718
			} else
				BUG_ON(page_private(subdir) != freed);
Linus Torvalds's avatar
Linus Torvalds committed
719
		}
720
		offset = 0;
Linus Torvalds's avatar
Linus Torvalds committed
721 722 723 724 725 726 727
	}
done1:
	shmem_dir_unmap(dir);
done2:
	if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
		/*
		 * Call truncate_inode_pages again: racing shmem_unuse_inode
728 729 730 731 732
		 * may have swizzled a page in from swap since
		 * truncate_pagecache or generic_delete_inode did it, before we
		 * lowered next_index.  Also, though shmem_getpage checks
		 * i_size before adding to cache, no recheck after: so fix the
		 * narrow window there too.
733 734 735 736 737
		 *
		 * Recalling truncate_inode_pages_range and unmap_mapping_range
		 * every time for punch_hole (which never got a chance to clear
		 * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
		 * yet hardly ever necessary: try to optimize them out later.
Linus Torvalds's avatar
Linus Torvalds committed
738
		 */
739
		truncate_inode_pages_range(inode->i_mapping, start, end);
740 741 742
		if (punch_hole)
			unmap_mapping_range(inode->i_mapping, start,
							end - start, 1);
Linus Torvalds's avatar
Linus Torvalds committed
743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764
	}

	spin_lock(&info->lock);
	info->flags &= ~SHMEM_TRUNCATE;
	info->swapped -= nr_swaps_freed;
	if (nr_pages_to_free)
		shmem_free_blocks(inode, nr_pages_to_free);
	shmem_recalc_inode(inode);
	spin_unlock(&info->lock);

	/*
	 * Empty swap vector directory pages to be freed?
	 */
	if (!list_empty(&pages_to_free)) {
		pages_to_free.prev->next = NULL;
		shmem_free_pages(pages_to_free.next);
	}
}

static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
{
	struct inode *inode = dentry->d_inode;
765
	loff_t newsize = attr->ia_size;
Linus Torvalds's avatar
Linus Torvalds committed
766 767
	int error;

768 769 770 771
	error = inode_change_ok(inode, attr);
	if (error)
		return error;

772 773
	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
					&& newsize != inode->i_size) {
774 775 776
		struct page *page = NULL;

		if (newsize < inode->i_size) {
Linus Torvalds's avatar
Linus Torvalds committed
777 778 779 780
			/*
			 * If truncating down to a partial page, then
			 * if that page is already allocated, hold it
			 * in memory until the truncation is over, so
781
			 * truncate_partial_page cannot miss it were
Linus Torvalds's avatar
Linus Torvalds committed
782 783
			 * it assigned to swap.
			 */
784
			if (newsize & (PAGE_CACHE_SIZE-1)) {
Linus Torvalds's avatar
Linus Torvalds committed
785
				(void) shmem_getpage(inode,
786
					newsize >> PAGE_CACHE_SHIFT,
Linus Torvalds's avatar
Linus Torvalds committed
787
						&page, SGP_READ, NULL);
788 789
				if (page)
					unlock_page(page);
Linus Torvalds's avatar
Linus Torvalds committed
790 791 792 793 794 795 796 797
			}
			/*
			 * Reset SHMEM_PAGEIN flag so that shmem_truncate can
			 * detect if any pages might have been added to cache
			 * after truncate_inode_pages.  But we needn't bother
			 * if it's being fully truncated to zero-length: the
			 * nrpages check is efficient enough in that case.
			 */
798
			if (newsize) {
Linus Torvalds's avatar
Linus Torvalds committed
799 800 801 802 803 804
				struct shmem_inode_info *info = SHMEM_I(inode);
				spin_lock(&info->lock);
				info->flags &= ~SHMEM_PAGEIN;
				spin_unlock(&info->lock);
			}
		}
805

806 807
		/* XXX(truncate): truncate_setsize should be called last */
		truncate_setsize(inode, newsize);
808 809 810
		if (page)
			page_cache_release(page);
		shmem_truncate_range(inode, newsize, (loff_t)-1);
Linus Torvalds's avatar
Linus Torvalds committed
811 812
	}

813
	setattr_copy(inode, attr);
814
#ifdef CONFIG_TMPFS_POSIX_ACL
815
	if (attr->ia_valid & ATTR_MODE)
816
		error = generic_acl_chmod(inode);
817
#endif
Linus Torvalds's avatar
Linus Torvalds committed
818 819 820
	return error;
}

Al Viro's avatar
Al Viro committed
821
static void shmem_evict_inode(struct inode *inode)
Linus Torvalds's avatar
Linus Torvalds committed
822 823 824
{
	struct shmem_inode_info *info = SHMEM_I(inode);

825
	if (inode->i_mapping->a_ops == &shmem_aops) {
826
		truncate_inode_pages(inode->i_mapping, 0);
Linus Torvalds's avatar
Linus Torvalds committed
827 828
		shmem_unacct_size(info->flags, inode->i_size);
		inode->i_size = 0;
829
		shmem_truncate_range(inode, 0, (loff_t)-1);
Linus Torvalds's avatar
Linus Torvalds committed
830
		if (!list_empty(&info->swaplist)) {
831
			mutex_lock(&shmem_swaplist_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
832
			list_del_init(&info->swaplist);
833
			mutex_unlock(&shmem_swaplist_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
834 835
		}
	}
836
	BUG_ON(inode->i_blocks);
837
	shmem_free_inode(inode->i_sb);
Al Viro's avatar
Al Viro committed
838
	end_writeback(inode);
Linus Torvalds's avatar
Linus Torvalds committed
839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
}

static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
{
	swp_entry_t *ptr;

	for (ptr = dir; ptr < edir; ptr++) {
		if (ptr->val == entry.val)
			return ptr - dir;
	}
	return -1;
}

static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
{
	struct inode *inode;
	unsigned long idx;
	unsigned long size;
	unsigned long limit;
	unsigned long stage;
	struct page **dir;
	struct page *subdir;
	swp_entry_t *ptr;
	int offset;
863
	int error;
Linus Torvalds's avatar
Linus Torvalds committed
864 865 866 867

	idx = 0;
	ptr = info->i_direct;
	spin_lock(&info->lock);
Hugh Dickins's avatar
Hugh Dickins committed
868 869 870 871
	if (!info->swapped) {
		list_del_init(&info->swaplist);
		goto lost2;
	}
Linus Torvalds's avatar
Linus Torvalds committed
872 873 874 875 876
	limit = info->next_index;
	size = limit;
	if (size > SHMEM_NR_DIRECT)
		size = SHMEM_NR_DIRECT;
	offset = shmem_find_swp(entry, ptr, ptr+size);
877
	if (offset >= 0)
Linus Torvalds's avatar
Linus Torvalds committed
878 879 880 881 882 883 884 885 886 887
		goto found;
	if (!info->i_indirect)
		goto lost2;

	dir = shmem_dir_map(info->i_indirect);
	stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;

	for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
		if (unlikely(idx == stage)) {
			shmem_dir_unmap(dir-1);
888 889 890 891 892 893 894 895
			if (cond_resched_lock(&info->lock)) {
				/* check it has not been truncated */
				if (limit > info->next_index) {
					limit = info->next_index;
					if (idx >= limit)
						goto lost2;
				}
			}
Linus Torvalds's avatar
Linus Torvalds committed
896 897 898 899 900 901 902 903 904 905 906 907 908 909
			dir = shmem_dir_map(info->i_indirect) +
			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
			while (!*dir) {
				dir++;
				idx += ENTRIES_PER_PAGEPAGE;
				if (idx >= limit)
					goto lost1;
			}
			stage = idx + ENTRIES_PER_PAGEPAGE;
			subdir = *dir;
			shmem_dir_unmap(dir);
			dir = shmem_dir_map(subdir);
		}
		subdir = *dir;
910
		if (subdir && page_private(subdir)) {
Linus Torvalds's avatar
Linus Torvalds committed
911 912 913 914 915
			ptr = shmem_swp_map(subdir);
			size = limit - idx;
			if (size > ENTRIES_PER_PAGE)
				size = ENTRIES_PER_PAGE;
			offset = shmem_find_swp(entry, ptr, ptr+size);
916
			shmem_swp_unmap(ptr);
Linus Torvalds's avatar
Linus Torvalds committed
917 918 919 920 921 922 923 924 925 926 927 928 929
			if (offset >= 0) {
				shmem_dir_unmap(dir);
				goto found;
			}
		}
	}
lost1:
	shmem_dir_unmap(dir-1);
lost2:
	spin_unlock(&info->lock);
	return 0;
found:
	idx += offset;
930 931 932
	inode = igrab(&info->vfs_inode);
	spin_unlock(&info->lock);

Hugh Dickins's avatar
Hugh Dickins committed
933 934
	/*
	 * Move _head_ to start search for next from here.
Al Viro's avatar
Al Viro committed
935
	 * But be careful: shmem_evict_inode checks list_empty without taking
Hugh Dickins's avatar
Hugh Dickins committed
936 937 938 939 940 941
	 * mutex, and there's an instant in list_move_tail when info->swaplist
	 * would appear empty, if it were the only one on shmem_swaplist.  We
	 * could avoid doing it if inode NULL; or use this minor optimization.
	 */
	if (shmem_swaplist.next != &info->swaplist)
		list_move_tail(&shmem_swaplist, &info->swaplist);
942 943 944 945 946
	mutex_unlock(&shmem_swaplist_mutex);

	error = 1;
	if (!inode)
		goto out;
KAMEZAWA Hiroyuki's avatar
KAMEZAWA Hiroyuki committed
947
	/*
948 949 950
	 * Charge page using GFP_KERNEL while we can wait.
	 * Charged back to the user(not to caller) when swap account is used.
	 * add_to_page_cache() will be called with GFP_NOWAIT.
KAMEZAWA Hiroyuki's avatar
KAMEZAWA Hiroyuki committed
951
	 */
952
	error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
Hugh Dickins's avatar
Hugh Dickins committed
953 954
	if (error)
		goto out;
955
	error = radix_tree_preload(GFP_KERNEL);
956 957 958 959
	if (error) {
		mem_cgroup_uncharge_cache_page(page);
		goto out;
	}
Hugh Dickins's avatar
Hugh Dickins committed
960
	error = 1;
961 962 963

	spin_lock(&info->lock);
	ptr = shmem_swp_entry(info, idx, NULL);
964
	if (ptr && ptr->val == entry.val) {
Nick Piggin's avatar
Nick Piggin committed
965
		error = add_to_page_cache_locked(page, inode->i_mapping,
Hugh Dickins's avatar
Hugh Dickins committed
966
						idx, GFP_NOWAIT);
967 968 969 970
		/* does mem_cgroup_uncharge_cache_page on error */
	} else	/* we must compensate for our precharge above */
		mem_cgroup_uncharge_cache_page(page);

971 972
	if (error == -EEXIST) {
		struct page *filepage = find_get_page(inode->i_mapping, idx);
973
		error = 1;
974 975 976 977 978 979 980 981 982 983 984
		if (filepage) {
			/*
			 * There might be a more uptodate page coming down
			 * from a stacked writepage: forget our swappage if so.
			 */
			if (PageUptodate(filepage))
				error = 0;
			page_cache_release(filepage);
		}
	}
	if (!error) {
985 986
		delete_from_swap_cache(page);
		set_page_dirty(page);
Linus Torvalds's avatar
Linus Torvalds committed
987
		info->flags |= SHMEM_PAGEIN;
988 989 990
		shmem_swp_set(info, ptr, 0);
		swap_free(entry);
		error = 1;	/* not an error, but entry was found */
Linus Torvalds's avatar
Linus Torvalds committed
991
	}
992 993
	if (ptr)
		shmem_swp_unmap(ptr);
Linus Torvalds's avatar
Linus Torvalds committed
994
	spin_unlock(&info->lock);
Hugh Dickins's avatar
Hugh Dickins committed
995
	radix_tree_preload_end();
996 997 998 999 1000
out:
	unlock_page(page);
	page_cache_release(page);
	iput(inode);		/* allows for NULL */
	return error;
Linus Torvalds's avatar
Linus Torvalds committed
1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011
}

/*
 * shmem_unuse() search for an eventually swapped out shmem page.
 */
int shmem_unuse(swp_entry_t entry, struct page *page)
{
	struct list_head *p, *next;
	struct shmem_inode_info *info;
	int found = 0;

1012
	mutex_lock(&shmem_swaplist_mutex);
Linus Torvalds's avatar
Linus Torvalds committed
1013 1014
	list_for_each_safe(p, next, &shmem_swaplist) {
		info = list_entry(p, struct shmem_inode_info, swaplist);
Hugh Dickins's avatar
Hugh Dickins committed
1015
		found = shmem_unuse_inode(info, entry, page);
1016
		cond_resched();
1017 1018
		if (found)
			goto out;
Linus Torvalds's avatar
Linus Torvalds committed
1019
	}
1020
	mutex_unlock(&shmem_swaplist_mutex);
Hugh Dickins's avatar
Hugh Dickins committed
1021 1022 1023 1024 1025 1026 1027 1028
	/*
	 * Can some race bring us here?  We've been holding page lock,
	 * so I think not; but would rather try again later than BUG()
	 */
	unlock_page(page);
	page_cache_release(page);
out:
	return (found < 0) ? found : 0;
Linus Torvalds's avatar
Linus Torvalds committed
1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048
}

/*
 * Move the page from the page cache to the swap cache.
 */
static int shmem_writepage(struct page *page, struct writeback_control *wbc)
{
	struct shmem_inode_info *info;
	swp_entry_t *entry, swap;
	struct address_space *mapping;
	unsigned long index;
	struct inode *inode;

	BUG_ON(!PageLocked(page));
	mapping = page->mapping;
	index = page->index;
	inode = mapping->host;
	info = SHMEM_I(inode);
	if (info->flags & VM_LOCKED)
		goto redirty;
1049
	if (!total_swap_pages)
Linus Torvalds's avatar
Linus Torvalds committed
1050 1051
		goto redirty;

1052 1053 1054 1055 1056
	/*
	 * shmem_backing_dev_info's capabilities prevent regular writeback or
	 * sync from ever calling shmem_writepage; but a stacking filesystem
	 * may use the ->writepage of its underlying filesystem, in which case
	 * tmpfs should write out to swap only in response to memory pressure,
1057 1058 1059
	 * and not for the writeback threads or sync.  However, in those cases,
	 * we do still want to check if there's a redundant swappage to be
	 * discarded.
1060 1061 1062 1063 1064 1065
	 */
	if (wbc->for_reclaim)
		swap = get_swap_page();
	else
		swap.val = 0;

Linus Torvalds's avatar
Linus Torvalds committed
1066 1067 1068 1069 1070 1071
	spin_lock(&info->lock);
	if (index >= info->next_index) {
		BUG_ON(!(info->flags & SHMEM_TRUNCATE));
		goto unlock;
	}
	entry = shmem_swp_entry(info, index, NULL);
1072 1073 1074 1075 1076 1077 1078 1079 1080
	if (entry->val) {
		/*
		 * The more uptodate page coming down from a stacked
		 * writepage should replace our old swappage.
		 */
		free_swap_and_cache(*entry);
		shmem_swp_set(info, entry, 0);
	}
	shmem_recalc_inode(inode);
Linus Torvalds's avatar
Linus Torvalds committed
1081

1082
	if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1083
		delete_from_page_cache(page);
Linus Torvalds's avatar
Linus Torvalds committed
1084 1085
		shmem_swp_set(info, entry, swap.val);
		shmem_swp_unmap(entry);
Hugh Dickins's avatar
Hugh Dickins committed
1086 1087 1088 1089
		if (list_empty(&info->swaplist))
			inode = igrab(inode);
		else
			inode = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
1090
		spin_unlock(&info->lock);
Hugh Dickins's avatar
Hugh Dickins committed
1091
		swap_shmem_alloc(swap);
1092
		BUG_ON(page_mapped(page));
1093
		swap_writepage(page, wbc);
Hugh Dickins's avatar
Hugh Dickins committed
1094 1095 1096 1097 1098 1099 1100
		if (inode) {
			mutex_lock(&shmem_swaplist_mutex);
			/* move instead of add in case we're racing */
			list_move_tail(&info->swaplist, &shmem_swaplist);
			mutex_unlock(&shmem_swaplist_mutex);
			iput(inode);
		}
Linus Torvalds's avatar
Linus Torvalds committed
1101 1102 1103 1104 1105 1106
		return 0;
	}

	shmem_swp_unmap(entry);
unlock:
	spin_unlock(&info->lock);
1107 1108 1109 1110
	/*
	 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
	 * clear SWAP_HAS_CACHE flag.
	 */
1111
	swapcache_free(swap, NULL);
Linus Torvalds's avatar
Linus Torvalds committed
1112 1113
redirty:
	set_page_dirty(page);
1114 1115 1116 1117
	if (wbc->for_reclaim)
		return AOP_WRITEPAGE_ACTIVATE;	/* Return with page locked */
	unlock_page(page);
	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
1118 1119 1120
}

#ifdef CONFIG_NUMA
1121
#ifdef CONFIG_TMPFS
1122
static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1123
{
1124
	char buffer[64];
1125

1126
	if (!mpol || mpol->mode == MPOL_DEFAULT)
1127
		return;		/* show nothing */
1128

1129
	mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1130 1131

	seq_printf(seq, ",mpol=%s", buffer);
1132
}
1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144

static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
	struct mempolicy *mpol = NULL;
	if (sbinfo->mpol) {
		spin_lock(&sbinfo->stat_lock);	/* prevent replace/use races */
		mpol = sbinfo->mpol;
		mpol_get(mpol);
		spin_unlock(&sbinfo->stat_lock);
	}
	return mpol;
}
1145 1146
#endif /* CONFIG_TMPFS */

1147 1148
static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
			struct shmem_inode_info *info, unsigned long idx)
Linus Torvalds's avatar
Linus Torvalds committed
1149
{
1150
	struct mempolicy mpol, *spol;
Linus Torvalds's avatar
Linus Torvalds committed
1151
	struct vm_area_struct pvma;
1152
	struct page *page;
Linus Torvalds's avatar
Linus Torvalds committed
1153

1154 1155 1156
	spol = mpol_cond_copy(&mpol,
				mpol_shared_policy_lookup(&info->policy, idx));

Linus Torvalds's avatar
Linus Torvalds committed
1157
	/* Create a pseudo vma that just contains the policy */
1158
	pvma.vm_start = 0;
Linus Torvalds's avatar
Linus Torvalds committed
1159
	pvma.vm_pgoff = idx;
1160
	pvma.vm_ops = NULL;
1161
	pvma.vm_policy = spol;
1162
	page = swapin_readahead(entry, gfp, &pvma, 0);
Linus Torvalds's avatar
Linus Torvalds committed
1163 1164 1165
	return page;
}

1166 1167
static struct page *shmem_alloc_page(gfp_t gfp,
			struct shmem_inode_info *info, unsigned long idx)
Linus Torvalds's avatar
Linus Torvalds committed
1168 1169 1170
{
	struct vm_area_struct pvma;

1171 1172
	/* Create a pseudo vma that just contains the policy */
	pvma.vm_start = 0;
Linus Torvalds's avatar
Linus Torvalds committed
1173
	pvma.vm_pgoff = idx;
1174 1175
	pvma.vm_ops = NULL;
	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1176 1177 1178 1179 1180

	/*
	 * alloc_page_vma() will drop the shared policy reference
	 */
	return alloc_page_vma(gfp, &pvma, 0);
Linus Torvalds's avatar
Linus Torvalds committed
1181
}
1182 1183
#else /* !CONFIG_NUMA */
#ifdef CONFIG_TMPFS
1184
static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1185 1186 1187 1188
{
}
#endif /* CONFIG_TMPFS */

1189 1190
static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
			struct shmem_inode_info *info, unsigned long idx)
Linus Torvalds's avatar
Linus Torvalds committed
1191
{
1192
	return swapin_readahead(entry, gfp, NULL, 0);
Linus Torvalds's avatar
Linus Torvalds committed
1193 1194
}

1195 1196
static inline struct page *shmem_alloc_page(gfp_t gfp,
			struct shmem_inode_info *info, unsigned long idx)
Linus Torvalds's avatar
Linus Torvalds committed
1197
{
1198
	return alloc_page(gfp);
Linus Torvalds's avatar
Linus Torvalds committed
1199
}
1200
#endif /* CONFIG_NUMA */
Linus Torvalds's avatar
Linus Torvalds committed
1201

1202 1203 1204 1205 1206 1207 1208
#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
	return NULL;
}
#endif