filemap.c 67.3 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11
/*
 *	linux/mm/filemap.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * This file handles the generic file mmap semantics used by
 * most "normal" filesystems (but you don't /have/ to use this:
 * the NFS filesystem used to do this differently, for example)
 */
12
#include <linux/export.h>
L
Linus Torvalds 已提交
13 14
#include <linux/compiler.h>
#include <linux/fs.h>
15
#include <linux/uaccess.h>
L
Linus Torvalds 已提交
16
#include <linux/aio.h>
17
#include <linux/capability.h>
L
Linus Torvalds 已提交
18
#include <linux/kernel_stat.h>
19
#include <linux/gfp.h>
L
Linus Torvalds 已提交
20 21 22 23 24 25 26 27
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/hash.h>
#include <linux/writeback.h>
28
#include <linux/backing-dev.h>
L
Linus Torvalds 已提交
29 30 31
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
32
#include <linux/cpuset.h>
N
Nick Piggin 已提交
33
#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34
#include <linux/memcontrol.h>
35
#include <linux/cleancache.h>
36 37
#include "internal.h"

L
Linus Torvalds 已提交
38 39 40
/*
 * FIXME: remove all knowledge of the buffer layer from the core VM
 */
41
#include <linux/buffer_head.h> /* for try_to_free_buffers */
L
Linus Torvalds 已提交
42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

#include <asm/mman.h>

/*
 * Shared mappings implemented 30.11.1994. It's not fully working yet,
 * though.
 *
 * Shared mappings now work. 15.8.1995  Bruno.
 *
 * finished 'unifying' the page and buffer cache and SMP-threaded the
 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
 *
 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
 */

/*
 * Lock ordering:
 *
60
 *  ->i_mmap_mutex		(truncate_pagecache)
L
Linus Torvalds 已提交
61
 *    ->private_lock		(__free_pte->__set_page_dirty_buffers)
62 63
 *      ->swap_lock		(exclusive_swap_page, others)
 *        ->mapping->tree_lock
L
Linus Torvalds 已提交
64
 *
65
 *  ->i_mutex
66
 *    ->i_mmap_mutex		(truncate->unmap_mapping_range)
L
Linus Torvalds 已提交
67 68
 *
 *  ->mmap_sem
69
 *    ->i_mmap_mutex
70
 *      ->page_table_lock or pte_lock	(various, mainly in memory.c)
L
Linus Torvalds 已提交
71 72 73 74 75
 *        ->mapping->tree_lock	(arch-dependent flush_dcache_mmap_lock)
 *
 *  ->mmap_sem
 *    ->lock_page		(access_process_vm)
 *
76 77
 *  ->i_mutex			(generic_file_buffered_write)
 *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
L
Linus Torvalds 已提交
78
 *
79
 *  bdi->wb.list_lock
80
 *    sb_lock			(fs/fs-writeback.c)
L
Linus Torvalds 已提交
81 82
 *    ->mapping->tree_lock	(__sync_single_inode)
 *
83
 *  ->i_mmap_mutex
L
Linus Torvalds 已提交
84 85 86
 *    ->anon_vma.lock		(vma_adjust)
 *
 *  ->anon_vma.lock
87
 *    ->page_table_lock or pte_lock	(anon_vma_prepare and various)
L
Linus Torvalds 已提交
88
 *
89
 *  ->page_table_lock or pte_lock
90
 *    ->swap_lock		(try_to_unmap_one)
L
Linus Torvalds 已提交
91 92 93
 *    ->private_lock		(try_to_unmap_one)
 *    ->tree_lock		(try_to_unmap_one)
 *    ->zone.lru_lock		(follow_page->mark_page_accessed)
94
 *    ->zone.lru_lock		(check_pte_range->isolate_lru_page)
L
Linus Torvalds 已提交
95 96
 *    ->private_lock		(page_remove_rmap->set_page_dirty)
 *    ->tree_lock		(page_remove_rmap->set_page_dirty)
97
 *    bdi.wb->list_lock		(page_remove_rmap->set_page_dirty)
98
 *    ->inode->i_lock		(page_remove_rmap->set_page_dirty)
99
 *    bdi.wb->list_lock		(zap_pte_range->set_page_dirty)
100
 *    ->inode->i_lock		(zap_pte_range->set_page_dirty)
L
Linus Torvalds 已提交
101 102
 *    ->private_lock		(zap_pte_range->__set_page_dirty_buffers)
 *
103 104
 * ->i_mmap_mutex
 *   ->tasklist_lock            (memory_failure, collect_procs_ao)
L
Linus Torvalds 已提交
105 106 107
 */

/*
108
 * Delete a page from the page cache and free it. Caller has to make
L
Linus Torvalds 已提交
109
 * sure the page is locked and that nobody else uses it - or that usage
N
Nick Piggin 已提交
110
 * is safe.  The caller must hold the mapping's tree_lock.
L
Linus Torvalds 已提交
111
 */
112
void __delete_from_page_cache(struct page *page)
L
Linus Torvalds 已提交
113 114 115
{
	struct address_space *mapping = page->mapping;

116 117 118 119 120 121 122 123
	/*
	 * if we're uptodate, flush out into the cleancache, otherwise
	 * invalidate any existing cleancache entries.  We can't leave
	 * stale data around in the cleancache once our page is gone
	 */
	if (PageUptodate(page) && PageMappedToDisk(page))
		cleancache_put_page(page);
	else
124
		cleancache_invalidate_page(mapping, page);
125

L
Linus Torvalds 已提交
126 127
	radix_tree_delete(&mapping->page_tree, page->index);
	page->mapping = NULL;
128
	/* Leave page->index set: truncation lookup relies upon it */
L
Linus Torvalds 已提交
129
	mapping->nrpages--;
130
	__dec_zone_page_state(page, NR_FILE_PAGES);
131 132
	if (PageSwapBacked(page))
		__dec_zone_page_state(page, NR_SHMEM);
133
	BUG_ON(page_mapped(page));
134 135 136 137 138 139 140 141 142 143 144 145

	/*
	 * Some filesystems seem to re-dirty the page even after
	 * the VM has canceled the dirty bit (eg ext3 journaling).
	 *
	 * Fix it up by doing a final dirty accounting check after
	 * having removed the page entirely.
	 */
	if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
		dec_zone_page_state(page, NR_FILE_DIRTY);
		dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
	}
L
Linus Torvalds 已提交
146 147
}

148 149 150 151 152 153 154 155 156
/**
 * delete_from_page_cache - delete page from page cache
 * @page: the page which the kernel is trying to remove from page cache
 *
 * This must be called only on pages that have been verified to be in the page
 * cache and locked.  It will never put the page into the free list, the caller
 * has a reference on the page.
 */
void delete_from_page_cache(struct page *page)
L
Linus Torvalds 已提交
157 158
{
	struct address_space *mapping = page->mapping;
159
	void (*freepage)(struct page *);
L
Linus Torvalds 已提交
160

M
Matt Mackall 已提交
161
	BUG_ON(!PageLocked(page));
L
Linus Torvalds 已提交
162

163
	freepage = mapping->a_ops->freepage;
N
Nick Piggin 已提交
164
	spin_lock_irq(&mapping->tree_lock);
165
	__delete_from_page_cache(page);
N
Nick Piggin 已提交
166
	spin_unlock_irq(&mapping->tree_lock);
167
	mem_cgroup_uncharge_cache_page(page);
168 169 170

	if (freepage)
		freepage(page);
171 172 173 174
	page_cache_release(page);
}
EXPORT_SYMBOL(delete_from_page_cache);

J
Jens Axboe 已提交
175
static int sleep_on_page(void *word)
L
Linus Torvalds 已提交
176 177 178 179 180
{
	io_schedule();
	return 0;
}

J
Jens Axboe 已提交
181
static int sleep_on_page_killable(void *word)
M
Matthew Wilcox 已提交
182
{
J
Jens Axboe 已提交
183
	sleep_on_page(word);
M
Matthew Wilcox 已提交
184 185 186
	return fatal_signal_pending(current) ? -EINTR : 0;
}

L
Linus Torvalds 已提交
187
/**
188
 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
189 190
 * @mapping:	address space structure to write
 * @start:	offset in bytes where the range starts
191
 * @end:	offset in bytes where the range ends (inclusive)
192
 * @sync_mode:	enable synchronous operation
L
Linus Torvalds 已提交
193
 *
194 195 196
 * Start writeback against all of a mapping's dirty pages that lie
 * within the byte offsets <start, end> inclusive.
 *
L
Linus Torvalds 已提交
197
 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
198
 * opposed to a regular memory cleansing writeback.  The difference between
L
Linus Torvalds 已提交
199 200 201
 * these two operations is that if a dirty page/buffer is encountered, it must
 * be waited upon, and not just skipped over.
 */
202 203
int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
				loff_t end, int sync_mode)
L
Linus Torvalds 已提交
204 205 206 207
{
	int ret;
	struct writeback_control wbc = {
		.sync_mode = sync_mode,
208
		.nr_to_write = LONG_MAX,
209 210
		.range_start = start,
		.range_end = end,
L
Linus Torvalds 已提交
211 212 213 214 215 216 217 218 219 220 221 222
	};

	if (!mapping_cap_writeback_dirty(mapping))
		return 0;

	ret = do_writepages(mapping, &wbc);
	return ret;
}

static inline int __filemap_fdatawrite(struct address_space *mapping,
	int sync_mode)
{
223
	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
L
Linus Torvalds 已提交
224 225 226 227 228 229 230 231
}

int filemap_fdatawrite(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite);

232
int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
233
				loff_t end)
L
Linus Torvalds 已提交
234 235 236
{
	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
237
EXPORT_SYMBOL(filemap_fdatawrite_range);
L
Linus Torvalds 已提交
238

239 240 241 242
/**
 * filemap_flush - mostly a non-blocking flush
 * @mapping:	target address_space
 *
L
Linus Torvalds 已提交
243 244 245 246 247 248 249 250 251
 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 * purposes - I/O may not be started against all dirty pages.
 */
int filemap_flush(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
}
EXPORT_SYMBOL(filemap_flush);

252
/**
253 254 255 256
 * filemap_fdatawait_range - wait for writeback to complete
 * @mapping:		address space structure to wait for
 * @start_byte:		offset in bytes where the range starts
 * @end_byte:		offset in bytes where the range ends (inclusive)
257
 *
258 259
 * Walk the list of under-writeback pages of the given address space
 * in the given range and wait for all of them.
L
Linus Torvalds 已提交
260
 */
261 262
int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
			    loff_t end_byte)
L
Linus Torvalds 已提交
263
{
264 265
	pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
	pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
L
Linus Torvalds 已提交
266 267 268 269
	struct pagevec pvec;
	int nr_pages;
	int ret = 0;

270
	if (end_byte < start_byte)
L
Linus Torvalds 已提交
271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287
		return 0;

	pagevec_init(&pvec, 0);
	while ((index <= end) &&
			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
			PAGECACHE_TAG_WRITEBACK,
			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
		unsigned i;

		for (i = 0; i < nr_pages; i++) {
			struct page *page = pvec.pages[i];

			/* until radix tree lookup accepts end_index */
			if (page->index > end)
				continue;

			wait_on_page_writeback(page);
288
			if (TestClearPageError(page))
L
Linus Torvalds 已提交
289 290 291 292 293 294 295 296 297 298 299 300 301 302
				ret = -EIO;
		}
		pagevec_release(&pvec);
		cond_resched();
	}

	/* Check for outstanding write errors */
	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
		ret = -ENOSPC;
	if (test_and_clear_bit(AS_EIO, &mapping->flags))
		ret = -EIO;

	return ret;
}
303 304
EXPORT_SYMBOL(filemap_fdatawait_range);

L
Linus Torvalds 已提交
305
/**
306
 * filemap_fdatawait - wait for all under-writeback pages to complete
L
Linus Torvalds 已提交
307
 * @mapping: address space structure to wait for
308 309 310
 *
 * Walk the list of under-writeback pages of the given address space
 * and wait for all of them.
L
Linus Torvalds 已提交
311 312 313 314 315 316 317 318
 */
int filemap_fdatawait(struct address_space *mapping)
{
	loff_t i_size = i_size_read(mapping->host);

	if (i_size == 0)
		return 0;

319
	return filemap_fdatawait_range(mapping, 0, i_size - 1);
L
Linus Torvalds 已提交
320 321 322 323 324
}
EXPORT_SYMBOL(filemap_fdatawait);

int filemap_write_and_wait(struct address_space *mapping)
{
325
	int err = 0;
L
Linus Torvalds 已提交
326 327

	if (mapping->nrpages) {
328 329 330 331 332 333 334 335 336 337 338 339
		err = filemap_fdatawrite(mapping);
		/*
		 * Even if the above returned error, the pages may be
		 * written partially (e.g. -ENOSPC), so we wait for it.
		 * But the -EIO is special case, it may indicate the worst
		 * thing (e.g. bug) happened, so we avoid waiting for it.
		 */
		if (err != -EIO) {
			int err2 = filemap_fdatawait(mapping);
			if (!err)
				err = err2;
		}
L
Linus Torvalds 已提交
340
	}
341
	return err;
L
Linus Torvalds 已提交
342
}
343
EXPORT_SYMBOL(filemap_write_and_wait);
L
Linus Torvalds 已提交
344

345 346 347 348 349 350
/**
 * filemap_write_and_wait_range - write out & wait on a file range
 * @mapping:	the address_space for the pages
 * @lstart:	offset in bytes where the range starts
 * @lend:	offset in bytes where the range ends (inclusive)
 *
351 352 353 354 355
 * Write out and wait upon file offsets lstart->lend, inclusive.
 *
 * Note that `lend' is inclusive (describes the last byte to be written) so
 * that this function can be used to write to the very end-of-file (end = -1).
 */
L
Linus Torvalds 已提交
356 357 358
int filemap_write_and_wait_range(struct address_space *mapping,
				 loff_t lstart, loff_t lend)
{
359
	int err = 0;
L
Linus Torvalds 已提交
360 361

	if (mapping->nrpages) {
362 363 364 365
		err = __filemap_fdatawrite_range(mapping, lstart, lend,
						 WB_SYNC_ALL);
		/* See comment of filemap_write_and_wait() */
		if (err != -EIO) {
366 367
			int err2 = filemap_fdatawait_range(mapping,
						lstart, lend);
368 369 370
			if (!err)
				err = err2;
		}
L
Linus Torvalds 已提交
371
	}
372
	return err;
L
Linus Torvalds 已提交
373
}
374
EXPORT_SYMBOL(filemap_write_and_wait_range);
L
Linus Torvalds 已提交
375

376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411
/**
 * replace_page_cache_page - replace a pagecache page with a new one
 * @old:	page to be replaced
 * @new:	page to replace with
 * @gfp_mask:	allocation mode
 *
 * This function replaces a page in the pagecache with a new one.  On
 * success it acquires the pagecache reference for the new page and
 * drops it for the old page.  Both the old and new pages must be
 * locked.  This function does not add the new page to the LRU, the
 * caller must do that.
 *
 * The remove + add is atomic.  The only way this function can fail is
 * memory allocation failure.
 */
int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
{
	int error;

	VM_BUG_ON(!PageLocked(old));
	VM_BUG_ON(!PageLocked(new));
	VM_BUG_ON(new->mapping);

	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
	if (!error) {
		struct address_space *mapping = old->mapping;
		void (*freepage)(struct page *);

		pgoff_t offset = old->index;
		freepage = mapping->a_ops->freepage;

		page_cache_get(new);
		new->mapping = mapping;
		new->index = offset;

		spin_lock_irq(&mapping->tree_lock);
412
		__delete_from_page_cache(old);
413 414 415 416 417 418 419
		error = radix_tree_insert(&mapping->page_tree, offset, new);
		BUG_ON(error);
		mapping->nrpages++;
		__inc_zone_page_state(new, NR_FILE_PAGES);
		if (PageSwapBacked(new))
			__inc_zone_page_state(new, NR_SHMEM);
		spin_unlock_irq(&mapping->tree_lock);
420 421
		/* mem_cgroup codes must not be called under tree_lock */
		mem_cgroup_replace_page_cache(old, new);
422 423 424 425 426 427 428 429 430 431
		radix_tree_preload_end();
		if (freepage)
			freepage(old);
		page_cache_release(old);
	}

	return error;
}
EXPORT_SYMBOL_GPL(replace_page_cache_page);

432
/**
N
Nick Piggin 已提交
433
 * add_to_page_cache_locked - add a locked page to the pagecache
434 435 436 437 438
 * @page:	page to add
 * @mapping:	the page's address_space
 * @offset:	page index
 * @gfp_mask:	page allocation mode
 *
N
Nick Piggin 已提交
439
 * This function is used to add a page to the pagecache. It must be locked.
L
Linus Torvalds 已提交
440 441
 * This function does not add the page to the LRU.  The caller must do that.
 */
N
Nick Piggin 已提交
442
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
A
Al Viro 已提交
443
		pgoff_t offset, gfp_t gfp_mask)
L
Linus Torvalds 已提交
444
{
N
Nick Piggin 已提交
445 446 447
	int error;

	VM_BUG_ON(!PageLocked(page));
448
	VM_BUG_ON(PageSwapBacked(page));
N
Nick Piggin 已提交
449 450

	error = mem_cgroup_cache_charge(page, current->mm,
K
KAMEZAWA Hiroyuki 已提交
451
					gfp_mask & GFP_RECLAIM_MASK);
B
Balbir Singh 已提交
452 453
	if (error)
		goto out;
L
Linus Torvalds 已提交
454

B
Balbir Singh 已提交
455
	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
L
Linus Torvalds 已提交
456
	if (error == 0) {
N
Nick Piggin 已提交
457 458 459 460
		page_cache_get(page);
		page->mapping = mapping;
		page->index = offset;

N
Nick Piggin 已提交
461
		spin_lock_irq(&mapping->tree_lock);
L
Linus Torvalds 已提交
462
		error = radix_tree_insert(&mapping->page_tree, offset, page);
N
Nick Piggin 已提交
463
		if (likely(!error)) {
L
Linus Torvalds 已提交
464
			mapping->nrpages++;
465
			__inc_zone_page_state(page, NR_FILE_PAGES);
466
			spin_unlock_irq(&mapping->tree_lock);
N
Nick Piggin 已提交
467 468
		} else {
			page->mapping = NULL;
469
			/* Leave page->index set: truncation relies upon it */
470
			spin_unlock_irq(&mapping->tree_lock);
471
			mem_cgroup_uncharge_cache_page(page);
N
Nick Piggin 已提交
472 473
			page_cache_release(page);
		}
L
Linus Torvalds 已提交
474
		radix_tree_preload_end();
B
Balbir Singh 已提交
475
	} else
476
		mem_cgroup_uncharge_cache_page(page);
477
out:
L
Linus Torvalds 已提交
478 479
	return error;
}
N
Nick Piggin 已提交
480
EXPORT_SYMBOL(add_to_page_cache_locked);
L
Linus Torvalds 已提交
481 482

int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
A
Al Viro 已提交
483
				pgoff_t offset, gfp_t gfp_mask)
L
Linus Torvalds 已提交
484
{
485 486 487
	int ret;

	ret = add_to_page_cache(page, mapping, offset, gfp_mask);
488 489
	if (ret == 0)
		lru_cache_add_file(page);
L
Linus Torvalds 已提交
490 491
	return ret;
}
492
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
L
Linus Torvalds 已提交
493

494
#ifdef CONFIG_NUMA
495
struct page *__page_cache_alloc(gfp_t gfp)
496
{
497 498 499
	int n;
	struct page *page;

500
	if (cpuset_do_page_mem_spread()) {
501 502 503 504 505 506 507
		unsigned int cpuset_mems_cookie;
		do {
			cpuset_mems_cookie = get_mems_allowed();
			n = cpuset_mem_spread_node();
			page = alloc_pages_exact_node(n, gfp, 0);
		} while (!put_mems_allowed(cpuset_mems_cookie) && !page);

508
		return page;
509
	}
510
	return alloc_pages(gfp, 0);
511
}
512
EXPORT_SYMBOL(__page_cache_alloc);
513 514
#endif

L
Linus Torvalds 已提交
515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536
/*
 * In order to wait for pages to become available there must be
 * waitqueues associated with pages. By using a hash table of
 * waitqueues where the bucket discipline is to maintain all
 * waiters on the same queue and wake all when any of the pages
 * become available, and for the woken contexts to check to be
 * sure the appropriate page became available, this saves space
 * at a cost of "thundering herd" phenomena during rare hash
 * collisions.
 */
static wait_queue_head_t *page_waitqueue(struct page *page)
{
	const struct zone *zone = page_zone(page);

	return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
}

static inline void wake_up_page(struct page *page, int bit)
{
	__wake_up_bit(page_waitqueue(page), &page->flags, bit);
}

H
Harvey Harrison 已提交
537
void wait_on_page_bit(struct page *page, int bit_nr)
L
Linus Torvalds 已提交
538 539 540 541
{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (test_bit(bit_nr, &page->flags))
J
Jens Axboe 已提交
542
		__wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
L
Linus Torvalds 已提交
543 544 545 546
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_on_page_bit);

547 548 549 550 551 552 553 554 555 556 557
int wait_on_page_bit_killable(struct page *page, int bit_nr)
{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (!test_bit(bit_nr, &page->flags))
		return 0;

	return __wait_on_bit(page_waitqueue(page), &wait,
			     sleep_on_page_killable, TASK_KILLABLE);
}

558 559
/**
 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
R
Randy Dunlap 已提交
560 561
 * @page: Page defining the wait queue of interest
 * @waiter: Waiter to add to the queue
562 563 564 565 566 567 568 569 570 571 572 573 574 575
 *
 * Add an arbitrary @waiter to the wait queue for the nominated @page.
 */
void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
{
	wait_queue_head_t *q = page_waitqueue(page);
	unsigned long flags;

	spin_lock_irqsave(&q->lock, flags);
	__add_wait_queue(q, waiter);
	spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(add_page_wait_queue);

L
Linus Torvalds 已提交
576
/**
577
 * unlock_page - unlock a locked page
L
Linus Torvalds 已提交
578 579 580 581 582 583 584
 * @page: the page
 *
 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
 * mechananism between PageLocked pages and PageWriteback pages is shared.
 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
 *
N
Nick Piggin 已提交
585 586
 * The mb is necessary to enforce ordering between the clear_bit and the read
 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
L
Linus Torvalds 已提交
587
 */
H
Harvey Harrison 已提交
588
void unlock_page(struct page *page)
L
Linus Torvalds 已提交
589
{
N
Nick Piggin 已提交
590 591 592
	VM_BUG_ON(!PageLocked(page));
	clear_bit_unlock(PG_locked, &page->flags);
	smp_mb__after_clear_bit();
L
Linus Torvalds 已提交
593 594 595 596
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

597 598 599
/**
 * end_page_writeback - end writeback against a page
 * @page: the page
L
Linus Torvalds 已提交
600 601 602
 */
void end_page_writeback(struct page *page)
{
603 604 605 606 607 608
	if (TestClearPageReclaim(page))
		rotate_reclaimable_page(page);

	if (!test_clear_page_writeback(page))
		BUG();

L
Linus Torvalds 已提交
609 610 611 612 613
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

614 615 616
/**
 * __lock_page - get a lock on the page, assuming we need to sleep to get it
 * @page: the page to lock
L
Linus Torvalds 已提交
617
 */
H
Harvey Harrison 已提交
618
void __lock_page(struct page *page)
L
Linus Torvalds 已提交
619 620 621
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

J
Jens Axboe 已提交
622
	__wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
L
Linus Torvalds 已提交
623 624 625 626
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_page);

H
Harvey Harrison 已提交
627
int __lock_page_killable(struct page *page)
M
Matthew Wilcox 已提交
628 629 630 631
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	return __wait_on_bit_lock(page_waitqueue(page), &wait,
J
Jens Axboe 已提交
632
					sleep_on_page_killable, TASK_KILLABLE);
M
Matthew Wilcox 已提交
633
}
634
EXPORT_SYMBOL_GPL(__lock_page_killable);
M
Matthew Wilcox 已提交
635

636 637 638
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
			 unsigned int flags)
{
639 640 641 642 643 644 645 646 647 648 649 650
	if (flags & FAULT_FLAG_ALLOW_RETRY) {
		/*
		 * CAUTION! In this case, mmap_sem is not released
		 * even though return 0.
		 */
		if (flags & FAULT_FLAG_RETRY_NOWAIT)
			return 0;

		up_read(&mm->mmap_sem);
		if (flags & FAULT_FLAG_KILLABLE)
			wait_on_page_locked_killable(page);
		else
651
			wait_on_page_locked(page);
652
		return 0;
653 654 655 656 657 658 659 660 661 662 663 664
	} else {
		if (flags & FAULT_FLAG_KILLABLE) {
			int ret;

			ret = __lock_page_killable(page);
			if (ret) {
				up_read(&mm->mmap_sem);
				return 0;
			}
		} else
			__lock_page(page);
		return 1;
665 666 667
	}
}

668 669 670 671 672
/**
 * find_get_page - find and get a page reference
 * @mapping: the address_space to search
 * @offset: the page index
 *
N
Nick Piggin 已提交
673 674
 * Is there a pagecache struct page at the given (mapping, offset) tuple?
 * If yes, increment its refcount and return it; if no, return NULL.
L
Linus Torvalds 已提交
675
 */
N
Nick Piggin 已提交
676
struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
677
{
N
Nick Piggin 已提交
678
	void **pagep;
L
Linus Torvalds 已提交
679 680
	struct page *page;

N
Nick Piggin 已提交
681 682 683 684 685 686
	rcu_read_lock();
repeat:
	page = NULL;
	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
	if (pagep) {
		page = radix_tree_deref_slot(pagep);
N
Nick Piggin 已提交
687 688
		if (unlikely(!page))
			goto out;
689
		if (radix_tree_exception(page)) {
690 691 692 693 694 695 696 697
			if (radix_tree_deref_retry(page))
				goto repeat;
			/*
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so return it without
			 * attempting to raise page count.
			 */
			goto out;
698
		}
N
Nick Piggin 已提交
699 700 701 702 703 704 705 706 707 708 709 710 711
		if (!page_cache_get_speculative(page))
			goto repeat;

		/*
		 * Has the page moved?
		 * This is part of the lockless pagecache protocol. See
		 * include/linux/pagemap.h for details.
		 */
		if (unlikely(page != *pagep)) {
			page_cache_release(page);
			goto repeat;
		}
	}
N
Nick Piggin 已提交
712
out:
N
Nick Piggin 已提交
713 714
	rcu_read_unlock();

L
Linus Torvalds 已提交
715 716 717 718 719 720
	return page;
}
EXPORT_SYMBOL(find_get_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
721 722
 * @mapping: the address_space to search
 * @offset: the page index
L
Linus Torvalds 已提交
723 724 725 726 727 728
 *
 * Locates the desired pagecache page, locks it, increments its reference
 * count and returns its address.
 *
 * Returns zero if the page was not present. find_lock_page() may sleep.
 */
N
Nick Piggin 已提交
729
struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
L
Linus Torvalds 已提交
730 731 732 733
{
	struct page *page;

repeat:
N
Nick Piggin 已提交
734
	page = find_get_page(mapping, offset);
735
	if (page && !radix_tree_exception(page)) {
N
Nick Piggin 已提交
736 737 738 739 740 741
		lock_page(page);
		/* Has the page been truncated? */
		if (unlikely(page->mapping != mapping)) {
			unlock_page(page);
			page_cache_release(page);
			goto repeat;
L
Linus Torvalds 已提交
742
		}
N
Nick Piggin 已提交
743
		VM_BUG_ON(page->index != offset);
L
Linus Torvalds 已提交
744 745 746 747 748 749 750
	}
	return page;
}
EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
751 752 753
 * @mapping: the page's address_space
 * @index: the page's index into the mapping
 * @gfp_mask: page allocation mode
L
Linus Torvalds 已提交
754 755 756 757 758 759 760 761 762 763 764 765 766
 *
 * Locates a page in the pagecache.  If the page is not present, a new page
 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
 * LRU list.  The returned page is locked and has its reference count
 * incremented.
 *
 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
 * allocation!
 *
 * find_or_create_page() returns the desired page's address, or zero on
 * memory exhaustion.
 */
struct page *find_or_create_page(struct address_space *mapping,
767
		pgoff_t index, gfp_t gfp_mask)
L
Linus Torvalds 已提交
768
{
N
Nick Piggin 已提交
769
	struct page *page;
L
Linus Torvalds 已提交
770 771 772 773
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
N
Nick Piggin 已提交
774 775 776
		page = __page_cache_alloc(gfp_mask);
		if (!page)
			return NULL;
N
Nick Piggin 已提交
777 778 779 780 781 782 783 784
		/*
		 * We want a regular kernel memory (not highmem or DMA etc)
		 * allocation for the radix tree nodes, but we need to honour
		 * the context-specific requirements the caller has asked for.
		 * GFP_RECLAIM_MASK collects those requirements.
		 */
		err = add_to_page_cache_lru(page, mapping, index,
			(gfp_mask & GFP_RECLAIM_MASK));
N
Nick Piggin 已提交
785 786 787 788 789
		if (unlikely(err)) {
			page_cache_release(page);
			page = NULL;
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814
		}
	}
	return page;
}
EXPORT_SYMBOL(find_or_create_page);

/**
 * find_get_pages - gang pagecache lookup
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages() will search for and return a group of up to
 * @nr_pages pages in the mapping.  The pages are placed at @pages.
 * find_get_pages() takes a reference against the returned pages.
 *
 * The search returns a group of mapping-contiguous pages with ascending
 * indexes.  There may be holes in the indices due to not-present pages.
 *
 * find_get_pages() returns the number of pages which were found.
 */
unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
			    unsigned int nr_pages, struct page **pages)
{
815 816 817 818 819 820
	struct radix_tree_iter iter;
	void **slot;
	unsigned ret = 0;

	if (unlikely(!nr_pages))
		return 0;
N
Nick Piggin 已提交
821 822 823

	rcu_read_lock();
restart:
824
	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
N
Nick Piggin 已提交
825 826
		struct page *page;
repeat:
827
		page = radix_tree_deref_slot(slot);
N
Nick Piggin 已提交
828 829
		if (unlikely(!page))
			continue;
830

831
		if (radix_tree_exception(page)) {
832 833 834 835 836 837
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
838
				WARN_ON(iter.index);
839 840
				goto restart;
			}
841
			/*
842 843 844
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so skip over it -
			 * we only reach this from invalidate_mapping_pages().
845
			 */
846
			continue;
N
Nick Piggin 已提交
847
		}
N
Nick Piggin 已提交
848 849 850 851 852

		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
853
		if (unlikely(page != *slot)) {
N
Nick Piggin 已提交
854 855 856
			page_cache_release(page);
			goto repeat;
		}
L
Linus Torvalds 已提交
857

N
Nick Piggin 已提交
858
		pages[ret] = page;
859 860
		if (++ret == nr_pages)
			break;
N
Nick Piggin 已提交
861
	}
862

N
Nick Piggin 已提交
863
	rcu_read_unlock();
L
Linus Torvalds 已提交
864 865 866
	return ret;
}

867 868 869 870 871 872 873 874 875 876 877 878 879 880 881
/**
 * find_get_pages_contig - gang contiguous pagecache lookup
 * @mapping:	The address_space to search
 * @index:	The starting page index
 * @nr_pages:	The maximum number of pages
 * @pages:	Where the resulting pages are placed
 *
 * find_get_pages_contig() works exactly like find_get_pages(), except
 * that the returned number of pages are guaranteed to be contiguous.
 *
 * find_get_pages_contig() returns the number of pages which were found.
 */
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
			       unsigned int nr_pages, struct page **pages)
{
882 883 884 885 886 887
	struct radix_tree_iter iter;
	void **slot;
	unsigned int ret = 0;

	if (unlikely(!nr_pages))
		return 0;
N
Nick Piggin 已提交
888 889 890

	rcu_read_lock();
restart:
891
	radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
N
Nick Piggin 已提交
892 893
		struct page *page;
repeat:
894 895
		page = radix_tree_deref_slot(slot);
		/* The hole, there no reason to continue */
N
Nick Piggin 已提交
896
		if (unlikely(!page))
897
			break;
898

899
		if (radix_tree_exception(page)) {
900 901 902 903 904 905 906 907
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
				goto restart;
			}
908
			/*
909 910 911
			 * Otherwise, shmem/tmpfs must be storing a swap entry
			 * here as an exceptional entry: so stop looking for
			 * contiguous pages.
912
			 */
913
			break;
914
		}
915

N
Nick Piggin 已提交
916 917 918 919
		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
920
		if (unlikely(page != *slot)) {
N
Nick Piggin 已提交
921 922 923 924
			page_cache_release(page);
			goto repeat;
		}

N
Nick Piggin 已提交
925 926 927 928 929
		/*
		 * must check mapping and index after taking the ref.
		 * otherwise we can get both false positives and false
		 * negatives, which is just confusing to the caller.
		 */
930
		if (page->mapping == NULL || page->index != iter.index) {
N
Nick Piggin 已提交
931 932 933 934
			page_cache_release(page);
			break;
		}

N
Nick Piggin 已提交
935
		pages[ret] = page;
936 937
		if (++ret == nr_pages)
			break;
938
	}
N
Nick Piggin 已提交
939 940
	rcu_read_unlock();
	return ret;
941
}
942
EXPORT_SYMBOL(find_get_pages_contig);
943

944 945 946 947 948 949 950 951
/**
 * find_get_pages_tag - find and return pages that match @tag
 * @mapping:	the address_space to search
 * @index:	the starting page index
 * @tag:	the tag index
 * @nr_pages:	the maximum number of pages
 * @pages:	where the resulting pages are placed
 *
L
Linus Torvalds 已提交
952
 * Like find_get_pages, except we only return pages which are tagged with
953
 * @tag.   We update @index to index the next page for the traversal.
L
Linus Torvalds 已提交
954 955 956 957
 */
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
			int tag, unsigned int nr_pages, struct page **pages)
{
958 959 960 961 962 963
	struct radix_tree_iter iter;
	void **slot;
	unsigned ret = 0;

	if (unlikely(!nr_pages))
		return 0;
N
Nick Piggin 已提交
964 965 966

	rcu_read_lock();
restart:
967 968
	radix_tree_for_each_tagged(slot, &mapping->page_tree,
				   &iter, *index, tag) {
N
Nick Piggin 已提交
969 970
		struct page *page;
repeat:
971
		page = radix_tree_deref_slot(slot);
N
Nick Piggin 已提交
972 973
		if (unlikely(!page))
			continue;
974

975
		if (radix_tree_exception(page)) {
976 977 978 979 980 981 982 983
			if (radix_tree_deref_retry(page)) {
				/*
				 * Transient condition which can only trigger
				 * when entry at index 0 moves out of or back
				 * to root: none yet gotten, safe to restart.
				 */
				goto restart;
			}
984
			/*
985 986
			 * This function is never used on a shmem/tmpfs
			 * mapping, so a swap entry won't be found here.
987
			 */
988
			BUG();
989
		}
N
Nick Piggin 已提交
990 991 992 993 994

		if (!page_cache_get_speculative(page))
			goto repeat;

		/* Has the page moved? */
995
		if (unlikely(page != *slot)) {
N
Nick Piggin 已提交
996 997 998 999 1000
			page_cache_release(page);
			goto repeat;
		}

		pages[ret] = page;
1001 1002
		if (++ret == nr_pages)
			break;
N
Nick Piggin 已提交
1003
	}
1004

N
Nick Piggin 已提交
1005
	rcu_read_unlock();
L
Linus Torvalds 已提交
1006 1007 1008

	if (ret)
		*index = pages[ret - 1]->index + 1;
N
Nick Piggin 已提交
1009

L
Linus Torvalds 已提交
1010 1011
	return ret;
}
1012
EXPORT_SYMBOL(find_get_pages_tag);
L
Linus Torvalds 已提交
1013

1014 1015 1016 1017 1018
/**
 * grab_cache_page_nowait - returns locked page at given index in given cache
 * @mapping: target address_space
 * @index: the page index
 *
1019
 * Same as grab_cache_page(), but do not wait if the page is unavailable.
L
Linus Torvalds 已提交
1020 1021 1022 1023 1024 1025 1026 1027
 * This is intended for speculative data generators, where the data can
 * be regenerated if the page couldn't be grabbed.  This routine should
 * be safe to call while holding the lock for another page.
 *
 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
 * and deadlock against the caller's locked page.
 */
struct page *
1028
grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
L
Linus Torvalds 已提交
1029 1030 1031 1032
{
	struct page *page = find_get_page(mapping, index);

	if (page) {
N
Nick Piggin 已提交
1033
		if (trylock_page(page))
L
Linus Torvalds 已提交
1034 1035 1036 1037
			return page;
		page_cache_release(page);
		return NULL;
	}
1038
	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
N
Nick Piggin 已提交
1039
	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
L
Linus Torvalds 已提交
1040 1041 1042 1043 1044 1045 1046
		page_cache_release(page);
		page = NULL;
	}
	return page;
}
EXPORT_SYMBOL(grab_cache_page_nowait);

1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067
/*
 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
 * a _large_ part of the i/o request. Imagine the worst scenario:
 *
 *      ---R__________________________________________B__________
 *         ^ reading here                             ^ bad block(assume 4k)
 *
 * read(R) => miss => readahead(R...B) => media error => frustrating retries
 * => failing the whole request => read(R) => read(R+1) =>
 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
 *
 * It is going insane. Fix it by quickly scaling down the readahead size.
 */
static void shrink_readahead_size_eio(struct file *filp,
					struct file_ra_state *ra)
{
	ra->ra_pages /= 4;
}

1068
/**
C
Christoph Hellwig 已提交
1069
 * do_generic_file_read - generic file read routine
1070 1071 1072 1073 1074
 * @filp:	the file to read
 * @ppos:	current file position
 * @desc:	read_descriptor
 * @actor:	read method
 *
L
Linus Torvalds 已提交
1075
 * This is a generic file read routine, and uses the
1076
 * mapping->a_ops->readpage() function for the actual low-level stuff.
L
Linus Torvalds 已提交
1077 1078 1079 1080
 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 */
C
Christoph Hellwig 已提交
1081 1082
static void do_generic_file_read(struct file *filp, loff_t *ppos,
		read_descriptor_t *desc, read_actor_t actor)
L
Linus Torvalds 已提交
1083
{
C
Christoph Hellwig 已提交
1084
	struct address_space *mapping = filp->f_mapping;
L
Linus Torvalds 已提交
1085
	struct inode *inode = mapping->host;
C
Christoph Hellwig 已提交
1086
	struct file_ra_state *ra = &filp->f_ra;
1087 1088 1089 1090
	pgoff_t index;
	pgoff_t last_index;
	pgoff_t prev_index;
	unsigned long offset;      /* offset into pagecache page */
1091
	unsigned int prev_offset;
L
Linus Torvalds 已提交
1092 1093 1094
	int error;

	index = *ppos >> PAGE_CACHE_SHIFT;
1095 1096
	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
L
Linus Torvalds 已提交
1097 1098 1099 1100 1101
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	for (;;) {
		struct page *page;
1102
		pgoff_t end_index;
N
NeilBrown 已提交
1103
		loff_t isize;
L
Linus Torvalds 已提交
1104 1105 1106 1107 1108
		unsigned long nr, ret;

		cond_resched();
find_page:
		page = find_get_page(mapping, index);
1109
		if (!page) {
1110
			page_cache_sync_readahead(mapping,
1111
					ra, filp,
1112 1113 1114 1115 1116 1117
					index, last_index - index);
			page = find_get_page(mapping, index);
			if (unlikely(page == NULL))
				goto no_cached_page;
		}
		if (PageReadahead(page)) {
1118
			page_cache_async_readahead(mapping,
1119
					ra, filp, page,
1120
					index, last_index - index);
L
Linus Torvalds 已提交
1121
		}
1122 1123 1124 1125
		if (!PageUptodate(page)) {
			if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
					!mapping->a_ops->is_partially_uptodate)
				goto page_not_up_to_date;
N
Nick Piggin 已提交
1126
			if (!trylock_page(page))
1127
				goto page_not_up_to_date;
1128 1129 1130
			/* Did it get truncated before we got the lock? */
			if (!page->mapping)
				goto page_not_up_to_date_locked;
1131 1132 1133 1134 1135
			if (!mapping->a_ops->is_partially_uptodate(page,
								desc, offset))
				goto page_not_up_to_date_locked;
			unlock_page(page);
		}
L
Linus Torvalds 已提交
1136
page_ok:
N
NeilBrown 已提交
1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162
		/*
		 * i_size must be checked after we know the page is Uptodate.
		 *
		 * Checking i_size after the check allows us to calculate
		 * the correct value for "nr", which means the zero-filled
		 * part of the page is not copied back to userspace (unless
		 * another truncate extends the file - this is desired though).
		 */

		isize = i_size_read(inode);
		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
		if (unlikely(!isize || index > end_index)) {
			page_cache_release(page);
			goto out;
		}

		/* nr is the maximum number of bytes to copy from this page */
		nr = PAGE_CACHE_SIZE;
		if (index == end_index) {
			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (nr <= offset) {
				page_cache_release(page);
				goto out;
			}
		}
		nr = nr - offset;
L
Linus Torvalds 已提交
1163 1164 1165 1166 1167 1168 1169 1170 1171

		/* If users can be writing to this page using arbitrary
		 * virtual addresses, take care about potential aliasing
		 * before reading the page on the kernel side.
		 */
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

		/*
1172 1173
		 * When a sequential read accesses a page several times,
		 * only mark it as accessed the first time.
L
Linus Torvalds 已提交
1174
		 */
1175
		if (prev_index != index || offset != prev_offset)
L
Linus Torvalds 已提交
1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192
			mark_page_accessed(page);
		prev_index = index;

		/*
		 * Ok, we have the page, and it's up-to-date, so
		 * now we can copy it to user space...
		 *
		 * The actor routine returns how many bytes were actually used..
		 * NOTE! This may not be the same as how much of a user buffer
		 * we filled up (we may be padding etc), so we can only update
		 * "pos" here (the actor routine has to update the user buffer
		 * pointers and the remaining count).
		 */
		ret = actor(desc, page, offset, nr);
		offset += ret;
		index += offset >> PAGE_CACHE_SHIFT;
		offset &= ~PAGE_CACHE_MASK;
J
Jan Kara 已提交
1193
		prev_offset = offset;
L
Linus Torvalds 已提交
1194 1195 1196 1197 1198 1199 1200 1201

		page_cache_release(page);
		if (ret == nr && desc->count)
			continue;
		goto out;

page_not_up_to_date:
		/* Get exclusive access to the page ... */
1202 1203 1204
		error = lock_page_killable(page);
		if (unlikely(error))
			goto readpage_error;
L
Linus Torvalds 已提交
1205

1206
page_not_up_to_date_locked:
N
Nick Piggin 已提交
1207
		/* Did it get truncated before we got the lock? */
L
Linus Torvalds 已提交
1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220
		if (!page->mapping) {
			unlock_page(page);
			page_cache_release(page);
			continue;
		}

		/* Did somebody else fill it already? */
		if (PageUptodate(page)) {
			unlock_page(page);
			goto page_ok;
		}

readpage:
1221 1222 1223 1224 1225 1226
		/*
		 * A previous I/O error may have been due to temporary
		 * failures, eg. multipath errors.
		 * PG_error will be set again if readpage fails.
		 */
		ClearPageError(page);
L
Linus Torvalds 已提交
1227 1228 1229
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

1230 1231 1232 1233 1234
		if (unlikely(error)) {
			if (error == AOP_TRUNCATED_PAGE) {
				page_cache_release(page);
				goto find_page;
			}
L
Linus Torvalds 已提交
1235
			goto readpage_error;
1236
		}
L
Linus Torvalds 已提交
1237 1238

		if (!PageUptodate(page)) {
1239 1240 1241
			error = lock_page_killable(page);
			if (unlikely(error))
				goto readpage_error;
L
Linus Torvalds 已提交
1242 1243 1244
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
1245
					 * invalidate_mapping_pages got it
L
Linus Torvalds 已提交
1246 1247 1248 1249 1250 1251
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
1252
				shrink_readahead_size_eio(filp, ra);
1253 1254
				error = -EIO;
				goto readpage_error;
L
Linus Torvalds 已提交
1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271
			}
			unlock_page(page);
		}

		goto page_ok;

readpage_error:
		/* UHHUH! A synchronous read error occurred. Report it */
		desc->error = error;
		page_cache_release(page);
		goto out;

no_cached_page:
		/*
		 * Ok, it wasn't cached, so we need to create a new
		 * page..
		 */
N
Nick Piggin 已提交
1272 1273 1274 1275
		page = page_cache_alloc_cold(mapping);
		if (!page) {
			desc->error = -ENOMEM;
			goto out;
L
Linus Torvalds 已提交
1276
		}
N
Nick Piggin 已提交
1277
		error = add_to_page_cache_lru(page, mapping,
L
Linus Torvalds 已提交
1278 1279
						index, GFP_KERNEL);
		if (error) {
N
Nick Piggin 已提交
1280
			page_cache_release(page);
L
Linus Torvalds 已提交
1281 1282 1283 1284 1285 1286 1287 1288 1289
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		goto readpage;
	}

out:
1290 1291 1292
	ra->prev_pos = prev_index;
	ra->prev_pos <<= PAGE_CACHE_SHIFT;
	ra->prev_pos |= prev_offset;
L
Linus Torvalds 已提交
1293

1294
	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1295
	file_accessed(filp);
L
Linus Torvalds 已提交
1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311
}

int file_read_actor(read_descriptor_t *desc, struct page *page,
			unsigned long offset, unsigned long size)
{
	char *kaddr;
	unsigned long left, count = desc->count;

	if (size > count)
		size = count;

	/*
	 * Faults on the destination of a read are common, so do it before
	 * taking the kmap.
	 */
	if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1312
		kaddr = kmap_atomic(page);
L
Linus Torvalds 已提交
1313 1314
		left = __copy_to_user_inatomic(desc->arg.buf,
						kaddr + offset, size);
1315
		kunmap_atomic(kaddr);
L
Linus Torvalds 已提交
1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335
		if (left == 0)
			goto success;
	}

	/* Do it the slow way */
	kaddr = kmap(page);
	left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
	kunmap(page);

	if (left) {
		size -= left;
		desc->error = -EFAULT;
	}
success:
	desc->count = count - size;
	desc->written += size;
	desc->arg.buf += size;
	return size;
}

1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374
/*
 * Performs necessary checks before doing a write
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
 * @count:	number of bytes to write
 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
 *
 * Adjust number of segments and amount of bytes to write (nr_segs should be
 * properly initialized first). Returns appropriate error code that caller
 * should return or zero in case that write should be allowed.
 */
int generic_segment_checks(const struct iovec *iov,
			unsigned long *nr_segs, size_t *count, int access_flags)
{
	unsigned long   seg;
	size_t cnt = 0;
	for (seg = 0; seg < *nr_segs; seg++) {
		const struct iovec *iv = &iov[seg];

		/*
		 * If any segment has a negative length, or the cumulative
		 * length ever wraps negative then return -EINVAL.
		 */
		cnt += iv->iov_len;
		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		*nr_segs = seg;
		cnt -= iv->iov_len;	/* This segment is no good */
		break;
	}
	*count = cnt;
	return 0;
}
EXPORT_SYMBOL(generic_segment_checks);

1375
/**
H
Henrik Kretzschmar 已提交
1376
 * generic_file_aio_read - generic filesystem read routine
1377 1378 1379
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
H
Henrik Kretzschmar 已提交
1380
 * @pos:	current file position
1381
 *
L
Linus Torvalds 已提交
1382 1383 1384 1385
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
1386 1387
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
1388 1389 1390
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
1391
	unsigned long seg = 0;
L
Linus Torvalds 已提交
1392
	size_t count;
1393
	loff_t *ppos = &iocb->ki_pos;
L
Linus Torvalds 已提交
1394 1395

	count = 0;
1396 1397 1398
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;
L
Linus Torvalds 已提交
1399 1400 1401

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
1402
		loff_t size;
L
Linus Torvalds 已提交
1403 1404 1405 1406 1407 1408 1409 1410 1411
		struct address_space *mapping;
		struct inode *inode;

		mapping = filp->f_mapping;
		inode = mapping->host;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);
		if (pos < size) {
1412 1413
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);
1414 1415 1416 1417
			if (!retval) {
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);
			}
1418
			if (retval > 0) {
L
Linus Torvalds 已提交
1419
				*ppos = pos + retval;
1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431
				count -= retval;
			}

			/*
			 * Btrfs can have a short DIO read if we encounter
			 * compressed extents, so if there was an error, or if
			 * we've already read everything we wanted to, or if
			 * there was a short read because we hit EOF, go ahead
			 * and return.  Otherwise fallthrough to buffered io for
			 * the rest of the read.
			 */
			if (retval < 0 || !count || *ppos >= size) {
H
Hugh Dickins 已提交
1432 1433 1434
				file_accessed(filp);
				goto out;
			}
1435
		}
L
Linus Torvalds 已提交
1436 1437
	}

1438
	count = retval;
H
Hugh Dickins 已提交
1439 1440
	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;
1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454
		loff_t offset = 0;

		/*
		 * If we did a short DIO read we need to skip the section of the
		 * iov that we've already read data into.
		 */
		if (count) {
			if (count > iov[seg].iov_len) {
				count -= iov[seg].iov_len;
				continue;
			}
			offset = count;
			count = 0;
		}
L
Linus Torvalds 已提交
1455

H
Hugh Dickins 已提交
1456
		desc.written = 0;
1457 1458
		desc.arg.buf = iov[seg].iov_base + offset;
		desc.count = iov[seg].iov_len - offset;
H
Hugh Dickins 已提交
1459 1460 1461 1462 1463 1464 1465 1466
		if (desc.count == 0)
			continue;
		desc.error = 0;
		do_generic_file_read(filp, ppos, &desc, file_read_actor);
		retval += desc.written;
		if (desc.error) {
			retval = retval ?: desc.error;
			break;
L
Linus Torvalds 已提交
1467
		}
H
Hugh Dickins 已提交
1468 1469
		if (desc.count > 0)
			break;
L
Linus Torvalds 已提交
1470 1471 1472 1473 1474 1475 1476
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

#ifdef CONFIG_MMU
1477 1478 1479 1480 1481
/**
 * page_cache_read - adds requested page to the page cache if not already there
 * @file:	file to read
 * @offset:	page index
 *
L
Linus Torvalds 已提交
1482 1483 1484
 * This adds the requested page to the page cache if it isn't already there,
 * and schedules an I/O to read in its contents from disk.
 */
H
Harvey Harrison 已提交
1485
static int page_cache_read(struct file *file, pgoff_t offset)
L
Linus Torvalds 已提交
1486 1487 1488
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
1489
	int ret;
L
Linus Torvalds 已提交
1490

1491 1492 1493 1494 1495 1496 1497 1498 1499 1500
	do {
		page = page_cache_alloc_cold(mapping);
		if (!page)
			return -ENOMEM;

		ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
		if (ret == 0)
			ret = mapping->a_ops->readpage(file, page);
		else if (ret == -EEXIST)
			ret = 0; /* losing race to add is OK */
L
Linus Torvalds 已提交
1501 1502 1503

		page_cache_release(page);

1504 1505 1506
	} while (ret == AOP_TRUNCATED_PAGE);
		
	return ret;
L
Linus Torvalds 已提交
1507 1508 1509 1510
}

#define MMAP_LOTSAMISS  (100)

1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525
/*
 * Synchronous readahead happens when we don't even find
 * a page in the page cache at all.
 */
static void do_sync_mmap_readahead(struct vm_area_struct *vma,
				   struct file_ra_state *ra,
				   struct file *file,
				   pgoff_t offset)
{
	unsigned long ra_pages;
	struct address_space *mapping = file->f_mapping;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(vma))
		return;
1526 1527
	if (!ra->ra_pages)
		return;
1528

1529
	if (VM_SequentialReadHint(vma)) {
1530 1531
		page_cache_sync_readahead(mapping, ra, file, offset,
					  ra->ra_pages);
1532 1533 1534
		return;
	}

1535 1536
	/* Avoid banging the cache line if not needed */
	if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1537 1538 1539 1540 1541 1542 1543 1544 1545
		ra->mmap_miss++;

	/*
	 * Do we miss much more than hit in this file? If so,
	 * stop bothering with read-ahead. It will only hurt.
	 */
	if (ra->mmap_miss > MMAP_LOTSAMISS)
		return;

1546 1547 1548
	/*
	 * mmap read-around
	 */
1549
	ra_pages = max_sane_readahead(ra->ra_pages);
1550 1551
	ra->start = max_t(long, 0, offset - ra_pages / 2);
	ra->size = ra_pages;
1552
	ra->async_size = ra_pages / 4;
1553
	ra_submit(ra, mapping, file);
1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573
}

/*
 * Asynchronous readahead happens when we find the page and PG_readahead,
 * so we want to possibly extend the readahead further..
 */
static void do_async_mmap_readahead(struct vm_area_struct *vma,
				    struct file_ra_state *ra,
				    struct file *file,
				    struct page *page,
				    pgoff_t offset)
{
	struct address_space *mapping = file->f_mapping;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(vma))
		return;
	if (ra->mmap_miss > 0)
		ra->mmap_miss--;
	if (PageReadahead(page))
1574 1575
		page_cache_async_readahead(mapping, ra, file,
					   page, offset, ra->ra_pages);
1576 1577
}

1578
/**
1579
 * filemap_fault - read in file data for page fault handling
N
Nick Piggin 已提交
1580 1581
 * @vma:	vma in which the fault was taken
 * @vmf:	struct vm_fault containing details of the fault
1582
 *
1583
 * filemap_fault() is invoked via the vma operations vector for a
L
Linus Torvalds 已提交
1584 1585 1586 1587 1588 1589
 * mapped memory region to read in file data during a page fault.
 *
 * The goto's are kind of ugly, but this streamlines the normal case of having
 * it in the page cache, and handles the special cases reasonably without
 * having a lot of duplicated code.
 */
N
Nick Piggin 已提交
1590
int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
L
Linus Torvalds 已提交
1591 1592
{
	int error;
1593
	struct file *file = vma->vm_file;
L
Linus Torvalds 已提交
1594 1595 1596
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
1597
	pgoff_t offset = vmf->pgoff;
L
Linus Torvalds 已提交
1598
	struct page *page;
J
Jan Kara 已提交
1599
	pgoff_t size;
N
Nick Piggin 已提交
1600
	int ret = 0;
L
Linus Torvalds 已提交
1601 1602

	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1603
	if (offset >= size)
1604
		return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1605 1606 1607 1608

	/*
	 * Do we have something in the page cache already?
	 */
1609
	page = find_get_page(mapping, offset);
1610
	if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
L
Linus Torvalds 已提交
1611
		/*
1612 1613
		 * We found the page, so try async readahead before
		 * waiting for the lock.
L
Linus Torvalds 已提交
1614
		 */
1615
		do_async_mmap_readahead(vma, ra, file, page, offset);
1616
	} else if (!page) {
1617 1618 1619
		/* No page in the page cache at all */
		do_sync_mmap_readahead(vma, ra, file, offset);
		count_vm_event(PGMAJFAULT);
1620
		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1621 1622
		ret = VM_FAULT_MAJOR;
retry_find:
1623
		page = find_get_page(mapping, offset);
L
Linus Torvalds 已提交
1624 1625 1626 1627
		if (!page)
			goto no_cached_page;
	}

1628 1629
	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
		page_cache_release(page);
1630
		return ret | VM_FAULT_RETRY;
1631
	}
1632 1633 1634 1635 1636 1637 1638 1639 1640

	/* Did it get truncated? */
	if (unlikely(page->mapping != mapping)) {
		unlock_page(page);
		put_page(page);
		goto retry_find;
	}
	VM_BUG_ON(page->index != offset);

L
Linus Torvalds 已提交
1641
	/*
1642 1643
	 * We have a locked page in the page cache, now we need to check
	 * that it's up-to-date. If not, it is going to be due to an error.
L
Linus Torvalds 已提交
1644
	 */
1645
	if (unlikely(!PageUptodate(page)))
L
Linus Torvalds 已提交
1646 1647
		goto page_not_uptodate;

1648 1649 1650 1651
	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
1652
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1653
	if (unlikely(offset >= size)) {
1654
		unlock_page(page);
1655
		page_cache_release(page);
1656
		return VM_FAULT_SIGBUS;
1657 1658
	}

N
Nick Piggin 已提交
1659
	vmf->page = page;
N
Nick Piggin 已提交
1660
	return ret | VM_FAULT_LOCKED;
L
Linus Torvalds 已提交
1661 1662 1663 1664 1665 1666

no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
1667
	error = page_cache_read(file, offset);
L
Linus Torvalds 已提交
1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682

	/*
	 * The page we want has now been added to the page cache.
	 * In the unlikely event that someone removed it in the
	 * meantime, we'll just come back here and read it again.
	 */
	if (error >= 0)
		goto retry_find;

	/*
	 * An error return from page_cache_read can result if the
	 * system is low on memory, or a problem occurs while trying
	 * to schedule I/O.
	 */
	if (error == -ENOMEM)
N
Nick Piggin 已提交
1683 1684
		return VM_FAULT_OOM;
	return VM_FAULT_SIGBUS;
L
Linus Torvalds 已提交
1685 1686 1687 1688 1689 1690 1691 1692 1693

page_not_uptodate:
	/*
	 * Umm, take care of errors if the page isn't up-to-date.
	 * Try to re-read it _once_. We do this synchronously,
	 * because there really aren't any performance issues here
	 * and we need to check for errors.
	 */
	ClearPageError(page);
1694
	error = mapping->a_ops->readpage(file, page);
1695 1696 1697 1698 1699
	if (!error) {
		wait_on_page_locked(page);
		if (!PageUptodate(page))
			error = -EIO;
	}
1700 1701 1702
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
1703
		goto retry_find;
L
Linus Torvalds 已提交
1704

1705
	/* Things didn't work out. Return zero to tell the mm layer so. */
1706
	shrink_readahead_size_eio(file, ra);
N
Nick Piggin 已提交
1707
	return VM_FAULT_SIGBUS;
1708 1709 1710
}
EXPORT_SYMBOL(filemap_fault);

1711 1712 1713
int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct page *page = vmf->page;
A
Al Viro 已提交
1714
	struct inode *inode = file_inode(vma->vm_file);
1715 1716
	int ret = VM_FAULT_LOCKED;

1717
	sb_start_pagefault(inode->i_sb);
1718 1719 1720 1721 1722 1723 1724
	file_update_time(vma->vm_file);
	lock_page(page);
	if (page->mapping != inode->i_mapping) {
		unlock_page(page);
		ret = VM_FAULT_NOPAGE;
		goto out;
	}
1725 1726 1727 1728 1729 1730
	/*
	 * We mark the page dirty already here so that when freeze is in
	 * progress, we are guaranteed that writeback during freezing will
	 * see the dirty page and writeprotect it again.
	 */
	set_page_dirty(page);
1731
out:
1732
	sb_end_pagefault(inode->i_sb);
1733 1734 1735 1736
	return ret;
}
EXPORT_SYMBOL(filemap_page_mkwrite);

1737
const struct vm_operations_struct generic_file_vm_ops = {
1738
	.fault		= filemap_fault,
1739
	.page_mkwrite	= filemap_page_mkwrite,
1740
	.remap_pages	= generic_file_remap_pages,
L
Linus Torvalds 已提交
1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778
};

/* This is used for a general mmap of a disk file */

int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
	struct address_space *mapping = file->f_mapping;

	if (!mapping->a_ops->readpage)
		return -ENOEXEC;
	file_accessed(file);
	vma->vm_ops = &generic_file_vm_ops;
	return 0;
}

/*
 * This is for filesystems which do not implement ->writepage.
 */
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
		return -EINVAL;
	return generic_file_mmap(file, vma);
}
#else
int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
{
	return -ENOSYS;
}
int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
{
	return -ENOSYS;
}
#endif /* CONFIG_MMU */

EXPORT_SYMBOL(generic_file_mmap);
EXPORT_SYMBOL(generic_file_readonly_mmap);

1779
static struct page *__read_cache_page(struct address_space *mapping,
1780
				pgoff_t index,
1781
				int (*filler)(void *, struct page *),
1782 1783
				void *data,
				gfp_t gfp)
L
Linus Torvalds 已提交
1784
{
N
Nick Piggin 已提交
1785
	struct page *page;
L
Linus Torvalds 已提交
1786 1787 1788 1789
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
1790
		page = __page_cache_alloc(gfp | __GFP_COLD);
N
Nick Piggin 已提交
1791 1792
		if (!page)
			return ERR_PTR(-ENOMEM);
1793
		err = add_to_page_cache_lru(page, mapping, index, gfp);
N
Nick Piggin 已提交
1794 1795 1796 1797
		if (unlikely(err)) {
			page_cache_release(page);
			if (err == -EEXIST)
				goto repeat;
L
Linus Torvalds 已提交
1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809
			/* Presumably ENOMEM for radix tree node */
			return ERR_PTR(err);
		}
		err = filler(data, page);
		if (err < 0) {
			page_cache_release(page);
			page = ERR_PTR(err);
		}
	}
	return page;
}

1810
static struct page *do_read_cache_page(struct address_space *mapping,
1811
				pgoff_t index,
1812
				int (*filler)(void *, struct page *),
1813 1814 1815
				void *data,
				gfp_t gfp)

L
Linus Torvalds 已提交
1816 1817 1818 1819 1820
{
	struct page *page;
	int err;

retry:
1821
	page = __read_cache_page(mapping, index, filler, data, gfp);
L
Linus Torvalds 已提交
1822
	if (IS_ERR(page))
1823
		return page;
L
Linus Torvalds 已提交
1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839
	if (PageUptodate(page))
		goto out;

	lock_page(page);
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry;
	}
	if (PageUptodate(page)) {
		unlock_page(page);
		goto out;
	}
	err = filler(data, page);
	if (err < 0) {
		page_cache_release(page);
1840
		return ERR_PTR(err);
L
Linus Torvalds 已提交
1841
	}
1842
out:
1843 1844 1845
	mark_page_accessed(page);
	return page;
}
1846 1847 1848 1849 1850 1851

/**
 * read_cache_page_async - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
1852
 * @data:	first arg to filler(data, page) function, often left as NULL
1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863
 *
 * Same as read_cache_page, but don't wait for page to become unlocked
 * after submitting it to the filler.
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page but don't wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page_async(struct address_space *mapping,
				pgoff_t index,
1864
				int (*filler)(void *, struct page *),
1865 1866 1867 1868
				void *data)
{
	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
}
1869 1870
EXPORT_SYMBOL(read_cache_page_async);

1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889
static struct page *wait_on_page_read(struct page *page)
{
	if (!IS_ERR(page)) {
		wait_on_page_locked(page);
		if (!PageUptodate(page)) {
			page_cache_release(page);
			page = ERR_PTR(-EIO);
		}
	}
	return page;
}

/**
 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
 * @mapping:	the page's address_space
 * @index:	the page index
 * @gfp:	the page allocator flags to use if allocating
 *
 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1890
 * any new page allocations done using the specified allocation flags.
1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page_gfp(struct address_space *mapping,
				pgoff_t index,
				gfp_t gfp)
{
	filler_t *filler = (filler_t *)mapping->a_ops->readpage;

	return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
}
EXPORT_SYMBOL(read_cache_page_gfp);

1904 1905 1906 1907 1908
/**
 * read_cache_page - read into page cache, fill it if needed
 * @mapping:	the page's address_space
 * @index:	the page index
 * @filler:	function to perform the read
1909
 * @data:	first arg to filler(data, page) function, often left as NULL
1910 1911 1912 1913 1914 1915 1916
 *
 * Read into the page cache. If a page already exists, and PageUptodate() is
 * not set, try to fill the page then wait for it to become unlocked.
 *
 * If the page does not get brought uptodate, return -EIO.
 */
struct page *read_cache_page(struct address_space *mapping,
1917
				pgoff_t index,
1918
				int (*filler)(void *, struct page *),
1919 1920
				void *data)
{
1921
	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
L
Linus Torvalds 已提交
1922 1923 1924
}
EXPORT_SYMBOL(read_cache_page);

N
Nick Piggin 已提交
1925
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
L
Linus Torvalds 已提交
1926 1927
			const struct iovec *iov, size_t base, size_t bytes)
{
1928
	size_t copied = 0, left = 0;
L
Linus Torvalds 已提交
1929 1930 1931 1932 1933 1934

	while (bytes) {
		char __user *buf = iov->iov_base + base;
		int copy = min(bytes, iov->iov_len - base);

		base = 0;
1935
		left = __copy_from_user_inatomic(vaddr, buf, copy);
L
Linus Torvalds 已提交
1936 1937 1938 1939 1940
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

1941
		if (unlikely(left))
L
Linus Torvalds 已提交
1942 1943 1944 1945 1946
			break;
	}
	return copied - left;
}

N
Nick Piggin 已提交
1947 1948
/*
 * Copy as much as we can into the page and return the number of bytes which
1949
 * were successfully copied.  If a fault is encountered then return the number of
N
Nick Piggin 已提交
1950 1951 1952 1953 1954 1955 1956 1957 1958
 * bytes which were copied.
 */
size_t iov_iter_copy_from_user_atomic(struct page *page,
		struct iov_iter *i, unsigned long offset, size_t bytes)
{
	char *kaddr;
	size_t copied;

	BUG_ON(!in_atomic());
1959
	kaddr = kmap_atomic(page);
N
Nick Piggin 已提交
1960 1961 1962
	if (likely(i->nr_segs == 1)) {
		int left;
		char __user *buf = i->iov->iov_base + i->iov_offset;
1963
		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1964 1965 1966 1967 1968
		copied = bytes - left;
	} else {
		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
						i->iov, i->iov_offset, bytes);
	}
1969
	kunmap_atomic(kaddr);
N
Nick Piggin 已提交
1970 1971 1972

	return copied;
}
N
Nick Piggin 已提交
1973
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
N
Nick Piggin 已提交
1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990

/*
 * This has the same sideeffects and return value as
 * iov_iter_copy_from_user_atomic().
 * The difference is that it attempts to resolve faults.
 * Page must not be locked.
 */
size_t iov_iter_copy_from_user(struct page *page,
		struct iov_iter *i, unsigned long offset, size_t bytes)
{
	char *kaddr;
	size_t copied;

	kaddr = kmap(page);
	if (likely(i->nr_segs == 1)) {
		int left;
		char __user *buf = i->iov->iov_base + i->iov_offset;
1991
		left = __copy_from_user(kaddr + offset, buf, bytes);
N
Nick Piggin 已提交
1992 1993 1994 1995 1996 1997 1998 1999
		copied = bytes - left;
	} else {
		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
						i->iov, i->iov_offset, bytes);
	}
	kunmap(page);
	return copied;
}
N
Nick Piggin 已提交
2000
EXPORT_SYMBOL(iov_iter_copy_from_user);
N
Nick Piggin 已提交
2001

N
Nick Piggin 已提交
2002
void iov_iter_advance(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
2003
{
N
Nick Piggin 已提交
2004 2005
	BUG_ON(i->count < bytes);

N
Nick Piggin 已提交
2006 2007
	if (likely(i->nr_segs == 1)) {
		i->iov_offset += bytes;
N
Nick Piggin 已提交
2008
		i->count -= bytes;
N
Nick Piggin 已提交
2009 2010 2011
	} else {
		const struct iovec *iov = i->iov;
		size_t base = i->iov_offset;
2012
		unsigned long nr_segs = i->nr_segs;
N
Nick Piggin 已提交
2013

2014 2015
		/*
		 * The !iov->iov_len check ensures we skip over unlikely
N
Nick Piggin 已提交
2016
		 * zero-length segments (without overruning the iovec).
2017
		 */
2018
		while (bytes || unlikely(i->count && !iov->iov_len)) {
N
Nick Piggin 已提交
2019
			int copy;
N
Nick Piggin 已提交
2020

N
Nick Piggin 已提交
2021 2022 2023
			copy = min(bytes, iov->iov_len - base);
			BUG_ON(!i->count || i->count < copy);
			i->count -= copy;
N
Nick Piggin 已提交
2024 2025 2026 2027
			bytes -= copy;
			base += copy;
			if (iov->iov_len == base) {
				iov++;
2028
				nr_segs--;
N
Nick Piggin 已提交
2029 2030 2031 2032 2033
				base = 0;
			}
		}
		i->iov = iov;
		i->iov_offset = base;
2034
		i->nr_segs = nr_segs;
N
Nick Piggin 已提交
2035 2036
	}
}
N
Nick Piggin 已提交
2037
EXPORT_SYMBOL(iov_iter_advance);
N
Nick Piggin 已提交
2038

2039 2040 2041 2042 2043 2044 2045 2046 2047 2048
/*
 * Fault in the first iovec of the given iov_iter, to a maximum length
 * of bytes. Returns 0 on success, or non-zero if the memory could not be
 * accessed (ie. because it is an invalid address).
 *
 * writev-intensive code may want this to prefault several iovecs -- that
 * would be possible (callers must not rely on the fact that _only_ the
 * first iovec will be faulted with the current implementation).
 */
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
N
Nick Piggin 已提交
2049 2050
{
	char __user *buf = i->iov->iov_base + i->iov_offset;
2051 2052
	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
	return fault_in_pages_readable(buf, bytes);
N
Nick Piggin 已提交
2053
}
N
Nick Piggin 已提交
2054
EXPORT_SYMBOL(iov_iter_fault_in_readable);
N
Nick Piggin 已提交
2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066

/*
 * Return the count of just the current iov_iter segment.
 */
size_t iov_iter_single_seg_count(struct iov_iter *i)
{
	const struct iovec *iov = i->iov;
	if (i->nr_segs == 1)
		return i->count;
	else
		return min(i->count, iov->iov_len - i->iov_offset);
}
N
Nick Piggin 已提交
2067
EXPORT_SYMBOL(iov_iter_single_seg_count);
N
Nick Piggin 已提交
2068

L
Linus Torvalds 已提交
2069 2070 2071
/*
 * Performs necessary checks before doing a write
 *
2072
 * Can adjust writing position or amount of bytes to write.
L
Linus Torvalds 已提交
2073 2074 2075 2076 2077 2078
 * Returns appropriate error code that caller should return or
 * zero in case that write should be allowed.
 */
inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
{
	struct inode *inode = file->f_mapping->host;
J
Jiri Slaby 已提交
2079
	unsigned long limit = rlimit(RLIMIT_FSIZE);
L
Linus Torvalds 已提交
2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130

        if (unlikely(*pos < 0))
                return -EINVAL;

	if (!isblk) {
		/* FIXME: this is for backwards compatibility with 2.4 */
		if (file->f_flags & O_APPEND)
                        *pos = i_size_read(inode);

		if (limit != RLIM_INFINITY) {
			if (*pos >= limit) {
				send_sig(SIGXFSZ, current, 0);
				return -EFBIG;
			}
			if (*count > limit - (typeof(limit))*pos) {
				*count = limit - (typeof(limit))*pos;
			}
		}
	}

	/*
	 * LFS rule
	 */
	if (unlikely(*pos + *count > MAX_NON_LFS &&
				!(file->f_flags & O_LARGEFILE))) {
		if (*pos >= MAX_NON_LFS) {
			return -EFBIG;
		}
		if (*count > MAX_NON_LFS - (unsigned long)*pos) {
			*count = MAX_NON_LFS - (unsigned long)*pos;
		}
	}

	/*
	 * Are we about to exceed the fs block limit ?
	 *
	 * If we have written data it becomes a short write.  If we have
	 * exceeded without writing data we send a signal and return EFBIG.
	 * Linus frestrict idea will clean these up nicely..
	 */
	if (likely(!isblk)) {
		if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
			if (*count || *pos > inode->i_sb->s_maxbytes) {
				return -EFBIG;
			}
			/* zero-length writes at ->s_maxbytes are OK */
		}

		if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
			*count = inode->i_sb->s_maxbytes - *pos;
	} else {
2131
#ifdef CONFIG_BLOCK
L
Linus Torvalds 已提交
2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142
		loff_t isize;
		if (bdev_read_only(I_BDEV(inode)))
			return -EPERM;
		isize = i_size_read(inode);
		if (*pos >= isize) {
			if (*count || *pos > isize)
				return -ENOSPC;
		}

		if (*pos + *count > isize)
			*count = isize - *pos;
2143 2144 2145
#else
		return -EPERM;
#endif
L
Linus Torvalds 已提交
2146 2147 2148 2149 2150
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

2151 2152 2153 2154 2155 2156
int pagecache_write_begin(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned flags,
				struct page **pagep, void **fsdata)
{
	const struct address_space_operations *aops = mapping->a_ops;

2157
	return aops->write_begin(file, mapping, pos, len, flags,
2158 2159 2160 2161 2162 2163 2164 2165 2166 2167
							pagep, fsdata);
}
EXPORT_SYMBOL(pagecache_write_begin);

int pagecache_write_end(struct file *file, struct address_space *mapping,
				loff_t pos, unsigned len, unsigned copied,
				struct page *page, void *fsdata)
{
	const struct address_space_operations *aops = mapping->a_ops;

2168 2169
	mark_page_accessed(page);
	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2170 2171 2172
}
EXPORT_SYMBOL(pagecache_write_end);

L
Linus Torvalds 已提交
2173 2174 2175 2176 2177 2178 2179 2180 2181
ssize_t
generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long *nr_segs, loff_t pos, loff_t *ppos,
		size_t count, size_t ocount)
{
	struct file	*file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode	*inode = mapping->host;
	ssize_t		written;
2182 2183
	size_t		write_len;
	pgoff_t		end;
L
Linus Torvalds 已提交
2184 2185 2186 2187

	if (count != ocount)
		*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);

2188 2189 2190
	write_len = iov_length(iov, *nr_segs);
	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;

2191
	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2192 2193 2194 2195 2196 2197 2198
	if (written)
		goto out;

	/*
	 * After a write we want buffered reads to be sure to go to disk to get
	 * the new data.  We invalidate clean cached page from the region we're
	 * about to write.  We do this *before* the write so that we can return
2199
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2200 2201 2202 2203
	 */
	if (mapping->nrpages) {
		written = invalidate_inode_pages2_range(mapping,
					pos >> PAGE_CACHE_SHIFT, end);
2204 2205 2206 2207 2208 2209 2210
		/*
		 * If a page can not be invalidated, return 0 to fall back
		 * to buffered write.
		 */
		if (written) {
			if (written == -EBUSY)
				return 0;
2211
			goto out;
2212
		}
2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229
	}

	written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);

	/*
	 * Finally, try again to invalidate clean pages which might have been
	 * cached by non-direct readahead, or faulted in by get_user_pages()
	 * if the source of the write was an mmap'ed region of the file
	 * we're writing.  Either one is a pretty crazy thing to do,
	 * so we don't support it 100%.  If this invalidation
	 * fails, tough, the write still worked...
	 */
	if (mapping->nrpages) {
		invalidate_inode_pages2_range(mapping,
					      pos >> PAGE_CACHE_SHIFT, end);
	}

L
Linus Torvalds 已提交
2230
	if (written > 0) {
2231 2232 2233
		pos += written;
		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode, pos);
L
Linus Torvalds 已提交
2234 2235
			mark_inode_dirty(inode);
		}
2236
		*ppos = pos;
L
Linus Torvalds 已提交
2237
	}
2238
out:
L
Linus Torvalds 已提交
2239 2240 2241 2242
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

N
Nick Piggin 已提交
2243 2244 2245 2246
/*
 * Find or create a page at the given pagecache position. Return the locked
 * page. This function is specifically for buffered writes.
 */
2247 2248
struct page *grab_cache_page_write_begin(struct address_space *mapping,
					pgoff_t index, unsigned flags)
N
Nick Piggin 已提交
2249 2250
{
	int status;
2251
	gfp_t gfp_mask;
N
Nick Piggin 已提交
2252
	struct page *page;
2253
	gfp_t gfp_notmask = 0;
2254

2255 2256 2257
	gfp_mask = mapping_gfp_mask(mapping);
	if (mapping_cap_account_dirty(mapping))
		gfp_mask |= __GFP_WRITE;
2258 2259
	if (flags & AOP_FLAG_NOFS)
		gfp_notmask = __GFP_FS;
N
Nick Piggin 已提交
2260 2261
repeat:
	page = find_lock_page(mapping, index);
2262
	if (page)
2263
		goto found;
N
Nick Piggin 已提交
2264

2265
	page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
N
Nick Piggin 已提交
2266 2267
	if (!page)
		return NULL;
2268 2269
	status = add_to_page_cache_lru(page, mapping, index,
						GFP_KERNEL & ~gfp_notmask);
N
Nick Piggin 已提交
2270 2271 2272 2273 2274 2275
	if (unlikely(status)) {
		page_cache_release(page);
		if (status == -EEXIST)
			goto repeat;
		return NULL;
	}
2276 2277
found:
	wait_on_page_writeback(page);
N
Nick Piggin 已提交
2278 2279
	return page;
}
2280
EXPORT_SYMBOL(grab_cache_page_write_begin);
N
Nick Piggin 已提交
2281

2282 2283 2284 2285 2286 2287 2288
static ssize_t generic_perform_write(struct file *file,
				struct iov_iter *i, loff_t pos)
{
	struct address_space *mapping = file->f_mapping;
	const struct address_space_operations *a_ops = mapping->a_ops;
	long status = 0;
	ssize_t written = 0;
N
Nick Piggin 已提交
2289 2290 2291 2292 2293 2294 2295
	unsigned int flags = 0;

	/*
	 * Copies from kernel address space cannot fail (NFSD is a big user).
	 */
	if (segment_eq(get_fs(), KERNEL_DS))
		flags |= AOP_FLAG_UNINTERRUPTIBLE;
2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */
		void *fsdata;

		offset = (pos & (PAGE_CACHE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
						iov_iter_count(i));

again:
		/*
		 * Bring in the user page that we will copy from _first_.
		 * Otherwise there's a nasty deadlock on copying from the
		 * same page as we're writing to, without it being marked
		 * up-to-date.
		 *
		 * Not only is this an optimisation, but it is also required
		 * to check that the address is actually valid, when atomic
		 * usercopies are used, below.
		 */
		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
			status = -EFAULT;
			break;
		}

N
Nick Piggin 已提交
2324
		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2325 2326 2327 2328
						&page, &fsdata);
		if (unlikely(status))
			break;

2329 2330 2331
		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

2332 2333 2334 2335 2336
		pagefault_disable();
		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
		pagefault_enable();
		flush_dcache_page(page);

2337
		mark_page_accessed(page);
2338 2339 2340 2341 2342 2343 2344 2345
		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status < 0))
			break;
		copied = status;

		cond_resched();

2346
		iov_iter_advance(i, copied);
2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363
		if (unlikely(copied == 0)) {
			/*
			 * If we were unable to copy any data at all, we must
			 * fall back to a single segment length write.
			 *
			 * If we didn't fallback here, we could livelock
			 * because not all segments in the iov can be copied at
			 * once without a pagefault.
			 */
			bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
						iov_iter_single_seg_count(i));
			goto again;
		}
		pos += copied;
		written += copied;

		balance_dirty_pages_ratelimited(mapping);
2364 2365 2366 2367
		if (fatal_signal_pending(current)) {
			status = -EINTR;
			break;
		}
2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382
	} while (iov_iter_count(i));

	return written ? written : status;
}

ssize_t
generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos, loff_t *ppos,
		size_t count, ssize_t written)
{
	struct file *file = iocb->ki_filp;
	ssize_t status;
	struct iov_iter i;

	iov_iter_init(&i, iov, nr_segs, count, written);
2383
	status = generic_perform_write(file, &i, pos);
L
Linus Torvalds 已提交
2384 2385

	if (likely(status >= 0)) {
2386 2387
		written += status;
		*ppos = pos + status;
L
Linus Torvalds 已提交
2388 2389 2390 2391 2392 2393
  	}
	
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414
/**
 * __generic_file_aio_write - write data to a file
 * @iocb:	IO state structure (file, offset, etc.)
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @ppos:	position where to write
 *
 * This function does all the work needed for actually writing data to a
 * file. It does all basic checks, removes SUID from the file, updates
 * modification times and calls proper subroutines depending on whether we
 * do direct IO or a standard buffered write.
 *
 * It expects i_mutex to be grabbed unless we work on a block device or similar
 * object which does not need locking at all.
 *
 * This function does *not* take care of syncing data in case of O_SYNC write.
 * A caller has to handle it. This is mainly due to the fact that we want to
 * avoid syncing under i_mutex.
 */
ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
				 unsigned long nr_segs, loff_t *ppos)
L
Linus Torvalds 已提交
2415 2416
{
	struct file *file = iocb->ki_filp;
2417
	struct address_space * mapping = file->f_mapping;
L
Linus Torvalds 已提交
2418 2419 2420 2421 2422 2423 2424 2425
	size_t ocount;		/* original count */
	size_t count;		/* after file limit checks */
	struct inode 	*inode = mapping->host;
	loff_t		pos;
	ssize_t		written;
	ssize_t		err;

	ocount = 0;
2426 2427 2428
	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
	if (err)
		return err;
L
Linus Torvalds 已提交
2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443

	count = ocount;
	pos = *ppos;

	/* We can write back this queue in page reclaim */
	current->backing_dev_info = mapping->backing_dev_info;
	written = 0;

	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
	if (err)
		goto out;

	if (count == 0)
		goto out;

2444
	err = file_remove_suid(file);
L
Linus Torvalds 已提交
2445 2446 2447
	if (err)
		goto out;

2448 2449 2450
	err = file_update_time(file);
	if (err)
		goto out;
L
Linus Torvalds 已提交
2451 2452 2453

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
2454 2455 2456 2457 2458
		loff_t endbyte;
		ssize_t written_buffered;

		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
							ppos, count, ocount);
L
Linus Torvalds 已提交
2459 2460 2461 2462 2463 2464 2465 2466
		if (written < 0 || written == count)
			goto out;
		/*
		 * direct-io write to a hole: fall through to buffered I/O
		 * for completing the rest of the request.
		 */
		pos += written;
		count -= written;
2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480
		written_buffered = generic_file_buffered_write(iocb, iov,
						nr_segs, pos, ppos, count,
						written);
		/*
		 * If generic_file_buffered_write() retuned a synchronous error
		 * then we want to return the number of bytes which were
		 * direct-written, or the error code if that was zero.  Note
		 * that this differs from normal direct-io semantics, which
		 * will return -EFOO even if some bytes were written.
		 */
		if (written_buffered < 0) {
			err = written_buffered;
			goto out;
		}
L
Linus Torvalds 已提交
2481

2482 2483 2484 2485 2486 2487
		/*
		 * We need to ensure that the page cache pages are written to
		 * disk and invalidated to preserve the expected O_DIRECT
		 * semantics.
		 */
		endbyte = pos + written_buffered - written - 1;
2488
		err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503
		if (err == 0) {
			written = written_buffered;
			invalidate_mapping_pages(mapping,
						 pos >> PAGE_CACHE_SHIFT,
						 endbyte >> PAGE_CACHE_SHIFT);
		} else {
			/*
			 * We don't know how much we wrote, so just return
			 * the number of bytes which were direct-written
			 */
		}
	} else {
		written = generic_file_buffered_write(iocb, iov, nr_segs,
				pos, ppos, count, written);
	}
L
Linus Torvalds 已提交
2504 2505 2506 2507
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520
EXPORT_SYMBOL(__generic_file_aio_write);

/**
 * generic_file_aio_write - write data to a file
 * @iocb:	IO state structure
 * @iov:	vector with data to write
 * @nr_segs:	number of segments in the vector
 * @pos:	position in file where to write
 *
 * This is a wrapper around __generic_file_aio_write() to be used by most
 * filesystems. It takes care of syncing the file in case of O_SYNC file
 * and acquires i_mutex as needed.
 */
2521 2522
ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
L
Linus Torvalds 已提交
2523 2524
{
	struct file *file = iocb->ki_filp;
2525
	struct inode *inode = file->f_mapping->host;
L
Linus Torvalds 已提交
2526 2527 2528 2529
	ssize_t ret;

	BUG_ON(iocb->ki_pos != pos);

2530
	sb_start_write(inode->i_sb);
2531
	mutex_lock(&inode->i_mutex);
2532
	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2533
	mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
2534

2535
	if (ret > 0 || ret == -EIOCBQUEUED) {
L
Linus Torvalds 已提交
2536 2537
		ssize_t err;

2538
		err = generic_write_sync(file, pos, ret);
2539
		if (err < 0 && ret > 0)
L
Linus Torvalds 已提交
2540 2541
			ret = err;
	}
2542
	sb_end_write(inode->i_sb);
L
Linus Torvalds 已提交
2543 2544 2545 2546
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

2547 2548 2549 2550 2551 2552 2553 2554 2555 2556
/**
 * try_to_release_page() - release old fs-specific metadata on a page
 *
 * @page: the page which the kernel is trying to free
 * @gfp_mask: memory allocation flags (and I/O mode)
 *
 * The address_space is to try to release any data against the page
 * (presumably at page->private).  If the release was successful, return `1'.
 * Otherwise return zero.
 *
2557 2558 2559
 * This may also be called if PG_fscache is set on a page, indicating that the
 * page is known to the local caching routines.
 *
2560
 * The @gfp_mask argument specifies whether I/O may be performed to release
2561
 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577
 *
 */
int try_to_release_page(struct page *page, gfp_t gfp_mask)
{
	struct address_space * const mapping = page->mapping;

	BUG_ON(!PageLocked(page));
	if (PageWriteback(page))
		return 0;

	if (mapping && mapping->a_ops->releasepage)
		return mapping->a_ops->releasepage(page, gfp_mask);
	return try_to_free_buffers(page);
}

EXPORT_SYMBOL(try_to_release_page);