xref: /openbmc/linux/mm/filemap.c (revision 9c1f8594)
1 /*
2  *	linux/mm/filemap.c
3  *
4  * Copyright (C) 1994-1999  Linus Torvalds
5  */
6 
7 /*
8  * This file handles the generic file mmap semantics used by
9  * most "normal" filesystems (but you don't /have/ to use this:
10  * the NFS filesystem used to do this differently, for example)
11  */
12 #include <linux/module.h>
13 #include <linux/compiler.h>
14 #include <linux/fs.h>
15 #include <linux/uaccess.h>
16 #include <linux/aio.h>
17 #include <linux/capability.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/gfp.h>
20 #include <linux/mm.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/security.h>
32 #include <linux/syscalls.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/memcontrol.h>
36 #include <linux/cleancache.h>
37 #include "internal.h"
38 
39 /*
40  * FIXME: remove all knowledge of the buffer layer from the core VM
41  */
42 #include <linux/buffer_head.h> /* for try_to_free_buffers */
43 
44 #include <asm/mman.h>
45 
46 /*
47  * Shared mappings implemented 30.11.1994. It's not fully working yet,
48  * though.
49  *
50  * Shared mappings now work. 15.8.1995  Bruno.
51  *
52  * finished 'unifying' the page and buffer cache and SMP-threaded the
53  * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
54  *
55  * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
56  */
57 
58 /*
59  * Lock ordering:
60  *
61  *  ->i_mmap_mutex		(truncate_pagecache)
62  *    ->private_lock		(__free_pte->__set_page_dirty_buffers)
63  *      ->swap_lock		(exclusive_swap_page, others)
64  *        ->mapping->tree_lock
65  *
66  *  ->i_mutex
67  *    ->i_mmap_mutex		(truncate->unmap_mapping_range)
68  *
69  *  ->mmap_sem
70  *    ->i_mmap_mutex
71  *      ->page_table_lock or pte_lock	(various, mainly in memory.c)
72  *        ->mapping->tree_lock	(arch-dependent flush_dcache_mmap_lock)
73  *
74  *  ->mmap_sem
75  *    ->lock_page		(access_process_vm)
76  *
77  *  ->i_mutex			(generic_file_buffered_write)
78  *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
79  *
80  *  bdi->wb.list_lock
81  *    sb_lock			(fs/fs-writeback.c)
82  *    ->mapping->tree_lock	(__sync_single_inode)
83  *
84  *  ->i_mmap_mutex
85  *    ->anon_vma.lock		(vma_adjust)
86  *
87  *  ->anon_vma.lock
88  *    ->page_table_lock or pte_lock	(anon_vma_prepare and various)
89  *
90  *  ->page_table_lock or pte_lock
91  *    ->swap_lock		(try_to_unmap_one)
92  *    ->private_lock		(try_to_unmap_one)
93  *    ->tree_lock		(try_to_unmap_one)
94  *    ->zone.lru_lock		(follow_page->mark_page_accessed)
95  *    ->zone.lru_lock		(check_pte_range->isolate_lru_page)
96  *    ->private_lock		(page_remove_rmap->set_page_dirty)
97  *    ->tree_lock		(page_remove_rmap->set_page_dirty)
98  *    bdi.wb->list_lock		(page_remove_rmap->set_page_dirty)
99  *    ->inode->i_lock		(page_remove_rmap->set_page_dirty)
100  *    bdi.wb->list_lock		(zap_pte_range->set_page_dirty)
101  *    ->inode->i_lock		(zap_pte_range->set_page_dirty)
102  *    ->private_lock		(zap_pte_range->__set_page_dirty_buffers)
103  *
104  *  (code doesn't rely on that order, so you could switch it around)
105  *  ->tasklist_lock             (memory_failure, collect_procs_ao)
106  *    ->i_mmap_mutex
107  */
108 
109 /*
110  * Delete a page from the page cache and free it. Caller has to make
111  * sure the page is locked and that nobody else uses it - or that usage
112  * is safe.  The caller must hold the mapping's tree_lock.
113  */
114 void __delete_from_page_cache(struct page *page)
115 {
116 	struct address_space *mapping = page->mapping;
117 
118 	/*
119 	 * if we're uptodate, flush out into the cleancache, otherwise
120 	 * invalidate any existing cleancache entries.  We can't leave
121 	 * stale data around in the cleancache once our page is gone
122 	 */
123 	if (PageUptodate(page) && PageMappedToDisk(page))
124 		cleancache_put_page(page);
125 	else
126 		cleancache_flush_page(mapping, page);
127 
128 	radix_tree_delete(&mapping->page_tree, page->index);
129 	page->mapping = NULL;
130 	/* Leave page->index set: truncation lookup relies upon it */
131 	mapping->nrpages--;
132 	__dec_zone_page_state(page, NR_FILE_PAGES);
133 	if (PageSwapBacked(page))
134 		__dec_zone_page_state(page, NR_SHMEM);
135 	BUG_ON(page_mapped(page));
136 
137 	/*
138 	 * Some filesystems seem to re-dirty the page even after
139 	 * the VM has canceled the dirty bit (eg ext3 journaling).
140 	 *
141 	 * Fix it up by doing a final dirty accounting check after
142 	 * having removed the page entirely.
143 	 */
144 	if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
145 		dec_zone_page_state(page, NR_FILE_DIRTY);
146 		dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
147 	}
148 }
149 
150 /**
151  * delete_from_page_cache - delete page from page cache
152  * @page: the page which the kernel is trying to remove from page cache
153  *
154  * This must be called only on pages that have been verified to be in the page
155  * cache and locked.  It will never put the page into the free list, the caller
156  * has a reference on the page.
157  */
158 void delete_from_page_cache(struct page *page)
159 {
160 	struct address_space *mapping = page->mapping;
161 	void (*freepage)(struct page *);
162 
163 	BUG_ON(!PageLocked(page));
164 
165 	freepage = mapping->a_ops->freepage;
166 	spin_lock_irq(&mapping->tree_lock);
167 	__delete_from_page_cache(page);
168 	spin_unlock_irq(&mapping->tree_lock);
169 	mem_cgroup_uncharge_cache_page(page);
170 
171 	if (freepage)
172 		freepage(page);
173 	page_cache_release(page);
174 }
175 EXPORT_SYMBOL(delete_from_page_cache);
176 
177 static int sleep_on_page(void *word)
178 {
179 	io_schedule();
180 	return 0;
181 }
182 
183 static int sleep_on_page_killable(void *word)
184 {
185 	sleep_on_page(word);
186 	return fatal_signal_pending(current) ? -EINTR : 0;
187 }
188 
189 /**
190  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
191  * @mapping:	address space structure to write
192  * @start:	offset in bytes where the range starts
193  * @end:	offset in bytes where the range ends (inclusive)
194  * @sync_mode:	enable synchronous operation
195  *
196  * Start writeback against all of a mapping's dirty pages that lie
197  * within the byte offsets <start, end> inclusive.
198  *
199  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
200  * opposed to a regular memory cleansing writeback.  The difference between
201  * these two operations is that if a dirty page/buffer is encountered, it must
202  * be waited upon, and not just skipped over.
203  */
204 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
205 				loff_t end, int sync_mode)
206 {
207 	int ret;
208 	struct writeback_control wbc = {
209 		.sync_mode = sync_mode,
210 		.nr_to_write = LONG_MAX,
211 		.range_start = start,
212 		.range_end = end,
213 	};
214 
215 	if (!mapping_cap_writeback_dirty(mapping))
216 		return 0;
217 
218 	ret = do_writepages(mapping, &wbc);
219 	return ret;
220 }
221 
222 static inline int __filemap_fdatawrite(struct address_space *mapping,
223 	int sync_mode)
224 {
225 	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
226 }
227 
228 int filemap_fdatawrite(struct address_space *mapping)
229 {
230 	return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
231 }
232 EXPORT_SYMBOL(filemap_fdatawrite);
233 
234 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
235 				loff_t end)
236 {
237 	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
238 }
239 EXPORT_SYMBOL(filemap_fdatawrite_range);
240 
241 /**
242  * filemap_flush - mostly a non-blocking flush
243  * @mapping:	target address_space
244  *
245  * This is a mostly non-blocking flush.  Not suitable for data-integrity
246  * purposes - I/O may not be started against all dirty pages.
247  */
248 int filemap_flush(struct address_space *mapping)
249 {
250 	return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
251 }
252 EXPORT_SYMBOL(filemap_flush);
253 
254 /**
255  * filemap_fdatawait_range - wait for writeback to complete
256  * @mapping:		address space structure to wait for
257  * @start_byte:		offset in bytes where the range starts
258  * @end_byte:		offset in bytes where the range ends (inclusive)
259  *
260  * Walk the list of under-writeback pages of the given address space
261  * in the given range and wait for all of them.
262  */
263 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
264 			    loff_t end_byte)
265 {
266 	pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
267 	pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
268 	struct pagevec pvec;
269 	int nr_pages;
270 	int ret = 0;
271 
272 	if (end_byte < start_byte)
273 		return 0;
274 
275 	pagevec_init(&pvec, 0);
276 	while ((index <= end) &&
277 			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
278 			PAGECACHE_TAG_WRITEBACK,
279 			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
280 		unsigned i;
281 
282 		for (i = 0; i < nr_pages; i++) {
283 			struct page *page = pvec.pages[i];
284 
285 			/* until radix tree lookup accepts end_index */
286 			if (page->index > end)
287 				continue;
288 
289 			wait_on_page_writeback(page);
290 			if (TestClearPageError(page))
291 				ret = -EIO;
292 		}
293 		pagevec_release(&pvec);
294 		cond_resched();
295 	}
296 
297 	/* Check for outstanding write errors */
298 	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
299 		ret = -ENOSPC;
300 	if (test_and_clear_bit(AS_EIO, &mapping->flags))
301 		ret = -EIO;
302 
303 	return ret;
304 }
305 EXPORT_SYMBOL(filemap_fdatawait_range);
306 
307 /**
308  * filemap_fdatawait - wait for all under-writeback pages to complete
309  * @mapping: address space structure to wait for
310  *
311  * Walk the list of under-writeback pages of the given address space
312  * and wait for all of them.
313  */
314 int filemap_fdatawait(struct address_space *mapping)
315 {
316 	loff_t i_size = i_size_read(mapping->host);
317 
318 	if (i_size == 0)
319 		return 0;
320 
321 	return filemap_fdatawait_range(mapping, 0, i_size - 1);
322 }
323 EXPORT_SYMBOL(filemap_fdatawait);
324 
325 int filemap_write_and_wait(struct address_space *mapping)
326 {
327 	int err = 0;
328 
329 	if (mapping->nrpages) {
330 		err = filemap_fdatawrite(mapping);
331 		/*
332 		 * Even if the above returned error, the pages may be
333 		 * written partially (e.g. -ENOSPC), so we wait for it.
334 		 * But the -EIO is special case, it may indicate the worst
335 		 * thing (e.g. bug) happened, so we avoid waiting for it.
336 		 */
337 		if (err != -EIO) {
338 			int err2 = filemap_fdatawait(mapping);
339 			if (!err)
340 				err = err2;
341 		}
342 	}
343 	return err;
344 }
345 EXPORT_SYMBOL(filemap_write_and_wait);
346 
347 /**
348  * filemap_write_and_wait_range - write out & wait on a file range
349  * @mapping:	the address_space for the pages
350  * @lstart:	offset in bytes where the range starts
351  * @lend:	offset in bytes where the range ends (inclusive)
352  *
353  * Write out and wait upon file offsets lstart->lend, inclusive.
354  *
355  * Note that `lend' is inclusive (describes the last byte to be written) so
356  * that this function can be used to write to the very end-of-file (end = -1).
357  */
358 int filemap_write_and_wait_range(struct address_space *mapping,
359 				 loff_t lstart, loff_t lend)
360 {
361 	int err = 0;
362 
363 	if (mapping->nrpages) {
364 		err = __filemap_fdatawrite_range(mapping, lstart, lend,
365 						 WB_SYNC_ALL);
366 		/* See comment of filemap_write_and_wait() */
367 		if (err != -EIO) {
368 			int err2 = filemap_fdatawait_range(mapping,
369 						lstart, lend);
370 			if (!err)
371 				err = err2;
372 		}
373 	}
374 	return err;
375 }
376 EXPORT_SYMBOL(filemap_write_and_wait_range);
377 
378 /**
379  * replace_page_cache_page - replace a pagecache page with a new one
380  * @old:	page to be replaced
381  * @new:	page to replace with
382  * @gfp_mask:	allocation mode
383  *
384  * This function replaces a page in the pagecache with a new one.  On
385  * success it acquires the pagecache reference for the new page and
386  * drops it for the old page.  Both the old and new pages must be
387  * locked.  This function does not add the new page to the LRU, the
388  * caller must do that.
389  *
390  * The remove + add is atomic.  The only way this function can fail is
391  * memory allocation failure.
392  */
393 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
394 {
395 	int error;
396 	struct mem_cgroup *memcg = NULL;
397 
398 	VM_BUG_ON(!PageLocked(old));
399 	VM_BUG_ON(!PageLocked(new));
400 	VM_BUG_ON(new->mapping);
401 
402 	/*
403 	 * This is not page migration, but prepare_migration and
404 	 * end_migration does enough work for charge replacement.
405 	 *
406 	 * In the longer term we probably want a specialized function
407 	 * for moving the charge from old to new in a more efficient
408 	 * manner.
409 	 */
410 	error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);
411 	if (error)
412 		return error;
413 
414 	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
415 	if (!error) {
416 		struct address_space *mapping = old->mapping;
417 		void (*freepage)(struct page *);
418 
419 		pgoff_t offset = old->index;
420 		freepage = mapping->a_ops->freepage;
421 
422 		page_cache_get(new);
423 		new->mapping = mapping;
424 		new->index = offset;
425 
426 		spin_lock_irq(&mapping->tree_lock);
427 		__delete_from_page_cache(old);
428 		error = radix_tree_insert(&mapping->page_tree, offset, new);
429 		BUG_ON(error);
430 		mapping->nrpages++;
431 		__inc_zone_page_state(new, NR_FILE_PAGES);
432 		if (PageSwapBacked(new))
433 			__inc_zone_page_state(new, NR_SHMEM);
434 		spin_unlock_irq(&mapping->tree_lock);
435 		radix_tree_preload_end();
436 		if (freepage)
437 			freepage(old);
438 		page_cache_release(old);
439 		mem_cgroup_end_migration(memcg, old, new, true);
440 	} else {
441 		mem_cgroup_end_migration(memcg, old, new, false);
442 	}
443 
444 	return error;
445 }
446 EXPORT_SYMBOL_GPL(replace_page_cache_page);
447 
448 /**
449  * add_to_page_cache_locked - add a locked page to the pagecache
450  * @page:	page to add
451  * @mapping:	the page's address_space
452  * @offset:	page index
453  * @gfp_mask:	page allocation mode
454  *
455  * This function is used to add a page to the pagecache. It must be locked.
456  * This function does not add the page to the LRU.  The caller must do that.
457  */
458 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
459 		pgoff_t offset, gfp_t gfp_mask)
460 {
461 	int error;
462 
463 	VM_BUG_ON(!PageLocked(page));
464 	VM_BUG_ON(PageSwapBacked(page));
465 
466 	error = mem_cgroup_cache_charge(page, current->mm,
467 					gfp_mask & GFP_RECLAIM_MASK);
468 	if (error)
469 		goto out;
470 
471 	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
472 	if (error == 0) {
473 		page_cache_get(page);
474 		page->mapping = mapping;
475 		page->index = offset;
476 
477 		spin_lock_irq(&mapping->tree_lock);
478 		error = radix_tree_insert(&mapping->page_tree, offset, page);
479 		if (likely(!error)) {
480 			mapping->nrpages++;
481 			__inc_zone_page_state(page, NR_FILE_PAGES);
482 			spin_unlock_irq(&mapping->tree_lock);
483 		} else {
484 			page->mapping = NULL;
485 			/* Leave page->index set: truncation relies upon it */
486 			spin_unlock_irq(&mapping->tree_lock);
487 			mem_cgroup_uncharge_cache_page(page);
488 			page_cache_release(page);
489 		}
490 		radix_tree_preload_end();
491 	} else
492 		mem_cgroup_uncharge_cache_page(page);
493 out:
494 	return error;
495 }
496 EXPORT_SYMBOL(add_to_page_cache_locked);
497 
498 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
499 				pgoff_t offset, gfp_t gfp_mask)
500 {
501 	int ret;
502 
503 	ret = add_to_page_cache(page, mapping, offset, gfp_mask);
504 	if (ret == 0)
505 		lru_cache_add_file(page);
506 	return ret;
507 }
508 EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
509 
510 #ifdef CONFIG_NUMA
511 struct page *__page_cache_alloc(gfp_t gfp)
512 {
513 	int n;
514 	struct page *page;
515 
516 	if (cpuset_do_page_mem_spread()) {
517 		get_mems_allowed();
518 		n = cpuset_mem_spread_node();
519 		page = alloc_pages_exact_node(n, gfp, 0);
520 		put_mems_allowed();
521 		return page;
522 	}
523 	return alloc_pages(gfp, 0);
524 }
525 EXPORT_SYMBOL(__page_cache_alloc);
526 #endif
527 
528 /*
529  * In order to wait for pages to become available there must be
530  * waitqueues associated with pages. By using a hash table of
531  * waitqueues where the bucket discipline is to maintain all
532  * waiters on the same queue and wake all when any of the pages
533  * become available, and for the woken contexts to check to be
534  * sure the appropriate page became available, this saves space
535  * at a cost of "thundering herd" phenomena during rare hash
536  * collisions.
537  */
538 static wait_queue_head_t *page_waitqueue(struct page *page)
539 {
540 	const struct zone *zone = page_zone(page);
541 
542 	return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
543 }
544 
545 static inline void wake_up_page(struct page *page, int bit)
546 {
547 	__wake_up_bit(page_waitqueue(page), &page->flags, bit);
548 }
549 
550 void wait_on_page_bit(struct page *page, int bit_nr)
551 {
552 	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
553 
554 	if (test_bit(bit_nr, &page->flags))
555 		__wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
556 							TASK_UNINTERRUPTIBLE);
557 }
558 EXPORT_SYMBOL(wait_on_page_bit);
559 
560 int wait_on_page_bit_killable(struct page *page, int bit_nr)
561 {
562 	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
563 
564 	if (!test_bit(bit_nr, &page->flags))
565 		return 0;
566 
567 	return __wait_on_bit(page_waitqueue(page), &wait,
568 			     sleep_on_page_killable, TASK_KILLABLE);
569 }
570 
571 /**
572  * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
573  * @page: Page defining the wait queue of interest
574  * @waiter: Waiter to add to the queue
575  *
576  * Add an arbitrary @waiter to the wait queue for the nominated @page.
577  */
578 void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
579 {
580 	wait_queue_head_t *q = page_waitqueue(page);
581 	unsigned long flags;
582 
583 	spin_lock_irqsave(&q->lock, flags);
584 	__add_wait_queue(q, waiter);
585 	spin_unlock_irqrestore(&q->lock, flags);
586 }
587 EXPORT_SYMBOL_GPL(add_page_wait_queue);
588 
589 /**
590  * unlock_page - unlock a locked page
591  * @page: the page
592  *
593  * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
594  * Also wakes sleepers in wait_on_page_writeback() because the wakeup
595  * mechananism between PageLocked pages and PageWriteback pages is shared.
596  * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
597  *
598  * The mb is necessary to enforce ordering between the clear_bit and the read
599  * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
600  */
601 void unlock_page(struct page *page)
602 {
603 	VM_BUG_ON(!PageLocked(page));
604 	clear_bit_unlock(PG_locked, &page->flags);
605 	smp_mb__after_clear_bit();
606 	wake_up_page(page, PG_locked);
607 }
608 EXPORT_SYMBOL(unlock_page);
609 
610 /**
611  * end_page_writeback - end writeback against a page
612  * @page: the page
613  */
614 void end_page_writeback(struct page *page)
615 {
616 	if (TestClearPageReclaim(page))
617 		rotate_reclaimable_page(page);
618 
619 	if (!test_clear_page_writeback(page))
620 		BUG();
621 
622 	smp_mb__after_clear_bit();
623 	wake_up_page(page, PG_writeback);
624 }
625 EXPORT_SYMBOL(end_page_writeback);
626 
627 /**
628  * __lock_page - get a lock on the page, assuming we need to sleep to get it
629  * @page: the page to lock
630  */
631 void __lock_page(struct page *page)
632 {
633 	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
634 
635 	__wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
636 							TASK_UNINTERRUPTIBLE);
637 }
638 EXPORT_SYMBOL(__lock_page);
639 
640 int __lock_page_killable(struct page *page)
641 {
642 	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
643 
644 	return __wait_on_bit_lock(page_waitqueue(page), &wait,
645 					sleep_on_page_killable, TASK_KILLABLE);
646 }
647 EXPORT_SYMBOL_GPL(__lock_page_killable);
648 
649 int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
650 			 unsigned int flags)
651 {
652 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
653 		/*
654 		 * CAUTION! In this case, mmap_sem is not released
655 		 * even though return 0.
656 		 */
657 		if (flags & FAULT_FLAG_RETRY_NOWAIT)
658 			return 0;
659 
660 		up_read(&mm->mmap_sem);
661 		if (flags & FAULT_FLAG_KILLABLE)
662 			wait_on_page_locked_killable(page);
663 		else
664 			wait_on_page_locked(page);
665 		return 0;
666 	} else {
667 		if (flags & FAULT_FLAG_KILLABLE) {
668 			int ret;
669 
670 			ret = __lock_page_killable(page);
671 			if (ret) {
672 				up_read(&mm->mmap_sem);
673 				return 0;
674 			}
675 		} else
676 			__lock_page(page);
677 		return 1;
678 	}
679 }
680 
681 /**
682  * find_get_page - find and get a page reference
683  * @mapping: the address_space to search
684  * @offset: the page index
685  *
686  * Is there a pagecache struct page at the given (mapping, offset) tuple?
687  * If yes, increment its refcount and return it; if no, return NULL.
688  */
689 struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
690 {
691 	void **pagep;
692 	struct page *page;
693 
694 	rcu_read_lock();
695 repeat:
696 	page = NULL;
697 	pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
698 	if (pagep) {
699 		page = radix_tree_deref_slot(pagep);
700 		if (unlikely(!page))
701 			goto out;
702 		if (radix_tree_exception(page)) {
703 			if (radix_tree_deref_retry(page))
704 				goto repeat;
705 			/*
706 			 * Otherwise, shmem/tmpfs must be storing a swap entry
707 			 * here as an exceptional entry: so return it without
708 			 * attempting to raise page count.
709 			 */
710 			goto out;
711 		}
712 		if (!page_cache_get_speculative(page))
713 			goto repeat;
714 
715 		/*
716 		 * Has the page moved?
717 		 * This is part of the lockless pagecache protocol. See
718 		 * include/linux/pagemap.h for details.
719 		 */
720 		if (unlikely(page != *pagep)) {
721 			page_cache_release(page);
722 			goto repeat;
723 		}
724 	}
725 out:
726 	rcu_read_unlock();
727 
728 	return page;
729 }
730 EXPORT_SYMBOL(find_get_page);
731 
732 /**
733  * find_lock_page - locate, pin and lock a pagecache page
734  * @mapping: the address_space to search
735  * @offset: the page index
736  *
737  * Locates the desired pagecache page, locks it, increments its reference
738  * count and returns its address.
739  *
740  * Returns zero if the page was not present. find_lock_page() may sleep.
741  */
742 struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
743 {
744 	struct page *page;
745 
746 repeat:
747 	page = find_get_page(mapping, offset);
748 	if (page && !radix_tree_exception(page)) {
749 		lock_page(page);
750 		/* Has the page been truncated? */
751 		if (unlikely(page->mapping != mapping)) {
752 			unlock_page(page);
753 			page_cache_release(page);
754 			goto repeat;
755 		}
756 		VM_BUG_ON(page->index != offset);
757 	}
758 	return page;
759 }
760 EXPORT_SYMBOL(find_lock_page);
761 
762 /**
763  * find_or_create_page - locate or add a pagecache page
764  * @mapping: the page's address_space
765  * @index: the page's index into the mapping
766  * @gfp_mask: page allocation mode
767  *
768  * Locates a page in the pagecache.  If the page is not present, a new page
769  * is allocated using @gfp_mask and is added to the pagecache and to the VM's
770  * LRU list.  The returned page is locked and has its reference count
771  * incremented.
772  *
773  * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
774  * allocation!
775  *
776  * find_or_create_page() returns the desired page's address, or zero on
777  * memory exhaustion.
778  */
779 struct page *find_or_create_page(struct address_space *mapping,
780 		pgoff_t index, gfp_t gfp_mask)
781 {
782 	struct page *page;
783 	int err;
784 repeat:
785 	page = find_lock_page(mapping, index);
786 	if (!page) {
787 		page = __page_cache_alloc(gfp_mask);
788 		if (!page)
789 			return NULL;
790 		/*
791 		 * We want a regular kernel memory (not highmem or DMA etc)
792 		 * allocation for the radix tree nodes, but we need to honour
793 		 * the context-specific requirements the caller has asked for.
794 		 * GFP_RECLAIM_MASK collects those requirements.
795 		 */
796 		err = add_to_page_cache_lru(page, mapping, index,
797 			(gfp_mask & GFP_RECLAIM_MASK));
798 		if (unlikely(err)) {
799 			page_cache_release(page);
800 			page = NULL;
801 			if (err == -EEXIST)
802 				goto repeat;
803 		}
804 	}
805 	return page;
806 }
807 EXPORT_SYMBOL(find_or_create_page);
808 
809 /**
810  * find_get_pages - gang pagecache lookup
811  * @mapping:	The address_space to search
812  * @start:	The starting page index
813  * @nr_pages:	The maximum number of pages
814  * @pages:	Where the resulting pages are placed
815  *
816  * find_get_pages() will search for and return a group of up to
817  * @nr_pages pages in the mapping.  The pages are placed at @pages.
818  * find_get_pages() takes a reference against the returned pages.
819  *
820  * The search returns a group of mapping-contiguous pages with ascending
821  * indexes.  There may be holes in the indices due to not-present pages.
822  *
823  * find_get_pages() returns the number of pages which were found.
824  */
825 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
826 			    unsigned int nr_pages, struct page **pages)
827 {
828 	unsigned int i;
829 	unsigned int ret;
830 	unsigned int nr_found, nr_skip;
831 
832 	rcu_read_lock();
833 restart:
834 	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
835 				(void ***)pages, NULL, start, nr_pages);
836 	ret = 0;
837 	nr_skip = 0;
838 	for (i = 0; i < nr_found; i++) {
839 		struct page *page;
840 repeat:
841 		page = radix_tree_deref_slot((void **)pages[i]);
842 		if (unlikely(!page))
843 			continue;
844 
845 		if (radix_tree_exception(page)) {
846 			if (radix_tree_deref_retry(page)) {
847 				/*
848 				 * Transient condition which can only trigger
849 				 * when entry at index 0 moves out of or back
850 				 * to root: none yet gotten, safe to restart.
851 				 */
852 				WARN_ON(start | i);
853 				goto restart;
854 			}
855 			/*
856 			 * Otherwise, shmem/tmpfs must be storing a swap entry
857 			 * here as an exceptional entry: so skip over it -
858 			 * we only reach this from invalidate_mapping_pages().
859 			 */
860 			nr_skip++;
861 			continue;
862 		}
863 
864 		if (!page_cache_get_speculative(page))
865 			goto repeat;
866 
867 		/* Has the page moved? */
868 		if (unlikely(page != *((void **)pages[i]))) {
869 			page_cache_release(page);
870 			goto repeat;
871 		}
872 
873 		pages[ret] = page;
874 		ret++;
875 	}
876 
877 	/*
878 	 * If all entries were removed before we could secure them,
879 	 * try again, because callers stop trying once 0 is returned.
880 	 */
881 	if (unlikely(!ret && nr_found > nr_skip))
882 		goto restart;
883 	rcu_read_unlock();
884 	return ret;
885 }
886 
887 /**
888  * find_get_pages_contig - gang contiguous pagecache lookup
889  * @mapping:	The address_space to search
890  * @index:	The starting page index
891  * @nr_pages:	The maximum number of pages
892  * @pages:	Where the resulting pages are placed
893  *
894  * find_get_pages_contig() works exactly like find_get_pages(), except
895  * that the returned number of pages are guaranteed to be contiguous.
896  *
897  * find_get_pages_contig() returns the number of pages which were found.
898  */
899 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
900 			       unsigned int nr_pages, struct page **pages)
901 {
902 	unsigned int i;
903 	unsigned int ret;
904 	unsigned int nr_found;
905 
906 	rcu_read_lock();
907 restart:
908 	nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
909 				(void ***)pages, NULL, index, nr_pages);
910 	ret = 0;
911 	for (i = 0; i < nr_found; i++) {
912 		struct page *page;
913 repeat:
914 		page = radix_tree_deref_slot((void **)pages[i]);
915 		if (unlikely(!page))
916 			continue;
917 
918 		if (radix_tree_exception(page)) {
919 			if (radix_tree_deref_retry(page)) {
920 				/*
921 				 * Transient condition which can only trigger
922 				 * when entry at index 0 moves out of or back
923 				 * to root: none yet gotten, safe to restart.
924 				 */
925 				goto restart;
926 			}
927 			/*
928 			 * Otherwise, shmem/tmpfs must be storing a swap entry
929 			 * here as an exceptional entry: so stop looking for
930 			 * contiguous pages.
931 			 */
932 			break;
933 		}
934 
935 		if (!page_cache_get_speculative(page))
936 			goto repeat;
937 
938 		/* Has the page moved? */
939 		if (unlikely(page != *((void **)pages[i]))) {
940 			page_cache_release(page);
941 			goto repeat;
942 		}
943 
944 		/*
945 		 * must check mapping and index after taking the ref.
946 		 * otherwise we can get both false positives and false
947 		 * negatives, which is just confusing to the caller.
948 		 */
949 		if (page->mapping == NULL || page->index != index) {
950 			page_cache_release(page);
951 			break;
952 		}
953 
954 		pages[ret] = page;
955 		ret++;
956 		index++;
957 	}
958 	rcu_read_unlock();
959 	return ret;
960 }
961 EXPORT_SYMBOL(find_get_pages_contig);
962 
963 /**
964  * find_get_pages_tag - find and return pages that match @tag
965  * @mapping:	the address_space to search
966  * @index:	the starting page index
967  * @tag:	the tag index
968  * @nr_pages:	the maximum number of pages
969  * @pages:	where the resulting pages are placed
970  *
971  * Like find_get_pages, except we only return pages which are tagged with
972  * @tag.   We update @index to index the next page for the traversal.
973  */
974 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
975 			int tag, unsigned int nr_pages, struct page **pages)
976 {
977 	unsigned int i;
978 	unsigned int ret;
979 	unsigned int nr_found;
980 
981 	rcu_read_lock();
982 restart:
983 	nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree,
984 				(void ***)pages, *index, nr_pages, tag);
985 	ret = 0;
986 	for (i = 0; i < nr_found; i++) {
987 		struct page *page;
988 repeat:
989 		page = radix_tree_deref_slot((void **)pages[i]);
990 		if (unlikely(!page))
991 			continue;
992 
993 		if (radix_tree_exception(page)) {
994 			if (radix_tree_deref_retry(page)) {
995 				/*
996 				 * Transient condition which can only trigger
997 				 * when entry at index 0 moves out of or back
998 				 * to root: none yet gotten, safe to restart.
999 				 */
1000 				goto restart;
1001 			}
1002 			/*
1003 			 * This function is never used on a shmem/tmpfs
1004 			 * mapping, so a swap entry won't be found here.
1005 			 */
1006 			BUG();
1007 		}
1008 
1009 		if (!page_cache_get_speculative(page))
1010 			goto repeat;
1011 
1012 		/* Has the page moved? */
1013 		if (unlikely(page != *((void **)pages[i]))) {
1014 			page_cache_release(page);
1015 			goto repeat;
1016 		}
1017 
1018 		pages[ret] = page;
1019 		ret++;
1020 	}
1021 
1022 	/*
1023 	 * If all entries were removed before we could secure them,
1024 	 * try again, because callers stop trying once 0 is returned.
1025 	 */
1026 	if (unlikely(!ret && nr_found))
1027 		goto restart;
1028 	rcu_read_unlock();
1029 
1030 	if (ret)
1031 		*index = pages[ret - 1]->index + 1;
1032 
1033 	return ret;
1034 }
1035 EXPORT_SYMBOL(find_get_pages_tag);
1036 
1037 /**
1038  * grab_cache_page_nowait - returns locked page at given index in given cache
1039  * @mapping: target address_space
1040  * @index: the page index
1041  *
1042  * Same as grab_cache_page(), but do not wait if the page is unavailable.
1043  * This is intended for speculative data generators, where the data can
1044  * be regenerated if the page couldn't be grabbed.  This routine should
1045  * be safe to call while holding the lock for another page.
1046  *
1047  * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1048  * and deadlock against the caller's locked page.
1049  */
1050 struct page *
1051 grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1052 {
1053 	struct page *page = find_get_page(mapping, index);
1054 
1055 	if (page) {
1056 		if (trylock_page(page))
1057 			return page;
1058 		page_cache_release(page);
1059 		return NULL;
1060 	}
1061 	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1062 	if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1063 		page_cache_release(page);
1064 		page = NULL;
1065 	}
1066 	return page;
1067 }
1068 EXPORT_SYMBOL(grab_cache_page_nowait);
1069 
1070 /*
1071  * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1072  * a _large_ part of the i/o request. Imagine the worst scenario:
1073  *
1074  *      ---R__________________________________________B__________
1075  *         ^ reading here                             ^ bad block(assume 4k)
1076  *
1077  * read(R) => miss => readahead(R...B) => media error => frustrating retries
1078  * => failing the whole request => read(R) => read(R+1) =>
1079  * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1080  * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1081  * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1082  *
1083  * It is going insane. Fix it by quickly scaling down the readahead size.
1084  */
1085 static void shrink_readahead_size_eio(struct file *filp,
1086 					struct file_ra_state *ra)
1087 {
1088 	ra->ra_pages /= 4;
1089 }
1090 
1091 /**
1092  * do_generic_file_read - generic file read routine
1093  * @filp:	the file to read
1094  * @ppos:	current file position
1095  * @desc:	read_descriptor
1096  * @actor:	read method
1097  *
1098  * This is a generic file read routine, and uses the
1099  * mapping->a_ops->readpage() function for the actual low-level stuff.
1100  *
1101  * This is really ugly. But the goto's actually try to clarify some
1102  * of the logic when it comes to error handling etc.
1103  */
1104 static void do_generic_file_read(struct file *filp, loff_t *ppos,
1105 		read_descriptor_t *desc, read_actor_t actor)
1106 {
1107 	struct address_space *mapping = filp->f_mapping;
1108 	struct inode *inode = mapping->host;
1109 	struct file_ra_state *ra = &filp->f_ra;
1110 	pgoff_t index;
1111 	pgoff_t last_index;
1112 	pgoff_t prev_index;
1113 	unsigned long offset;      /* offset into pagecache page */
1114 	unsigned int prev_offset;
1115 	int error;
1116 
1117 	index = *ppos >> PAGE_CACHE_SHIFT;
1118 	prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1119 	prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1120 	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1121 	offset = *ppos & ~PAGE_CACHE_MASK;
1122 
1123 	for (;;) {
1124 		struct page *page;
1125 		pgoff_t end_index;
1126 		loff_t isize;
1127 		unsigned long nr, ret;
1128 
1129 		cond_resched();
1130 find_page:
1131 		page = find_get_page(mapping, index);
1132 		if (!page) {
1133 			page_cache_sync_readahead(mapping,
1134 					ra, filp,
1135 					index, last_index - index);
1136 			page = find_get_page(mapping, index);
1137 			if (unlikely(page == NULL))
1138 				goto no_cached_page;
1139 		}
1140 		if (PageReadahead(page)) {
1141 			page_cache_async_readahead(mapping,
1142 					ra, filp, page,
1143 					index, last_index - index);
1144 		}
1145 		if (!PageUptodate(page)) {
1146 			if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1147 					!mapping->a_ops->is_partially_uptodate)
1148 				goto page_not_up_to_date;
1149 			if (!trylock_page(page))
1150 				goto page_not_up_to_date;
1151 			/* Did it get truncated before we got the lock? */
1152 			if (!page->mapping)
1153 				goto page_not_up_to_date_locked;
1154 			if (!mapping->a_ops->is_partially_uptodate(page,
1155 								desc, offset))
1156 				goto page_not_up_to_date_locked;
1157 			unlock_page(page);
1158 		}
1159 page_ok:
1160 		/*
1161 		 * i_size must be checked after we know the page is Uptodate.
1162 		 *
1163 		 * Checking i_size after the check allows us to calculate
1164 		 * the correct value for "nr", which means the zero-filled
1165 		 * part of the page is not copied back to userspace (unless
1166 		 * another truncate extends the file - this is desired though).
1167 		 */
1168 
1169 		isize = i_size_read(inode);
1170 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1171 		if (unlikely(!isize || index > end_index)) {
1172 			page_cache_release(page);
1173 			goto out;
1174 		}
1175 
1176 		/* nr is the maximum number of bytes to copy from this page */
1177 		nr = PAGE_CACHE_SIZE;
1178 		if (index == end_index) {
1179 			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1180 			if (nr <= offset) {
1181 				page_cache_release(page);
1182 				goto out;
1183 			}
1184 		}
1185 		nr = nr - offset;
1186 
1187 		/* If users can be writing to this page using arbitrary
1188 		 * virtual addresses, take care about potential aliasing
1189 		 * before reading the page on the kernel side.
1190 		 */
1191 		if (mapping_writably_mapped(mapping))
1192 			flush_dcache_page(page);
1193 
1194 		/*
1195 		 * When a sequential read accesses a page several times,
1196 		 * only mark it as accessed the first time.
1197 		 */
1198 		if (prev_index != index || offset != prev_offset)
1199 			mark_page_accessed(page);
1200 		prev_index = index;
1201 
1202 		/*
1203 		 * Ok, we have the page, and it's up-to-date, so
1204 		 * now we can copy it to user space...
1205 		 *
1206 		 * The actor routine returns how many bytes were actually used..
1207 		 * NOTE! This may not be the same as how much of a user buffer
1208 		 * we filled up (we may be padding etc), so we can only update
1209 		 * "pos" here (the actor routine has to update the user buffer
1210 		 * pointers and the remaining count).
1211 		 */
1212 		ret = actor(desc, page, offset, nr);
1213 		offset += ret;
1214 		index += offset >> PAGE_CACHE_SHIFT;
1215 		offset &= ~PAGE_CACHE_MASK;
1216 		prev_offset = offset;
1217 
1218 		page_cache_release(page);
1219 		if (ret == nr && desc->count)
1220 			continue;
1221 		goto out;
1222 
1223 page_not_up_to_date:
1224 		/* Get exclusive access to the page ... */
1225 		error = lock_page_killable(page);
1226 		if (unlikely(error))
1227 			goto readpage_error;
1228 
1229 page_not_up_to_date_locked:
1230 		/* Did it get truncated before we got the lock? */
1231 		if (!page->mapping) {
1232 			unlock_page(page);
1233 			page_cache_release(page);
1234 			continue;
1235 		}
1236 
1237 		/* Did somebody else fill it already? */
1238 		if (PageUptodate(page)) {
1239 			unlock_page(page);
1240 			goto page_ok;
1241 		}
1242 
1243 readpage:
1244 		/*
1245 		 * A previous I/O error may have been due to temporary
1246 		 * failures, eg. multipath errors.
1247 		 * PG_error will be set again if readpage fails.
1248 		 */
1249 		ClearPageError(page);
1250 		/* Start the actual read. The read will unlock the page. */
1251 		error = mapping->a_ops->readpage(filp, page);
1252 
1253 		if (unlikely(error)) {
1254 			if (error == AOP_TRUNCATED_PAGE) {
1255 				page_cache_release(page);
1256 				goto find_page;
1257 			}
1258 			goto readpage_error;
1259 		}
1260 
1261 		if (!PageUptodate(page)) {
1262 			error = lock_page_killable(page);
1263 			if (unlikely(error))
1264 				goto readpage_error;
1265 			if (!PageUptodate(page)) {
1266 				if (page->mapping == NULL) {
1267 					/*
1268 					 * invalidate_mapping_pages got it
1269 					 */
1270 					unlock_page(page);
1271 					page_cache_release(page);
1272 					goto find_page;
1273 				}
1274 				unlock_page(page);
1275 				shrink_readahead_size_eio(filp, ra);
1276 				error = -EIO;
1277 				goto readpage_error;
1278 			}
1279 			unlock_page(page);
1280 		}
1281 
1282 		goto page_ok;
1283 
1284 readpage_error:
1285 		/* UHHUH! A synchronous read error occurred. Report it */
1286 		desc->error = error;
1287 		page_cache_release(page);
1288 		goto out;
1289 
1290 no_cached_page:
1291 		/*
1292 		 * Ok, it wasn't cached, so we need to create a new
1293 		 * page..
1294 		 */
1295 		page = page_cache_alloc_cold(mapping);
1296 		if (!page) {
1297 			desc->error = -ENOMEM;
1298 			goto out;
1299 		}
1300 		error = add_to_page_cache_lru(page, mapping,
1301 						index, GFP_KERNEL);
1302 		if (error) {
1303 			page_cache_release(page);
1304 			if (error == -EEXIST)
1305 				goto find_page;
1306 			desc->error = error;
1307 			goto out;
1308 		}
1309 		goto readpage;
1310 	}
1311 
1312 out:
1313 	ra->prev_pos = prev_index;
1314 	ra->prev_pos <<= PAGE_CACHE_SHIFT;
1315 	ra->prev_pos |= prev_offset;
1316 
1317 	*ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1318 	file_accessed(filp);
1319 }
1320 
1321 int file_read_actor(read_descriptor_t *desc, struct page *page,
1322 			unsigned long offset, unsigned long size)
1323 {
1324 	char *kaddr;
1325 	unsigned long left, count = desc->count;
1326 
1327 	if (size > count)
1328 		size = count;
1329 
1330 	/*
1331 	 * Faults on the destination of a read are common, so do it before
1332 	 * taking the kmap.
1333 	 */
1334 	if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1335 		kaddr = kmap_atomic(page, KM_USER0);
1336 		left = __copy_to_user_inatomic(desc->arg.buf,
1337 						kaddr + offset, size);
1338 		kunmap_atomic(kaddr, KM_USER0);
1339 		if (left == 0)
1340 			goto success;
1341 	}
1342 
1343 	/* Do it the slow way */
1344 	kaddr = kmap(page);
1345 	left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1346 	kunmap(page);
1347 
1348 	if (left) {
1349 		size -= left;
1350 		desc->error = -EFAULT;
1351 	}
1352 success:
1353 	desc->count = count - size;
1354 	desc->written += size;
1355 	desc->arg.buf += size;
1356 	return size;
1357 }
1358 
1359 /*
1360  * Performs necessary checks before doing a write
1361  * @iov:	io vector request
1362  * @nr_segs:	number of segments in the iovec
1363  * @count:	number of bytes to write
1364  * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1365  *
1366  * Adjust number of segments and amount of bytes to write (nr_segs should be
1367  * properly initialized first). Returns appropriate error code that caller
1368  * should return or zero in case that write should be allowed.
1369  */
1370 int generic_segment_checks(const struct iovec *iov,
1371 			unsigned long *nr_segs, size_t *count, int access_flags)
1372 {
1373 	unsigned long   seg;
1374 	size_t cnt = 0;
1375 	for (seg = 0; seg < *nr_segs; seg++) {
1376 		const struct iovec *iv = &iov[seg];
1377 
1378 		/*
1379 		 * If any segment has a negative length, or the cumulative
1380 		 * length ever wraps negative then return -EINVAL.
1381 		 */
1382 		cnt += iv->iov_len;
1383 		if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1384 			return -EINVAL;
1385 		if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1386 			continue;
1387 		if (seg == 0)
1388 			return -EFAULT;
1389 		*nr_segs = seg;
1390 		cnt -= iv->iov_len;	/* This segment is no good */
1391 		break;
1392 	}
1393 	*count = cnt;
1394 	return 0;
1395 }
1396 EXPORT_SYMBOL(generic_segment_checks);
1397 
1398 /**
1399  * generic_file_aio_read - generic filesystem read routine
1400  * @iocb:	kernel I/O control block
1401  * @iov:	io vector request
1402  * @nr_segs:	number of segments in the iovec
1403  * @pos:	current file position
1404  *
1405  * This is the "read()" routine for all filesystems
1406  * that can use the page cache directly.
1407  */
1408 ssize_t
1409 generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1410 		unsigned long nr_segs, loff_t pos)
1411 {
1412 	struct file *filp = iocb->ki_filp;
1413 	ssize_t retval;
1414 	unsigned long seg = 0;
1415 	size_t count;
1416 	loff_t *ppos = &iocb->ki_pos;
1417 	struct blk_plug plug;
1418 
1419 	count = 0;
1420 	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1421 	if (retval)
1422 		return retval;
1423 
1424 	blk_start_plug(&plug);
1425 
1426 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1427 	if (filp->f_flags & O_DIRECT) {
1428 		loff_t size;
1429 		struct address_space *mapping;
1430 		struct inode *inode;
1431 
1432 		mapping = filp->f_mapping;
1433 		inode = mapping->host;
1434 		if (!count)
1435 			goto out; /* skip atime */
1436 		size = i_size_read(inode);
1437 		if (pos < size) {
1438 			retval = filemap_write_and_wait_range(mapping, pos,
1439 					pos + iov_length(iov, nr_segs) - 1);
1440 			if (!retval) {
1441 				retval = mapping->a_ops->direct_IO(READ, iocb,
1442 							iov, pos, nr_segs);
1443 			}
1444 			if (retval > 0) {
1445 				*ppos = pos + retval;
1446 				count -= retval;
1447 			}
1448 
1449 			/*
1450 			 * Btrfs can have a short DIO read if we encounter
1451 			 * compressed extents, so if there was an error, or if
1452 			 * we've already read everything we wanted to, or if
1453 			 * there was a short read because we hit EOF, go ahead
1454 			 * and return.  Otherwise fallthrough to buffered io for
1455 			 * the rest of the read.
1456 			 */
1457 			if (retval < 0 || !count || *ppos >= size) {
1458 				file_accessed(filp);
1459 				goto out;
1460 			}
1461 		}
1462 	}
1463 
1464 	count = retval;
1465 	for (seg = 0; seg < nr_segs; seg++) {
1466 		read_descriptor_t desc;
1467 		loff_t offset = 0;
1468 
1469 		/*
1470 		 * If we did a short DIO read we need to skip the section of the
1471 		 * iov that we've already read data into.
1472 		 */
1473 		if (count) {
1474 			if (count > iov[seg].iov_len) {
1475 				count -= iov[seg].iov_len;
1476 				continue;
1477 			}
1478 			offset = count;
1479 			count = 0;
1480 		}
1481 
1482 		desc.written = 0;
1483 		desc.arg.buf = iov[seg].iov_base + offset;
1484 		desc.count = iov[seg].iov_len - offset;
1485 		if (desc.count == 0)
1486 			continue;
1487 		desc.error = 0;
1488 		do_generic_file_read(filp, ppos, &desc, file_read_actor);
1489 		retval += desc.written;
1490 		if (desc.error) {
1491 			retval = retval ?: desc.error;
1492 			break;
1493 		}
1494 		if (desc.count > 0)
1495 			break;
1496 	}
1497 out:
1498 	blk_finish_plug(&plug);
1499 	return retval;
1500 }
1501 EXPORT_SYMBOL(generic_file_aio_read);
1502 
1503 static ssize_t
1504 do_readahead(struct address_space *mapping, struct file *filp,
1505 	     pgoff_t index, unsigned long nr)
1506 {
1507 	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
1508 		return -EINVAL;
1509 
1510 	force_page_cache_readahead(mapping, filp, index, nr);
1511 	return 0;
1512 }
1513 
1514 SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
1515 {
1516 	ssize_t ret;
1517 	struct file *file;
1518 
1519 	ret = -EBADF;
1520 	file = fget(fd);
1521 	if (file) {
1522 		if (file->f_mode & FMODE_READ) {
1523 			struct address_space *mapping = file->f_mapping;
1524 			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
1525 			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
1526 			unsigned long len = end - start + 1;
1527 			ret = do_readahead(mapping, file, start, len);
1528 		}
1529 		fput(file);
1530 	}
1531 	return ret;
1532 }
1533 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1534 asmlinkage long SyS_readahead(long fd, loff_t offset, long count)
1535 {
1536 	return SYSC_readahead((int) fd, offset, (size_t) count);
1537 }
1538 SYSCALL_ALIAS(sys_readahead, SyS_readahead);
1539 #endif
1540 
1541 #ifdef CONFIG_MMU
1542 /**
1543  * page_cache_read - adds requested page to the page cache if not already there
1544  * @file:	file to read
1545  * @offset:	page index
1546  *
1547  * This adds the requested page to the page cache if it isn't already there,
1548  * and schedules an I/O to read in its contents from disk.
1549  */
1550 static int page_cache_read(struct file *file, pgoff_t offset)
1551 {
1552 	struct address_space *mapping = file->f_mapping;
1553 	struct page *page;
1554 	int ret;
1555 
1556 	do {
1557 		page = page_cache_alloc_cold(mapping);
1558 		if (!page)
1559 			return -ENOMEM;
1560 
1561 		ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1562 		if (ret == 0)
1563 			ret = mapping->a_ops->readpage(file, page);
1564 		else if (ret == -EEXIST)
1565 			ret = 0; /* losing race to add is OK */
1566 
1567 		page_cache_release(page);
1568 
1569 	} while (ret == AOP_TRUNCATED_PAGE);
1570 
1571 	return ret;
1572 }
1573 
1574 #define MMAP_LOTSAMISS  (100)
1575 
1576 /*
1577  * Synchronous readahead happens when we don't even find
1578  * a page in the page cache at all.
1579  */
1580 static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1581 				   struct file_ra_state *ra,
1582 				   struct file *file,
1583 				   pgoff_t offset)
1584 {
1585 	unsigned long ra_pages;
1586 	struct address_space *mapping = file->f_mapping;
1587 
1588 	/* If we don't want any read-ahead, don't bother */
1589 	if (VM_RandomReadHint(vma))
1590 		return;
1591 	if (!ra->ra_pages)
1592 		return;
1593 
1594 	if (VM_SequentialReadHint(vma)) {
1595 		page_cache_sync_readahead(mapping, ra, file, offset,
1596 					  ra->ra_pages);
1597 		return;
1598 	}
1599 
1600 	/* Avoid banging the cache line if not needed */
1601 	if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1602 		ra->mmap_miss++;
1603 
1604 	/*
1605 	 * Do we miss much more than hit in this file? If so,
1606 	 * stop bothering with read-ahead. It will only hurt.
1607 	 */
1608 	if (ra->mmap_miss > MMAP_LOTSAMISS)
1609 		return;
1610 
1611 	/*
1612 	 * mmap read-around
1613 	 */
1614 	ra_pages = max_sane_readahead(ra->ra_pages);
1615 	ra->start = max_t(long, 0, offset - ra_pages / 2);
1616 	ra->size = ra_pages;
1617 	ra->async_size = ra_pages / 4;
1618 	ra_submit(ra, mapping, file);
1619 }
1620 
1621 /*
1622  * Asynchronous readahead happens when we find the page and PG_readahead,
1623  * so we want to possibly extend the readahead further..
1624  */
1625 static void do_async_mmap_readahead(struct vm_area_struct *vma,
1626 				    struct file_ra_state *ra,
1627 				    struct file *file,
1628 				    struct page *page,
1629 				    pgoff_t offset)
1630 {
1631 	struct address_space *mapping = file->f_mapping;
1632 
1633 	/* If we don't want any read-ahead, don't bother */
1634 	if (VM_RandomReadHint(vma))
1635 		return;
1636 	if (ra->mmap_miss > 0)
1637 		ra->mmap_miss--;
1638 	if (PageReadahead(page))
1639 		page_cache_async_readahead(mapping, ra, file,
1640 					   page, offset, ra->ra_pages);
1641 }
1642 
1643 /**
1644  * filemap_fault - read in file data for page fault handling
1645  * @vma:	vma in which the fault was taken
1646  * @vmf:	struct vm_fault containing details of the fault
1647  *
1648  * filemap_fault() is invoked via the vma operations vector for a
1649  * mapped memory region to read in file data during a page fault.
1650  *
1651  * The goto's are kind of ugly, but this streamlines the normal case of having
1652  * it in the page cache, and handles the special cases reasonably without
1653  * having a lot of duplicated code.
1654  */
1655 int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1656 {
1657 	int error;
1658 	struct file *file = vma->vm_file;
1659 	struct address_space *mapping = file->f_mapping;
1660 	struct file_ra_state *ra = &file->f_ra;
1661 	struct inode *inode = mapping->host;
1662 	pgoff_t offset = vmf->pgoff;
1663 	struct page *page;
1664 	pgoff_t size;
1665 	int ret = 0;
1666 
1667 	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1668 	if (offset >= size)
1669 		return VM_FAULT_SIGBUS;
1670 
1671 	/*
1672 	 * Do we have something in the page cache already?
1673 	 */
1674 	page = find_get_page(mapping, offset);
1675 	if (likely(page)) {
1676 		/*
1677 		 * We found the page, so try async readahead before
1678 		 * waiting for the lock.
1679 		 */
1680 		do_async_mmap_readahead(vma, ra, file, page, offset);
1681 	} else {
1682 		/* No page in the page cache at all */
1683 		do_sync_mmap_readahead(vma, ra, file, offset);
1684 		count_vm_event(PGMAJFAULT);
1685 		mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1686 		ret = VM_FAULT_MAJOR;
1687 retry_find:
1688 		page = find_get_page(mapping, offset);
1689 		if (!page)
1690 			goto no_cached_page;
1691 	}
1692 
1693 	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1694 		page_cache_release(page);
1695 		return ret | VM_FAULT_RETRY;
1696 	}
1697 
1698 	/* Did it get truncated? */
1699 	if (unlikely(page->mapping != mapping)) {
1700 		unlock_page(page);
1701 		put_page(page);
1702 		goto retry_find;
1703 	}
1704 	VM_BUG_ON(page->index != offset);
1705 
1706 	/*
1707 	 * We have a locked page in the page cache, now we need to check
1708 	 * that it's up-to-date. If not, it is going to be due to an error.
1709 	 */
1710 	if (unlikely(!PageUptodate(page)))
1711 		goto page_not_uptodate;
1712 
1713 	/*
1714 	 * Found the page and have a reference on it.
1715 	 * We must recheck i_size under page lock.
1716 	 */
1717 	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1718 	if (unlikely(offset >= size)) {
1719 		unlock_page(page);
1720 		page_cache_release(page);
1721 		return VM_FAULT_SIGBUS;
1722 	}
1723 
1724 	vmf->page = page;
1725 	return ret | VM_FAULT_LOCKED;
1726 
1727 no_cached_page:
1728 	/*
1729 	 * We're only likely to ever get here if MADV_RANDOM is in
1730 	 * effect.
1731 	 */
1732 	error = page_cache_read(file, offset);
1733 
1734 	/*
1735 	 * The page we want has now been added to the page cache.
1736 	 * In the unlikely event that someone removed it in the
1737 	 * meantime, we'll just come back here and read it again.
1738 	 */
1739 	if (error >= 0)
1740 		goto retry_find;
1741 
1742 	/*
1743 	 * An error return from page_cache_read can result if the
1744 	 * system is low on memory, or a problem occurs while trying
1745 	 * to schedule I/O.
1746 	 */
1747 	if (error == -ENOMEM)
1748 		return VM_FAULT_OOM;
1749 	return VM_FAULT_SIGBUS;
1750 
1751 page_not_uptodate:
1752 	/*
1753 	 * Umm, take care of errors if the page isn't up-to-date.
1754 	 * Try to re-read it _once_. We do this synchronously,
1755 	 * because there really aren't any performance issues here
1756 	 * and we need to check for errors.
1757 	 */
1758 	ClearPageError(page);
1759 	error = mapping->a_ops->readpage(file, page);
1760 	if (!error) {
1761 		wait_on_page_locked(page);
1762 		if (!PageUptodate(page))
1763 			error = -EIO;
1764 	}
1765 	page_cache_release(page);
1766 
1767 	if (!error || error == AOP_TRUNCATED_PAGE)
1768 		goto retry_find;
1769 
1770 	/* Things didn't work out. Return zero to tell the mm layer so. */
1771 	shrink_readahead_size_eio(file, ra);
1772 	return VM_FAULT_SIGBUS;
1773 }
1774 EXPORT_SYMBOL(filemap_fault);
1775 
1776 const struct vm_operations_struct generic_file_vm_ops = {
1777 	.fault		= filemap_fault,
1778 };
1779 
1780 /* This is used for a general mmap of a disk file */
1781 
1782 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1783 {
1784 	struct address_space *mapping = file->f_mapping;
1785 
1786 	if (!mapping->a_ops->readpage)
1787 		return -ENOEXEC;
1788 	file_accessed(file);
1789 	vma->vm_ops = &generic_file_vm_ops;
1790 	vma->vm_flags |= VM_CAN_NONLINEAR;
1791 	return 0;
1792 }
1793 
1794 /*
1795  * This is for filesystems which do not implement ->writepage.
1796  */
1797 int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1798 {
1799 	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1800 		return -EINVAL;
1801 	return generic_file_mmap(file, vma);
1802 }
1803 #else
1804 int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1805 {
1806 	return -ENOSYS;
1807 }
1808 int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1809 {
1810 	return -ENOSYS;
1811 }
1812 #endif /* CONFIG_MMU */
1813 
1814 EXPORT_SYMBOL(generic_file_mmap);
1815 EXPORT_SYMBOL(generic_file_readonly_mmap);
1816 
1817 static struct page *__read_cache_page(struct address_space *mapping,
1818 				pgoff_t index,
1819 				int (*filler)(void *, struct page *),
1820 				void *data,
1821 				gfp_t gfp)
1822 {
1823 	struct page *page;
1824 	int err;
1825 repeat:
1826 	page = find_get_page(mapping, index);
1827 	if (!page) {
1828 		page = __page_cache_alloc(gfp | __GFP_COLD);
1829 		if (!page)
1830 			return ERR_PTR(-ENOMEM);
1831 		err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
1832 		if (unlikely(err)) {
1833 			page_cache_release(page);
1834 			if (err == -EEXIST)
1835 				goto repeat;
1836 			/* Presumably ENOMEM for radix tree node */
1837 			return ERR_PTR(err);
1838 		}
1839 		err = filler(data, page);
1840 		if (err < 0) {
1841 			page_cache_release(page);
1842 			page = ERR_PTR(err);
1843 		}
1844 	}
1845 	return page;
1846 }
1847 
1848 static struct page *do_read_cache_page(struct address_space *mapping,
1849 				pgoff_t index,
1850 				int (*filler)(void *, struct page *),
1851 				void *data,
1852 				gfp_t gfp)
1853 
1854 {
1855 	struct page *page;
1856 	int err;
1857 
1858 retry:
1859 	page = __read_cache_page(mapping, index, filler, data, gfp);
1860 	if (IS_ERR(page))
1861 		return page;
1862 	if (PageUptodate(page))
1863 		goto out;
1864 
1865 	lock_page(page);
1866 	if (!page->mapping) {
1867 		unlock_page(page);
1868 		page_cache_release(page);
1869 		goto retry;
1870 	}
1871 	if (PageUptodate(page)) {
1872 		unlock_page(page);
1873 		goto out;
1874 	}
1875 	err = filler(data, page);
1876 	if (err < 0) {
1877 		page_cache_release(page);
1878 		return ERR_PTR(err);
1879 	}
1880 out:
1881 	mark_page_accessed(page);
1882 	return page;
1883 }
1884 
1885 /**
1886  * read_cache_page_async - read into page cache, fill it if needed
1887  * @mapping:	the page's address_space
1888  * @index:	the page index
1889  * @filler:	function to perform the read
1890  * @data:	first arg to filler(data, page) function, often left as NULL
1891  *
1892  * Same as read_cache_page, but don't wait for page to become unlocked
1893  * after submitting it to the filler.
1894  *
1895  * Read into the page cache. If a page already exists, and PageUptodate() is
1896  * not set, try to fill the page but don't wait for it to become unlocked.
1897  *
1898  * If the page does not get brought uptodate, return -EIO.
1899  */
1900 struct page *read_cache_page_async(struct address_space *mapping,
1901 				pgoff_t index,
1902 				int (*filler)(void *, struct page *),
1903 				void *data)
1904 {
1905 	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1906 }
1907 EXPORT_SYMBOL(read_cache_page_async);
1908 
1909 static struct page *wait_on_page_read(struct page *page)
1910 {
1911 	if (!IS_ERR(page)) {
1912 		wait_on_page_locked(page);
1913 		if (!PageUptodate(page)) {
1914 			page_cache_release(page);
1915 			page = ERR_PTR(-EIO);
1916 		}
1917 	}
1918 	return page;
1919 }
1920 
1921 /**
1922  * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1923  * @mapping:	the page's address_space
1924  * @index:	the page index
1925  * @gfp:	the page allocator flags to use if allocating
1926  *
1927  * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1928  * any new page allocations done using the specified allocation flags. Note
1929  * that the Radix tree operations will still use GFP_KERNEL, so you can't
1930  * expect to do this atomically or anything like that - but you can pass in
1931  * other page requirements.
1932  *
1933  * If the page does not get brought uptodate, return -EIO.
1934  */
1935 struct page *read_cache_page_gfp(struct address_space *mapping,
1936 				pgoff_t index,
1937 				gfp_t gfp)
1938 {
1939 	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1940 
1941 	return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1942 }
1943 EXPORT_SYMBOL(read_cache_page_gfp);
1944 
1945 /**
1946  * read_cache_page - read into page cache, fill it if needed
1947  * @mapping:	the page's address_space
1948  * @index:	the page index
1949  * @filler:	function to perform the read
1950  * @data:	first arg to filler(data, page) function, often left as NULL
1951  *
1952  * Read into the page cache. If a page already exists, and PageUptodate() is
1953  * not set, try to fill the page then wait for it to become unlocked.
1954  *
1955  * If the page does not get brought uptodate, return -EIO.
1956  */
1957 struct page *read_cache_page(struct address_space *mapping,
1958 				pgoff_t index,
1959 				int (*filler)(void *, struct page *),
1960 				void *data)
1961 {
1962 	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1963 }
1964 EXPORT_SYMBOL(read_cache_page);
1965 
1966 /*
1967  * The logic we want is
1968  *
1969  *	if suid or (sgid and xgrp)
1970  *		remove privs
1971  */
1972 int should_remove_suid(struct dentry *dentry)
1973 {
1974 	mode_t mode = dentry->d_inode->i_mode;
1975 	int kill = 0;
1976 
1977 	/* suid always must be killed */
1978 	if (unlikely(mode & S_ISUID))
1979 		kill = ATTR_KILL_SUID;
1980 
1981 	/*
1982 	 * sgid without any exec bits is just a mandatory locking mark; leave
1983 	 * it alone.  If some exec bits are set, it's a real sgid; kill it.
1984 	 */
1985 	if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
1986 		kill |= ATTR_KILL_SGID;
1987 
1988 	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
1989 		return kill;
1990 
1991 	return 0;
1992 }
1993 EXPORT_SYMBOL(should_remove_suid);
1994 
1995 static int __remove_suid(struct dentry *dentry, int kill)
1996 {
1997 	struct iattr newattrs;
1998 
1999 	newattrs.ia_valid = ATTR_FORCE | kill;
2000 	return notify_change(dentry, &newattrs);
2001 }
2002 
2003 int file_remove_suid(struct file *file)
2004 {
2005 	struct dentry *dentry = file->f_path.dentry;
2006 	struct inode *inode = dentry->d_inode;
2007 	int killsuid;
2008 	int killpriv;
2009 	int error = 0;
2010 
2011 	/* Fast path for nothing security related */
2012 	if (IS_NOSEC(inode))
2013 		return 0;
2014 
2015 	killsuid = should_remove_suid(dentry);
2016 	killpriv = security_inode_need_killpriv(dentry);
2017 
2018 	if (killpriv < 0)
2019 		return killpriv;
2020 	if (killpriv)
2021 		error = security_inode_killpriv(dentry);
2022 	if (!error && killsuid)
2023 		error = __remove_suid(dentry, killsuid);
2024 	if (!error && (inode->i_sb->s_flags & MS_NOSEC))
2025 		inode->i_flags |= S_NOSEC;
2026 
2027 	return error;
2028 }
2029 EXPORT_SYMBOL(file_remove_suid);
2030 
2031 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
2032 			const struct iovec *iov, size_t base, size_t bytes)
2033 {
2034 	size_t copied = 0, left = 0;
2035 
2036 	while (bytes) {
2037 		char __user *buf = iov->iov_base + base;
2038 		int copy = min(bytes, iov->iov_len - base);
2039 
2040 		base = 0;
2041 		left = __copy_from_user_inatomic(vaddr, buf, copy);
2042 		copied += copy;
2043 		bytes -= copy;
2044 		vaddr += copy;
2045 		iov++;
2046 
2047 		if (unlikely(left))
2048 			break;
2049 	}
2050 	return copied - left;
2051 }
2052 
2053 /*
2054  * Copy as much as we can into the page and return the number of bytes which
2055  * were successfully copied.  If a fault is encountered then return the number of
2056  * bytes which were copied.
2057  */
2058 size_t iov_iter_copy_from_user_atomic(struct page *page,
2059 		struct iov_iter *i, unsigned long offset, size_t bytes)
2060 {
2061 	char *kaddr;
2062 	size_t copied;
2063 
2064 	BUG_ON(!in_atomic());
2065 	kaddr = kmap_atomic(page, KM_USER0);
2066 	if (likely(i->nr_segs == 1)) {
2067 		int left;
2068 		char __user *buf = i->iov->iov_base + i->iov_offset;
2069 		left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
2070 		copied = bytes - left;
2071 	} else {
2072 		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2073 						i->iov, i->iov_offset, bytes);
2074 	}
2075 	kunmap_atomic(kaddr, KM_USER0);
2076 
2077 	return copied;
2078 }
2079 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
2080 
2081 /*
2082  * This has the same sideeffects and return value as
2083  * iov_iter_copy_from_user_atomic().
2084  * The difference is that it attempts to resolve faults.
2085  * Page must not be locked.
2086  */
2087 size_t iov_iter_copy_from_user(struct page *page,
2088 		struct iov_iter *i, unsigned long offset, size_t bytes)
2089 {
2090 	char *kaddr;
2091 	size_t copied;
2092 
2093 	kaddr = kmap(page);
2094 	if (likely(i->nr_segs == 1)) {
2095 		int left;
2096 		char __user *buf = i->iov->iov_base + i->iov_offset;
2097 		left = __copy_from_user(kaddr + offset, buf, bytes);
2098 		copied = bytes - left;
2099 	} else {
2100 		copied = __iovec_copy_from_user_inatomic(kaddr + offset,
2101 						i->iov, i->iov_offset, bytes);
2102 	}
2103 	kunmap(page);
2104 	return copied;
2105 }
2106 EXPORT_SYMBOL(iov_iter_copy_from_user);
2107 
2108 void iov_iter_advance(struct iov_iter *i, size_t bytes)
2109 {
2110 	BUG_ON(i->count < bytes);
2111 
2112 	if (likely(i->nr_segs == 1)) {
2113 		i->iov_offset += bytes;
2114 		i->count -= bytes;
2115 	} else {
2116 		const struct iovec *iov = i->iov;
2117 		size_t base = i->iov_offset;
2118 
2119 		/*
2120 		 * The !iov->iov_len check ensures we skip over unlikely
2121 		 * zero-length segments (without overruning the iovec).
2122 		 */
2123 		while (bytes || unlikely(i->count && !iov->iov_len)) {
2124 			int copy;
2125 
2126 			copy = min(bytes, iov->iov_len - base);
2127 			BUG_ON(!i->count || i->count < copy);
2128 			i->count -= copy;
2129 			bytes -= copy;
2130 			base += copy;
2131 			if (iov->iov_len == base) {
2132 				iov++;
2133 				base = 0;
2134 			}
2135 		}
2136 		i->iov = iov;
2137 		i->iov_offset = base;
2138 	}
2139 }
2140 EXPORT_SYMBOL(iov_iter_advance);
2141 
2142 /*
2143  * Fault in the first iovec of the given iov_iter, to a maximum length
2144  * of bytes. Returns 0 on success, or non-zero if the memory could not be
2145  * accessed (ie. because it is an invalid address).
2146  *
2147  * writev-intensive code may want this to prefault several iovecs -- that
2148  * would be possible (callers must not rely on the fact that _only_ the
2149  * first iovec will be faulted with the current implementation).
2150  */
2151 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2152 {
2153 	char __user *buf = i->iov->iov_base + i->iov_offset;
2154 	bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2155 	return fault_in_pages_readable(buf, bytes);
2156 }
2157 EXPORT_SYMBOL(iov_iter_fault_in_readable);
2158 
2159 /*
2160  * Return the count of just the current iov_iter segment.
2161  */
2162 size_t iov_iter_single_seg_count(struct iov_iter *i)
2163 {
2164 	const struct iovec *iov = i->iov;
2165 	if (i->nr_segs == 1)
2166 		return i->count;
2167 	else
2168 		return min(i->count, iov->iov_len - i->iov_offset);
2169 }
2170 EXPORT_SYMBOL(iov_iter_single_seg_count);
2171 
2172 /*
2173  * Performs necessary checks before doing a write
2174  *
2175  * Can adjust writing position or amount of bytes to write.
2176  * Returns appropriate error code that caller should return or
2177  * zero in case that write should be allowed.
2178  */
2179 inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2180 {
2181 	struct inode *inode = file->f_mapping->host;
2182 	unsigned long limit = rlimit(RLIMIT_FSIZE);
2183 
2184         if (unlikely(*pos < 0))
2185                 return -EINVAL;
2186 
2187 	if (!isblk) {
2188 		/* FIXME: this is for backwards compatibility with 2.4 */
2189 		if (file->f_flags & O_APPEND)
2190                         *pos = i_size_read(inode);
2191 
2192 		if (limit != RLIM_INFINITY) {
2193 			if (*pos >= limit) {
2194 				send_sig(SIGXFSZ, current, 0);
2195 				return -EFBIG;
2196 			}
2197 			if (*count > limit - (typeof(limit))*pos) {
2198 				*count = limit - (typeof(limit))*pos;
2199 			}
2200 		}
2201 	}
2202 
2203 	/*
2204 	 * LFS rule
2205 	 */
2206 	if (unlikely(*pos + *count > MAX_NON_LFS &&
2207 				!(file->f_flags & O_LARGEFILE))) {
2208 		if (*pos >= MAX_NON_LFS) {
2209 			return -EFBIG;
2210 		}
2211 		if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2212 			*count = MAX_NON_LFS - (unsigned long)*pos;
2213 		}
2214 	}
2215 
2216 	/*
2217 	 * Are we about to exceed the fs block limit ?
2218 	 *
2219 	 * If we have written data it becomes a short write.  If we have
2220 	 * exceeded without writing data we send a signal and return EFBIG.
2221 	 * Linus frestrict idea will clean these up nicely..
2222 	 */
2223 	if (likely(!isblk)) {
2224 		if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2225 			if (*count || *pos > inode->i_sb->s_maxbytes) {
2226 				return -EFBIG;
2227 			}
2228 			/* zero-length writes at ->s_maxbytes are OK */
2229 		}
2230 
2231 		if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2232 			*count = inode->i_sb->s_maxbytes - *pos;
2233 	} else {
2234 #ifdef CONFIG_BLOCK
2235 		loff_t isize;
2236 		if (bdev_read_only(I_BDEV(inode)))
2237 			return -EPERM;
2238 		isize = i_size_read(inode);
2239 		if (*pos >= isize) {
2240 			if (*count || *pos > isize)
2241 				return -ENOSPC;
2242 		}
2243 
2244 		if (*pos + *count > isize)
2245 			*count = isize - *pos;
2246 #else
2247 		return -EPERM;
2248 #endif
2249 	}
2250 	return 0;
2251 }
2252 EXPORT_SYMBOL(generic_write_checks);
2253 
2254 int pagecache_write_begin(struct file *file, struct address_space *mapping,
2255 				loff_t pos, unsigned len, unsigned flags,
2256 				struct page **pagep, void **fsdata)
2257 {
2258 	const struct address_space_operations *aops = mapping->a_ops;
2259 
2260 	return aops->write_begin(file, mapping, pos, len, flags,
2261 							pagep, fsdata);
2262 }
2263 EXPORT_SYMBOL(pagecache_write_begin);
2264 
2265 int pagecache_write_end(struct file *file, struct address_space *mapping,
2266 				loff_t pos, unsigned len, unsigned copied,
2267 				struct page *page, void *fsdata)
2268 {
2269 	const struct address_space_operations *aops = mapping->a_ops;
2270 
2271 	mark_page_accessed(page);
2272 	return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2273 }
2274 EXPORT_SYMBOL(pagecache_write_end);
2275 
2276 ssize_t
2277 generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2278 		unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2279 		size_t count, size_t ocount)
2280 {
2281 	struct file	*file = iocb->ki_filp;
2282 	struct address_space *mapping = file->f_mapping;
2283 	struct inode	*inode = mapping->host;
2284 	ssize_t		written;
2285 	size_t		write_len;
2286 	pgoff_t		end;
2287 
2288 	if (count != ocount)
2289 		*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2290 
2291 	write_len = iov_length(iov, *nr_segs);
2292 	end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2293 
2294 	written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2295 	if (written)
2296 		goto out;
2297 
2298 	/*
2299 	 * After a write we want buffered reads to be sure to go to disk to get
2300 	 * the new data.  We invalidate clean cached page from the region we're
2301 	 * about to write.  We do this *before* the write so that we can return
2302 	 * without clobbering -EIOCBQUEUED from ->direct_IO().
2303 	 */
2304 	if (mapping->nrpages) {
2305 		written = invalidate_inode_pages2_range(mapping,
2306 					pos >> PAGE_CACHE_SHIFT, end);
2307 		/*
2308 		 * If a page can not be invalidated, return 0 to fall back
2309 		 * to buffered write.
2310 		 */
2311 		if (written) {
2312 			if (written == -EBUSY)
2313 				return 0;
2314 			goto out;
2315 		}
2316 	}
2317 
2318 	written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2319 
2320 	/*
2321 	 * Finally, try again to invalidate clean pages which might have been
2322 	 * cached by non-direct readahead, or faulted in by get_user_pages()
2323 	 * if the source of the write was an mmap'ed region of the file
2324 	 * we're writing.  Either one is a pretty crazy thing to do,
2325 	 * so we don't support it 100%.  If this invalidation
2326 	 * fails, tough, the write still worked...
2327 	 */
2328 	if (mapping->nrpages) {
2329 		invalidate_inode_pages2_range(mapping,
2330 					      pos >> PAGE_CACHE_SHIFT, end);
2331 	}
2332 
2333 	if (written > 0) {
2334 		pos += written;
2335 		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2336 			i_size_write(inode, pos);
2337 			mark_inode_dirty(inode);
2338 		}
2339 		*ppos = pos;
2340 	}
2341 out:
2342 	return written;
2343 }
2344 EXPORT_SYMBOL(generic_file_direct_write);
2345 
2346 /*
2347  * Find or create a page at the given pagecache position. Return the locked
2348  * page. This function is specifically for buffered writes.
2349  */
2350 struct page *grab_cache_page_write_begin(struct address_space *mapping,
2351 					pgoff_t index, unsigned flags)
2352 {
2353 	int status;
2354 	struct page *page;
2355 	gfp_t gfp_notmask = 0;
2356 	if (flags & AOP_FLAG_NOFS)
2357 		gfp_notmask = __GFP_FS;
2358 repeat:
2359 	page = find_lock_page(mapping, index);
2360 	if (page)
2361 		goto found;
2362 
2363 	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
2364 	if (!page)
2365 		return NULL;
2366 	status = add_to_page_cache_lru(page, mapping, index,
2367 						GFP_KERNEL & ~gfp_notmask);
2368 	if (unlikely(status)) {
2369 		page_cache_release(page);
2370 		if (status == -EEXIST)
2371 			goto repeat;
2372 		return NULL;
2373 	}
2374 found:
2375 	wait_on_page_writeback(page);
2376 	return page;
2377 }
2378 EXPORT_SYMBOL(grab_cache_page_write_begin);
2379 
2380 static ssize_t generic_perform_write(struct file *file,
2381 				struct iov_iter *i, loff_t pos)
2382 {
2383 	struct address_space *mapping = file->f_mapping;
2384 	const struct address_space_operations *a_ops = mapping->a_ops;
2385 	long status = 0;
2386 	ssize_t written = 0;
2387 	unsigned int flags = 0;
2388 
2389 	/*
2390 	 * Copies from kernel address space cannot fail (NFSD is a big user).
2391 	 */
2392 	if (segment_eq(get_fs(), KERNEL_DS))
2393 		flags |= AOP_FLAG_UNINTERRUPTIBLE;
2394 
2395 	do {
2396 		struct page *page;
2397 		unsigned long offset;	/* Offset into pagecache page */
2398 		unsigned long bytes;	/* Bytes to write to page */
2399 		size_t copied;		/* Bytes copied from user */
2400 		void *fsdata;
2401 
2402 		offset = (pos & (PAGE_CACHE_SIZE - 1));
2403 		bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2404 						iov_iter_count(i));
2405 
2406 again:
2407 
2408 		/*
2409 		 * Bring in the user page that we will copy from _first_.
2410 		 * Otherwise there's a nasty deadlock on copying from the
2411 		 * same page as we're writing to, without it being marked
2412 		 * up-to-date.
2413 		 *
2414 		 * Not only is this an optimisation, but it is also required
2415 		 * to check that the address is actually valid, when atomic
2416 		 * usercopies are used, below.
2417 		 */
2418 		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2419 			status = -EFAULT;
2420 			break;
2421 		}
2422 
2423 		status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2424 						&page, &fsdata);
2425 		if (unlikely(status))
2426 			break;
2427 
2428 		if (mapping_writably_mapped(mapping))
2429 			flush_dcache_page(page);
2430 
2431 		pagefault_disable();
2432 		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2433 		pagefault_enable();
2434 		flush_dcache_page(page);
2435 
2436 		mark_page_accessed(page);
2437 		status = a_ops->write_end(file, mapping, pos, bytes, copied,
2438 						page, fsdata);
2439 		if (unlikely(status < 0))
2440 			break;
2441 		copied = status;
2442 
2443 		cond_resched();
2444 
2445 		iov_iter_advance(i, copied);
2446 		if (unlikely(copied == 0)) {
2447 			/*
2448 			 * If we were unable to copy any data at all, we must
2449 			 * fall back to a single segment length write.
2450 			 *
2451 			 * If we didn't fallback here, we could livelock
2452 			 * because not all segments in the iov can be copied at
2453 			 * once without a pagefault.
2454 			 */
2455 			bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2456 						iov_iter_single_seg_count(i));
2457 			goto again;
2458 		}
2459 		pos += copied;
2460 		written += copied;
2461 
2462 		balance_dirty_pages_ratelimited(mapping);
2463 
2464 	} while (iov_iter_count(i));
2465 
2466 	return written ? written : status;
2467 }
2468 
2469 ssize_t
2470 generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2471 		unsigned long nr_segs, loff_t pos, loff_t *ppos,
2472 		size_t count, ssize_t written)
2473 {
2474 	struct file *file = iocb->ki_filp;
2475 	ssize_t status;
2476 	struct iov_iter i;
2477 
2478 	iov_iter_init(&i, iov, nr_segs, count, written);
2479 	status = generic_perform_write(file, &i, pos);
2480 
2481 	if (likely(status >= 0)) {
2482 		written += status;
2483 		*ppos = pos + status;
2484   	}
2485 
2486 	return written ? written : status;
2487 }
2488 EXPORT_SYMBOL(generic_file_buffered_write);
2489 
2490 /**
2491  * __generic_file_aio_write - write data to a file
2492  * @iocb:	IO state structure (file, offset, etc.)
2493  * @iov:	vector with data to write
2494  * @nr_segs:	number of segments in the vector
2495  * @ppos:	position where to write
2496  *
2497  * This function does all the work needed for actually writing data to a
2498  * file. It does all basic checks, removes SUID from the file, updates
2499  * modification times and calls proper subroutines depending on whether we
2500  * do direct IO or a standard buffered write.
2501  *
2502  * It expects i_mutex to be grabbed unless we work on a block device or similar
2503  * object which does not need locking at all.
2504  *
2505  * This function does *not* take care of syncing data in case of O_SYNC write.
2506  * A caller has to handle it. This is mainly due to the fact that we want to
2507  * avoid syncing under i_mutex.
2508  */
2509 ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2510 				 unsigned long nr_segs, loff_t *ppos)
2511 {
2512 	struct file *file = iocb->ki_filp;
2513 	struct address_space * mapping = file->f_mapping;
2514 	size_t ocount;		/* original count */
2515 	size_t count;		/* after file limit checks */
2516 	struct inode 	*inode = mapping->host;
2517 	loff_t		pos;
2518 	ssize_t		written;
2519 	ssize_t		err;
2520 
2521 	ocount = 0;
2522 	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2523 	if (err)
2524 		return err;
2525 
2526 	count = ocount;
2527 	pos = *ppos;
2528 
2529 	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2530 
2531 	/* We can write back this queue in page reclaim */
2532 	current->backing_dev_info = mapping->backing_dev_info;
2533 	written = 0;
2534 
2535 	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2536 	if (err)
2537 		goto out;
2538 
2539 	if (count == 0)
2540 		goto out;
2541 
2542 	err = file_remove_suid(file);
2543 	if (err)
2544 		goto out;
2545 
2546 	file_update_time(file);
2547 
2548 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2549 	if (unlikely(file->f_flags & O_DIRECT)) {
2550 		loff_t endbyte;
2551 		ssize_t written_buffered;
2552 
2553 		written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2554 							ppos, count, ocount);
2555 		if (written < 0 || written == count)
2556 			goto out;
2557 		/*
2558 		 * direct-io write to a hole: fall through to buffered I/O
2559 		 * for completing the rest of the request.
2560 		 */
2561 		pos += written;
2562 		count -= written;
2563 		written_buffered = generic_file_buffered_write(iocb, iov,
2564 						nr_segs, pos, ppos, count,
2565 						written);
2566 		/*
2567 		 * If generic_file_buffered_write() retuned a synchronous error
2568 		 * then we want to return the number of bytes which were
2569 		 * direct-written, or the error code if that was zero.  Note
2570 		 * that this differs from normal direct-io semantics, which
2571 		 * will return -EFOO even if some bytes were written.
2572 		 */
2573 		if (written_buffered < 0) {
2574 			err = written_buffered;
2575 			goto out;
2576 		}
2577 
2578 		/*
2579 		 * We need to ensure that the page cache pages are written to
2580 		 * disk and invalidated to preserve the expected O_DIRECT
2581 		 * semantics.
2582 		 */
2583 		endbyte = pos + written_buffered - written - 1;
2584 		err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2585 		if (err == 0) {
2586 			written = written_buffered;
2587 			invalidate_mapping_pages(mapping,
2588 						 pos >> PAGE_CACHE_SHIFT,
2589 						 endbyte >> PAGE_CACHE_SHIFT);
2590 		} else {
2591 			/*
2592 			 * We don't know how much we wrote, so just return
2593 			 * the number of bytes which were direct-written
2594 			 */
2595 		}
2596 	} else {
2597 		written = generic_file_buffered_write(iocb, iov, nr_segs,
2598 				pos, ppos, count, written);
2599 	}
2600 out:
2601 	current->backing_dev_info = NULL;
2602 	return written ? written : err;
2603 }
2604 EXPORT_SYMBOL(__generic_file_aio_write);
2605 
2606 /**
2607  * generic_file_aio_write - write data to a file
2608  * @iocb:	IO state structure
2609  * @iov:	vector with data to write
2610  * @nr_segs:	number of segments in the vector
2611  * @pos:	position in file where to write
2612  *
2613  * This is a wrapper around __generic_file_aio_write() to be used by most
2614  * filesystems. It takes care of syncing the file in case of O_SYNC file
2615  * and acquires i_mutex as needed.
2616  */
2617 ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2618 		unsigned long nr_segs, loff_t pos)
2619 {
2620 	struct file *file = iocb->ki_filp;
2621 	struct inode *inode = file->f_mapping->host;
2622 	struct blk_plug plug;
2623 	ssize_t ret;
2624 
2625 	BUG_ON(iocb->ki_pos != pos);
2626 
2627 	mutex_lock(&inode->i_mutex);
2628 	blk_start_plug(&plug);
2629 	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2630 	mutex_unlock(&inode->i_mutex);
2631 
2632 	if (ret > 0 || ret == -EIOCBQUEUED) {
2633 		ssize_t err;
2634 
2635 		err = generic_write_sync(file, pos, ret);
2636 		if (err < 0 && ret > 0)
2637 			ret = err;
2638 	}
2639 	blk_finish_plug(&plug);
2640 	return ret;
2641 }
2642 EXPORT_SYMBOL(generic_file_aio_write);
2643 
2644 /**
2645  * try_to_release_page() - release old fs-specific metadata on a page
2646  *
2647  * @page: the page which the kernel is trying to free
2648  * @gfp_mask: memory allocation flags (and I/O mode)
2649  *
2650  * The address_space is to try to release any data against the page
2651  * (presumably at page->private).  If the release was successful, return `1'.
2652  * Otherwise return zero.
2653  *
2654  * This may also be called if PG_fscache is set on a page, indicating that the
2655  * page is known to the local caching routines.
2656  *
2657  * The @gfp_mask argument specifies whether I/O may be performed to release
2658  * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2659  *
2660  */
2661 int try_to_release_page(struct page *page, gfp_t gfp_mask)
2662 {
2663 	struct address_space * const mapping = page->mapping;
2664 
2665 	BUG_ON(!PageLocked(page));
2666 	if (PageWriteback(page))
2667 		return 0;
2668 
2669 	if (mapping && mapping->a_ops->releasepage)
2670 		return mapping->a_ops->releasepage(page, gfp_mask);
2671 	return try_to_free_buffers(page);
2672 }
2673 
2674 EXPORT_SYMBOL(try_to_release_page);
2675