aboutsummaryrefslogblamecommitdiffstats
path: root/mm/filemap.c
blob: 8aa344e8848997cb7766b6a874e313a753d3cbb5 (plain) (tree)
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
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
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
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
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398





























                                                               
                    
  






                                                                   



                                                                           
















                                                                      

                                                             




























                                                                       
                                                  































                                                                          
                                  













                                                                      


















                                                                        











                                                                        



                                                      




































































































































                                                                               


                                                                













                                                                          






















































                                                                               
                                               






















                                                                             
                                                               




































































































































                                                                                   

                                        





































                                                                                


                                            












                                                                             
                                                    


























































































                                                                            
                       



































































































































































































































































































































                                                                                   
                                                               


































































































































































































































































































































































































                                                                                                          




                                                 
                                       
         








































































































                                                                              


                                                                                    

                               
 





                                                              
                                                  


                                                                                








































































































































































































                                                                               
      


























                                                                               













                                                                                         





























































































                                                                             




                                                                              
































                                                                            
                                                   




                                     
                                     













                                                                         



                                                     




































                                                                                
                                                            

                                                                           


                                                                         

                                                           
                                 









































                                                                              
              


































































































                                                                               
              























































































































                                                                              
              

































                                                                             
/*
 *	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)
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/aio.h>
#include <linux/kernel_stat.h>
#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>
#include <linux/pagevec.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include "filemap.h"
/*
 * FIXME: remove all knowledge of the buffer layer from the core VM
 */
#include <linux/buffer_head.h> /* for generic_osync_inode */

#include <asm/uaccess.h>
#include <asm/mman.h>

static ssize_t
generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
	loff_t offset, unsigned long nr_segs);

/*
 * 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:
 *
 *  ->i_mmap_lock		(vmtruncate)
 *    ->private_lock		(__free_pte->__set_page_dirty_buffers)
 *      ->swap_lock		(exclusive_swap_page, others)
 *        ->mapping->tree_lock
 *
 *  ->i_sem
 *    ->i_mmap_lock		(truncate->unmap_mapping_range)
 *
 *  ->mmap_sem
 *    ->i_mmap_lock
 *      ->page_table_lock	(various places, mainly in mmap.c)
 *        ->mapping->tree_lock	(arch-dependent flush_dcache_mmap_lock)
 *
 *  ->mmap_sem
 *    ->lock_page		(access_process_vm)
 *
 *  ->mmap_sem
 *    ->i_sem			(msync)
 *
 *  ->i_sem
 *    ->i_alloc_sem             (various)
 *
 *  ->inode_lock
 *    ->sb_lock			(fs/fs-writeback.c)
 *    ->mapping->tree_lock	(__sync_single_inode)
 *
 *  ->i_mmap_lock
 *    ->anon_vma.lock		(vma_adjust)
 *
 *  ->anon_vma.lock
 *    ->page_table_lock		(anon_vma_prepare and various)
 *
 *  ->page_table_lock
 *    ->swap_lock		(try_to_unmap_one)
 *    ->private_lock		(try_to_unmap_one)
 *    ->tree_lock		(try_to_unmap_one)
 *    ->zone.lru_lock		(follow_page->mark_page_accessed)
 *    ->private_lock		(page_remove_rmap->set_page_dirty)
 *    ->tree_lock		(page_remove_rmap->set_page_dirty)
 *    ->inode_lock		(page_remove_rmap->set_page_dirty)
 *    ->inode_lock		(zap_pte_range->set_page_dirty)
 *    ->private_lock		(zap_pte_range->__set_page_dirty_buffers)
 *
 *  ->task->proc_lock
 *    ->dcache_lock		(proc_pid_lookup)
 */

/*
 * Remove a page from the page cache and free it. Caller has to make
 * sure the page is locked and that nobody else uses it - or that usage
 * is safe.  The caller must hold a write_lock on the mapping's tree_lock.
 */
void __remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;

	radix_tree_delete(&mapping->page_tree, page->index);
	page->mapping = NULL;
	mapping->nrpages--;
	pagecache_acct(-1);
}

void remove_from_page_cache(struct page *page)
{
	struct address_space *mapping = page->mapping;

	BUG_ON(!PageLocked(page));

	write_lock_irq(&mapping->tree_lock);
	__remove_from_page_cache(page);
	write_unlock_irq(&mapping->tree_lock);
}

static int sync_page(void *word)
{
	struct address_space *mapping;
	struct page *page;

	page = container_of((page_flags_t *)word, struct page, flags);

	/*
	 * page_mapping() is being called without PG_locked held.
	 * Some knowledge of the state and use of the page is used to
	 * reduce the requirements down to a memory barrier.
	 * The danger here is of a stale page_mapping() return value
	 * indicating a struct address_space different from the one it's
	 * associated with when it is associated with one.
	 * After smp_mb(), it's either the correct page_mapping() for
	 * the page, or an old page_mapping() and the page's own
	 * page_mapping() has gone NULL.
	 * The ->sync_page() address_space operation must tolerate
	 * page_mapping() going NULL. By an amazing coincidence,
	 * this comes about because none of the users of the page
	 * in the ->sync_page() methods make essential use of the
	 * page_mapping(), merely passing the page down to the backing
	 * device's unplug functions when it's non-NULL, which in turn
	 * ignore it for all cases but swap, where only page->private is
	 * of interest. When page_mapping() does go NULL, the entire
	 * call stack gracefully ignores the page and returns.
	 * -- wli
	 */
	smp_mb();
	mapping = page_mapping(page);
	if (mapping && mapping->a_ops && mapping->a_ops->sync_page)
		mapping->a_ops->sync_page(page);
	io_schedule();
	return 0;
}

/**
 * filemap_fdatawrite_range - start writeback against all of a mapping's
 * dirty pages that lie within the byte offsets <start, end>
 * @mapping:	address space structure to write
 * @start:	offset in bytes where the range starts
 * @end:	offset in bytes where the range ends
 * @sync_mode:	enable synchronous operation
 *
 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 * opposed to a regular memory * cleansing writeback.  The difference between
 * these two operations is that if a dirty page/buffer is encountered, it must
 * be waited upon, and not just skipped over.
 */
static int __filemap_fdatawrite_range(struct address_space *mapping,
	loff_t start, loff_t end, int sync_mode)
{
	int ret;
	struct writeback_control wbc = {
		.sync_mode = sync_mode,
		.nr_to_write = mapping->nrpages * 2,
		.start = start,
		.end = end,
	};

	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)
{
	return __filemap_fdatawrite_range(mapping, 0, 0, sync_mode);
}

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

static int filemap_fdatawrite_range(struct address_space *mapping,
	loff_t start, loff_t end)
{
	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}

/*
 * 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);

/*
 * Wait for writeback to complete against pages indexed by start->end
 * inclusive
 */
static int wait_on_page_writeback_range(struct address_space *mapping,
				pgoff_t start, pgoff_t end)
{
	struct pagevec pvec;
	int nr_pages;
	int ret = 0;
	pgoff_t index;

	if (end < start)
		return 0;

	pagevec_init(&pvec, 0);
	index = start;
	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);
			if (PageError(page))
				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;
}

/*
 * Write and wait upon all the pages in the passed range.  This is a "data
 * integrity" operation.  It waits upon in-flight writeout before starting and
 * waiting upon new writeout.  If there was an IO error, return it.
 *
 * We need to re-take i_sem during the generic_osync_inode list walk because
 * it is otherwise livelockable.
 */
int sync_page_range(struct inode *inode, struct address_space *mapping,
			loff_t pos, size_t count)
{
	pgoff_t start = pos >> PAGE_CACHE_SHIFT;
	pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
	int ret;

	if (!mapping_cap_writeback_dirty(mapping) || !count)
		return 0;
	ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
	if (ret == 0) {
		down(&inode->i_sem);
		ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
		up(&inode->i_sem);
	}
	if (ret == 0)
		ret = wait_on_page_writeback_range(mapping, start, end);
	return ret;
}
EXPORT_SYMBOL(sync_page_range);

/*
 * Note: Holding i_sem across sync_page_range_nolock is not a good idea
 * as it forces O_SYNC writers to different parts of the same file
 * to be serialised right until io completion.
 */
static int sync_page_range_nolock(struct inode *inode,
				  struct address_space *mapping,
				  loff_t pos, size_t count)
{
	pgoff_t start = pos >> PAGE_CACHE_SHIFT;
	pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
	int ret;

	if (!mapping_cap_writeback_dirty(mapping) || !count)
		return 0;
	ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
	if (ret == 0)
		ret = generic_osync_inode(inode, mapping, OSYNC_METADATA);
	if (ret == 0)
		ret = wait_on_page_writeback_range(mapping, start, end);
	return ret;
}

/**
 * filemap_fdatawait - walk the list of under-writeback pages of the given
 *     address space and wait for all of them.
 *
 * @mapping: address space structure to wait for
 */
int filemap_fdatawait(struct address_space *mapping)
{
	loff_t i_size = i_size_read(mapping->host);

	if (i_size == 0)
		return 0;

	return wait_on_page_writeback_range(mapping, 0,
				(i_size - 1) >> PAGE_CACHE_SHIFT);
}
EXPORT_SYMBOL(filemap_fdatawait);

int filemap_write_and_wait(struct address_space *mapping)
{
	int retval = 0;

	if (mapping->nrpages) {
		retval = filemap_fdatawrite(mapping);
		if (retval == 0)
			retval = filemap_fdatawait(mapping);
	}
	return retval;
}

int filemap_write_and_wait_range(struct address_space *mapping,
				 loff_t lstart, loff_t lend)
{
	int retval = 0;

	if (mapping->nrpages) {
		retval = __filemap_fdatawrite_range(mapping, lstart, lend,
						    WB_SYNC_ALL);
		if (retval == 0)
			retval = wait_on_page_writeback_range(mapping,
						    lstart >> PAGE_CACHE_SHIFT,
						    lend >> PAGE_CACHE_SHIFT);
	}
	return retval;
}

/*
 * This function is used to add newly allocated pagecache pages:
 * the page is new, so we can just run SetPageLocked() against it.
 * The other page state flags were set by rmqueue().
 *
 * This function does not add the page to the LRU.  The caller must do that.
 */
int add_to_page_cache(struct page *page, struct address_space *mapping,
		pgoff_t offset, gfp_t gfp_mask)
{
	int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);

	if (error == 0) {
		write_lock_irq(&mapping->tree_lock);
		error = radix_tree_insert(&mapping->page_tree, offset, page);
		if (!error) {
			page_cache_get(page);
			SetPageLocked(page);
			page->mapping = mapping;
			page->index = offset;
			mapping->nrpages++;
			pagecache_acct(1);
		}
		write_unlock_irq(&mapping->tree_lock);
		radix_tree_preload_end();
	}
	return error;
}

EXPORT_SYMBOL(add_to_page_cache);

int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
				pgoff_t offset, gfp_t gfp_mask)
{
	int ret = add_to_page_cache(page, mapping, offset, gfp_mask);
	if (ret == 0)
		lru_cache_add(page);
	return ret;
}

/*
 * 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);
}

void fastcall wait_on_page_bit(struct page *page, int bit_nr)
{
	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);

	if (test_bit(bit_nr, &page->flags))
		__wait_on_bit(page_waitqueue(page), &wait, sync_page,
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(wait_on_page_bit);

/**
 * unlock_page() - unlock a locked page
 *
 * @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.
 *
 * The first mb is necessary to safely close the critical section opened by the
 * TestSetPageLocked(), the second 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()).
 */
void fastcall unlock_page(struct page *page)
{
	smp_mb__before_clear_bit();
	if (!TestClearPageLocked(page))
		BUG();
	smp_mb__after_clear_bit(); 
	wake_up_page(page, PG_locked);
}
EXPORT_SYMBOL(unlock_page);

/*
 * End writeback against a page.
 */
void end_page_writeback(struct page *page)
{
	if (!TestClearPageReclaim(page) || rotate_reclaimable_page(page)) {
		if (!test_clear_page_writeback(page))
			BUG();
	}
	smp_mb__after_clear_bit();
	wake_up_page(page, PG_writeback);
}
EXPORT_SYMBOL(end_page_writeback);

/*
 * Get a lock on the page, assuming we need to sleep to get it.
 *
 * Ugly: running sync_page() in state TASK_UNINTERRUPTIBLE is scary.  If some
 * random driver's requestfn sets TASK_RUNNING, we could busywait.  However
 * chances are that on the second loop, the block layer's plug list is empty,
 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
 */
void fastcall __lock_page(struct page *page)
{
	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);

	__wait_on_bit_lock(page_waitqueue(page), &wait, sync_page,
							TASK_UNINTERRUPTIBLE);
}
EXPORT_SYMBOL(__lock_page);

/*
 * a rather lightweight function, finding and getting a reference to a
 * hashed page atomically.
 */
struct page * find_get_page(struct address_space *mapping, unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page)
		page_cache_get(page);
	read_unlock_irq(&mapping->tree_lock);
	return page;
}

EXPORT_SYMBOL(find_get_page);

/*
 * Same as above, but trylock it instead of incrementing the count.
 */
struct page *find_trylock_page(struct address_space *mapping, unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page && TestSetPageLocked(page))
		page = NULL;
	read_unlock_irq(&mapping->tree_lock);
	return page;
}

EXPORT_SYMBOL(find_trylock_page);

/**
 * find_lock_page - locate, pin and lock a pagecache page
 *
 * @mapping: the address_space to search
 * @offset: the page index
 *
 * 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.
 */
struct page *find_lock_page(struct address_space *mapping,
				unsigned long offset)
{
	struct page *page;

	read_lock_irq(&mapping->tree_lock);
repeat:
	page = radix_tree_lookup(&mapping->page_tree, offset);
	if (page) {
		page_cache_get(page);
		if (TestSetPageLocked(page)) {
			read_unlock_irq(&mapping->tree_lock);
			lock_page(page);
			read_lock_irq(&mapping->tree_lock);

			/* Has the page been truncated while we slept? */
			if (page->mapping != mapping || page->index != offset) {
				unlock_page(page);
				page_cache_release(page);
				goto repeat;
			}
		}
	}
	read_unlock_irq(&mapping->tree_lock);
	return page;
}

EXPORT_SYMBOL(find_lock_page);

/**
 * find_or_create_page - locate or add a pagecache page
 *
 * @mapping: the page's address_space
 * @index: the page's index into the mapping
 * @gfp_mask: page allocation mode
 *
 * 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,
		unsigned long index, gfp_t gfp_mask)
{
	struct page *page, *cached_page = NULL;
	int err;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
		if (!cached_page) {
			cached_page = alloc_page(gfp_mask);
			if (!cached_page)
				return NULL;
		}
		err = add_to_page_cache_lru(cached_page, mapping,
					index, gfp_mask);
		if (!err) {
			page = cached_page;
			cached_page = NULL;
		} else if (err == -EEXIST)
			goto repeat;
	}
	if (cached_page)
		page_cache_release(cached_page);
	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)
{
	unsigned int i;
	unsigned int ret;

	read_lock_irq(&mapping->tree_lock);
	ret = radix_tree_gang_lookup(&mapping->page_tree,
				(void **)pages, start, nr_pages);
	for (i = 0; i < ret; i++)
		page_cache_get(pages[i]);
	read_unlock_irq(&mapping->tree_lock);
	return ret;
}

/*
 * Like find_get_pages, except we only return pages which are tagged with
 * `tag'.   We update *index to index the next page for the traversal.
 */
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
			int tag, unsigned int nr_pages, struct page **pages)
{
	unsigned int i;
	unsigned int ret;

	read_lock_irq(&mapping->tree_lock);
	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
				(void **)pages, *index, nr_pages, tag);
	for (i = 0; i < ret; i++)
		page_cache_get(pages[i]);
	if (ret)
		*index = pages[ret - 1]->index + 1;
	read_unlock_irq(&mapping->tree_lock);
	return ret;
}

/*
 * Same as grab_cache_page, but do not wait if the page is unavailable.
 * 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 *
grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
{
	struct page *page = find_get_page(mapping, index);
	gfp_t gfp_mask;

	if (page) {
		if (!TestSetPageLocked(page))
			return page;
		page_cache_release(page);
		return NULL;
	}
	gfp_mask = mapping_gfp_mask(mapping) & ~__GFP_FS;
	page = alloc_pages(gfp_mask, 0);
	if (page && add_to_page_cache_lru(page, mapping, index, gfp_mask)) {
		page_cache_release(page);
		page = NULL;
	}
	return page;
}

EXPORT_SYMBOL(grab_cache_page_nowait);

/*
 * This is a generic file read routine, and uses the
 * mapping->a_ops->readpage() function for the actual low-level
 * stuff.
 *
 * This is really ugly. But the goto's actually try to clarify some
 * of the logic when it comes to error handling etc.
 *
 * Note the struct file* is only passed for the use of readpage.  It may be
 * NULL.
 */
void do_generic_mapping_read(struct address_space *mapping,
			     struct file_ra_state *_ra,
			     struct file *filp,
			     loff_t *ppos,
			     read_descriptor_t *desc,
			     read_actor_t actor)
{
	struct inode *inode = mapping->host;
	unsigned long index;
	unsigned long end_index;
	unsigned long offset;
	unsigned long last_index;
	unsigned long next_index;
	unsigned long prev_index;
	loff_t isize;
	struct page *cached_page;
	int error;
	struct file_ra_state ra = *_ra;

	cached_page = NULL;
	index = *ppos >> PAGE_CACHE_SHIFT;
	next_index = index;
	prev_index = ra.prev_page;
	last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
	offset = *ppos & ~PAGE_CACHE_MASK;

	isize = i_size_read(inode);
	if (!isize)
		goto out;

	end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
	for (;;) {
		struct page *page;
		unsigned long nr, ret;

		/* nr is the maximum number of bytes to copy from this page */
		nr = PAGE_CACHE_SIZE;
		if (index >= end_index) {
			if (index > end_index)
				goto out;
			nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
			if (nr <= offset) {
				goto out;
			}
		}
		nr = nr - offset;

		cond_resched();
		if (index == next_index)
			next_index = page_cache_readahead(mapping, &ra, filp,
					index, last_index - index);

find_page:
		page = find_get_page(mapping, index);
		if (unlikely(page == NULL)) {
			handle_ra_miss(mapping, &ra, index);
			goto no_cached_page;
		}
		if (!PageUptodate(page))
			goto page_not_up_to_date;
page_ok:

		/* 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);

		/*
		 * When (part of) the same page is read multiple times
		 * in succession, only mark it as accessed the first time.
		 */
		if (prev_index != index)
			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;

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

page_not_up_to_date:
		/* Get exclusive access to the page ... */
		lock_page(page);

		/* Did it get unhashed before we got the lock? */
		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:
		/* Start the actual read. The read will unlock the page. */
		error = mapping->a_ops->readpage(filp, page);

		if (unlikely(error))
			goto readpage_error;

		if (!PageUptodate(page)) {
			lock_page(page);
			if (!PageUptodate(page)) {
				if (page->mapping == NULL) {
					/*
					 * invalidate_inode_pages got it
					 */
					unlock_page(page);
					page_cache_release(page);
					goto find_page;
				}
				unlock_page(page);
				error = -EIO;
				goto readpage_error;
			}
			unlock_page(page);
		}

		/*
		 * i_size must be checked after we have done ->readpage.
		 *
		 * Checking i_size after the readpage 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;
		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..
		 */
		if (!cached_page) {
			cached_page = page_cache_alloc_cold(mapping);
			if (!cached_page) {
				desc->error = -ENOMEM;
				goto out;
			}
		}
		error = add_to_page_cache_lru(cached_page, mapping,
						index, GFP_KERNEL);
		if (error) {
			if (error == -EEXIST)
				goto find_page;
			desc->error = error;
			goto out;
		}
		page = cached_page;
		cached_page = NULL;
		goto readpage;
	}

out:
	*_ra = ra;

	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
	if (cached_page)
		page_cache_release(cached_page);
	if (filp)
		file_accessed(filp);
}

EXPORT_SYMBOL(do_generic_mapping_read);

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)) {
		kaddr = kmap_atomic(page, KM_USER0);
		left = __copy_to_user_inatomic(desc->arg.buf,
						kaddr + offset, size);
		kunmap_atomic(kaddr, KM_USER0);
		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;
}

/*
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
__generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t *ppos)
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
	unsigned long seg;
	size_t count;

	count = 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.
		 */
		count += iv->iov_len;
		if (unlikely((ssize_t)(count|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		nr_segs = seg;
		count -= iv->iov_len;	/* This segment is no good */
		break;
	}

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
		loff_t pos = *ppos, size;
		struct address_space *mapping;
		struct inode *inode;

		mapping = filp->f_mapping;
		inode = mapping->host;
		retval = 0;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);
		if (pos < size) {
			retval = generic_file_direct_IO(READ, iocb,
						iov, pos, nr_segs);
			if (retval > 0 && !is_sync_kiocb(iocb))
				retval = -EIOCBQUEUED;
			if (retval > 0)
				*ppos = pos + retval;
		}
		file_accessed(filp);
		goto out;
	}

	retval = 0;
	if (count) {
		for (seg = 0; seg < nr_segs; seg++) {
			read_descriptor_t desc;

			desc.written = 0;
			desc.arg.buf = iov[seg].iov_base;
			desc.count = iov[seg].iov_len;
			if (desc.count == 0)
				continue;
			desc.error = 0;
			do_generic_file_read(filp,ppos,&desc,file_read_actor);
			retval += desc.written;
			if (!retval) {
				retval = desc.error;
				break;
			}
		}
	}
out:
	return retval;
}

EXPORT_SYMBOL(__generic_file_aio_read);

ssize_t
generic_file_aio_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
{
	struct iovec local_iov = { .iov_base = buf, .iov_len = count };

	BUG_ON(iocb->ki_pos != pos);
	return __generic_file_aio_read(iocb, &local_iov, 1, &iocb->ki_pos);
}

EXPORT_SYMBOL(generic_file_aio_read);

ssize_t
generic_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
{
	struct iovec local_iov = { .iov_base = buf, .iov_len = count };
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, filp);
	ret = __generic_file_aio_read(&kiocb, &local_iov, 1, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}

EXPORT_SYMBOL(generic_file_read);

int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size)
{
	ssize_t written;
	unsigned long count = desc->count;
	struct file *file = desc->arg.data;

	if (size > count)
		size = count;

	written = file->f_op->sendpage(file, page, offset,
				       size, &file->f_pos, size<count);
	if (written < 0) {
		desc->error = written;
		written = 0;
	}
	desc->count = count - written;
	desc->written += written;
	return written;
}

ssize_t generic_file_sendfile(struct file *in_file, loff_t *ppos,
			 size_t count, read_actor_t actor, void *target)
{
	read_descriptor_t desc;

	if (!count)
		return 0;

	desc.written = 0;
	desc.count = count;
	desc.arg.data = target;
	desc.error = 0;

	do_generic_file_read(in_file, ppos, &desc, actor);
	if (desc.written)
		return desc.written;
	return desc.error;
}

EXPORT_SYMBOL(generic_file_sendfile);

static ssize_t
do_readahead(struct address_space *mapping, struct file *filp,
	     unsigned long index, unsigned long nr)
{
	if (!mapping || !mapping->a_ops || !mapping->a_ops->readpage)
		return -EINVAL;

	force_page_cache_readahead(mapping, filp, index,
					max_sane_readahead(nr));
	return 0;
}

asmlinkage ssize_t sys_readahead(int fd, loff_t offset, size_t count)
{
	ssize_t ret;
	struct file *file;

	ret = -EBADF;
	file = fget(fd);
	if (file) {
		if (file->f_mode & FMODE_READ) {
			struct address_space *mapping = file->f_mapping;
			unsigned long start = offset >> PAGE_CACHE_SHIFT;
			unsigned long end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
			unsigned long len = end - start + 1;
			ret = do_readahead(mapping, file, start, len);
		}
		fput(file);
	}
	return ret;
}

#ifdef CONFIG_MMU
/*
 * 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.
 */
static int FASTCALL(page_cache_read(struct file * file, unsigned long offset));
static int fastcall page_cache_read(struct file * file, unsigned long offset)
{
	struct address_space *mapping = file->f_mapping;
	struct page *page; 
	int error;

	page = page_cache_alloc_cold(mapping);
	if (!page)
		return -ENOMEM;

	error = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
	if (!error) {
		error = mapping->a_ops->readpage(file, page);
		page_cache_release(page);
		return error;
	}

	/*
	 * We arrive here in the unlikely event that someone 
	 * raced with us and added our page to the cache first
	 * or we are out of memory for radix-tree nodes.
	 */
	page_cache_release(page);
	return error == -EEXIST ? 0 : error;
}

#define MMAP_LOTSAMISS  (100)

/*
 * filemap_nopage() is invoked via the vma operations vector for a
 * 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.
 */
struct page *filemap_nopage(struct vm_area_struct *area,
				unsigned long address, int *type)
{
	int error;
	struct file *file = area->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct file_ra_state *ra = &file->f_ra;
	struct inode *inode = mapping->host;
	struct page *page;
	unsigned long size, pgoff;
	int did_readaround = 0, majmin = VM_FAULT_MINOR;

	pgoff = ((address-area->vm_start) >> PAGE_CACHE_SHIFT) + area->vm_pgoff;

retry_all:
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	if (pgoff >= size)
		goto outside_data_content;

	/* If we don't want any read-ahead, don't bother */
	if (VM_RandomReadHint(area))
		goto no_cached_page;

	/*
	 * The readahead code wants to be told about each and every page
	 * so it can build and shrink its windows appropriately
	 *
	 * For sequential accesses, we use the generic readahead logic.
	 */
	if (VM_SequentialReadHint(area))
		page_cache_readahead(mapping, ra, file, pgoff, 1);

	/*
	 * Do we have something in the page cache already?
	 */
retry_find:
	page = find_get_page(mapping, pgoff);
	if (!page) {
		unsigned long ra_pages;

		if (VM_SequentialReadHint(area)) {
			handle_ra_miss(mapping, ra, pgoff);
			goto no_cached_page;
		}
		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 > ra->mmap_hit + MMAP_LOTSAMISS)
			goto no_cached_page;

		/*
		 * To keep the pgmajfault counter straight, we need to
		 * check did_readaround, as this is an inner loop.
		 */
		if (!did_readaround) {
			majmin = VM_FAULT_MAJOR;
			inc_page_state(pgmajfault);
		}
		did_readaround = 1;
		ra_pages = max_sane_readahead(file->f_ra.ra_pages);
		if (ra_pages) {
			pgoff_t start = 0;

			if (pgoff > ra_pages / 2)
				start = pgoff - ra_pages / 2;
			do_page_cache_readahead(mapping, file, start, ra_pages);
		}
		page = find_get_page(mapping, pgoff);
		if (!page)
			goto no_cached_page;
	}

	if (!did_readaround)
		ra->mmap_hit++;

	/*
	 * Ok, found a page in the page cache, now we need to check
	 * that it's up-to-date.
	 */
	if (!PageUptodate(page))
		goto page_not_uptodate;

success:
	/*
	 * Found the page and have a reference on it.
	 */
	mark_page_accessed(page);
	if (type)
		*type = majmin;
	return page;

outside_data_content:
	/*
	 * An external ptracer can access pages that normally aren't
	 * accessible..
	 */
	if (area->vm_mm == current->mm)
		return NULL;
	/* Fall through to the non-read-ahead case */
no_cached_page:
	/*
	 * We're only likely to ever get here if MADV_RANDOM is in
	 * effect.
	 */
	error = page_cache_read(file, pgoff);
	grab_swap_token();

	/*
	 * 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)
		return NOPAGE_OOM;
	return NULL;

page_not_uptodate:
	if (!did_readaround) {
		majmin = VM_FAULT_MAJOR;
		inc_page_state(pgmajfault);
	}
	lock_page(page);

	/* Did it get unhashed while we waited for it? */
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry_all;
	}

	/* Did somebody else get it up-to-date? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

	if (!mapping->a_ops->readpage(file, page)) {
		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
	}

	/*
	 * 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.
	 */
	lock_page(page);

	/* Somebody truncated the page on us? */
	if (!page->mapping) {
		unlock_page(page);
		page_cache_release(page);
		goto retry_all;
	}

	/* Somebody else successfully read it in? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}
	ClearPageError(page);
	if (!mapping->a_ops->readpage(file, page)) {
		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
	}

	/*
	 * Things didn't work out. Return zero to tell the
	 * mm layer so, possibly freeing the page cache page first.
	 */
	page_cache_release(page);
	return NULL;
}

EXPORT_SYMBOL(filemap_nopage);

static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
					int nonblock)
{
	struct address_space *mapping = file->f_mapping;
	struct page *page;
	int error;

	/*
	 * Do we have something in the page cache already?
	 */
retry_find:
	page = find_get_page(mapping, pgoff);
	if (!page) {
		if (nonblock)
			return NULL;
		goto no_cached_page;
	}

	/*
	 * Ok, found a page in the page cache, now we need to check
	 * that it's up-to-date.
	 */
	if (!PageUptodate(page)) {
		if (nonblock) {
			page_cache_release(page);
			return NULL;
		}
		goto page_not_uptodate;
	}

success:
	/*
	 * Found the page and have a reference on it.
	 */
	mark_page_accessed(page);
	return page;

no_cached_page:
	error = page_cache_read(file, pgoff);

	/*
	 * 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.
	 */
	return NULL;

page_not_uptodate:
	lock_page(page);

	/* Did it get unhashed while we waited for it? */
	if (!page->mapping) {
		unlock_page(page);
		goto err;
	}

	/* Did somebody else get it up-to-date? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

	if (!mapping->a_ops->readpage(file, page)) {
		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
	}

	/*
	 * 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.
	 */
	lock_page(page);

	/* Somebody truncated the page on us? */
	if (!page->mapping) {
		unlock_page(page);
		goto err;
	}
	/* Somebody else successfully read it in? */
	if (PageUptodate(page)) {
		unlock_page(page);
		goto success;
	}

	ClearPageError(page);
	if (!mapping->a_ops->readpage(file, page)) {
		wait_on_page_locked(page);
		if (PageUptodate(page))
			goto success;
	}

	/*
	 * Things didn't work out. Return zero to tell the
	 * mm layer so, possibly freeing the page cache page first.
	 */
err:
	page_cache_release(page);

	return NULL;
}

int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
		unsigned long len, pgprot_t prot, unsigned long pgoff,
		int nonblock)
{
	struct file *file = vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	unsigned long size;
	struct mm_struct *mm = vma->vm_mm;
	struct page *page;
	int err;

	if (!nonblock)
		force_page_cache_readahead(mapping, vma->vm_file,
					pgoff, len >> PAGE_CACHE_SHIFT);

repeat:
	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
	if (pgoff + (len >> PAGE_CACHE_SHIFT) > size)
		return -EINVAL;

	page = filemap_getpage(file, pgoff, nonblock);

	/* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
	 * done in shmem_populate calling shmem_getpage */
	if (!page && !nonblock)
		return -ENOMEM;

	if (page) {
		err = install_page(mm, vma, addr, page, prot);
		if (err) {
			page_cache_release(page);
			return err;
		}
	} else if (vma->vm_flags & VM_NONLINEAR) {
		/* No page was found just because we can't read it in now (being
		 * here implies nonblock != 0), but the page may exist, so set
		 * the PTE to fault it in later. */
		err = install_file_pte(mm, vma, addr, pgoff, prot);
		if (err)
			return err;
	}

	len -= PAGE_SIZE;
	addr += PAGE_SIZE;
	pgoff++;
	if (len)
		goto repeat;

	return 0;
}

struct vm_operations_struct generic_file_vm_ops = {
	.nopage		= filemap_nopage,
	.populate	= filemap_populate,
};

/* 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;
}
EXPORT_SYMBOL(filemap_populate);

/*
 * 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);

static inline struct page *__read_cache_page(struct address_space *mapping,
				unsigned long index,
				int (*filler)(void *,struct page*),
				void *data)
{
	struct page *page, *cached_page = NULL;
	int err;
repeat:
	page = find_get_page(mapping, index);
	if (!page) {
		if (!cached_page) {
			cached_page = page_cache_alloc_cold(mapping);
			if (!cached_page)
				return ERR_PTR(-ENOMEM);
		}
		err = add_to_page_cache_lru(cached_page, mapping,
					index, GFP_KERNEL);
		if (err == -EEXIST)
			goto repeat;
		if (err < 0) {
			/* Presumably ENOMEM for radix tree node */
			page_cache_release(cached_page);
			return ERR_PTR(err);
		}
		page = cached_page;
		cached_page = NULL;
		err = filler(data, page);
		if (err < 0) {
			page_cache_release(page);
			page = ERR_PTR(err);
		}
	}
	if (cached_page)
		page_cache_release(cached_page);
	return page;
}

/*
 * Read into the page cache. If a page already exists,
 * and PageUptodate() is not set, try to fill the page.
 */
struct page *read_cache_page(struct address_space *mapping,
				unsigned long index,
				int (*filler)(void *,struct page*),
				void *data)
{
	struct page *page;
	int err;

retry:
	page = __read_cache_page(mapping, index, filler, data);
	if (IS_ERR(page))
		goto out;
	mark_page_accessed(page);
	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);
		page = ERR_PTR(err);
	}
 out:
	return page;
}

EXPORT_SYMBOL(read_cache_page);

/*
 * If the page was newly created, increment its refcount and add it to the
 * caller's lru-buffering pagevec.  This function is specifically for
 * generic_file_write().
 */
static inline struct page *
__grab_cache_page(struct address_space *mapping, unsigned long index,
			struct page **cached_page, struct pagevec *lru_pvec)
{
	int err;
	struct page *page;
repeat:
	page = find_lock_page(mapping, index);
	if (!page) {
		if (!*cached_page) {
			*cached_page = page_cache_alloc(mapping);
			if (!*cached_page)
				return NULL;
		}
		err = add_to_page_cache(*cached_page, mapping,
					index, GFP_KERNEL);
		if (err == -EEXIST)
			goto repeat;
		if (err == 0) {
			page = *cached_page;
			page_cache_get(page);
			if (!pagevec_add(lru_pvec, page))
				__pagevec_lru_add(lru_pvec);
			*cached_page = NULL;
		}
	}
	return page;
}

/*
 * The logic we want is
 *
 *	if suid or (sgid and xgrp)
 *		remove privs
 */
int remove_suid(struct dentry *dentry)
{
	mode_t mode = dentry->d_inode->i_mode;
	int kill = 0;
	int result = 0;

	/* suid always must be killed */
	if (unlikely(mode & S_ISUID))
		kill = ATTR_KILL_SUID;

	/*
	 * sgid without any exec bits is just a mandatory locking mark; leave
	 * it alone.  If some exec bits are set, it's a real sgid; kill it.
	 */
	if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
		kill |= ATTR_KILL_SGID;

	if (unlikely(kill && !capable(CAP_FSETID))) {
		struct iattr newattrs;

		newattrs.ia_valid = ATTR_FORCE | kill;
		result = notify_change(dentry, &newattrs);
	}
	return result;
}
EXPORT_SYMBOL(remove_suid);

size_t
__filemap_copy_from_user_iovec(char *vaddr, 
			const struct iovec *iov, size_t base, size_t bytes)
{
	size_t copied = 0, left = 0;

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

		base = 0;
		left = __copy_from_user_inatomic(vaddr, buf, copy);
		copied += copy;
		bytes -= copy;
		vaddr += copy;
		iov++;

		if (unlikely(left)) {
			/* zero the rest of the target like __copy_from_user */
			if (bytes)
				memset(vaddr, 0, bytes);
			break;
		}
	}
	return copied - left;
}

/*
 * Performs necessary checks before doing a write
 *
 * Can adjust writing position aor amount of bytes to write.
 * 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;
	unsigned long limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;

        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) {
			send_sig(SIGXFSZ, current, 0);
			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) {
				send_sig(SIGXFSZ, current, 0);
				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 {
		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;
	}
	return 0;
}
EXPORT_SYMBOL(generic_write_checks);

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;

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

	written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
	if (written > 0) {
		loff_t end = pos + written;
		if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode,  end);
			mark_inode_dirty(inode);
		}
		*ppos = end;
	}

	/*
	 * Sync the fs metadata but not the minor inode changes and
	 * of course not the data as we did direct DMA for the IO.
	 * i_sem is held, which protects generic_osync_inode() from
	 * livelocking.
	 */
	if (written >= 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err = generic_osync_inode(inode, mapping, OSYNC_METADATA);
		if (err < 0)
			written = err;
	}
	if (written == count && !is_sync_kiocb(iocb))
		written = -EIOCBQUEUED;
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

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;
	struct address_space * mapping = file->f_mapping;
	struct address_space_operations *a_ops = mapping->a_ops;
	struct inode 	*inode = mapping->host;
	long		status = 0;
	struct page	*page;
	struct page	*cached_page = NULL;
	size_t		bytes;
	struct pagevec	lru_pvec;
	const struct iovec *cur_iov = iov; /* current iovec */
	size_t		iov_base = 0;	   /* offset in the current iovec */
	char __user	*buf;

	pagevec_init(&lru_pvec, 0);

	/*
	 * handle partial DIO write.  Adjust cur_iov if needed.
	 */
	if (likely(nr_segs == 1))
		buf = iov->iov_base + written;
	else {
		filemap_set_next_iovec(&cur_iov, &iov_base, written);
		buf = cur_iov->iov_base + iov_base;
	}

	do {
		unsigned long index;
		unsigned long offset;
		unsigned long maxlen;
		size_t copied;

		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
		index = pos >> PAGE_CACHE_SHIFT;
		bytes = PAGE_CACHE_SIZE - offset;
		if (bytes > count)
			bytes = count;

		/*
		 * 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.
		 */
		maxlen = cur_iov->iov_len - iov_base;
		if (maxlen > bytes)
			maxlen = bytes;
		fault_in_pages_readable(buf, maxlen);

		page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
		if (!page) {
			status = -ENOMEM;
			break;
		}

		status = a_ops->prepare_write(file, page, offset, offset+bytes);
		if (unlikely(status)) {
			loff_t isize = i_size_read(inode);
			/*
			 * prepare_write() may have instantiated a few blocks
			 * outside i_size.  Trim these off again.
			 */
			unlock_page(page);
			page_cache_release(page);
			if (pos + bytes > isize)
				vmtruncate(inode, isize);
			break;
		}
		if (likely(nr_segs == 1))
			copied = filemap_copy_from_user(page, offset,
							buf, bytes);
		else
			copied = filemap_copy_from_user_iovec(page, offset,
						cur_iov, iov_base, bytes);
		flush_dcache_page(page);
		status = a_ops->commit_write(file, page, offset, offset+bytes);
		if (likely(copied > 0)) {
			if (!status)
				status = copied;

			if (status >= 0) {
				written += status;
				count -= status;
				pos += status;
				buf += status;
				if (unlikely(nr_segs > 1)) {
					filemap_set_next_iovec(&cur_iov,
							&iov_base, status);
					if (count)
						buf = cur_iov->iov_base +
							iov_base;
				} else {
					iov_base += status;
				}
			}
		}
		if (unlikely(copied != bytes))
			if (status >= 0)
				status = -EFAULT;
		unlock_page(page);
		mark_page_accessed(page);
		page_cache_release(page);
		if (status < 0)
			break;
		balance_dirty_pages_ratelimited(mapping);
		cond_resched();
	} while (count);
	*ppos = pos;

	if (cached_page)
		page_cache_release(cached_page);

	/*
	 * For now, when the user asks for O_SYNC, we'll actually give O_DSYNC
	 */
	if (likely(status >= 0)) {
		if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
			if (!a_ops->writepage || !is_sync_kiocb(iocb))
				status = generic_osync_inode(inode, mapping,
						OSYNC_METADATA|OSYNC_DATA);
		}
  	}
	
	/*
	 * If we get here for O_DIRECT writes then we must have fallen through
	 * to buffered writes (block instantiation inside i_size).  So we sync
	 * the file data here, to try to honour O_DIRECT expectations.
	 */
	if (unlikely(file->f_flags & O_DIRECT) && written)
		status = filemap_write_and_wait(mapping);

	pagevec_lru_add(&lru_pvec);
	return written ? written : status;
}
EXPORT_SYMBOL(generic_file_buffered_write);

static ssize_t
__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct file *file = iocb->ki_filp;
	struct address_space * mapping = file->f_mapping;
	size_t ocount;		/* original count */
	size_t count;		/* after file limit checks */
	struct inode 	*inode = mapping->host;
	unsigned long	seg;
	loff_t		pos;
	ssize_t		written;
	ssize_t		err;

	ocount = 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.
		 */
		ocount += iv->iov_len;
		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
			return -EINVAL;
		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
			continue;
		if (seg == 0)
			return -EFAULT;
		nr_segs = seg;
		ocount -= iv->iov_len;	/* This segment is no good */
		break;
	}

	count = ocount;
	pos = *ppos;

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

	/* 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;

	err = remove_suid(file->f_dentry);
	if (err)
		goto out;

	inode_update_time(inode, 1);

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (unlikely(file->f_flags & O_DIRECT)) {
		written = generic_file_direct_write(iocb, iov,
				&nr_segs, pos, ppos, count, ocount);
		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;
	}

	written = generic_file_buffered_write(iocb, iov, nr_segs,
			pos, ppos, count, written);
out:
	current->backing_dev_info = NULL;
	return written ? written : err;
}
EXPORT_SYMBOL(generic_file_aio_write_nolock);

ssize_t
generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;
	loff_t pos = *ppos;

	ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, ppos);

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err;

		err = sync_page_range_nolock(inode, mapping, pos, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}

static ssize_t
__generic_file_write_nolock(struct file *file, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, file);
	ret = __generic_file_aio_write_nolock(&kiocb, iov, nr_segs, ppos);
	if (ret == -EIOCBQUEUED)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}

ssize_t
generic_file_write_nolock(struct file *file, const struct iovec *iov,
				unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, file);
	ret = generic_file_aio_write_nolock(&kiocb, iov, nr_segs, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}
EXPORT_SYMBOL(generic_file_write_nolock);

ssize_t generic_file_aio_write(struct kiocb *iocb, const char __user *buf,
			       size_t count, loff_t pos)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;
	struct iovec local_iov = { .iov_base = (void __user *)buf,
					.iov_len = count };

	BUG_ON(iocb->ki_pos != pos);

	down(&inode->i_sem);
	ret = __generic_file_aio_write_nolock(iocb, &local_iov, 1,
						&iocb->ki_pos);
	up(&inode->i_sem);

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		ssize_t err;

		err = sync_page_range(inode, mapping, pos, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_aio_write);

ssize_t generic_file_write(struct file *file, const char __user *buf,
			   size_t count, loff_t *ppos)
{
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t	ret;
	struct iovec local_iov = { .iov_base = (void __user *)buf,
					.iov_len = count };

	down(&inode->i_sem);
	ret = __generic_file_write_nolock(file, &local_iov, 1, ppos);
	up(&inode->i_sem);

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		ssize_t err;

		err = sync_page_range(inode, mapping, *ppos - ret, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_write);

ssize_t generic_file_readv(struct file *filp, const struct iovec *iov,
			unsigned long nr_segs, loff_t *ppos)
{
	struct kiocb kiocb;
	ssize_t ret;

	init_sync_kiocb(&kiocb, filp);
	ret = __generic_file_aio_read(&kiocb, iov, nr_segs, ppos);
	if (-EIOCBQUEUED == ret)
		ret = wait_on_sync_kiocb(&kiocb);
	return ret;
}
EXPORT_SYMBOL(generic_file_readv);

ssize_t generic_file_writev(struct file *file, const struct iovec *iov,
			unsigned long nr_segs, loff_t *ppos)
{
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

	down(&inode->i_sem);
	ret = __generic_file_write_nolock(file, iov, nr_segs, ppos);
	up(&inode->i_sem);

	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
		int err;

		err = sync_page_range(inode, mapping, *ppos - ret, ret);
		if (err < 0)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(generic_file_writev);

/*
 * Called under i_sem for writes to S_ISREG files.   Returns -EIO if something
 * went wrong during pagecache shootdown.
 */
static ssize_t
generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
	loff_t offset, unsigned long nr_segs)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	ssize_t retval;
	size_t write_len = 0;

	/*
	 * If it's a write, unmap all mmappings of the file up-front.  This
	 * will cause any pte dirty bits to be propagated into the pageframes
	 * for the subsequent filemap_write_and_wait().
	 */
	if (rw == WRITE) {
		write_len = iov_length(iov, nr_segs);
	       	if (mapping_mapped(mapping))
			unmap_mapping_range(mapping, offset, write_len, 0);
	}

	retval = filemap_write_and_wait(mapping);
	if (retval == 0) {
		retval = mapping->a_ops->direct_IO(rw, iocb, iov,
						offset, nr_segs);
		if (rw == WRITE && mapping->nrpages) {
			pgoff_t end = (offset + write_len - 1)
						>> PAGE_CACHE_SHIFT;
			int err = invalidate_inode_pages2_range(mapping,
					offset >> PAGE_CACHE_SHIFT, end);
			if (err)
				retval = err;
		}
	}
	return retval;
}