1/*
2 *   Copyright (C) International Business Machines Corp., 2000-2005
3 *   Portions Copyright (C) Christoph Hellwig, 2001-2002
4 *
5 *   This program is free software;  you can redistribute it and/or modify
6 *   it under the terms of the GNU General Public License as published by
7 *   the Free Software Foundation; either version 2 of the License, or
8 *   (at your option) any later version.
9 *
10 *   This program is distributed in the hope that it will be useful,
11 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
12 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
13 *   the GNU General Public License for more details.
14 *
15 *   You should have received a copy of the GNU General Public License
16 *   along with this program;  if not, write to the Free Software
17 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 */
19
20#include <linux/fs.h>
21#include <linux/mm.h>
22#include <linux/module.h>
23#include <linux/bio.h>
24#include <linux/slab.h>
25#include <linux/init.h>
26#include <linux/buffer_head.h>
27#include <linux/mempool.h>
28#include <linux/seq_file.h>
29#include "jfs_incore.h"
30#include "jfs_superblock.h"
31#include "jfs_filsys.h"
32#include "jfs_metapage.h"
33#include "jfs_txnmgr.h"
34#include "jfs_debug.h"
35
36#ifdef CONFIG_JFS_STATISTICS
37static struct {
38	uint	pagealloc;	/* # of page allocations */
39	uint	pagefree;	/* # of page frees */
40	uint	lockwait;	/* # of sleeping lock_metapage() calls */
41} mpStat;
42#endif
43
44#define metapage_locked(mp) test_bit(META_locked, &(mp)->flag)
45#define trylock_metapage(mp) test_and_set_bit_lock(META_locked, &(mp)->flag)
46
47static inline void unlock_metapage(struct metapage *mp)
48{
49	clear_bit_unlock(META_locked, &mp->flag);
50	wake_up(&mp->wait);
51}
52
53static inline void __lock_metapage(struct metapage *mp)
54{
55	DECLARE_WAITQUEUE(wait, current);
56	INCREMENT(mpStat.lockwait);
57	add_wait_queue_exclusive(&mp->wait, &wait);
58	do {
59		set_current_state(TASK_UNINTERRUPTIBLE);
60		if (metapage_locked(mp)) {
61			unlock_page(mp->page);
62			io_schedule();
63			lock_page(mp->page);
64		}
65	} while (trylock_metapage(mp));
66	__set_current_state(TASK_RUNNING);
67	remove_wait_queue(&mp->wait, &wait);
68}
69
70/*
71 * Must have mp->page locked
72 */
73static inline void lock_metapage(struct metapage *mp)
74{
75	if (trylock_metapage(mp))
76		__lock_metapage(mp);
77}
78
79#define METAPOOL_MIN_PAGES 32
80static struct kmem_cache *metapage_cache;
81static mempool_t *metapage_mempool;
82
83#define MPS_PER_PAGE (PAGE_CACHE_SIZE >> L2PSIZE)
84
85#if MPS_PER_PAGE > 1
86
87struct meta_anchor {
88	int mp_count;
89	atomic_t io_count;
90	struct metapage *mp[MPS_PER_PAGE];
91};
92#define mp_anchor(page) ((struct meta_anchor *)page_private(page))
93
94static inline struct metapage *page_to_mp(struct page *page, int offset)
95{
96	if (!PagePrivate(page))
97		return NULL;
98	return mp_anchor(page)->mp[offset >> L2PSIZE];
99}
100
101static inline int insert_metapage(struct page *page, struct metapage *mp)
102{
103	struct meta_anchor *a;
104	int index;
105	int l2mp_blocks;	/* log2 blocks per metapage */
106
107	if (PagePrivate(page))
108		a = mp_anchor(page);
109	else {
110		a = kzalloc(sizeof(struct meta_anchor), GFP_NOFS);
111		if (!a)
112			return -ENOMEM;
113		set_page_private(page, (unsigned long)a);
114		SetPagePrivate(page);
115		kmap(page);
116	}
117
118	if (mp) {
119		l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
120		index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
121		a->mp_count++;
122		a->mp[index] = mp;
123	}
124
125	return 0;
126}
127
128static inline void remove_metapage(struct page *page, struct metapage *mp)
129{
130	struct meta_anchor *a = mp_anchor(page);
131	int l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
132	int index;
133
134	index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
135
136	BUG_ON(a->mp[index] != mp);
137
138	a->mp[index] = NULL;
139	if (--a->mp_count == 0) {
140		kfree(a);
141		set_page_private(page, 0);
142		ClearPagePrivate(page);
143		kunmap(page);
144	}
145}
146
147static inline void inc_io(struct page *page)
148{
149	atomic_inc(&mp_anchor(page)->io_count);
150}
151
152static inline void dec_io(struct page *page, void (*handler) (struct page *))
153{
154	if (atomic_dec_and_test(&mp_anchor(page)->io_count))
155		handler(page);
156}
157
158#else
159static inline struct metapage *page_to_mp(struct page *page, int offset)
160{
161	return PagePrivate(page) ? (struct metapage *)page_private(page) : NULL;
162}
163
164static inline int insert_metapage(struct page *page, struct metapage *mp)
165{
166	if (mp) {
167		set_page_private(page, (unsigned long)mp);
168		SetPagePrivate(page);
169		kmap(page);
170	}
171	return 0;
172}
173
174static inline void remove_metapage(struct page *page, struct metapage *mp)
175{
176	set_page_private(page, 0);
177	ClearPagePrivate(page);
178	kunmap(page);
179}
180
181#define inc_io(page) do {} while(0)
182#define dec_io(page, handler) handler(page)
183
184#endif
185
186static void init_once(void *foo)
187{
188	struct metapage *mp = (struct metapage *)foo;
189
190	mp->lid = 0;
191	mp->lsn = 0;
192	mp->flag = 0;
193	mp->data = NULL;
194	mp->clsn = 0;
195	mp->log = NULL;
196	set_bit(META_free, &mp->flag);
197	init_waitqueue_head(&mp->wait);
198}
199
200static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
201{
202	return mempool_alloc(metapage_mempool, gfp_mask);
203}
204
205static inline void free_metapage(struct metapage *mp)
206{
207	mp->flag = 0;
208	set_bit(META_free, &mp->flag);
209
210	mempool_free(mp, metapage_mempool);
211}
212
213int __init metapage_init(void)
214{
215	/*
216	 * Allocate the metapage structures
217	 */
218	metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
219					   0, 0, init_once);
220	if (metapage_cache == NULL)
221		return -ENOMEM;
222
223	metapage_mempool = mempool_create_slab_pool(METAPOOL_MIN_PAGES,
224						    metapage_cache);
225
226	if (metapage_mempool == NULL) {
227		kmem_cache_destroy(metapage_cache);
228		return -ENOMEM;
229	}
230
231	return 0;
232}
233
234void metapage_exit(void)
235{
236	mempool_destroy(metapage_mempool);
237	kmem_cache_destroy(metapage_cache);
238}
239
240static inline void drop_metapage(struct page *page, struct metapage *mp)
241{
242	if (mp->count || mp->nohomeok || test_bit(META_dirty, &mp->flag) ||
243	    test_bit(META_io, &mp->flag))
244		return;
245	remove_metapage(page, mp);
246	INCREMENT(mpStat.pagefree);
247	free_metapage(mp);
248}
249
250/*
251 * Metapage address space operations
252 */
253
254static sector_t metapage_get_blocks(struct inode *inode, sector_t lblock,
255				    int *len)
256{
257	int rc = 0;
258	int xflag;
259	s64 xaddr;
260	sector_t file_blocks = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
261			       inode->i_blkbits;
262
263	if (lblock >= file_blocks)
264		return 0;
265	if (lblock + *len > file_blocks)
266		*len = file_blocks - lblock;
267
268	if (inode->i_ino) {
269		rc = xtLookup(inode, (s64)lblock, *len, &xflag, &xaddr, len, 0);
270		if ((rc == 0) && *len)
271			lblock = (sector_t)xaddr;
272		else
273			lblock = 0;
274	} /* else no mapping */
275
276	return lblock;
277}
278
279static void last_read_complete(struct page *page)
280{
281	if (!PageError(page))
282		SetPageUptodate(page);
283	unlock_page(page);
284}
285
286static void metapage_read_end_io(struct bio *bio, int err)
287{
288	struct page *page = bio->bi_private;
289
290	if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
291		printk(KERN_ERR "metapage_read_end_io: I/O error\n");
292		SetPageError(page);
293	}
294
295	dec_io(page, last_read_complete);
296	bio_put(bio);
297}
298
299static void remove_from_logsync(struct metapage *mp)
300{
301	struct jfs_log *log = mp->log;
302	unsigned long flags;
303/*
304 * This can race.  Recheck that log hasn't been set to null, and after
305 * acquiring logsync lock, recheck lsn
306 */
307	if (!log)
308		return;
309
310	LOGSYNC_LOCK(log, flags);
311	if (mp->lsn) {
312		mp->log = NULL;
313		mp->lsn = 0;
314		mp->clsn = 0;
315		log->count--;
316		list_del(&mp->synclist);
317	}
318	LOGSYNC_UNLOCK(log, flags);
319}
320
321static void last_write_complete(struct page *page)
322{
323	struct metapage *mp;
324	unsigned int offset;
325
326	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
327		mp = page_to_mp(page, offset);
328		if (mp && test_bit(META_io, &mp->flag)) {
329			if (mp->lsn)
330				remove_from_logsync(mp);
331			clear_bit(META_io, &mp->flag);
332		}
333		/*
334		 * I'd like to call drop_metapage here, but I don't think it's
335		 * safe unless I have the page locked
336		 */
337	}
338	end_page_writeback(page);
339}
340
341static void metapage_write_end_io(struct bio *bio, int err)
342{
343	struct page *page = bio->bi_private;
344
345	BUG_ON(!PagePrivate(page));
346
347	if (! test_bit(BIO_UPTODATE, &bio->bi_flags)) {
348		printk(KERN_ERR "metapage_write_end_io: I/O error\n");
349		SetPageError(page);
350	}
351	dec_io(page, last_write_complete);
352	bio_put(bio);
353}
354
355static int metapage_writepage(struct page *page, struct writeback_control *wbc)
356{
357	struct bio *bio = NULL;
358	int block_offset;	/* block offset of mp within page */
359	struct inode *inode = page->mapping->host;
360	int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
361	int len;
362	int xlen;
363	struct metapage *mp;
364	int redirty = 0;
365	sector_t lblock;
366	int nr_underway = 0;
367	sector_t pblock;
368	sector_t next_block = 0;
369	sector_t page_start;
370	unsigned long bio_bytes = 0;
371	unsigned long bio_offset = 0;
372	int offset;
373	int bad_blocks = 0;
374
375	page_start = (sector_t)page->index <<
376		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
377	BUG_ON(!PageLocked(page));
378	BUG_ON(PageWriteback(page));
379	set_page_writeback(page);
380
381	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
382		mp = page_to_mp(page, offset);
383
384		if (!mp || !test_bit(META_dirty, &mp->flag))
385			continue;
386
387		if (mp->nohomeok && !test_bit(META_forcewrite, &mp->flag)) {
388			redirty = 1;
389			/*
390			 * Make sure this page isn't blocked indefinitely.
391			 * If the journal isn't undergoing I/O, push it
392			 */
393			if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
394				jfs_flush_journal(mp->log, 0);
395			continue;
396		}
397
398		clear_bit(META_dirty, &mp->flag);
399		set_bit(META_io, &mp->flag);
400		block_offset = offset >> inode->i_blkbits;
401		lblock = page_start + block_offset;
402		if (bio) {
403			if (xlen && lblock == next_block) {
404				/* Contiguous, in memory & on disk */
405				len = min(xlen, blocks_per_mp);
406				xlen -= len;
407				bio_bytes += len << inode->i_blkbits;
408				continue;
409			}
410			/* Not contiguous */
411			if (bio_add_page(bio, page, bio_bytes, bio_offset) <
412			    bio_bytes)
413				goto add_failed;
414			/*
415			 * Increment counter before submitting i/o to keep
416			 * count from hitting zero before we're through
417			 */
418			inc_io(page);
419			if (!bio->bi_size)
420				goto dump_bio;
421			submit_bio(WRITE, bio);
422			nr_underway++;
423			bio = NULL;
424		} else
425			inc_io(page);
426		xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
427		pblock = metapage_get_blocks(inode, lblock, &xlen);
428		if (!pblock) {
429			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
430			/*
431			 * We already called inc_io(), but can't cancel it
432			 * with dec_io() until we're done with the page
433			 */
434			bad_blocks++;
435			continue;
436		}
437		len = min(xlen, (int)JFS_SBI(inode->i_sb)->nbperpage);
438
439		bio = bio_alloc(GFP_NOFS, 1);
440		bio->bi_bdev = inode->i_sb->s_bdev;
441		bio->bi_sector = pblock << (inode->i_blkbits - 9);
442		bio->bi_end_io = metapage_write_end_io;
443		bio->bi_private = page;
444
445		/* Don't call bio_add_page yet, we may add to this vec */
446		bio_offset = offset;
447		bio_bytes = len << inode->i_blkbits;
448
449		xlen -= len;
450		next_block = lblock + len;
451	}
452	if (bio) {
453		if (bio_add_page(bio, page, bio_bytes, bio_offset) < bio_bytes)
454				goto add_failed;
455		if (!bio->bi_size)
456			goto dump_bio;
457
458		submit_bio(WRITE, bio);
459		nr_underway++;
460	}
461	if (redirty)
462		redirty_page_for_writepage(wbc, page);
463
464	unlock_page(page);
465
466	if (bad_blocks)
467		goto err_out;
468
469	if (nr_underway == 0)
470		end_page_writeback(page);
471
472	return 0;
473add_failed:
474	/* We should never reach here, since we're only adding one vec */
475	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
476	goto skip;
477dump_bio:
478	print_hex_dump(KERN_ERR, "JFS: dump of bio: ", DUMP_PREFIX_ADDRESS, 16,
479		       4, bio, sizeof(*bio), 0);
480skip:
481	bio_put(bio);
482	unlock_page(page);
483	dec_io(page, last_write_complete);
484err_out:
485	while (bad_blocks--)
486		dec_io(page, last_write_complete);
487	return -EIO;
488}
489
490static int metapage_readpage(struct file *fp, struct page *page)
491{
492	struct inode *inode = page->mapping->host;
493	struct bio *bio = NULL;
494	int block_offset;
495	int blocks_per_page = PAGE_CACHE_SIZE >> inode->i_blkbits;
496	sector_t page_start;	/* address of page in fs blocks */
497	sector_t pblock;
498	int xlen;
499	unsigned int len;
500	int offset;
501
502	BUG_ON(!PageLocked(page));
503	page_start = (sector_t)page->index <<
504		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
505
506	block_offset = 0;
507	while (block_offset < blocks_per_page) {
508		xlen = blocks_per_page - block_offset;
509		pblock = metapage_get_blocks(inode, page_start + block_offset,
510					     &xlen);
511		if (pblock) {
512			if (!PagePrivate(page))
513				insert_metapage(page, NULL);
514			inc_io(page);
515			if (bio)
516				submit_bio(READ, bio);
517
518			bio = bio_alloc(GFP_NOFS, 1);
519			bio->bi_bdev = inode->i_sb->s_bdev;
520			bio->bi_sector = pblock << (inode->i_blkbits - 9);
521			bio->bi_end_io = metapage_read_end_io;
522			bio->bi_private = page;
523			len = xlen << inode->i_blkbits;
524			offset = block_offset << inode->i_blkbits;
525			if (bio_add_page(bio, page, len, offset) < len)
526				goto add_failed;
527			block_offset += xlen;
528		} else
529			block_offset++;
530	}
531	if (bio)
532		submit_bio(READ, bio);
533	else
534		unlock_page(page);
535
536	return 0;
537
538add_failed:
539	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
540	bio_put(bio);
541	dec_io(page, last_read_complete);
542	return -EIO;
543}
544
545static int metapage_releasepage(struct page *page, gfp_t gfp_mask)
546{
547	struct metapage *mp;
548	int ret = 1;
549	int offset;
550
551	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
552		mp = page_to_mp(page, offset);
553
554		if (!mp)
555			continue;
556
557		jfs_info("metapage_releasepage: mp = 0x%p", mp);
558		if (mp->count || mp->nohomeok ||
559		    test_bit(META_dirty, &mp->flag)) {
560			jfs_info("count = %ld, nohomeok = %d", mp->count,
561				 mp->nohomeok);
562			ret = 0;
563			continue;
564		}
565		if (mp->lsn)
566			remove_from_logsync(mp);
567		remove_metapage(page, mp);
568		INCREMENT(mpStat.pagefree);
569		free_metapage(mp);
570	}
571	return ret;
572}
573
574static void metapage_invalidatepage(struct page *page, unsigned long offset)
575{
576	BUG_ON(offset);
577
578	BUG_ON(PageWriteback(page));
579
580	metapage_releasepage(page, 0);
581}
582
583const struct address_space_operations jfs_metapage_aops = {
584	.readpage	= metapage_readpage,
585	.writepage	= metapage_writepage,
586	.sync_page	= block_sync_page,
587	.releasepage	= metapage_releasepage,
588	.invalidatepage	= metapage_invalidatepage,
589	.set_page_dirty	= __set_page_dirty_nobuffers,
590};
591
592struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
593				unsigned int size, int absolute,
594				unsigned long new)
595{
596	int l2BlocksPerPage;
597	int l2bsize;
598	struct address_space *mapping;
599	struct metapage *mp = NULL;
600	struct page *page;
601	unsigned long page_index;
602	unsigned long page_offset;
603
604	jfs_info("__get_metapage: ino = %ld, lblock = 0x%lx, abs=%d",
605		 inode->i_ino, lblock, absolute);
606
607	l2bsize = inode->i_blkbits;
608	l2BlocksPerPage = PAGE_CACHE_SHIFT - l2bsize;
609	page_index = lblock >> l2BlocksPerPage;
610	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
611	if ((page_offset + size) > PAGE_CACHE_SIZE) {
612		jfs_err("MetaData crosses page boundary!!");
613		jfs_err("lblock = %lx, size  = %d", lblock, size);
614		dump_stack();
615		return NULL;
616	}
617	if (absolute)
618		mapping = JFS_SBI(inode->i_sb)->direct_inode->i_mapping;
619	else {
620		/*
621		 * If an nfs client tries to read an inode that is larger
622		 * than any existing inodes, we may try to read past the
623		 * end of the inode map
624		 */
625		if ((lblock << inode->i_blkbits) >= inode->i_size)
626			return NULL;
627		mapping = inode->i_mapping;
628	}
629
630	if (new && (PSIZE == PAGE_CACHE_SIZE)) {
631		page = grab_cache_page(mapping, page_index);
632		if (!page) {
633			jfs_err("grab_cache_page failed!");
634			return NULL;
635		}
636		SetPageUptodate(page);
637	} else {
638		page = read_mapping_page(mapping, page_index, NULL);
639		if (IS_ERR(page) || !PageUptodate(page)) {
640			jfs_err("read_mapping_page failed!");
641			return NULL;
642		}
643		lock_page(page);
644	}
645
646	mp = page_to_mp(page, page_offset);
647	if (mp) {
648		if (mp->logical_size != size) {
649			jfs_error(inode->i_sb,
650				  "__get_metapage: mp->logical_size != size");
651			jfs_err("logical_size = %d, size = %d",
652				mp->logical_size, size);
653			dump_stack();
654			goto unlock;
655		}
656		mp->count++;
657		lock_metapage(mp);
658		if (test_bit(META_discard, &mp->flag)) {
659			if (!new) {
660				jfs_error(inode->i_sb,
661					  "__get_metapage: using a "
662					  "discarded metapage");
663				discard_metapage(mp);
664				goto unlock;
665			}
666			clear_bit(META_discard, &mp->flag);
667		}
668	} else {
669		INCREMENT(mpStat.pagealloc);
670		mp = alloc_metapage(GFP_NOFS);
671		mp->page = page;
672		mp->flag = 0;
673		mp->xflag = COMMIT_PAGE;
674		mp->count = 1;
675		mp->nohomeok = 0;
676		mp->logical_size = size;
677		mp->data = page_address(page) + page_offset;
678		mp->index = lblock;
679		if (unlikely(insert_metapage(page, mp))) {
680			free_metapage(mp);
681			goto unlock;
682		}
683		lock_metapage(mp);
684	}
685
686	if (new) {
687		jfs_info("zeroing mp = 0x%p", mp);
688		memset(mp->data, 0, PSIZE);
689	}
690
691	unlock_page(page);
692	jfs_info("__get_metapage: returning = 0x%p data = 0x%p", mp, mp->data);
693	return mp;
694
695unlock:
696	unlock_page(page);
697	return NULL;
698}
699
700void grab_metapage(struct metapage * mp)
701{
702	jfs_info("grab_metapage: mp = 0x%p", mp);
703	page_cache_get(mp->page);
704	lock_page(mp->page);
705	mp->count++;
706	lock_metapage(mp);
707	unlock_page(mp->page);
708}
709
710void force_metapage(struct metapage *mp)
711{
712	struct page *page = mp->page;
713	jfs_info("force_metapage: mp = 0x%p", mp);
714	set_bit(META_forcewrite, &mp->flag);
715	clear_bit(META_sync, &mp->flag);
716	page_cache_get(page);
717	lock_page(page);
718	set_page_dirty(page);
719	write_one_page(page, 1);
720	clear_bit(META_forcewrite, &mp->flag);
721	page_cache_release(page);
722}
723
724void hold_metapage(struct metapage *mp)
725{
726	lock_page(mp->page);
727}
728
729void put_metapage(struct metapage *mp)
730{
731	if (mp->count || mp->nohomeok) {
732		/* Someone else will release this */
733		unlock_page(mp->page);
734		return;
735	}
736	page_cache_get(mp->page);
737	mp->count++;
738	lock_metapage(mp);
739	unlock_page(mp->page);
740	release_metapage(mp);
741}
742
743void release_metapage(struct metapage * mp)
744{
745	struct page *page = mp->page;
746	jfs_info("release_metapage: mp = 0x%p, flag = 0x%lx", mp, mp->flag);
747
748	BUG_ON(!page);
749
750	lock_page(page);
751	unlock_metapage(mp);
752
753	assert(mp->count);
754	if (--mp->count || mp->nohomeok) {
755		unlock_page(page);
756		page_cache_release(page);
757		return;
758	}
759
760	if (test_bit(META_dirty, &mp->flag)) {
761		set_page_dirty(page);
762		if (test_bit(META_sync, &mp->flag)) {
763			clear_bit(META_sync, &mp->flag);
764			write_one_page(page, 1);
765			lock_page(page); /* write_one_page unlocks the page */
766		}
767	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
768		remove_from_logsync(mp);
769
770	/* Try to keep metapages from using up too much memory */
771	drop_metapage(page, mp);
772
773	unlock_page(page);
774	page_cache_release(page);
775}
776
777void __invalidate_metapages(struct inode *ip, s64 addr, int len)
778{
779	sector_t lblock;
780	int l2BlocksPerPage = PAGE_CACHE_SHIFT - ip->i_blkbits;
781	int BlocksPerPage = 1 << l2BlocksPerPage;
782	/* All callers are interested in block device's mapping */
783	struct address_space *mapping =
784		JFS_SBI(ip->i_sb)->direct_inode->i_mapping;
785	struct metapage *mp;
786	struct page *page;
787	unsigned int offset;
788
789	/*
790	 * Mark metapages to discard.  They will eventually be
791	 * released, but should not be written.
792	 */
793	for (lblock = addr & ~(BlocksPerPage - 1); lblock < addr + len;
794	     lblock += BlocksPerPage) {
795		page = find_lock_page(mapping, lblock >> l2BlocksPerPage);
796		if (!page)
797			continue;
798		for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
799			mp = page_to_mp(page, offset);
800			if (!mp)
801				continue;
802			if (mp->index < addr)
803				continue;
804			if (mp->index >= addr + len)
805				break;
806
807			clear_bit(META_dirty, &mp->flag);
808			set_bit(META_discard, &mp->flag);
809			if (mp->lsn)
810				remove_from_logsync(mp);
811		}
812		unlock_page(page);
813		page_cache_release(page);
814	}
815}
816
817#ifdef CONFIG_JFS_STATISTICS
818static int jfs_mpstat_proc_show(struct seq_file *m, void *v)
819{
820	seq_printf(m,
821		       "JFS Metapage statistics\n"
822		       "=======================\n"
823		       "page allocations = %d\n"
824		       "page frees = %d\n"
825		       "lock waits = %d\n",
826		       mpStat.pagealloc,
827		       mpStat.pagefree,
828		       mpStat.lockwait);
829	return 0;
830}
831
832static int jfs_mpstat_proc_open(struct inode *inode, struct file *file)
833{
834	return single_open(file, jfs_mpstat_proc_show, NULL);
835}
836
837const struct file_operations jfs_mpstat_proc_fops = {
838	.owner		= THIS_MODULE,
839	.open		= jfs_mpstat_proc_open,
840	.read		= seq_read,
841	.llseek		= seq_lseek,
842	.release	= single_release,
843};
844#endif
845