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 inline struct metapage *alloc_metapage(gfp_t gfp_mask)
187{
188	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
189
190	if (mp) {
191		mp->lid = 0;
192		mp->lsn = 0;
193		mp->data = NULL;
194		mp->clsn = 0;
195		mp->log = NULL;
196		init_waitqueue_head(&mp->wait);
197	}
198	return mp;
199}
200
201static inline void free_metapage(struct metapage *mp)
202{
203	mempool_free(mp, metapage_mempool);
204}
205
206int __init metapage_init(void)
207{
208	/*
209	 * Allocate the metapage structures
210	 */
211	metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
212					   0, 0, NULL);
213	if (metapage_cache == NULL)
214		return -ENOMEM;
215
216	metapage_mempool = mempool_create_slab_pool(METAPOOL_MIN_PAGES,
217						    metapage_cache);
218
219	if (metapage_mempool == NULL) {
220		kmem_cache_destroy(metapage_cache);
221		return -ENOMEM;
222	}
223
224	return 0;
225}
226
227void metapage_exit(void)
228{
229	mempool_destroy(metapage_mempool);
230	kmem_cache_destroy(metapage_cache);
231}
232
233static inline void drop_metapage(struct page *page, struct metapage *mp)
234{
235	if (mp->count || mp->nohomeok || test_bit(META_dirty, &mp->flag) ||
236	    test_bit(META_io, &mp->flag))
237		return;
238	remove_metapage(page, mp);
239	INCREMENT(mpStat.pagefree);
240	free_metapage(mp);
241}
242
243/*
244 * Metapage address space operations
245 */
246
247static sector_t metapage_get_blocks(struct inode *inode, sector_t lblock,
248				    int *len)
249{
250	int rc = 0;
251	int xflag;
252	s64 xaddr;
253	sector_t file_blocks = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
254			       inode->i_blkbits;
255
256	if (lblock >= file_blocks)
257		return 0;
258	if (lblock + *len > file_blocks)
259		*len = file_blocks - lblock;
260
261	if (inode->i_ino) {
262		rc = xtLookup(inode, (s64)lblock, *len, &xflag, &xaddr, len, 0);
263		if ((rc == 0) && *len)
264			lblock = (sector_t)xaddr;
265		else
266			lblock = 0;
267	} /* else no mapping */
268
269	return lblock;
270}
271
272static void last_read_complete(struct page *page)
273{
274	if (!PageError(page))
275		SetPageUptodate(page);
276	unlock_page(page);
277}
278
279static void metapage_read_end_io(struct bio *bio, int err)
280{
281	struct page *page = bio->bi_private;
282
283	if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
284		printk(KERN_ERR "metapage_read_end_io: I/O error\n");
285		SetPageError(page);
286	}
287
288	dec_io(page, last_read_complete);
289	bio_put(bio);
290}
291
292static void remove_from_logsync(struct metapage *mp)
293{
294	struct jfs_log *log = mp->log;
295	unsigned long flags;
296/*
297 * This can race.  Recheck that log hasn't been set to null, and after
298 * acquiring logsync lock, recheck lsn
299 */
300	if (!log)
301		return;
302
303	LOGSYNC_LOCK(log, flags);
304	if (mp->lsn) {
305		mp->log = NULL;
306		mp->lsn = 0;
307		mp->clsn = 0;
308		log->count--;
309		list_del(&mp->synclist);
310	}
311	LOGSYNC_UNLOCK(log, flags);
312}
313
314static void last_write_complete(struct page *page)
315{
316	struct metapage *mp;
317	unsigned int offset;
318
319	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
320		mp = page_to_mp(page, offset);
321		if (mp && test_bit(META_io, &mp->flag)) {
322			if (mp->lsn)
323				remove_from_logsync(mp);
324			clear_bit(META_io, &mp->flag);
325		}
326		/*
327		 * I'd like to call drop_metapage here, but I don't think it's
328		 * safe unless I have the page locked
329		 */
330	}
331	end_page_writeback(page);
332}
333
334static void metapage_write_end_io(struct bio *bio, int err)
335{
336	struct page *page = bio->bi_private;
337
338	BUG_ON(!PagePrivate(page));
339
340	if (! test_bit(BIO_UPTODATE, &bio->bi_flags)) {
341		printk(KERN_ERR "metapage_write_end_io: I/O error\n");
342		SetPageError(page);
343	}
344	dec_io(page, last_write_complete);
345	bio_put(bio);
346}
347
348static int metapage_writepage(struct page *page, struct writeback_control *wbc)
349{
350	struct bio *bio = NULL;
351	int block_offset;	/* block offset of mp within page */
352	struct inode *inode = page->mapping->host;
353	int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
354	int len;
355	int xlen;
356	struct metapage *mp;
357	int redirty = 0;
358	sector_t lblock;
359	int nr_underway = 0;
360	sector_t pblock;
361	sector_t next_block = 0;
362	sector_t page_start;
363	unsigned long bio_bytes = 0;
364	unsigned long bio_offset = 0;
365	int offset;
366	int bad_blocks = 0;
367
368	page_start = (sector_t)page->index <<
369		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
370	BUG_ON(!PageLocked(page));
371	BUG_ON(PageWriteback(page));
372	set_page_writeback(page);
373
374	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
375		mp = page_to_mp(page, offset);
376
377		if (!mp || !test_bit(META_dirty, &mp->flag))
378			continue;
379
380		if (mp->nohomeok && !test_bit(META_forcewrite, &mp->flag)) {
381			redirty = 1;
382			/*
383			 * Make sure this page isn't blocked indefinitely.
384			 * If the journal isn't undergoing I/O, push it
385			 */
386			if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
387				jfs_flush_journal(mp->log, 0);
388			continue;
389		}
390
391		clear_bit(META_dirty, &mp->flag);
392		set_bit(META_io, &mp->flag);
393		block_offset = offset >> inode->i_blkbits;
394		lblock = page_start + block_offset;
395		if (bio) {
396			if (xlen && lblock == next_block) {
397				/* Contiguous, in memory & on disk */
398				len = min(xlen, blocks_per_mp);
399				xlen -= len;
400				bio_bytes += len << inode->i_blkbits;
401				continue;
402			}
403			/* Not contiguous */
404			if (bio_add_page(bio, page, bio_bytes, bio_offset) <
405			    bio_bytes)
406				goto add_failed;
407			/*
408			 * Increment counter before submitting i/o to keep
409			 * count from hitting zero before we're through
410			 */
411			inc_io(page);
412			if (!bio->bi_iter.bi_size)
413				goto dump_bio;
414			submit_bio(WRITE, bio);
415			nr_underway++;
416			bio = NULL;
417		} else
418			inc_io(page);
419		xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
420		pblock = metapage_get_blocks(inode, lblock, &xlen);
421		if (!pblock) {
422			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
423			/*
424			 * We already called inc_io(), but can't cancel it
425			 * with dec_io() until we're done with the page
426			 */
427			bad_blocks++;
428			continue;
429		}
430		len = min(xlen, (int)JFS_SBI(inode->i_sb)->nbperpage);
431
432		bio = bio_alloc(GFP_NOFS, 1);
433		bio->bi_bdev = inode->i_sb->s_bdev;
434		bio->bi_iter.bi_sector = pblock << (inode->i_blkbits - 9);
435		bio->bi_end_io = metapage_write_end_io;
436		bio->bi_private = page;
437
438		/* Don't call bio_add_page yet, we may add to this vec */
439		bio_offset = offset;
440		bio_bytes = len << inode->i_blkbits;
441
442		xlen -= len;
443		next_block = lblock + len;
444	}
445	if (bio) {
446		if (bio_add_page(bio, page, bio_bytes, bio_offset) < bio_bytes)
447				goto add_failed;
448		if (!bio->bi_iter.bi_size)
449			goto dump_bio;
450
451		submit_bio(WRITE, bio);
452		nr_underway++;
453	}
454	if (redirty)
455		redirty_page_for_writepage(wbc, page);
456
457	unlock_page(page);
458
459	if (bad_blocks)
460		goto err_out;
461
462	if (nr_underway == 0)
463		end_page_writeback(page);
464
465	return 0;
466add_failed:
467	/* We should never reach here, since we're only adding one vec */
468	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
469	goto skip;
470dump_bio:
471	print_hex_dump(KERN_ERR, "JFS: dump of bio: ", DUMP_PREFIX_ADDRESS, 16,
472		       4, bio, sizeof(*bio), 0);
473skip:
474	bio_put(bio);
475	unlock_page(page);
476	dec_io(page, last_write_complete);
477err_out:
478	while (bad_blocks--)
479		dec_io(page, last_write_complete);
480	return -EIO;
481}
482
483static int metapage_readpage(struct file *fp, struct page *page)
484{
485	struct inode *inode = page->mapping->host;
486	struct bio *bio = NULL;
487	int block_offset;
488	int blocks_per_page = PAGE_CACHE_SIZE >> inode->i_blkbits;
489	sector_t page_start;	/* address of page in fs blocks */
490	sector_t pblock;
491	int xlen;
492	unsigned int len;
493	int offset;
494
495	BUG_ON(!PageLocked(page));
496	page_start = (sector_t)page->index <<
497		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
498
499	block_offset = 0;
500	while (block_offset < blocks_per_page) {
501		xlen = blocks_per_page - block_offset;
502		pblock = metapage_get_blocks(inode, page_start + block_offset,
503					     &xlen);
504		if (pblock) {
505			if (!PagePrivate(page))
506				insert_metapage(page, NULL);
507			inc_io(page);
508			if (bio)
509				submit_bio(READ, bio);
510
511			bio = bio_alloc(GFP_NOFS, 1);
512			bio->bi_bdev = inode->i_sb->s_bdev;
513			bio->bi_iter.bi_sector =
514				pblock << (inode->i_blkbits - 9);
515			bio->bi_end_io = metapage_read_end_io;
516			bio->bi_private = page;
517			len = xlen << inode->i_blkbits;
518			offset = block_offset << inode->i_blkbits;
519			if (bio_add_page(bio, page, len, offset) < len)
520				goto add_failed;
521			block_offset += xlen;
522		} else
523			block_offset++;
524	}
525	if (bio)
526		submit_bio(READ, bio);
527	else
528		unlock_page(page);
529
530	return 0;
531
532add_failed:
533	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
534	bio_put(bio);
535	dec_io(page, last_read_complete);
536	return -EIO;
537}
538
539static int metapage_releasepage(struct page *page, gfp_t gfp_mask)
540{
541	struct metapage *mp;
542	int ret = 1;
543	int offset;
544
545	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
546		mp = page_to_mp(page, offset);
547
548		if (!mp)
549			continue;
550
551		jfs_info("metapage_releasepage: mp = 0x%p", mp);
552		if (mp->count || mp->nohomeok ||
553		    test_bit(META_dirty, &mp->flag)) {
554			jfs_info("count = %ld, nohomeok = %d", mp->count,
555				 mp->nohomeok);
556			ret = 0;
557			continue;
558		}
559		if (mp->lsn)
560			remove_from_logsync(mp);
561		remove_metapage(page, mp);
562		INCREMENT(mpStat.pagefree);
563		free_metapage(mp);
564	}
565	return ret;
566}
567
568static void metapage_invalidatepage(struct page *page, unsigned int offset,
569				    unsigned int length)
570{
571	BUG_ON(offset || length < PAGE_CACHE_SIZE);
572
573	BUG_ON(PageWriteback(page));
574
575	metapage_releasepage(page, 0);
576}
577
578const struct address_space_operations jfs_metapage_aops = {
579	.readpage	= metapage_readpage,
580	.writepage	= metapage_writepage,
581	.releasepage	= metapage_releasepage,
582	.invalidatepage	= metapage_invalidatepage,
583	.set_page_dirty	= __set_page_dirty_nobuffers,
584};
585
586struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
587				unsigned int size, int absolute,
588				unsigned long new)
589{
590	int l2BlocksPerPage;
591	int l2bsize;
592	struct address_space *mapping;
593	struct metapage *mp = NULL;
594	struct page *page;
595	unsigned long page_index;
596	unsigned long page_offset;
597
598	jfs_info("__get_metapage: ino = %ld, lblock = 0x%lx, abs=%d",
599		 inode->i_ino, lblock, absolute);
600
601	l2bsize = inode->i_blkbits;
602	l2BlocksPerPage = PAGE_CACHE_SHIFT - l2bsize;
603	page_index = lblock >> l2BlocksPerPage;
604	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
605	if ((page_offset + size) > PAGE_CACHE_SIZE) {
606		jfs_err("MetaData crosses page boundary!!");
607		jfs_err("lblock = %lx, size  = %d", lblock, size);
608		dump_stack();
609		return NULL;
610	}
611	if (absolute)
612		mapping = JFS_SBI(inode->i_sb)->direct_inode->i_mapping;
613	else {
614		/*
615		 * If an nfs client tries to read an inode that is larger
616		 * than any existing inodes, we may try to read past the
617		 * end of the inode map
618		 */
619		if ((lblock << inode->i_blkbits) >= inode->i_size)
620			return NULL;
621		mapping = inode->i_mapping;
622	}
623
624	if (new && (PSIZE == PAGE_CACHE_SIZE)) {
625		page = grab_cache_page(mapping, page_index);
626		if (!page) {
627			jfs_err("grab_cache_page failed!");
628			return NULL;
629		}
630		SetPageUptodate(page);
631	} else {
632		page = read_mapping_page(mapping, page_index, NULL);
633		if (IS_ERR(page) || !PageUptodate(page)) {
634			jfs_err("read_mapping_page failed!");
635			return NULL;
636		}
637		lock_page(page);
638	}
639
640	mp = page_to_mp(page, page_offset);
641	if (mp) {
642		if (mp->logical_size != size) {
643			jfs_error(inode->i_sb,
644				  "get_mp->logical_size != size\n");
645			jfs_err("logical_size = %d, size = %d",
646				mp->logical_size, size);
647			dump_stack();
648			goto unlock;
649		}
650		mp->count++;
651		lock_metapage(mp);
652		if (test_bit(META_discard, &mp->flag)) {
653			if (!new) {
654				jfs_error(inode->i_sb,
655					  "using a discarded metapage\n");
656				discard_metapage(mp);
657				goto unlock;
658			}
659			clear_bit(META_discard, &mp->flag);
660		}
661	} else {
662		INCREMENT(mpStat.pagealloc);
663		mp = alloc_metapage(GFP_NOFS);
664		mp->page = page;
665		mp->flag = 0;
666		mp->xflag = COMMIT_PAGE;
667		mp->count = 1;
668		mp->nohomeok = 0;
669		mp->logical_size = size;
670		mp->data = page_address(page) + page_offset;
671		mp->index = lblock;
672		if (unlikely(insert_metapage(page, mp))) {
673			free_metapage(mp);
674			goto unlock;
675		}
676		lock_metapage(mp);
677	}
678
679	if (new) {
680		jfs_info("zeroing mp = 0x%p", mp);
681		memset(mp->data, 0, PSIZE);
682	}
683
684	unlock_page(page);
685	jfs_info("__get_metapage: returning = 0x%p data = 0x%p", mp, mp->data);
686	return mp;
687
688unlock:
689	unlock_page(page);
690	return NULL;
691}
692
693void grab_metapage(struct metapage * mp)
694{
695	jfs_info("grab_metapage: mp = 0x%p", mp);
696	page_cache_get(mp->page);
697	lock_page(mp->page);
698	mp->count++;
699	lock_metapage(mp);
700	unlock_page(mp->page);
701}
702
703void force_metapage(struct metapage *mp)
704{
705	struct page *page = mp->page;
706	jfs_info("force_metapage: mp = 0x%p", mp);
707	set_bit(META_forcewrite, &mp->flag);
708	clear_bit(META_sync, &mp->flag);
709	page_cache_get(page);
710	lock_page(page);
711	set_page_dirty(page);
712	write_one_page(page, 1);
713	clear_bit(META_forcewrite, &mp->flag);
714	page_cache_release(page);
715}
716
717void hold_metapage(struct metapage *mp)
718{
719	lock_page(mp->page);
720}
721
722void put_metapage(struct metapage *mp)
723{
724	if (mp->count || mp->nohomeok) {
725		/* Someone else will release this */
726		unlock_page(mp->page);
727		return;
728	}
729	page_cache_get(mp->page);
730	mp->count++;
731	lock_metapage(mp);
732	unlock_page(mp->page);
733	release_metapage(mp);
734}
735
736void release_metapage(struct metapage * mp)
737{
738	struct page *page = mp->page;
739	jfs_info("release_metapage: mp = 0x%p, flag = 0x%lx", mp, mp->flag);
740
741	BUG_ON(!page);
742
743	lock_page(page);
744	unlock_metapage(mp);
745
746	assert(mp->count);
747	if (--mp->count || mp->nohomeok) {
748		unlock_page(page);
749		page_cache_release(page);
750		return;
751	}
752
753	if (test_bit(META_dirty, &mp->flag)) {
754		set_page_dirty(page);
755		if (test_bit(META_sync, &mp->flag)) {
756			clear_bit(META_sync, &mp->flag);
757			write_one_page(page, 1);
758			lock_page(page); /* write_one_page unlocks the page */
759		}
760	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
761		remove_from_logsync(mp);
762
763	/* Try to keep metapages from using up too much memory */
764	drop_metapage(page, mp);
765
766	unlock_page(page);
767	page_cache_release(page);
768}
769
770void __invalidate_metapages(struct inode *ip, s64 addr, int len)
771{
772	sector_t lblock;
773	int l2BlocksPerPage = PAGE_CACHE_SHIFT - ip->i_blkbits;
774	int BlocksPerPage = 1 << l2BlocksPerPage;
775	/* All callers are interested in block device's mapping */
776	struct address_space *mapping =
777		JFS_SBI(ip->i_sb)->direct_inode->i_mapping;
778	struct metapage *mp;
779	struct page *page;
780	unsigned int offset;
781
782	/*
783	 * Mark metapages to discard.  They will eventually be
784	 * released, but should not be written.
785	 */
786	for (lblock = addr & ~(BlocksPerPage - 1); lblock < addr + len;
787	     lblock += BlocksPerPage) {
788		page = find_lock_page(mapping, lblock >> l2BlocksPerPage);
789		if (!page)
790			continue;
791		for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
792			mp = page_to_mp(page, offset);
793			if (!mp)
794				continue;
795			if (mp->index < addr)
796				continue;
797			if (mp->index >= addr + len)
798				break;
799
800			clear_bit(META_dirty, &mp->flag);
801			set_bit(META_discard, &mp->flag);
802			if (mp->lsn)
803				remove_from_logsync(mp);
804		}
805		unlock_page(page);
806		page_cache_release(page);
807	}
808}
809
810#ifdef CONFIG_JFS_STATISTICS
811static int jfs_mpstat_proc_show(struct seq_file *m, void *v)
812{
813	seq_printf(m,
814		       "JFS Metapage statistics\n"
815		       "=======================\n"
816		       "page allocations = %d\n"
817		       "page frees = %d\n"
818		       "lock waits = %d\n",
819		       mpStat.pagealloc,
820		       mpStat.pagefree,
821		       mpStat.lockwait);
822	return 0;
823}
824
825static int jfs_mpstat_proc_open(struct inode *inode, struct file *file)
826{
827	return single_open(file, jfs_mpstat_proc_show, NULL);
828}
829
830const struct file_operations jfs_mpstat_proc_fops = {
831	.owner		= THIS_MODULE,
832	.open		= jfs_mpstat_proc_open,
833	.read		= seq_read,
834	.llseek		= seq_lseek,
835	.release	= single_release,
836};
837#endif
838