xref: /openbmc/linux/fs/jfs/jfs_metapage.c (revision 195c5ad9)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *   Copyright (C) International Business Machines Corp., 2000-2005
4  *   Portions Copyright (C) Christoph Hellwig, 2001-2002
5  */
6 
7 #include <linux/fs.h>
8 #include <linux/mm.h>
9 #include <linux/module.h>
10 #include <linux/bio.h>
11 #include <linux/slab.h>
12 #include <linux/init.h>
13 #include <linux/buffer_head.h>
14 #include <linux/mempool.h>
15 #include <linux/seq_file.h>
16 #include <linux/writeback.h>
17 #include "jfs_incore.h"
18 #include "jfs_superblock.h"
19 #include "jfs_filsys.h"
20 #include "jfs_metapage.h"
21 #include "jfs_txnmgr.h"
22 #include "jfs_debug.h"
23 
24 #ifdef CONFIG_JFS_STATISTICS
25 static struct {
26 	uint	pagealloc;	/* # of page allocations */
27 	uint	pagefree;	/* # of page frees */
28 	uint	lockwait;	/* # of sleeping lock_metapage() calls */
29 } mpStat;
30 #endif
31 
32 #define metapage_locked(mp) test_bit(META_locked, &(mp)->flag)
33 #define trylock_metapage(mp) test_and_set_bit_lock(META_locked, &(mp)->flag)
34 
35 static inline void unlock_metapage(struct metapage *mp)
36 {
37 	clear_bit_unlock(META_locked, &mp->flag);
38 	wake_up(&mp->wait);
39 }
40 
41 static inline void __lock_metapage(struct metapage *mp)
42 {
43 	DECLARE_WAITQUEUE(wait, current);
44 	INCREMENT(mpStat.lockwait);
45 	add_wait_queue_exclusive(&mp->wait, &wait);
46 	do {
47 		set_current_state(TASK_UNINTERRUPTIBLE);
48 		if (metapage_locked(mp)) {
49 			unlock_page(mp->page);
50 			io_schedule();
51 			lock_page(mp->page);
52 		}
53 	} while (trylock_metapage(mp));
54 	__set_current_state(TASK_RUNNING);
55 	remove_wait_queue(&mp->wait, &wait);
56 }
57 
58 /*
59  * Must have mp->page locked
60  */
61 static inline void lock_metapage(struct metapage *mp)
62 {
63 	if (trylock_metapage(mp))
64 		__lock_metapage(mp);
65 }
66 
67 #define METAPOOL_MIN_PAGES 32
68 static struct kmem_cache *metapage_cache;
69 static mempool_t *metapage_mempool;
70 
71 #define MPS_PER_PAGE (PAGE_SIZE >> L2PSIZE)
72 
73 #if MPS_PER_PAGE > 1
74 
75 struct meta_anchor {
76 	int mp_count;
77 	atomic_t io_count;
78 	struct metapage *mp[MPS_PER_PAGE];
79 };
80 #define mp_anchor(page) ((struct meta_anchor *)page_private(page))
81 
82 static inline struct metapage *page_to_mp(struct page *page, int offset)
83 {
84 	if (!PagePrivate(page))
85 		return NULL;
86 	return mp_anchor(page)->mp[offset >> L2PSIZE];
87 }
88 
89 static inline int insert_metapage(struct page *page, struct metapage *mp)
90 {
91 	struct meta_anchor *a;
92 	int index;
93 	int l2mp_blocks;	/* log2 blocks per metapage */
94 
95 	if (PagePrivate(page))
96 		a = mp_anchor(page);
97 	else {
98 		a = kzalloc(sizeof(struct meta_anchor), GFP_NOFS);
99 		if (!a)
100 			return -ENOMEM;
101 		set_page_private(page, (unsigned long)a);
102 		SetPagePrivate(page);
103 		kmap(page);
104 	}
105 
106 	if (mp) {
107 		l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
108 		index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
109 		a->mp_count++;
110 		a->mp[index] = mp;
111 	}
112 
113 	return 0;
114 }
115 
116 static inline void remove_metapage(struct page *page, struct metapage *mp)
117 {
118 	struct meta_anchor *a = mp_anchor(page);
119 	int l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
120 	int index;
121 
122 	index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
123 
124 	BUG_ON(a->mp[index] != mp);
125 
126 	a->mp[index] = NULL;
127 	if (--a->mp_count == 0) {
128 		kfree(a);
129 		set_page_private(page, 0);
130 		ClearPagePrivate(page);
131 		kunmap(page);
132 	}
133 }
134 
135 static inline void inc_io(struct page *page)
136 {
137 	atomic_inc(&mp_anchor(page)->io_count);
138 }
139 
140 static inline void dec_io(struct page *page, void (*handler) (struct page *))
141 {
142 	if (atomic_dec_and_test(&mp_anchor(page)->io_count))
143 		handler(page);
144 }
145 
146 #else
147 static inline struct metapage *page_to_mp(struct page *page, int offset)
148 {
149 	return PagePrivate(page) ? (struct metapage *)page_private(page) : NULL;
150 }
151 
152 static inline int insert_metapage(struct page *page, struct metapage *mp)
153 {
154 	if (mp) {
155 		set_page_private(page, (unsigned long)mp);
156 		SetPagePrivate(page);
157 		kmap(page);
158 	}
159 	return 0;
160 }
161 
162 static inline void remove_metapage(struct page *page, struct metapage *mp)
163 {
164 	set_page_private(page, 0);
165 	ClearPagePrivate(page);
166 	kunmap(page);
167 }
168 
169 #define inc_io(page) do {} while(0)
170 #define dec_io(page, handler) handler(page)
171 
172 #endif
173 
174 static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
175 {
176 	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
177 
178 	if (mp) {
179 		mp->lid = 0;
180 		mp->lsn = 0;
181 		mp->data = NULL;
182 		mp->clsn = 0;
183 		mp->log = NULL;
184 		init_waitqueue_head(&mp->wait);
185 	}
186 	return mp;
187 }
188 
189 static inline void free_metapage(struct metapage *mp)
190 {
191 	mempool_free(mp, metapage_mempool);
192 }
193 
194 int __init metapage_init(void)
195 {
196 	/*
197 	 * Allocate the metapage structures
198 	 */
199 	metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
200 					   0, 0, NULL);
201 	if (metapage_cache == NULL)
202 		return -ENOMEM;
203 
204 	metapage_mempool = mempool_create_slab_pool(METAPOOL_MIN_PAGES,
205 						    metapage_cache);
206 
207 	if (metapage_mempool == NULL) {
208 		kmem_cache_destroy(metapage_cache);
209 		return -ENOMEM;
210 	}
211 
212 	return 0;
213 }
214 
215 void metapage_exit(void)
216 {
217 	mempool_destroy(metapage_mempool);
218 	kmem_cache_destroy(metapage_cache);
219 }
220 
221 static inline void drop_metapage(struct page *page, struct metapage *mp)
222 {
223 	if (mp->count || mp->nohomeok || test_bit(META_dirty, &mp->flag) ||
224 	    test_bit(META_io, &mp->flag))
225 		return;
226 	remove_metapage(page, mp);
227 	INCREMENT(mpStat.pagefree);
228 	free_metapage(mp);
229 }
230 
231 /*
232  * Metapage address space operations
233  */
234 
235 static sector_t metapage_get_blocks(struct inode *inode, sector_t lblock,
236 				    int *len)
237 {
238 	int rc = 0;
239 	int xflag;
240 	s64 xaddr;
241 	sector_t file_blocks = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
242 			       inode->i_blkbits;
243 
244 	if (lblock >= file_blocks)
245 		return 0;
246 	if (lblock + *len > file_blocks)
247 		*len = file_blocks - lblock;
248 
249 	if (inode->i_ino) {
250 		rc = xtLookup(inode, (s64)lblock, *len, &xflag, &xaddr, len, 0);
251 		if ((rc == 0) && *len)
252 			lblock = (sector_t)xaddr;
253 		else
254 			lblock = 0;
255 	} /* else no mapping */
256 
257 	return lblock;
258 }
259 
260 static void last_read_complete(struct page *page)
261 {
262 	if (!PageError(page))
263 		SetPageUptodate(page);
264 	unlock_page(page);
265 }
266 
267 static void metapage_read_end_io(struct bio *bio)
268 {
269 	struct page *page = bio->bi_private;
270 
271 	if (bio->bi_status) {
272 		printk(KERN_ERR "metapage_read_end_io: I/O error\n");
273 		SetPageError(page);
274 	}
275 
276 	dec_io(page, last_read_complete);
277 	bio_put(bio);
278 }
279 
280 static void remove_from_logsync(struct metapage *mp)
281 {
282 	struct jfs_log *log = mp->log;
283 	unsigned long flags;
284 /*
285  * This can race.  Recheck that log hasn't been set to null, and after
286  * acquiring logsync lock, recheck lsn
287  */
288 	if (!log)
289 		return;
290 
291 	LOGSYNC_LOCK(log, flags);
292 	if (mp->lsn) {
293 		mp->log = NULL;
294 		mp->lsn = 0;
295 		mp->clsn = 0;
296 		log->count--;
297 		list_del(&mp->synclist);
298 	}
299 	LOGSYNC_UNLOCK(log, flags);
300 }
301 
302 static void last_write_complete(struct page *page)
303 {
304 	struct metapage *mp;
305 	unsigned int offset;
306 
307 	for (offset = 0; offset < PAGE_SIZE; offset += PSIZE) {
308 		mp = page_to_mp(page, offset);
309 		if (mp && test_bit(META_io, &mp->flag)) {
310 			if (mp->lsn)
311 				remove_from_logsync(mp);
312 			clear_bit(META_io, &mp->flag);
313 		}
314 		/*
315 		 * I'd like to call drop_metapage here, but I don't think it's
316 		 * safe unless I have the page locked
317 		 */
318 	}
319 	end_page_writeback(page);
320 }
321 
322 static void metapage_write_end_io(struct bio *bio)
323 {
324 	struct page *page = bio->bi_private;
325 
326 	BUG_ON(!PagePrivate(page));
327 
328 	if (bio->bi_status) {
329 		printk(KERN_ERR "metapage_write_end_io: I/O error\n");
330 		SetPageError(page);
331 	}
332 	dec_io(page, last_write_complete);
333 	bio_put(bio);
334 }
335 
336 static int metapage_writepage(struct page *page, struct writeback_control *wbc)
337 {
338 	struct bio *bio = NULL;
339 	int block_offset;	/* block offset of mp within page */
340 	struct inode *inode = page->mapping->host;
341 	int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
342 	int len;
343 	int xlen;
344 	struct metapage *mp;
345 	int redirty = 0;
346 	sector_t lblock;
347 	int nr_underway = 0;
348 	sector_t pblock;
349 	sector_t next_block = 0;
350 	sector_t page_start;
351 	unsigned long bio_bytes = 0;
352 	unsigned long bio_offset = 0;
353 	int offset;
354 	int bad_blocks = 0;
355 
356 	page_start = (sector_t)page->index <<
357 		     (PAGE_SHIFT - inode->i_blkbits);
358 	BUG_ON(!PageLocked(page));
359 	BUG_ON(PageWriteback(page));
360 	set_page_writeback(page);
361 
362 	for (offset = 0; offset < PAGE_SIZE; offset += PSIZE) {
363 		mp = page_to_mp(page, offset);
364 
365 		if (!mp || !test_bit(META_dirty, &mp->flag))
366 			continue;
367 
368 		if (mp->nohomeok && !test_bit(META_forcewrite, &mp->flag)) {
369 			redirty = 1;
370 			/*
371 			 * Make sure this page isn't blocked indefinitely.
372 			 * If the journal isn't undergoing I/O, push it
373 			 */
374 			if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
375 				jfs_flush_journal(mp->log, 0);
376 			continue;
377 		}
378 
379 		clear_bit(META_dirty, &mp->flag);
380 		set_bit(META_io, &mp->flag);
381 		block_offset = offset >> inode->i_blkbits;
382 		lblock = page_start + block_offset;
383 		if (bio) {
384 			if (xlen && lblock == next_block) {
385 				/* Contiguous, in memory & on disk */
386 				len = min(xlen, blocks_per_mp);
387 				xlen -= len;
388 				bio_bytes += len << inode->i_blkbits;
389 				continue;
390 			}
391 			/* Not contiguous */
392 			if (bio_add_page(bio, page, bio_bytes, bio_offset) <
393 			    bio_bytes)
394 				goto add_failed;
395 			/*
396 			 * Increment counter before submitting i/o to keep
397 			 * count from hitting zero before we're through
398 			 */
399 			inc_io(page);
400 			if (!bio->bi_iter.bi_size)
401 				goto dump_bio;
402 			submit_bio(bio);
403 			nr_underway++;
404 			bio = NULL;
405 		} else
406 			inc_io(page);
407 		xlen = (PAGE_SIZE - offset) >> inode->i_blkbits;
408 		pblock = metapage_get_blocks(inode, lblock, &xlen);
409 		if (!pblock) {
410 			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
411 			/*
412 			 * We already called inc_io(), but can't cancel it
413 			 * with dec_io() until we're done with the page
414 			 */
415 			bad_blocks++;
416 			continue;
417 		}
418 		len = min(xlen, (int)JFS_SBI(inode->i_sb)->nbperpage);
419 
420 		bio = bio_alloc(inode->i_sb->s_bdev, 1, REQ_OP_WRITE, GFP_NOFS);
421 		bio->bi_iter.bi_sector = pblock << (inode->i_blkbits - 9);
422 		bio->bi_end_io = metapage_write_end_io;
423 		bio->bi_private = page;
424 
425 		/* Don't call bio_add_page yet, we may add to this vec */
426 		bio_offset = offset;
427 		bio_bytes = len << inode->i_blkbits;
428 
429 		xlen -= len;
430 		next_block = lblock + len;
431 	}
432 	if (bio) {
433 		if (bio_add_page(bio, page, bio_bytes, bio_offset) < bio_bytes)
434 				goto add_failed;
435 		if (!bio->bi_iter.bi_size)
436 			goto dump_bio;
437 
438 		submit_bio(bio);
439 		nr_underway++;
440 	}
441 	if (redirty)
442 		redirty_page_for_writepage(wbc, page);
443 
444 	unlock_page(page);
445 
446 	if (bad_blocks)
447 		goto err_out;
448 
449 	if (nr_underway == 0)
450 		end_page_writeback(page);
451 
452 	return 0;
453 add_failed:
454 	/* We should never reach here, since we're only adding one vec */
455 	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
456 	goto skip;
457 dump_bio:
458 	print_hex_dump(KERN_ERR, "JFS: dump of bio: ", DUMP_PREFIX_ADDRESS, 16,
459 		       4, bio, sizeof(*bio), 0);
460 skip:
461 	bio_put(bio);
462 	unlock_page(page);
463 	dec_io(page, last_write_complete);
464 err_out:
465 	while (bad_blocks--)
466 		dec_io(page, last_write_complete);
467 	return -EIO;
468 }
469 
470 static int metapage_read_folio(struct file *fp, struct folio *folio)
471 {
472 	struct page *page = &folio->page;
473 	struct inode *inode = page->mapping->host;
474 	struct bio *bio = NULL;
475 	int block_offset;
476 	int blocks_per_page = i_blocks_per_page(inode, page);
477 	sector_t page_start;	/* address of page in fs blocks */
478 	sector_t pblock;
479 	int xlen;
480 	unsigned int len;
481 	int offset;
482 
483 	BUG_ON(!PageLocked(page));
484 	page_start = (sector_t)page->index <<
485 		     (PAGE_SHIFT - inode->i_blkbits);
486 
487 	block_offset = 0;
488 	while (block_offset < blocks_per_page) {
489 		xlen = blocks_per_page - block_offset;
490 		pblock = metapage_get_blocks(inode, page_start + block_offset,
491 					     &xlen);
492 		if (pblock) {
493 			if (!PagePrivate(page))
494 				insert_metapage(page, NULL);
495 			inc_io(page);
496 			if (bio)
497 				submit_bio(bio);
498 
499 			bio = bio_alloc(inode->i_sb->s_bdev, 1, REQ_OP_READ,
500 					GFP_NOFS);
501 			bio->bi_iter.bi_sector =
502 				pblock << (inode->i_blkbits - 9);
503 			bio->bi_end_io = metapage_read_end_io;
504 			bio->bi_private = page;
505 			len = xlen << inode->i_blkbits;
506 			offset = block_offset << inode->i_blkbits;
507 			if (bio_add_page(bio, page, len, offset) < len)
508 				goto add_failed;
509 			block_offset += xlen;
510 		} else
511 			block_offset++;
512 	}
513 	if (bio)
514 		submit_bio(bio);
515 	else
516 		unlock_page(page);
517 
518 	return 0;
519 
520 add_failed:
521 	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
522 	bio_put(bio);
523 	dec_io(page, last_read_complete);
524 	return -EIO;
525 }
526 
527 static bool metapage_release_folio(struct folio *folio, gfp_t gfp_mask)
528 {
529 	struct metapage *mp;
530 	bool ret = true;
531 	int offset;
532 
533 	for (offset = 0; offset < PAGE_SIZE; offset += PSIZE) {
534 		mp = page_to_mp(&folio->page, offset);
535 
536 		if (!mp)
537 			continue;
538 
539 		jfs_info("metapage_release_folio: mp = 0x%p", mp);
540 		if (mp->count || mp->nohomeok ||
541 		    test_bit(META_dirty, &mp->flag)) {
542 			jfs_info("count = %ld, nohomeok = %d", mp->count,
543 				 mp->nohomeok);
544 			ret = false;
545 			continue;
546 		}
547 		if (mp->lsn)
548 			remove_from_logsync(mp);
549 		remove_metapage(&folio->page, mp);
550 		INCREMENT(mpStat.pagefree);
551 		free_metapage(mp);
552 	}
553 	return ret;
554 }
555 
556 static void metapage_invalidate_folio(struct folio *folio, size_t offset,
557 				    size_t length)
558 {
559 	BUG_ON(offset || length < folio_size(folio));
560 
561 	BUG_ON(folio_test_writeback(folio));
562 
563 	metapage_release_folio(folio, 0);
564 }
565 
566 const struct address_space_operations jfs_metapage_aops = {
567 	.read_folio	= metapage_read_folio,
568 	.writepage	= metapage_writepage,
569 	.release_folio	= metapage_release_folio,
570 	.invalidate_folio = metapage_invalidate_folio,
571 	.dirty_folio	= filemap_dirty_folio,
572 };
573 
574 struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
575 				unsigned int size, int absolute,
576 				unsigned long new)
577 {
578 	int l2BlocksPerPage;
579 	int l2bsize;
580 	struct address_space *mapping;
581 	struct metapage *mp = NULL;
582 	struct page *page;
583 	unsigned long page_index;
584 	unsigned long page_offset;
585 
586 	jfs_info("__get_metapage: ino = %ld, lblock = 0x%lx, abs=%d",
587 		 inode->i_ino, lblock, absolute);
588 
589 	l2bsize = inode->i_blkbits;
590 	l2BlocksPerPage = PAGE_SHIFT - l2bsize;
591 	page_index = lblock >> l2BlocksPerPage;
592 	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
593 	if ((page_offset + size) > PAGE_SIZE) {
594 		jfs_err("MetaData crosses page boundary!!");
595 		jfs_err("lblock = %lx, size  = %d", lblock, size);
596 		dump_stack();
597 		return NULL;
598 	}
599 	if (absolute)
600 		mapping = JFS_SBI(inode->i_sb)->direct_inode->i_mapping;
601 	else {
602 		/*
603 		 * If an nfs client tries to read an inode that is larger
604 		 * than any existing inodes, we may try to read past the
605 		 * end of the inode map
606 		 */
607 		if ((lblock << inode->i_blkbits) >= inode->i_size)
608 			return NULL;
609 		mapping = inode->i_mapping;
610 	}
611 
612 	if (new && (PSIZE == PAGE_SIZE)) {
613 		page = grab_cache_page(mapping, page_index);
614 		if (!page) {
615 			jfs_err("grab_cache_page failed!");
616 			return NULL;
617 		}
618 		SetPageUptodate(page);
619 	} else {
620 		page = read_mapping_page(mapping, page_index, NULL);
621 		if (IS_ERR(page)) {
622 			jfs_err("read_mapping_page failed!");
623 			return NULL;
624 		}
625 		lock_page(page);
626 	}
627 
628 	mp = page_to_mp(page, page_offset);
629 	if (mp) {
630 		if (mp->logical_size != size) {
631 			jfs_error(inode->i_sb,
632 				  "get_mp->logical_size != size\n");
633 			jfs_err("logical_size = %d, size = %d",
634 				mp->logical_size, size);
635 			dump_stack();
636 			goto unlock;
637 		}
638 		mp->count++;
639 		lock_metapage(mp);
640 		if (test_bit(META_discard, &mp->flag)) {
641 			if (!new) {
642 				jfs_error(inode->i_sb,
643 					  "using a discarded metapage\n");
644 				discard_metapage(mp);
645 				goto unlock;
646 			}
647 			clear_bit(META_discard, &mp->flag);
648 		}
649 	} else {
650 		INCREMENT(mpStat.pagealloc);
651 		mp = alloc_metapage(GFP_NOFS);
652 		if (!mp)
653 			goto unlock;
654 		mp->page = page;
655 		mp->sb = inode->i_sb;
656 		mp->flag = 0;
657 		mp->xflag = COMMIT_PAGE;
658 		mp->count = 1;
659 		mp->nohomeok = 0;
660 		mp->logical_size = size;
661 		mp->data = page_address(page) + page_offset;
662 		mp->index = lblock;
663 		if (unlikely(insert_metapage(page, mp))) {
664 			free_metapage(mp);
665 			goto unlock;
666 		}
667 		lock_metapage(mp);
668 	}
669 
670 	if (new) {
671 		jfs_info("zeroing mp = 0x%p", mp);
672 		memset(mp->data, 0, PSIZE);
673 	}
674 
675 	unlock_page(page);
676 	jfs_info("__get_metapage: returning = 0x%p data = 0x%p", mp, mp->data);
677 	return mp;
678 
679 unlock:
680 	unlock_page(page);
681 	return NULL;
682 }
683 
684 void grab_metapage(struct metapage * mp)
685 {
686 	jfs_info("grab_metapage: mp = 0x%p", mp);
687 	get_page(mp->page);
688 	lock_page(mp->page);
689 	mp->count++;
690 	lock_metapage(mp);
691 	unlock_page(mp->page);
692 }
693 
694 void force_metapage(struct metapage *mp)
695 {
696 	struct page *page = mp->page;
697 	jfs_info("force_metapage: mp = 0x%p", mp);
698 	set_bit(META_forcewrite, &mp->flag);
699 	clear_bit(META_sync, &mp->flag);
700 	get_page(page);
701 	lock_page(page);
702 	set_page_dirty(page);
703 	if (write_one_page(page))
704 		jfs_error(mp->sb, "write_one_page() failed\n");
705 	clear_bit(META_forcewrite, &mp->flag);
706 	put_page(page);
707 }
708 
709 void hold_metapage(struct metapage *mp)
710 {
711 	lock_page(mp->page);
712 }
713 
714 void put_metapage(struct metapage *mp)
715 {
716 	if (mp->count || mp->nohomeok) {
717 		/* Someone else will release this */
718 		unlock_page(mp->page);
719 		return;
720 	}
721 	get_page(mp->page);
722 	mp->count++;
723 	lock_metapage(mp);
724 	unlock_page(mp->page);
725 	release_metapage(mp);
726 }
727 
728 void release_metapage(struct metapage * mp)
729 {
730 	struct page *page = mp->page;
731 	jfs_info("release_metapage: mp = 0x%p, flag = 0x%lx", mp, mp->flag);
732 
733 	BUG_ON(!page);
734 
735 	lock_page(page);
736 	unlock_metapage(mp);
737 
738 	assert(mp->count);
739 	if (--mp->count || mp->nohomeok) {
740 		unlock_page(page);
741 		put_page(page);
742 		return;
743 	}
744 
745 	if (test_bit(META_dirty, &mp->flag)) {
746 		set_page_dirty(page);
747 		if (test_bit(META_sync, &mp->flag)) {
748 			clear_bit(META_sync, &mp->flag);
749 			if (write_one_page(page))
750 				jfs_error(mp->sb, "write_one_page() failed\n");
751 			lock_page(page); /* write_one_page unlocks the page */
752 		}
753 	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
754 		remove_from_logsync(mp);
755 
756 	/* Try to keep metapages from using up too much memory */
757 	drop_metapage(page, mp);
758 
759 	unlock_page(page);
760 	put_page(page);
761 }
762 
763 void __invalidate_metapages(struct inode *ip, s64 addr, int len)
764 {
765 	sector_t lblock;
766 	int l2BlocksPerPage = PAGE_SHIFT - ip->i_blkbits;
767 	int BlocksPerPage = 1 << l2BlocksPerPage;
768 	/* All callers are interested in block device's mapping */
769 	struct address_space *mapping =
770 		JFS_SBI(ip->i_sb)->direct_inode->i_mapping;
771 	struct metapage *mp;
772 	struct page *page;
773 	unsigned int offset;
774 
775 	/*
776 	 * Mark metapages to discard.  They will eventually be
777 	 * released, but should not be written.
778 	 */
779 	for (lblock = addr & ~(BlocksPerPage - 1); lblock < addr + len;
780 	     lblock += BlocksPerPage) {
781 		page = find_lock_page(mapping, lblock >> l2BlocksPerPage);
782 		if (!page)
783 			continue;
784 		for (offset = 0; offset < PAGE_SIZE; offset += PSIZE) {
785 			mp = page_to_mp(page, offset);
786 			if (!mp)
787 				continue;
788 			if (mp->index < addr)
789 				continue;
790 			if (mp->index >= addr + len)
791 				break;
792 
793 			clear_bit(META_dirty, &mp->flag);
794 			set_bit(META_discard, &mp->flag);
795 			if (mp->lsn)
796 				remove_from_logsync(mp);
797 		}
798 		unlock_page(page);
799 		put_page(page);
800 	}
801 }
802 
803 #ifdef CONFIG_JFS_STATISTICS
804 int jfs_mpstat_proc_show(struct seq_file *m, void *v)
805 {
806 	seq_printf(m,
807 		       "JFS Metapage statistics\n"
808 		       "=======================\n"
809 		       "page allocations = %d\n"
810 		       "page frees = %d\n"
811 		       "lock waits = %d\n",
812 		       mpStat.pagealloc,
813 		       mpStat.pagefree,
814 		       mpStat.lockwait);
815 	return 0;
816 }
817 #endif
818