fs/jfs/jfs_metapage.c - kernel/msm-4.9 - Gitiles

 /*
  *   Copyright (C) International Business Machines Corp., 2000-2005
  *   Portions Copyright (C) Christoph Hellwig, 2001-2002
  *
  *   This program is free software;  you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
  *   the Free Software Foundation; either version 2 of the License, or
  *   (at your option) any later version.
  *
  *   This program is distributed in the hope that it will be useful,
  *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  *   the GNU General Public License for more details.
  *
  *   You should have received a copy of the GNU General Public License
  *   along with this program;  if not, write to the Free Software
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */

 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/bio.h>
 #include <linux/init.h>
 #include <linux/buffer_head.h>
 #include <linux/mempool.h>
 #include "jfs_incore.h"
 #include "jfs_superblock.h"
 #include "jfs_filsys.h"
 #include "jfs_metapage.h"
 #include "jfs_txnmgr.h"
 #include "jfs_debug.h"

 #ifdef CONFIG_JFS_STATISTICS
 static struct {
 	uint	pagealloc;	/* # of page allocations */
 	uint	pagefree;	/* # of page frees */
 	uint	lockwait;	/* # of sleeping lock_metapage() calls */
 } mpStat;
 #endif

 #define metapage_locked(mp) test_bit(META_locked, &(mp)->flag)
 #define trylock_metapage(mp) test_and_set_bit(META_locked, &(mp)->flag)

 static inline void unlock_metapage(struct metapage *mp)
 {
 	clear_bit(META_locked, &mp->flag);
 	wake_up(&mp->wait);
 }

 static inline void __lock_metapage(struct metapage *mp)
 {
 	DECLARE_WAITQUEUE(wait, current);
 	INCREMENT(mpStat.lockwait);
 	add_wait_queue_exclusive(&mp->wait, &wait);
 	do {
 		set_current_state(TASK_UNINTERRUPTIBLE);
 		if (metapage_locked(mp)) {
 			unlock_page(mp->page);
 			schedule();
 			lock_page(mp->page);
 		}
 	} while (trylock_metapage(mp));
 	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(&mp->wait, &wait);
 }

 /*
  * Must have mp->page locked
  */
 static inline void lock_metapage(struct metapage *mp)
 {
 	if (trylock_metapage(mp))
 		__lock_metapage(mp);
 }

 #define METAPOOL_MIN_PAGES 32
 static kmem_cache_t *metapage_cache;
 static mempool_t *metapage_mempool;

 #define MPS_PER_PAGE (PAGE_CACHE_SIZE >> L2PSIZE)

 #if MPS_PER_PAGE > 1

 struct meta_anchor {
 	int mp_count;
 	atomic_t io_count;
 	struct metapage *mp[MPS_PER_PAGE];
 };
 #define mp_anchor(page) ((struct meta_anchor *)page->private)

 static inline struct metapage *page_to_mp(struct page *page, uint offset)
 {
 	if (!PagePrivate(page))
 		return NULL;
 	return mp_anchor(page)->mp[offset >> L2PSIZE];
 }

 static inline int insert_metapage(struct page *page, struct metapage *mp)
 {
 	struct meta_anchor *a;
 	int index;
 	int l2mp_blocks;	/* log2 blocks per metapage */

 	if (PagePrivate(page))
 		a = mp_anchor(page);
 	else {
 		a = kmalloc(sizeof(struct meta_anchor), GFP_NOFS);
 		if (!a)
 			return -ENOMEM;
 		memset(a, 0, sizeof(struct meta_anchor));
 		page->private = (unsigned long)a;
 		SetPagePrivate(page);
 		kmap(page);
 	}

 	if (mp) {
 		l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
 		index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
 		a->mp_count++;
 		a->mp[index] = mp;
 	}

 	return 0;
 }

 static inline void remove_metapage(struct page *page, struct metapage *mp)
 {
 	struct meta_anchor *a = mp_anchor(page);
 	int l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
 	int index;

 	index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);

 	BUG_ON(a->mp[index] != mp);

 	a->mp[index] = NULL;
 	if (--a->mp_count == 0) {
 		kfree(a);
 		page->private = 0;
 		ClearPagePrivate(page);
 		kunmap(page);
 	}
 }

 static inline void inc_io(struct page *page)
 {
 	atomic_inc(&mp_anchor(page)->io_count);
 }

 static inline void dec_io(struct page *page, void (*handler) (struct page *))
 {
 	if (atomic_dec_and_test(&mp_anchor(page)->io_count))
 		handler(page);
 }

 #else
 static inline struct metapage *page_to_mp(struct page *page, uint offset)
 {
 	return PagePrivate(page) ? (struct metapage *)page->private : NULL;
 }

 static inline int insert_metapage(struct page *page, struct metapage *mp)
 {
 	if (mp) {
 		page->private = (unsigned long)mp;
 		SetPagePrivate(page);
 		kmap(page);
 	}
 	return 0;
 }

 static inline void remove_metapage(struct page *page, struct metapage *mp)
 {
 	page->private = 0;
 	ClearPagePrivate(page);
 	kunmap(page);
 }

 #define inc_io(page) do {} while(0)
 #define dec_io(page, handler) handler(page)

 #endif

 static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
 {
 	struct metapage *mp = (struct metapage *)foo;

 	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
 	    SLAB_CTOR_CONSTRUCTOR) {
 		mp->lid = 0;
 		mp->lsn = 0;
 		mp->flag = 0;
 		mp->data = NULL;
 		mp->clsn = 0;
 		mp->log = NULL;
 		set_bit(META_free, &mp->flag);
 		init_waitqueue_head(&mp->wait);
 	}
 }

 static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
 {
 	return mempool_alloc(metapage_mempool, gfp_mask);
 }

 static inline void free_metapage(struct metapage *mp)
 {
 	mp->flag = 0;
 	set_bit(META_free, &mp->flag);

 	mempool_free(mp, metapage_mempool);
 }

 int __init metapage_init(void)
 {
 	/*
 	 * Allocate the metapage structures
 	 */
 	metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
 					   0, 0, init_once, NULL);
 	if (metapage_cache == NULL)
 		return -ENOMEM;

 	metapage_mempool = mempool_create(METAPOOL_MIN_PAGES, mempool_alloc_slab,
 					  mempool_free_slab, metapage_cache);

 	if (metapage_mempool == NULL) {
 		kmem_cache_destroy(metapage_cache);
 		return -ENOMEM;
 	}

 	return 0;
 }

 void metapage_exit(void)
 {
 	mempool_destroy(metapage_mempool);
 	kmem_cache_destroy(metapage_cache);
 }

 static inline void drop_metapage(struct page *page, struct metapage *mp)
 {
 	if (mp->count || mp->nohomeok || test_bit(META_dirty, &mp->flag) ||
 	    test_bit(META_io, &mp->flag))
 		return;
 	remove_metapage(page, mp);
 	INCREMENT(mpStat.pagefree);
 	free_metapage(mp);
 }

 /*
  * Metapage address space operations
  */

 static sector_t metapage_get_blocks(struct inode *inode, sector_t lblock,
 				    unsigned int *len)
 {
 	int rc = 0;
 	int xflag;
 	s64 xaddr;
 	sector_t file_blocks = (inode->i_size + inode->i_blksize - 1) >>
 			       inode->i_blkbits;

 	if (lblock >= file_blocks)
 		return 0;
 	if (lblock + *len > file_blocks)
 		*len = file_blocks - lblock;

 	if (inode->i_ino) {
 		rc = xtLookup(inode, (s64)lblock, *len, &xflag, &xaddr, len, 0);
 		if ((rc == 0) && *len)
 			lblock = (sector_t)xaddr;
 		else
 			lblock = 0;
 	} /* else no mapping */

 	return lblock;
 }

 static void last_read_complete(struct page *page)
 {
 	if (!PageError(page))
 		SetPageUptodate(page);
 	unlock_page(page);
 }

 static int metapage_read_end_io(struct bio *bio, unsigned int bytes_done,
 				int err)
 {
 	struct page *page = bio->bi_private;

 	if (bio->bi_size)
 		return 1;

 	if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
 		printk(KERN_ERR "metapage_read_end_io: I/O error\n");
 		SetPageError(page);
 	}

 	dec_io(page, last_read_complete);
 	bio_put(bio);

 	return 0;
 }

 static void remove_from_logsync(struct metapage *mp)
 {
 	struct jfs_log *log = mp->log;
 	unsigned long flags;
 /*
  * This can race.  Recheck that log hasn't been set to null, and after
  * acquiring logsync lock, recheck lsn
  */
 	if (!log)
 		return;

 	LOGSYNC_LOCK(log, flags);
 	if (mp->lsn) {
 		mp->log = NULL;
 		mp->lsn = 0;
 		mp->clsn = 0;
 		log->count--;
 		list_del(&mp->synclist);
 	}
 	LOGSYNC_UNLOCK(log, flags);
 }

 static void last_write_complete(struct page *page)
 {
 	struct metapage *mp;
 	unsigned int offset;

 	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
 		mp = page_to_mp(page, offset);
 		if (mp && test_bit(META_io, &mp->flag)) {
 			if (mp->lsn)
 				remove_from_logsync(mp);
 			clear_bit(META_io, &mp->flag);
 		}
 		/*
 		 * I'd like to call drop_metapage here, but I don't think it's
 		 * safe unless I have the page locked
 		 */
 	}
 	end_page_writeback(page);
 }

 static int metapage_write_end_io(struct bio *bio, unsigned int bytes_done,
 				 int err)
 {
 	struct page *page = bio->bi_private;

 	BUG_ON(!PagePrivate(page));

 	if (bio->bi_size)
 		return 1;

 	if (! test_bit(BIO_UPTODATE, &bio->bi_flags)) {
 		printk(KERN_ERR "metapage_write_end_io: I/O error\n");
 		SetPageError(page);
 	}
 	dec_io(page, last_write_complete);
 	bio_put(bio);
 	return 0;
 }

 static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct bio *bio = NULL;
 	unsigned int block_offset;	/* block offset of mp within page */
 	struct inode *inode = page->mapping->host;
 	unsigned int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
 	unsigned int len;
 	unsigned int xlen;
 	struct metapage *mp;
 	int redirty = 0;
 	sector_t lblock;
 	sector_t pblock;
 	sector_t next_block = 0;
 	sector_t page_start;
 	unsigned long bio_bytes = 0;
 	unsigned long bio_offset = 0;
 	unsigned int offset;

 	page_start = (sector_t)page->index <<
 		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
 	BUG_ON(!PageLocked(page));
 	BUG_ON(PageWriteback(page));

 	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
 		mp = page_to_mp(page, offset);

 		if (!mp || !test_bit(META_dirty, &mp->flag))
 			continue;

 		if (mp->nohomeok && !test_bit(META_forcewrite, &mp->flag)) {
 			redirty = 1;
 			/*
 			 * Make sure this page isn't blocked indefinitely.
 			 * If the journal isn't undergoing I/O, push it
 			 */
 			if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
 				jfs_flush_journal(mp->log, 0);
 			continue;
 		}

 		clear_bit(META_dirty, &mp->flag);
 		block_offset = offset >> inode->i_blkbits;
 		lblock = page_start + block_offset;
 		if (bio) {
 			if (xlen && lblock == next_block) {
 				/* Contiguous, in memory & on disk */
 				len = min(xlen, blocks_per_mp);
 				xlen -= len;
 				bio_bytes += len << inode->i_blkbits;
 				set_bit(META_io, &mp->flag);
 				continue;
 			}
 			/* Not contiguous */
 			if (bio_add_page(bio, page, bio_bytes, bio_offset) <
 			    bio_bytes)
 				goto add_failed;
 			/*
 			 * Increment counter before submitting i/o to keep
 			 * count from hitting zero before we're through
 			 */
 			inc_io(page);
 			if (!bio->bi_size)
 				goto dump_bio;
 			submit_bio(WRITE, bio);
 			bio = NULL;
 		} else {
 			set_page_writeback(page);
 			inc_io(page);
 		}
 		xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
 		pblock = metapage_get_blocks(inode, lblock, &xlen);
 		if (!pblock) {
 			/* Need better error handling */
 			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
 			dec_io(page, last_write_complete);
 			continue;
 		}
 		set_bit(META_io, &mp->flag);
 		len = min(xlen, (uint) JFS_SBI(inode->i_sb)->nbperpage);

 		bio = bio_alloc(GFP_NOFS, 1);
 		bio->bi_bdev = inode->i_sb->s_bdev;
 		bio->bi_sector = pblock << (inode->i_blkbits - 9);
 		bio->bi_end_io = metapage_write_end_io;
 		bio->bi_private = page;

 		/* Don't call bio_add_page yet, we may add to this vec */
 		bio_offset = offset;
 		bio_bytes = len << inode->i_blkbits;

 		xlen -= len;
 		next_block = lblock + len;
 	}
 	if (bio) {
 		if (bio_add_page(bio, page, bio_bytes, bio_offset) < bio_bytes)
 				goto add_failed;
 		if (!bio->bi_size)
 			goto dump_bio;

 		submit_bio(WRITE, bio);
 	}
 	if (redirty)
 		redirty_page_for_writepage(wbc, page);

 	unlock_page(page);

 	return 0;
 add_failed:
 	/* We should never reach here, since we're only adding one vec */
 	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
 	goto skip;
 dump_bio:
 	dump_mem("bio", bio, sizeof(*bio));
 skip:
 	bio_put(bio);
 	unlock_page(page);
 	dec_io(page, last_write_complete);

 	return -EIO;
 }

 static int metapage_readpage(struct file *fp, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	struct bio *bio = NULL;
 	unsigned int block_offset;
 	unsigned int blocks_per_page = PAGE_CACHE_SIZE >> inode->i_blkbits;
 	sector_t page_start;	/* address of page in fs blocks */
 	sector_t pblock;
 	unsigned int xlen;
 	unsigned int len;
 	unsigned int offset;

 	BUG_ON(!PageLocked(page));
 	page_start = (sector_t)page->index <<
 		     (PAGE_CACHE_SHIFT - inode->i_blkbits);

 	block_offset = 0;
 	while (block_offset < blocks_per_page) {
 		xlen = blocks_per_page - block_offset;
 		pblock = metapage_get_blocks(inode, page_start + block_offset,
 					     &xlen);
 		if (pblock) {
 			if (!PagePrivate(page))
 				insert_metapage(page, NULL);
 			inc_io(page);
 			if (bio)
 				submit_bio(READ, bio);

 			bio = bio_alloc(GFP_NOFS, 1);
 			bio->bi_bdev = inode->i_sb->s_bdev;
 			bio->bi_sector = pblock << (inode->i_blkbits - 9);
 			bio->bi_end_io = metapage_read_end_io;
 			bio->bi_private = page;
 			len = xlen << inode->i_blkbits;
 			offset = block_offset << inode->i_blkbits;
 			if (bio_add_page(bio, page, len, offset) < len)
 				goto add_failed;
 			block_offset += xlen;
 		} else
 			block_offset++;
 	}
 	if (bio)
 		submit_bio(READ, bio);
 	else
 		unlock_page(page);

 	return 0;

 add_failed:
 	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
 	bio_put(bio);
 	dec_io(page, last_read_complete);
 	return -EIO;
 }

 static int metapage_releasepage(struct page *page, gfp_t gfp_mask)
 {
 	struct metapage *mp;
 	int busy = 0;
 	unsigned int offset;

 	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
 		mp = page_to_mp(page, offset);

 		if (!mp)
 			continue;

 		jfs_info("metapage_releasepage: mp = 0x%p", mp);
 		if (mp->count || mp->nohomeok) {
 			jfs_info("count = %ld, nohomeok = %d", mp->count,
 				 mp->nohomeok);
 			busy = 1;
 			continue;
 		}
 		wait_on_page_writeback(page);
 		//WARN_ON(test_bit(META_dirty, &mp->flag));
 		if (test_bit(META_dirty, &mp->flag)) {
 			dump_mem("dirty mp in metapage_releasepage", mp,
 				 sizeof(struct metapage));
 			dump_mem("page", page, sizeof(struct page));
 			dump_stack();
 		}
 		if (mp->lsn)
 			remove_from_logsync(mp);
 		remove_metapage(page, mp);
 		INCREMENT(mpStat.pagefree);
 		free_metapage(mp);
 	}
 	if (busy)
 		return -1;

 	return 0;
 }

 static int metapage_invalidatepage(struct page *page, unsigned long offset)
 {
 	BUG_ON(offset);

 	if (PageWriteback(page))
 		return 0;

 	return metapage_releasepage(page, 0);
 }

 struct address_space_operations jfs_metapage_aops = {
 	.readpage	= metapage_readpage,
 	.writepage	= metapage_writepage,
 	.sync_page	= block_sync_page,
 	.releasepage	= metapage_releasepage,
 	.invalidatepage	= metapage_invalidatepage,
 	.set_page_dirty	= __set_page_dirty_nobuffers,
 };

 struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
 				unsigned int size, int absolute,
 				unsigned long new)
 {
 	int l2BlocksPerPage;
 	int l2bsize;
 	struct address_space *mapping;
 	struct metapage *mp = NULL;
 	struct page *page;
 	unsigned long page_index;
 	unsigned long page_offset;

 	jfs_info("__get_metapage: ino = %ld, lblock = 0x%lx, abs=%d",
 		 inode->i_ino, lblock, absolute);

 	l2bsize = inode->i_blkbits;
 	l2BlocksPerPage = PAGE_CACHE_SHIFT - l2bsize;
 	page_index = lblock >> l2BlocksPerPage;
 	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
 	if ((page_offset + size) > PAGE_CACHE_SIZE) {
 		jfs_err("MetaData crosses page boundary!!");
 		jfs_err("lblock = %lx, size  = %d", lblock, size);
 		dump_stack();
 		return NULL;
 	}
 	if (absolute)
 		mapping = JFS_SBI(inode->i_sb)->direct_inode->i_mapping;
 	else {
 		/*
 		 * If an nfs client tries to read an inode that is larger
 		 * than any existing inodes, we may try to read past the
 		 * end of the inode map
 		 */
 		if ((lblock << inode->i_blkbits) >= inode->i_size)
 			return NULL;
 		mapping = inode->i_mapping;
 	}

 	if (new && (PSIZE == PAGE_CACHE_SIZE)) {
 		page = grab_cache_page(mapping, page_index);
 		if (!page) {
 			jfs_err("grab_cache_page failed!");
 			return NULL;
 		}
 		SetPageUptodate(page);
 	} else {
 		page = read_cache_page(mapping, page_index,
 			    (filler_t *)mapping->a_ops->readpage, NULL);
 		if (IS_ERR(page) || !PageUptodate(page)) {
 			jfs_err("read_cache_page failed!");
 			return NULL;
 		}
 		lock_page(page);
 	}

 	mp = page_to_mp(page, page_offset);
 	if (mp) {
 		if (mp->logical_size != size) {
 			jfs_error(inode->i_sb,
 				  "__get_metapage: mp->logical_size != size");
 			jfs_err("logical_size = %d, size = %d",
 				mp->logical_size, size);
 			dump_stack();
 			goto unlock;
 		}
 		mp->count++;
 		lock_metapage(mp);
 		if (test_bit(META_discard, &mp->flag)) {
 			if (!new) {
 				jfs_error(inode->i_sb,
 					  "__get_metapage: using a "
 					  "discarded metapage");
 				discard_metapage(mp);
 				goto unlock;
 			}
 			clear_bit(META_discard, &mp->flag);
 		}
 	} else {
 		INCREMENT(mpStat.pagealloc);
 		mp = alloc_metapage(GFP_NOFS);
 		mp->page = page;
 		mp->flag = 0;
 		mp->xflag = COMMIT_PAGE;
 		mp->count = 1;
 		mp->nohomeok = 0;
 		mp->logical_size = size;
 		mp->data = page_address(page) + page_offset;
 		mp->index = lblock;
 		if (unlikely(insert_metapage(page, mp))) {
 			free_metapage(mp);
 			goto unlock;
 		}
 		lock_metapage(mp);
 	}

 	if (new) {
 		jfs_info("zeroing mp = 0x%p", mp);
 		memset(mp->data, 0, PSIZE);
 	}

 	unlock_page(page);
 	jfs_info("__get_metapage: returning = 0x%p data = 0x%p", mp, mp->data);
 	return mp;

 unlock:
 	unlock_page(page);
 	return NULL;
 }

 void grab_metapage(struct metapage * mp)
 {
 	jfs_info("grab_metapage: mp = 0x%p", mp);
 	page_cache_get(mp->page);
 	lock_page(mp->page);
 	mp->count++;
 	lock_metapage(mp);
 	unlock_page(mp->page);
 }

 void force_metapage(struct metapage *mp)
 {
 	struct page *page = mp->page;
 	jfs_info("force_metapage: mp = 0x%p", mp);
 	set_bit(META_forcewrite, &mp->flag);
 	clear_bit(META_sync, &mp->flag);
 	page_cache_get(page);
 	lock_page(page);
 	set_page_dirty(page);
 	write_one_page(page, 1);
 	clear_bit(META_forcewrite, &mp->flag);
 	page_cache_release(page);
 }

 void hold_metapage(struct metapage *mp)
 {
 	lock_page(mp->page);
 }

 void put_metapage(struct metapage *mp)
 {
 	if (mp->count || mp->nohomeok) {
 		/* Someone else will release this */
 		unlock_page(mp->page);
 		return;
 	}
 	page_cache_get(mp->page);
 	mp->count++;
 	lock_metapage(mp);
 	unlock_page(mp->page);
 	release_metapage(mp);
 }

 void release_metapage(struct metapage * mp)
 {
 	struct page *page = mp->page;
 	jfs_info("release_metapage: mp = 0x%p, flag = 0x%lx", mp, mp->flag);

 	BUG_ON(!page);

 	lock_page(page);
 	unlock_metapage(mp);

 	assert(mp->count);
 	if (--mp->count || mp->nohomeok) {
 		unlock_page(page);
 		page_cache_release(page);
 		return;
 	}

 	if (test_bit(META_dirty, &mp->flag)) {
 		set_page_dirty(page);
 		if (test_bit(META_sync, &mp->flag)) {
 			clear_bit(META_sync, &mp->flag);
 			write_one_page(page, 1);
 			lock_page(page); /* write_one_page unlocks the page */
 		}
 	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
 		remove_from_logsync(mp);

 #if MPS_PER_PAGE == 1
 	/*
 	 * If we know this is the only thing in the page, we can throw
 	 * the page out of the page cache.  If pages are larger, we
 	 * don't want to do this.
 	 */

 	/* Retest mp->count since we may have released page lock */
 	if (test_bit(META_discard, &mp->flag) && !mp->count) {
 		clear_page_dirty(page);
 		ClearPageUptodate(page);
 	}
 #else
 	/* Try to keep metapages from using up too much memory */
 	drop_metapage(page, mp);
 #endif
 	unlock_page(page);
 	page_cache_release(page);
 }

 void __invalidate_metapages(struct inode *ip, s64 addr, int len)
 {
 	sector_t lblock;
 	int l2BlocksPerPage = PAGE_CACHE_SHIFT - ip->i_blkbits;
 	int BlocksPerPage = 1 << l2BlocksPerPage;
 	/* All callers are interested in block device's mapping */
 	struct address_space *mapping =
 		JFS_SBI(ip->i_sb)->direct_inode->i_mapping;
 	struct metapage *mp;
 	struct page *page;
 	unsigned int offset;

 	/*
 	 * Mark metapages to discard.  They will eventually be
 	 * released, but should not be written.
 	 */
 	for (lblock = addr & ~(BlocksPerPage - 1); lblock < addr + len;
 	     lblock += BlocksPerPage) {
 		page = find_lock_page(mapping, lblock >> l2BlocksPerPage);
 		if (!page)
 			continue;
 		for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
 			mp = page_to_mp(page, offset);
 			if (!mp)
 				continue;
 			if (mp->index < addr)
 				continue;
 			if (mp->index >= addr + len)
 				break;

 			clear_bit(META_dirty, &mp->flag);
 			set_bit(META_discard, &mp->flag);
 			if (mp->lsn)
 				remove_from_logsync(mp);
 		}
 		unlock_page(page);
 		page_cache_release(page);
 	}
 }

 #ifdef CONFIG_JFS_STATISTICS
 int jfs_mpstat_read(char *buffer, char **start, off_t offset, int length,
 		    int *eof, void *data)
 {
 	int len = 0;
 	off_t begin;

 	len += sprintf(buffer,
 		       "JFS Metapage statistics\n"
 		       "=======================\n"
 		       "page allocations = %d\n"
 		       "page frees = %d\n"
 		       "lock waits = %d\n",
 		       mpStat.pagealloc,
 		       mpStat.pagefree,
 		       mpStat.lockwait);

 	begin = offset;
 	*start = buffer + begin;
 	len -= begin;

 	if (len > length)
 		len = length;
 	else
 		*eof = 1;

 	if (len < 0)
 		len = 0;

 	return len;
 }
 #endif
	/*
	* Copyright (C) International Business Machines Corp., 2000-2005
	* Portions Copyright (C) Christoph Hellwig, 2001-2002
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
	* the GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/bio.h>
	#include <linux/init.h>
	#include <linux/buffer_head.h>
	#include <linux/mempool.h>
	#include "jfs_incore.h"
	#include "jfs_superblock.h"
	#include "jfs_filsys.h"
	#include "jfs_metapage.h"
	#include "jfs_txnmgr.h"
	#include "jfs_debug.h"

	#ifdef CONFIG_JFS_STATISTICS
	static struct {
	uint pagealloc; /* # of page allocations */
	uint pagefree; /* # of page frees */
	uint lockwait; /* # of sleeping lock_metapage() calls */
	} mpStat;
	#endif

	#define metapage_locked(mp) test_bit(META_locked, &(mp)->flag)
	#define trylock_metapage(mp) test_and_set_bit(META_locked, &(mp)->flag)

	static inline void unlock_metapage(struct metapage *mp)
	{
	clear_bit(META_locked, &mp->flag);
	wake_up(&mp->wait);
	}

	static inline void __lock_metapage(struct metapage *mp)
	{
	DECLARE_WAITQUEUE(wait, current);
	INCREMENT(mpStat.lockwait);
	add_wait_queue_exclusive(&mp->wait, &wait);
	do {
	set_current_state(TASK_UNINTERRUPTIBLE);
	if (metapage_locked(mp)) {
	unlock_page(mp->page);
	schedule();
	lock_page(mp->page);
	}
	} while (trylock_metapage(mp));
	__set_current_state(TASK_RUNNING);
	remove_wait_queue(&mp->wait, &wait);
	}

	/*
	* Must have mp->page locked
	*/
	static inline void lock_metapage(struct metapage *mp)
	{
	if (trylock_metapage(mp))
	__lock_metapage(mp);
	}

	#define METAPOOL_MIN_PAGES 32
	static kmem_cache_t *metapage_cache;
	static mempool_t *metapage_mempool;

	#define MPS_PER_PAGE (PAGE_CACHE_SIZE >> L2PSIZE)

	#if MPS_PER_PAGE > 1

	struct meta_anchor {
	int mp_count;
	atomic_t io_count;
	struct metapage *mp[MPS_PER_PAGE];
	};
	#define mp_anchor(page) ((struct meta_anchor *)page->private)

	static inline struct metapage page_to_mp(struct page page, uint offset)
	{
	if (!PagePrivate(page))
	return NULL;
	return mp_anchor(page)->mp[offset >> L2PSIZE];
	}

	static inline int insert_metapage(struct page page, struct metapage mp)
	{
	struct meta_anchor *a;
	int index;
	int l2mp_blocks; /* log2 blocks per metapage */

	if (PagePrivate(page))
	a = mp_anchor(page);
	else {
	a = kmalloc(sizeof(struct meta_anchor), GFP_NOFS);
	if (!a)
	return -ENOMEM;
	memset(a, 0, sizeof(struct meta_anchor));
	page->private = (unsigned long)a;
	SetPagePrivate(page);
	kmap(page);
	}

	if (mp) {
	l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
	index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);
	a->mp_count++;
	a->mp[index] = mp;
	}

	return 0;
	}

	static inline void remove_metapage(struct page page, struct metapage mp)
	{
	struct meta_anchor *a = mp_anchor(page);
	int l2mp_blocks = L2PSIZE - page->mapping->host->i_blkbits;
	int index;

	index = (mp->index >> l2mp_blocks) & (MPS_PER_PAGE - 1);

	BUG_ON(a->mp[index] != mp);

	a->mp[index] = NULL;
	if (--a->mp_count == 0) {
	kfree(a);
	page->private = 0;
	ClearPagePrivate(page);
	kunmap(page);
	}
	}

	static inline void inc_io(struct page *page)
	{
	atomic_inc(&mp_anchor(page)->io_count);
	}

	static inline void dec_io(struct page page, void (handler) (struct page *))
	{
	if (atomic_dec_and_test(&mp_anchor(page)->io_count))
	handler(page);
	}

	#else
	static inline struct metapage page_to_mp(struct page page, uint offset)
	{
	return PagePrivate(page) ? (struct metapage *)page->private : NULL;
	}

	static inline int insert_metapage(struct page page, struct metapage mp)
	{
	if (mp) {
	page->private = (unsigned long)mp;
	SetPagePrivate(page);
	kmap(page);
	}
	return 0;
	}

	static inline void remove_metapage(struct page page, struct metapage mp)
	{
	page->private = 0;
	ClearPagePrivate(page);
	kunmap(page);
	}

	#define inc_io(page) do {} while(0)
	#define dec_io(page, handler) handler(page)

	#endif

	static void init_once(void foo, kmem_cache_t cachep, unsigned long flags)
	{
	struct metapage mp = (struct metapage )foo;

	if ((flags & (SLAB_CTOR_VERIFY\|SLAB_CTOR_CONSTRUCTOR)) ==
	SLAB_CTOR_CONSTRUCTOR) {
	mp->lid = 0;
	mp->lsn = 0;
	mp->flag = 0;
	mp->data = NULL;
	mp->clsn = 0;
	mp->log = NULL;
	set_bit(META_free, &mp->flag);
	init_waitqueue_head(&mp->wait);
	}
	}

	static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
	{
	return mempool_alloc(metapage_mempool, gfp_mask);
	}

	static inline void free_metapage(struct metapage *mp)
	{
	mp->flag = 0;
	set_bit(META_free, &mp->flag);

	mempool_free(mp, metapage_mempool);
	}

	int __init metapage_init(void)
	{
	/*
	* Allocate the metapage structures
	*/
	metapage_cache = kmem_cache_create("jfs_mp", sizeof(struct metapage),
	0, 0, init_once, NULL);
	if (metapage_cache == NULL)
	return -ENOMEM;

	metapage_mempool = mempool_create(METAPOOL_MIN_PAGES, mempool_alloc_slab,
	mempool_free_slab, metapage_cache);

	if (metapage_mempool == NULL) {
	kmem_cache_destroy(metapage_cache);
	return -ENOMEM;
	}

	return 0;
	}

	void metapage_exit(void)
	{
	mempool_destroy(metapage_mempool);
	kmem_cache_destroy(metapage_cache);
	}

	static inline void drop_metapage(struct page page, struct metapage mp)
	{
	if (mp->count \|\| mp->nohomeok \|\| test_bit(META_dirty, &mp->flag) \|\|
	test_bit(META_io, &mp->flag))
	return;
	remove_metapage(page, mp);
	INCREMENT(mpStat.pagefree);
	free_metapage(mp);
	}

	/*
	* Metapage address space operations
	*/

	static sector_t metapage_get_blocks(struct inode *inode, sector_t lblock,
	unsigned int *len)
	{
	int rc = 0;
	int xflag;
	s64 xaddr;
	sector_t file_blocks = (inode->i_size + inode->i_blksize - 1) >>
	inode->i_blkbits;

	if (lblock >= file_blocks)
	return 0;
	if (lblock + *len > file_blocks)
	*len = file_blocks - lblock;

	if (inode->i_ino) {
	rc = xtLookup(inode, (s64)lblock, *len, &xflag, &xaddr, len, 0);
	if ((rc == 0) && *len)
	lblock = (sector_t)xaddr;
	else
	lblock = 0;
	} /* else no mapping */

	return lblock;
	}

	static void last_read_complete(struct page *page)
	{
	if (!PageError(page))
	SetPageUptodate(page);
	unlock_page(page);
	}

	static int metapage_read_end_io(struct bio *bio, unsigned int bytes_done,
	int err)
	{
	struct page *page = bio->bi_private;

	if (bio->bi_size)
	return 1;

	if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
	printk(KERN_ERR "metapage_read_end_io: I/O error\n");
	SetPageError(page);
	}

	dec_io(page, last_read_complete);
	bio_put(bio);

	return 0;
	}

	static void remove_from_logsync(struct metapage *mp)
	{
	struct jfs_log *log = mp->log;
	unsigned long flags;
	/*
	* This can race. Recheck that log hasn't been set to null, and after
	* acquiring logsync lock, recheck lsn
	*/
	if (!log)
	return;

	LOGSYNC_LOCK(log, flags);
	if (mp->lsn) {
	mp->log = NULL;
	mp->lsn = 0;
	mp->clsn = 0;
	log->count--;
	list_del(&mp->synclist);
	}
	LOGSYNC_UNLOCK(log, flags);
	}

	static void last_write_complete(struct page *page)
	{
	struct metapage *mp;
	unsigned int offset;

	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
	mp = page_to_mp(page, offset);
	if (mp && test_bit(META_io, &mp->flag)) {
	if (mp->lsn)
	remove_from_logsync(mp);
	clear_bit(META_io, &mp->flag);
	}
	/*
	* I'd like to call drop_metapage here, but I don't think it's
	* safe unless I have the page locked
	*/
	}
	end_page_writeback(page);
	}

	static int metapage_write_end_io(struct bio *bio, unsigned int bytes_done,
	int err)
	{
	struct page *page = bio->bi_private;

	BUG_ON(!PagePrivate(page));

	if (bio->bi_size)
	return 1;

	if (! test_bit(BIO_UPTODATE, &bio->bi_flags)) {
	printk(KERN_ERR "metapage_write_end_io: I/O error\n");
	SetPageError(page);
	}
	dec_io(page, last_write_complete);
	bio_put(bio);
	return 0;
	}

	static int metapage_writepage(struct page page, struct writeback_control wbc)
	{
	struct bio *bio = NULL;
	unsigned int block_offset; /* block offset of mp within page */
	struct inode *inode = page->mapping->host;
	unsigned int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
	unsigned int len;
	unsigned int xlen;
	struct metapage *mp;
	int redirty = 0;
	sector_t lblock;
	sector_t pblock;
	sector_t next_block = 0;
	sector_t page_start;
	unsigned long bio_bytes = 0;
	unsigned long bio_offset = 0;
	unsigned int offset;

	page_start = (sector_t)page->index <<
	(PAGE_CACHE_SHIFT - inode->i_blkbits);
	BUG_ON(!PageLocked(page));
	BUG_ON(PageWriteback(page));

	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
	mp = page_to_mp(page, offset);

	if (!mp \|\| !test_bit(META_dirty, &mp->flag))
	continue;

	if (mp->nohomeok && !test_bit(META_forcewrite, &mp->flag)) {
	redirty = 1;
	/*
	* Make sure this page isn't blocked indefinitely.
	* If the journal isn't undergoing I/O, push it
	*/
	if (mp->log && !(mp->log->cflag & logGC_PAGEOUT))
	jfs_flush_journal(mp->log, 0);
	continue;
	}

	clear_bit(META_dirty, &mp->flag);
	block_offset = offset >> inode->i_blkbits;
	lblock = page_start + block_offset;
	if (bio) {
	if (xlen && lblock == next_block) {
	/* Contiguous, in memory & on disk */
	len = min(xlen, blocks_per_mp);
	xlen -= len;
	bio_bytes += len << inode->i_blkbits;
	set_bit(META_io, &mp->flag);
	continue;
	}
	/* Not contiguous */
	if (bio_add_page(bio, page, bio_bytes, bio_offset) <
	bio_bytes)
	goto add_failed;
	/*
	* Increment counter before submitting i/o to keep
	* count from hitting zero before we're through
	*/
	inc_io(page);
	if (!bio->bi_size)
	goto dump_bio;
	submit_bio(WRITE, bio);
	bio = NULL;
	} else {
	set_page_writeback(page);
	inc_io(page);
	}
	xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
	pblock = metapage_get_blocks(inode, lblock, &xlen);
	if (!pblock) {
	/* Need better error handling */
	printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
	dec_io(page, last_write_complete);
	continue;
	}
	set_bit(META_io, &mp->flag);
	len = min(xlen, (uint) JFS_SBI(inode->i_sb)->nbperpage);

	bio = bio_alloc(GFP_NOFS, 1);
	bio->bi_bdev = inode->i_sb->s_bdev;
	bio->bi_sector = pblock << (inode->i_blkbits - 9);
	bio->bi_end_io = metapage_write_end_io;
	bio->bi_private = page;

	/* Don't call bio_add_page yet, we may add to this vec */
	bio_offset = offset;
	bio_bytes = len << inode->i_blkbits;

	xlen -= len;
	next_block = lblock + len;
	}
	if (bio) {
	if (bio_add_page(bio, page, bio_bytes, bio_offset) < bio_bytes)
	goto add_failed;
	if (!bio->bi_size)
	goto dump_bio;

	submit_bio(WRITE, bio);
	}
	if (redirty)
	redirty_page_for_writepage(wbc, page);

	unlock_page(page);

	return 0;
	add_failed:
	/* We should never reach here, since we're only adding one vec */
	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
	goto skip;
	dump_bio:
	dump_mem("bio", bio, sizeof(*bio));
	skip:
	bio_put(bio);
	unlock_page(page);
	dec_io(page, last_write_complete);

	return -EIO;
	}

	static int metapage_readpage(struct file fp, struct page page)
	{
	struct inode *inode = page->mapping->host;
	struct bio *bio = NULL;
	unsigned int block_offset;
	unsigned int blocks_per_page = PAGE_CACHE_SIZE >> inode->i_blkbits;
	sector_t page_start; /* address of page in fs blocks */
	sector_t pblock;
	unsigned int xlen;
	unsigned int len;
	unsigned int offset;

	BUG_ON(!PageLocked(page));
	page_start = (sector_t)page->index <<
	(PAGE_CACHE_SHIFT - inode->i_blkbits);

	block_offset = 0;
	while (block_offset < blocks_per_page) {
	xlen = blocks_per_page - block_offset;
	pblock = metapage_get_blocks(inode, page_start + block_offset,
	&xlen);
	if (pblock) {
	if (!PagePrivate(page))
	insert_metapage(page, NULL);
	inc_io(page);
	if (bio)
	submit_bio(READ, bio);

	bio = bio_alloc(GFP_NOFS, 1);
	bio->bi_bdev = inode->i_sb->s_bdev;
	bio->bi_sector = pblock << (inode->i_blkbits - 9);
	bio->bi_end_io = metapage_read_end_io;
	bio->bi_private = page;
	len = xlen << inode->i_blkbits;
	offset = block_offset << inode->i_blkbits;
	if (bio_add_page(bio, page, len, offset) < len)
	goto add_failed;
	block_offset += xlen;
	} else
	block_offset++;
	}
	if (bio)
	submit_bio(READ, bio);
	else
	unlock_page(page);

	return 0;

	add_failed:
	printk(KERN_ERR "JFS: bio_add_page failed unexpectedly\n");
	bio_put(bio);
	dec_io(page, last_read_complete);
	return -EIO;
	}

	static int metapage_releasepage(struct page *page, gfp_t gfp_mask)
	{
	struct metapage *mp;
	int busy = 0;
	unsigned int offset;

	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
	mp = page_to_mp(page, offset);

	if (!mp)
	continue;

	jfs_info("metapage_releasepage: mp = 0x%p", mp);
	if (mp->count \|\| mp->nohomeok) {
	jfs_info("count = %ld, nohomeok = %d", mp->count,
	mp->nohomeok);
	busy = 1;
	continue;
	}
	wait_on_page_writeback(page);
	//WARN_ON(test_bit(META_dirty, &mp->flag));
	if (test_bit(META_dirty, &mp->flag)) {
	dump_mem("dirty mp in metapage_releasepage", mp,
	sizeof(struct metapage));
	dump_mem("page", page, sizeof(struct page));
	dump_stack();
	}
	if (mp->lsn)
	remove_from_logsync(mp);
	remove_metapage(page, mp);
	INCREMENT(mpStat.pagefree);
	free_metapage(mp);
	}
	if (busy)
	return -1;

	return 0;
	}

	static int metapage_invalidatepage(struct page *page, unsigned long offset)
	{
	BUG_ON(offset);

	if (PageWriteback(page))
	return 0;

	return metapage_releasepage(page, 0);
	}

	struct address_space_operations jfs_metapage_aops = {
	.readpage = metapage_readpage,
	.writepage = metapage_writepage,
	.sync_page = block_sync_page,
	.releasepage = metapage_releasepage,
	.invalidatepage = metapage_invalidatepage,
	.set_page_dirty = __set_page_dirty_nobuffers,
	};

	struct metapage __get_metapage(struct inode inode, unsigned long lblock,
	unsigned int size, int absolute,
	unsigned long new)
	{
	int l2BlocksPerPage;
	int l2bsize;
	struct address_space *mapping;
	struct metapage *mp = NULL;
	struct page *page;
	unsigned long page_index;
	unsigned long page_offset;

	jfs_info("__get_metapage: ino = %ld, lblock = 0x%lx, abs=%d",
	inode->i_ino, lblock, absolute);

	l2bsize = inode->i_blkbits;
	l2BlocksPerPage = PAGE_CACHE_SHIFT - l2bsize;
	page_index = lblock >> l2BlocksPerPage;
	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
	if ((page_offset + size) > PAGE_CACHE_SIZE) {
	jfs_err("MetaData crosses page boundary!!");
	jfs_err("lblock = %lx, size = %d", lblock, size);
	dump_stack();
	return NULL;
	}
	if (absolute)
	mapping = JFS_SBI(inode->i_sb)->direct_inode->i_mapping;
	else {
	/*
	* If an nfs client tries to read an inode that is larger
	* than any existing inodes, we may try to read past the
	* end of the inode map
	*/
	if ((lblock << inode->i_blkbits) >= inode->i_size)
	return NULL;
	mapping = inode->i_mapping;
	}

	if (new && (PSIZE == PAGE_CACHE_SIZE)) {
	page = grab_cache_page(mapping, page_index);
	if (!page) {
	jfs_err("grab_cache_page failed!");
	return NULL;
	}
	SetPageUptodate(page);
	} else {
	page = read_cache_page(mapping, page_index,
	(filler_t *)mapping->a_ops->readpage, NULL);
	if (IS_ERR(page) \|\| !PageUptodate(page)) {
	jfs_err("read_cache_page failed!");
	return NULL;
	}
	lock_page(page);
	}

	mp = page_to_mp(page, page_offset);
	if (mp) {
	if (mp->logical_size != size) {
	jfs_error(inode->i_sb,
	"__get_metapage: mp->logical_size != size");
	jfs_err("logical_size = %d, size = %d",
	mp->logical_size, size);
	dump_stack();
	goto unlock;
	}
	mp->count++;
	lock_metapage(mp);
	if (test_bit(META_discard, &mp->flag)) {
	if (!new) {
	jfs_error(inode->i_sb,
	"__get_metapage: using a "
	"discarded metapage");
	discard_metapage(mp);
	goto unlock;
	}
	clear_bit(META_discard, &mp->flag);
	}
	} else {
	INCREMENT(mpStat.pagealloc);
	mp = alloc_metapage(GFP_NOFS);
	mp->page = page;
	mp->flag = 0;
	mp->xflag = COMMIT_PAGE;
	mp->count = 1;
	mp->nohomeok = 0;
	mp->logical_size = size;
	mp->data = page_address(page) + page_offset;
	mp->index = lblock;
	if (unlikely(insert_metapage(page, mp))) {
	free_metapage(mp);
	goto unlock;
	}
	lock_metapage(mp);
	}

	if (new) {
	jfs_info("zeroing mp = 0x%p", mp);
	memset(mp->data, 0, PSIZE);
	}

	unlock_page(page);
	jfs_info("__get_metapage: returning = 0x%p data = 0x%p", mp, mp->data);
	return mp;

	unlock:
	unlock_page(page);
	return NULL;
	}

	void grab_metapage(struct metapage * mp)
	{
	jfs_info("grab_metapage: mp = 0x%p", mp);
	page_cache_get(mp->page);
	lock_page(mp->page);
	mp->count++;
	lock_metapage(mp);
	unlock_page(mp->page);
	}

	void force_metapage(struct metapage *mp)
	{
	struct page *page = mp->page;
	jfs_info("force_metapage: mp = 0x%p", mp);
	set_bit(META_forcewrite, &mp->flag);
	clear_bit(META_sync, &mp->flag);
	page_cache_get(page);
	lock_page(page);
	set_page_dirty(page);
	write_one_page(page, 1);
	clear_bit(META_forcewrite, &mp->flag);
	page_cache_release(page);
	}

	void hold_metapage(struct metapage *mp)
	{
	lock_page(mp->page);
	}

	void put_metapage(struct metapage *mp)
	{
	if (mp->count \|\| mp->nohomeok) {
	/* Someone else will release this */
	unlock_page(mp->page);
	return;
	}
	page_cache_get(mp->page);
	mp->count++;
	lock_metapage(mp);
	unlock_page(mp->page);
	release_metapage(mp);
	}

	void release_metapage(struct metapage * mp)
	{
	struct page *page = mp->page;
	jfs_info("release_metapage: mp = 0x%p, flag = 0x%lx", mp, mp->flag);

	BUG_ON(!page);

	lock_page(page);
	unlock_metapage(mp);

	assert(mp->count);
	if (--mp->count \|\| mp->nohomeok) {
	unlock_page(page);
	page_cache_release(page);
	return;
	}

	if (test_bit(META_dirty, &mp->flag)) {
	set_page_dirty(page);
	if (test_bit(META_sync, &mp->flag)) {
	clear_bit(META_sync, &mp->flag);
	write_one_page(page, 1);
	lock_page(page); /* write_one_page unlocks the page */
	}
	} else if (mp->lsn) /* discard_metapage doesn't remove it */
	remove_from_logsync(mp);

	#if MPS_PER_PAGE == 1
	/*
	* If we know this is the only thing in the page, we can throw
	* the page out of the page cache. If pages are larger, we
	* don't want to do this.
	*/

	/* Retest mp->count since we may have released page lock */
	if (test_bit(META_discard, &mp->flag) && !mp->count) {
	clear_page_dirty(page);
	ClearPageUptodate(page);
	}
	#else
	/* Try to keep metapages from using up too much memory */
	drop_metapage(page, mp);
	#endif
	unlock_page(page);
	page_cache_release(page);
	}

	void __invalidate_metapages(struct inode *ip, s64 addr, int len)
	{
	sector_t lblock;
	int l2BlocksPerPage = PAGE_CACHE_SHIFT - ip->i_blkbits;
	int BlocksPerPage = 1 << l2BlocksPerPage;
	/* All callers are interested in block device's mapping */
	struct address_space *mapping =
	JFS_SBI(ip->i_sb)->direct_inode->i_mapping;
	struct metapage *mp;
	struct page *page;
	unsigned int offset;

	/*
	* Mark metapages to discard. They will eventually be
	* released, but should not be written.
	*/
	for (lblock = addr & ~(BlocksPerPage - 1); lblock < addr + len;
	lblock += BlocksPerPage) {
	page = find_lock_page(mapping, lblock >> l2BlocksPerPage);
	if (!page)
	continue;
	for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
	mp = page_to_mp(page, offset);
	if (!mp)
	continue;
	if (mp->index < addr)
	continue;
	if (mp->index >= addr + len)
	break;

	clear_bit(META_dirty, &mp->flag);
	set_bit(META_discard, &mp->flag);
	if (mp->lsn)
	remove_from_logsync(mp);
	}
	unlock_page(page);
	page_cache_release(page);
	}
	}

	#ifdef CONFIG_JFS_STATISTICS
	int jfs_mpstat_read(char buffer, char *start, off_t offset, int length,
	int eof, void data)
	{
	int len = 0;
	off_t begin;

	len += sprintf(buffer,
	"JFS Metapage statistics\n"
	"=======================\n"
	"page allocations = %d\n"
	"page frees = %d\n"
	"lock waits = %d\n",
	mpStat.pagealloc,
	mpStat.pagefree,
	mpStat.lockwait);

	begin = offset;
	*start = buffer + begin;
	len -= begin;

	if (len > length)
	len = length;
	else
	*eof = 1;

	if (len < 0)
	len = 0;

	return len;
	}
	#endif