Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 817 insertions, 0 deletions

diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
new file mode 100644
index 000000000..2e8461ce7
--- /dev/null
+++ b/fs/jfs/jfs_metapage.c
@@ -0,0 +1,817 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) International Business Machines Corp., 2000-2005
+ *   Portions Copyright (C) Christoph Hellwig, 2001-2002
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/buffer_head.h>
+#include <linux/mempool.h>
+#include <linux/seq_file.h>
+#include <linux/writeback.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_lock(META_locked, &(mp)->flag)
+
+static inline void unlock_metapage(struct metapage *mp)
+{
+	clear_bit_unlock(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);
+			io_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 struct kmem_cache *metapage_cache;
+static mempool_t *metapage_mempool;
+
+#define MPS_PER_PAGE (PAGE_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(page))
+
+static inline struct metapage *page_to_mp(struct page *page, int 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 = kzalloc(sizeof(struct meta_anchor), GFP_NOFS);
+		if (!a)
+			return -ENOMEM;
+		set_page_private(page, (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);
+		set_page_private(page, 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, int offset)
+{
+	return PagePrivate(page) ? (struct metapage *)page_private(page) : NULL;
+}
+
+static inline int insert_metapage(struct page *page, struct metapage *mp)
+{
+	if (mp) {
+		set_page_private(page, (unsigned long)mp);
+		SetPagePrivate(page);
+		kmap(page);
+	}
+	return 0;
+}
+
+static inline void remove_metapage(struct page *page, struct metapage *mp)
+{
+	set_page_private(page, 0);
+	ClearPagePrivate(page);
+	kunmap(page);
+}
+
+#define inc_io(page) do {} while(0)
+#define dec_io(page, handler) handler(page)
+
+#endif
+
+static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
+{
+	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
+
+	if (mp) {
+		mp->lid = 0;
+		mp->lsn = 0;
+		mp->data = NULL;
+		mp->clsn = 0;
+		mp->log = NULL;
+		init_waitqueue_head(&mp->wait);
+	}
+	return mp;
+}
+
+static inline void free_metapage(struct metapage *mp)
+{
+	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, NULL);
+	if (metapage_cache == NULL)
+		return -ENOMEM;
+
+	metapage_mempool = mempool_create_slab_pool(METAPOOL_MIN_PAGES,
+						    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,
+				    int *len)
+{
+	int rc = 0;
+	int xflag;
+	s64 xaddr;
+	sector_t file_blocks = (inode->i_size + inode->i_sb->s_blocksize - 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 void metapage_read_end_io(struct bio *bio)
+{
+	struct page *page = bio->bi_private;
+
+	if (bio->bi_status) {
+		printk(KERN_ERR "metapage_read_end_io: I/O error\n");
+		SetPageError(page);
+	}
+
+	dec_io(page, last_read_complete);
+	bio_put(bio);
+}
+
+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_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 void metapage_write_end_io(struct bio *bio)
+{
+	struct page *page = bio->bi_private;
+
+	BUG_ON(!PagePrivate(page));
+
+	if (bio->bi_status) {
+		printk(KERN_ERR "metapage_write_end_io: I/O error\n");
+		SetPageError(page);
+	}
+	dec_io(page, last_write_complete);
+	bio_put(bio);
+}
+
+static int metapage_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct bio *bio = NULL;
+	int block_offset;	/* block offset of mp within page */
+	struct inode *inode = page->mapping->host;
+	int blocks_per_mp = JFS_SBI(inode->i_sb)->nbperpage;
+	int len;
+	int xlen;
+	struct metapage *mp;
+	int redirty = 0;
+	sector_t lblock;
+	int nr_underway = 0;
+	sector_t pblock;
+	sector_t next_block = 0;
+	sector_t page_start;
+	unsigned long bio_bytes = 0;
+	unsigned long bio_offset = 0;
+	int offset;
+	int bad_blocks = 0;
+
+	page_start = (sector_t)page->index <<
+		     (PAGE_SHIFT - inode->i_blkbits);
+	BUG_ON(!PageLocked(page));
+	BUG_ON(PageWriteback(page));
+	set_page_writeback(page);
+
+	for (offset = 0; offset < PAGE_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);
+		set_bit(META_io, &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;
+				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_iter.bi_size)
+				goto dump_bio;
+			submit_bio(bio);
+			nr_underway++;
+			bio = NULL;
+		} else
+			inc_io(page);
+		xlen = (PAGE_SIZE - offset) >> inode->i_blkbits;
+		pblock = metapage_get_blocks(inode, lblock, &xlen);
+		if (!pblock) {
+			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
+			/*
+			 * We already called inc_io(), but can't cancel it
+			 * with dec_io() until we're done with the page
+			 */
+			bad_blocks++;
+			continue;
+		}
+		len = min(xlen, (int)JFS_SBI(inode->i_sb)->nbperpage);
+
+		bio = bio_alloc(inode->i_sb->s_bdev, 1, REQ_OP_WRITE, GFP_NOFS);
+		bio->bi_iter.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_iter.bi_size)
+			goto dump_bio;
+
+		submit_bio(bio);
+		nr_underway++;
+	}
+	if (redirty)
+		redirty_page_for_writepage(wbc, page);
+
+	unlock_page(page);
+
+	if (bad_blocks)
+		goto err_out;
+
+	if (nr_underway == 0)
+		end_page_writeback(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:
+	print_hex_dump(KERN_ERR, "JFS: dump of bio: ", DUMP_PREFIX_ADDRESS, 16,
+		       4, bio, sizeof(*bio), 0);
+skip:
+	bio_put(bio);
+	unlock_page(page);
+	dec_io(page, last_write_complete);
+err_out:
+	while (bad_blocks--)
+		dec_io(page, last_write_complete);
+	return -EIO;
+}
+
+static int metapage_read_folio(struct file *fp, struct folio *folio)
+{
+	struct page *page = &folio->page;
+	struct inode *inode = page->mapping->host;
+	struct bio *bio = NULL;
+	int block_offset;
+	int blocks_per_page = i_blocks_per_page(inode, page);
+	sector_t page_start;	/* address of page in fs blocks */
+	sector_t pblock;
+	int xlen;
+	unsigned int len;
+	int offset;
+
+	BUG_ON(!PageLocked(page));
+	page_start = (sector_t)page->index <<
+		     (PAGE_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(bio);
+
+			bio = bio_alloc(inode->i_sb->s_bdev, 1, REQ_OP_READ,
+					GFP_NOFS);
+			bio->bi_iter.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(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 bool metapage_release_folio(struct folio *folio, gfp_t gfp_mask)
+{
+	struct metapage *mp;
+	bool ret = true;
+	int offset;
+
+	for (offset = 0; offset < PAGE_SIZE; offset += PSIZE) {
+		mp = page_to_mp(&folio->page, offset);
+
+		if (!mp)
+			continue;
+
+		jfs_info("metapage_release_folio: mp = 0x%p", mp);
+		if (mp->count || mp->nohomeok ||
+		    test_bit(META_dirty, &mp->flag)) {
+			jfs_info("count = %ld, nohomeok = %d", mp->count,
+				 mp->nohomeok);
+			ret = false;
+			continue;
+		}
+		if (mp->lsn)
+			remove_from_logsync(mp);
+		remove_metapage(&folio->page, mp);
+		INCREMENT(mpStat.pagefree);
+		free_metapage(mp);
+	}
+	return ret;
+}
+
+static void metapage_invalidate_folio(struct folio *folio, size_t offset,
+				    size_t length)
+{
+	BUG_ON(offset || length < folio_size(folio));
+
+	BUG_ON(folio_test_writeback(folio));
+
+	metapage_release_folio(folio, 0);
+}
+
+const struct address_space_operations jfs_metapage_aops = {
+	.read_folio	= metapage_read_folio,
+	.writepage	= metapage_writepage,
+	.release_folio	= metapage_release_folio,
+	.invalidate_folio = metapage_invalidate_folio,
+	.dirty_folio	= filemap_dirty_folio,
+};
+
+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_SHIFT - l2bsize;
+	page_index = lblock >> l2BlocksPerPage;
+	page_offset = (lblock - (page_index << l2BlocksPerPage)) << l2bsize;
+	if ((page_offset + size) > PAGE_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_SIZE)) {
+		page = grab_cache_page(mapping, page_index);
+		if (!page) {
+			jfs_err("grab_cache_page failed!");
+			return NULL;
+		}
+		SetPageUptodate(page);
+	} else {
+		page = read_mapping_page(mapping, page_index, NULL);
+		if (IS_ERR(page)) {
+			jfs_err("read_mapping_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_mp->logical_size != size\n");
+			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,
+					  "using a discarded metapage\n");
+				discard_metapage(mp);
+				goto unlock;
+			}
+			clear_bit(META_discard, &mp->flag);
+		}
+	} else {
+		INCREMENT(mpStat.pagealloc);
+		mp = alloc_metapage(GFP_NOFS);
+		if (!mp)
+			goto unlock;
+		mp->page = page;
+		mp->sb = inode->i_sb;
+		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);
+	get_page(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);
+	get_page(page);
+	lock_page(page);
+	set_page_dirty(page);
+	if (write_one_page(page))
+		jfs_error(mp->sb, "write_one_page() failed\n");
+	clear_bit(META_forcewrite, &mp->flag);
+	put_page(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;
+	}
+	get_page(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);
+		put_page(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);
+			if (write_one_page(page))
+				jfs_error(mp->sb, "write_one_page() failed\n");
+			lock_page(page); /* write_one_page unlocks the page */
+		}
+	} else if (mp->lsn)	/* discard_metapage doesn't remove it */
+		remove_from_logsync(mp);
+
+	/* Try to keep metapages from using up too much memory */
+	drop_metapage(page, mp);
+
+	unlock_page(page);
+	put_page(page);
+}
+
+void __invalidate_metapages(struct inode *ip, s64 addr, int len)
+{
+	sector_t lblock;
+	int l2BlocksPerPage = PAGE_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_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);
+		put_page(page);
+	}
+}
+
+#ifdef CONFIG_JFS_STATISTICS
+int jfs_mpstat_proc_show(struct seq_file *m, void *v)
+{
+	seq_printf(m,
+		       "JFS Metapage statistics\n"
+		       "=======================\n"
+		       "page allocations = %d\n"
+		       "page frees = %d\n"
+		       "lock waits = %d\n",
+		       mpStat.pagealloc,
+		       mpStat.pagefree,
+		       mpStat.lockwait);
+	return 0;
+}
+#endif