Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 2298 insertions, 0 deletions

diff --git a/kernel/fs/logfs/readwrite.c b/kernel/fs/logfs/readwrite.c
new file mode 100644
index 000000000..380d86e1a
--- /dev/null
+++ b/kernel/fs/logfs/readwrite.c
@@ -0,0 +1,2298 @@
+/*
+ * fs/logfs/readwrite.c
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
+ *
+ *
+ * Actually contains five sets of very similar functions:
+ * read		read blocks from a file
+ * seek_hole	find next hole
+ * seek_data	find next data block
+ * valid	check whether a block still belongs to a file
+ * write	write blocks to a file
+ * delete	delete a block (for directories and ifile)
+ * rewrite	move existing blocks of a file to a new location (gc helper)
+ * truncate	truncate a file
+ */
+#include "logfs.h"
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+static u64 adjust_bix(u64 bix, level_t level)
+{
+	switch (level) {
+	case 0:
+		return bix;
+	case LEVEL(1):
+		return max_t(u64, bix, I0_BLOCKS);
+	case LEVEL(2):
+		return max_t(u64, bix, I1_BLOCKS);
+	case LEVEL(3):
+		return max_t(u64, bix, I2_BLOCKS);
+	case LEVEL(4):
+		return max_t(u64, bix, I3_BLOCKS);
+	case LEVEL(5):
+		return max_t(u64, bix, I4_BLOCKS);
+	default:
+		WARN_ON(1);
+		return bix;
+	}
+}
+
+static inline u64 maxbix(u8 height)
+{
+	return 1ULL << (LOGFS_BLOCK_BITS * height);
+}
+
+/**
+ * The inode address space is cut in two halves.  Lower half belongs to data
+ * pages, upper half to indirect blocks.  If the high bit (INDIRECT_BIT) is
+ * set, the actual block index (bix) and level can be derived from the page
+ * index.
+ *
+ * The lowest three bits of the block index are set to 0 after packing and
+ * unpacking.  Since the lowest n bits (9 for 4KiB blocksize) are ignored
+ * anyway this is harmless.
+ */
+#define ARCH_SHIFT	(BITS_PER_LONG - 32)
+#define INDIRECT_BIT	(0x80000000UL << ARCH_SHIFT)
+#define LEVEL_SHIFT	(28 + ARCH_SHIFT)
+static inline pgoff_t first_indirect_block(void)
+{
+	return INDIRECT_BIT | (1ULL << LEVEL_SHIFT);
+}
+
+pgoff_t logfs_pack_index(u64 bix, level_t level)
+{
+	pgoff_t index;
+
+	BUG_ON(bix >= INDIRECT_BIT);
+	if (level == 0)
+		return bix;
+
+	index  = INDIRECT_BIT;
+	index |= (__force long)level << LEVEL_SHIFT;
+	index |= bix >> ((__force u8)level * LOGFS_BLOCK_BITS);
+	return index;
+}
+
+void logfs_unpack_index(pgoff_t index, u64 *bix, level_t *level)
+{
+	u8 __level;
+
+	if (!(index & INDIRECT_BIT)) {
+		*bix = index;
+		*level = 0;
+		return;
+	}
+
+	__level = (index & ~INDIRECT_BIT) >> LEVEL_SHIFT;
+	*level = LEVEL(__level);
+	*bix = (index << (__level * LOGFS_BLOCK_BITS)) & ~INDIRECT_BIT;
+	*bix = adjust_bix(*bix, *level);
+	return;
+}
+#undef ARCH_SHIFT
+#undef INDIRECT_BIT
+#undef LEVEL_SHIFT
+
+/*
+ * Time is stored as nanoseconds since the epoch.
+ */
+static struct timespec be64_to_timespec(__be64 betime)
+{
+	return ns_to_timespec(be64_to_cpu(betime));
+}
+
+static __be64 timespec_to_be64(struct timespec tsp)
+{
+	return cpu_to_be64((u64)tsp.tv_sec * NSEC_PER_SEC + tsp.tv_nsec);
+}
+
+static void logfs_disk_to_inode(struct logfs_disk_inode *di, struct inode*inode)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	int i;
+
+	inode->i_mode	= be16_to_cpu(di->di_mode);
+	li->li_height	= di->di_height;
+	li->li_flags	= be32_to_cpu(di->di_flags);
+	i_uid_write(inode, be32_to_cpu(di->di_uid));
+	i_gid_write(inode, be32_to_cpu(di->di_gid));
+	inode->i_size	= be64_to_cpu(di->di_size);
+	logfs_set_blocks(inode, be64_to_cpu(di->di_used_bytes));
+	inode->i_atime	= be64_to_timespec(di->di_atime);
+	inode->i_ctime	= be64_to_timespec(di->di_ctime);
+	inode->i_mtime	= be64_to_timespec(di->di_mtime);
+	set_nlink(inode, be32_to_cpu(di->di_refcount));
+	inode->i_generation = be32_to_cpu(di->di_generation);
+
+	switch (inode->i_mode & S_IFMT) {
+	case S_IFSOCK:	/* fall through */
+	case S_IFBLK:	/* fall through */
+	case S_IFCHR:	/* fall through */
+	case S_IFIFO:
+		inode->i_rdev = be64_to_cpu(di->di_data[0]);
+		break;
+	case S_IFDIR:	/* fall through */
+	case S_IFREG:	/* fall through */
+	case S_IFLNK:
+		for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
+			li->li_data[i] = be64_to_cpu(di->di_data[i]);
+		break;
+	default:
+		BUG();
+	}
+}
+
+static void logfs_inode_to_disk(struct inode *inode, struct logfs_disk_inode*di)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	int i;
+
+	di->di_mode	= cpu_to_be16(inode->i_mode);
+	di->di_height	= li->li_height;
+	di->di_pad	= 0;
+	di->di_flags	= cpu_to_be32(li->li_flags);
+	di->di_uid	= cpu_to_be32(i_uid_read(inode));
+	di->di_gid	= cpu_to_be32(i_gid_read(inode));
+	di->di_size	= cpu_to_be64(i_size_read(inode));
+	di->di_used_bytes = cpu_to_be64(li->li_used_bytes);
+	di->di_atime	= timespec_to_be64(inode->i_atime);
+	di->di_ctime	= timespec_to_be64(inode->i_ctime);
+	di->di_mtime	= timespec_to_be64(inode->i_mtime);
+	di->di_refcount	= cpu_to_be32(inode->i_nlink);
+	di->di_generation = cpu_to_be32(inode->i_generation);
+
+	switch (inode->i_mode & S_IFMT) {
+	case S_IFSOCK:	/* fall through */
+	case S_IFBLK:	/* fall through */
+	case S_IFCHR:	/* fall through */
+	case S_IFIFO:
+		di->di_data[0] = cpu_to_be64(inode->i_rdev);
+		break;
+	case S_IFDIR:	/* fall through */
+	case S_IFREG:	/* fall through */
+	case S_IFLNK:
+		for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
+			di->di_data[i] = cpu_to_be64(li->li_data[i]);
+		break;
+	default:
+		BUG();
+	}
+}
+
+static void __logfs_set_blocks(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct logfs_inode *li = logfs_inode(inode);
+
+	inode->i_blocks = ULONG_MAX;
+	if (li->li_used_bytes >> sb->s_blocksize_bits < ULONG_MAX)
+		inode->i_blocks = ALIGN(li->li_used_bytes, 512) >> 9;
+}
+
+void logfs_set_blocks(struct inode *inode, u64 bytes)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	li->li_used_bytes = bytes;
+	__logfs_set_blocks(inode);
+}
+
+static void prelock_page(struct super_block *sb, struct page *page, int lock)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	BUG_ON(!PageLocked(page));
+	if (lock) {
+		BUG_ON(PagePreLocked(page));
+		SetPagePreLocked(page);
+	} else {
+		/* We are in GC path. */
+		if (PagePreLocked(page))
+			super->s_lock_count++;
+		else
+			SetPagePreLocked(page);
+	}
+}
+
+static void preunlock_page(struct super_block *sb, struct page *page, int lock)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	BUG_ON(!PageLocked(page));
+	if (lock)
+		ClearPagePreLocked(page);
+	else {
+		/* We are in GC path. */
+		BUG_ON(!PagePreLocked(page));
+		if (super->s_lock_count)
+			super->s_lock_count--;
+		else
+			ClearPagePreLocked(page);
+	}
+}
+
+/*
+ * Logfs is prone to an AB-BA deadlock where one task tries to acquire
+ * s_write_mutex with a locked page and GC tries to get that page while holding
+ * s_write_mutex.
+ * To solve this issue logfs will ignore the page lock iff the page in question
+ * is waiting for s_write_mutex.  We annotate this fact by setting PG_pre_locked
+ * in addition to PG_locked.
+ */
+void logfs_get_wblocks(struct super_block *sb, struct page *page, int lock)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	if (page)
+		prelock_page(sb, page, lock);
+
+	if (lock) {
+		mutex_lock(&super->s_write_mutex);
+		logfs_gc_pass(sb);
+		/* FIXME: We also have to check for shadowed space
+		 * and mempool fill grade */
+	}
+}
+
+void logfs_put_wblocks(struct super_block *sb, struct page *page, int lock)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	if (page)
+		preunlock_page(sb, page, lock);
+	/* Order matters - we must clear PG_pre_locked before releasing
+	 * s_write_mutex or we could race against another task. */
+	if (lock)
+		mutex_unlock(&super->s_write_mutex);
+}
+
+static struct page *logfs_get_read_page(struct inode *inode, u64 bix,
+		level_t level)
+{
+	return find_or_create_page(inode->i_mapping,
+			logfs_pack_index(bix, level), GFP_NOFS);
+}
+
+static void logfs_put_read_page(struct page *page)
+{
+	unlock_page(page);
+	page_cache_release(page);
+}
+
+static void logfs_lock_write_page(struct page *page)
+{
+	int loop = 0;
+
+	while (unlikely(!trylock_page(page))) {
+		if (loop++ > 0x1000) {
+			/* Has been observed once so far... */
+			printk(KERN_ERR "stack at %p\n", &loop);
+			BUG();
+		}
+		if (PagePreLocked(page)) {
+			/* Holder of page lock is waiting for us, it
+			 * is safe to use this page. */
+			break;
+		}
+		/* Some other process has this page locked and has
+		 * nothing to do with us.  Wait for it to finish.
+		 */
+		schedule();
+	}
+	BUG_ON(!PageLocked(page));
+}
+
+static struct page *logfs_get_write_page(struct inode *inode, u64 bix,
+		level_t level)
+{
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index = logfs_pack_index(bix, level);
+	struct page *page;
+	int err;
+
+repeat:
+	page = find_get_page(mapping, index);
+	if (!page) {
+		page = __page_cache_alloc(GFP_NOFS);
+		if (!page)
+			return NULL;
+		err = add_to_page_cache_lru(page, mapping, index, GFP_NOFS);
+		if (unlikely(err)) {
+			page_cache_release(page);
+			if (err == -EEXIST)
+				goto repeat;
+			return NULL;
+		}
+	} else logfs_lock_write_page(page);
+	BUG_ON(!PageLocked(page));
+	return page;
+}
+
+static void logfs_unlock_write_page(struct page *page)
+{
+	if (!PagePreLocked(page))
+		unlock_page(page);
+}
+
+static void logfs_put_write_page(struct page *page)
+{
+	logfs_unlock_write_page(page);
+	page_cache_release(page);
+}
+
+static struct page *logfs_get_page(struct inode *inode, u64 bix, level_t level,
+		int rw)
+{
+	if (rw == READ)
+		return logfs_get_read_page(inode, bix, level);
+	else
+		return logfs_get_write_page(inode, bix, level);
+}
+
+static void logfs_put_page(struct page *page, int rw)
+{
+	if (rw == READ)
+		logfs_put_read_page(page);
+	else
+		logfs_put_write_page(page);
+}
+
+static unsigned long __get_bits(u64 val, int skip, int no)
+{
+	u64 ret = val;
+
+	ret >>= skip * no;
+	ret <<= 64 - no;
+	ret >>= 64 - no;
+	return ret;
+}
+
+static unsigned long get_bits(u64 val, level_t skip)
+{
+	return __get_bits(val, (__force int)skip, LOGFS_BLOCK_BITS);
+}
+
+static inline void init_shadow_tree(struct super_block *sb,
+		struct shadow_tree *tree)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	btree_init_mempool64(&tree->new, super->s_btree_pool);
+	btree_init_mempool64(&tree->old, super->s_btree_pool);
+}
+
+static void indirect_write_block(struct logfs_block *block)
+{
+	struct page *page;
+	struct inode *inode;
+	int ret;
+
+	page = block->page;
+	inode = page->mapping->host;
+	logfs_lock_write_page(page);
+	ret = logfs_write_buf(inode, page, 0);
+	logfs_unlock_write_page(page);
+	/*
+	 * This needs some rework.  Unless you want your filesystem to run
+	 * completely synchronously (you don't), the filesystem will always
+	 * report writes as 'successful' before the actual work has been
+	 * done.  The actual work gets done here and this is where any errors
+	 * will show up.  And there isn't much we can do about it, really.
+	 *
+	 * Some attempts to fix the errors (move from bad blocks, retry io,...)
+	 * have already been done, so anything left should be either a broken
+	 * device or a bug somewhere in logfs itself.  Being relatively new,
+	 * the odds currently favor a bug, so for now the line below isn't
+	 * entirely tasteles.
+	 */
+	BUG_ON(ret);
+}
+
+static void inode_write_block(struct logfs_block *block)
+{
+	struct inode *inode;
+	int ret;
+
+	inode = block->inode;
+	if (inode->i_ino == LOGFS_INO_MASTER)
+		logfs_write_anchor(inode->i_sb);
+	else {
+		ret = __logfs_write_inode(inode, NULL, 0);
+		/* see indirect_write_block comment */
+		BUG_ON(ret);
+	}
+}
+
+/*
+ * This silences a false, yet annoying gcc warning.  I hate it when my editor
+ * jumps into bitops.h each time I recompile this file.
+ * TODO: Complain to gcc folks about this and upgrade compiler.
+ */
+static unsigned long fnb(const unsigned long *addr,
+		unsigned long size, unsigned long offset)
+{
+	return find_next_bit(addr, size, offset);
+}
+
+static __be64 inode_val0(struct inode *inode)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	u64 val;
+
+	/*
+	 * Explicit shifting generates good code, but must match the format
+	 * of the structure.  Add some paranoia just in case.
+	 */
+	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_mode) != 0);
+	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_height) != 2);
+	BUILD_BUG_ON(offsetof(struct logfs_disk_inode, di_flags) != 4);
+
+	val =	(u64)inode->i_mode << 48 |
+		(u64)li->li_height << 40 |
+		(u64)li->li_flags;
+	return cpu_to_be64(val);
+}
+
+static int inode_write_alias(struct super_block *sb,
+		struct logfs_block *block, write_alias_t *write_one_alias)
+{
+	struct inode *inode = block->inode;
+	struct logfs_inode *li = logfs_inode(inode);
+	unsigned long pos;
+	u64 ino , bix;
+	__be64 val;
+	level_t level;
+	int err;
+
+	for (pos = 0; ; pos++) {
+		pos = fnb(block->alias_map, LOGFS_BLOCK_FACTOR, pos);
+		if (pos >= LOGFS_EMBEDDED_FIELDS + INODE_POINTER_OFS)
+			return 0;
+
+		switch (pos) {
+		case INODE_HEIGHT_OFS:
+			val = inode_val0(inode);
+			break;
+		case INODE_USED_OFS:
+			val = cpu_to_be64(li->li_used_bytes);
+			break;
+		case INODE_SIZE_OFS:
+			val = cpu_to_be64(i_size_read(inode));
+			break;
+		case INODE_POINTER_OFS ... INODE_POINTER_OFS + LOGFS_EMBEDDED_FIELDS - 1:
+			val = cpu_to_be64(li->li_data[pos - INODE_POINTER_OFS]);
+			break;
+		default:
+			BUG();
+		}
+
+		ino = LOGFS_INO_MASTER;
+		bix = inode->i_ino;
+		level = LEVEL(0);
+		err = write_one_alias(sb, ino, bix, level, pos, val);
+		if (err)
+			return err;
+	}
+}
+
+static int indirect_write_alias(struct super_block *sb,
+		struct logfs_block *block, write_alias_t *write_one_alias)
+{
+	unsigned long pos;
+	struct page *page = block->page;
+	u64 ino , bix;
+	__be64 *child, val;
+	level_t level;
+	int err;
+
+	for (pos = 0; ; pos++) {
+		pos = fnb(block->alias_map, LOGFS_BLOCK_FACTOR, pos);
+		if (pos >= LOGFS_BLOCK_FACTOR)
+			return 0;
+
+		ino = page->mapping->host->i_ino;
+		logfs_unpack_index(page->index, &bix, &level);
+		child = kmap_atomic(page);
+		val = child[pos];
+		kunmap_atomic(child);
+		err = write_one_alias(sb, ino, bix, level, pos, val);
+		if (err)
+			return err;
+	}
+}
+
+int logfs_write_obj_aliases_pagecache(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_block *block;
+	int err;
+
+	list_for_each_entry(block, &super->s_object_alias, alias_list) {
+		err = block->ops->write_alias(sb, block, write_alias_journal);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
+void __free_block(struct super_block *sb, struct logfs_block *block)
+{
+	BUG_ON(!list_empty(&block->item_list));
+	list_del(&block->alias_list);
+	mempool_free(block, logfs_super(sb)->s_block_pool);
+}
+
+static void inode_free_block(struct super_block *sb, struct logfs_block *block)
+{
+	struct inode *inode = block->inode;
+
+	logfs_inode(inode)->li_block = NULL;
+	__free_block(sb, block);
+}
+
+static void indirect_free_block(struct super_block *sb,
+		struct logfs_block *block)
+{
+	struct page *page = block->page;
+
+	if (PagePrivate(page)) {
+		ClearPagePrivate(page);
+		page_cache_release(page);
+		set_page_private(page, 0);
+	}
+	__free_block(sb, block);
+}
+
+
+static struct logfs_block_ops inode_block_ops = {
+	.write_block = inode_write_block,
+	.free_block = inode_free_block,
+	.write_alias = inode_write_alias,
+};
+
+struct logfs_block_ops indirect_block_ops = {
+	.write_block = indirect_write_block,
+	.free_block = indirect_free_block,
+	.write_alias = indirect_write_alias,
+};
+
+struct logfs_block *__alloc_block(struct super_block *sb,
+		u64 ino, u64 bix, level_t level)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_block *block;
+
+	block = mempool_alloc(super->s_block_pool, GFP_NOFS);
+	memset(block, 0, sizeof(*block));
+	INIT_LIST_HEAD(&block->alias_list);
+	INIT_LIST_HEAD(&block->item_list);
+	block->sb = sb;
+	block->ino = ino;
+	block->bix = bix;
+	block->level = level;
+	return block;
+}
+
+static void alloc_inode_block(struct inode *inode)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct logfs_block *block;
+
+	if (li->li_block)
+		return;
+
+	block = __alloc_block(inode->i_sb, LOGFS_INO_MASTER, inode->i_ino, 0);
+	block->inode = inode;
+	li->li_block = block;
+	block->ops = &inode_block_ops;
+}
+
+void initialize_block_counters(struct page *page, struct logfs_block *block,
+		__be64 *array, int page_is_empty)
+{
+	u64 ptr;
+	int i, start;
+
+	block->partial = 0;
+	block->full = 0;
+	start = 0;
+	if (page->index < first_indirect_block()) {
+		/* Counters are pointless on level 0 */
+		return;
+	}
+	if (page->index == first_indirect_block()) {
+		/* Skip unused pointers */
+		start = I0_BLOCKS;
+		block->full = I0_BLOCKS;
+	}
+	if (!page_is_empty) {
+		for (i = start; i < LOGFS_BLOCK_FACTOR; i++) {
+			ptr = be64_to_cpu(array[i]);
+			if (ptr)
+				block->partial++;
+			if (ptr & LOGFS_FULLY_POPULATED)
+				block->full++;
+		}
+	}
+}
+
+static void alloc_data_block(struct inode *inode, struct page *page)
+{
+	struct logfs_block *block;
+	u64 bix;
+	level_t level;
+
+	if (PagePrivate(page))
+		return;
+
+	logfs_unpack_index(page->index, &bix, &level);
+	block = __alloc_block(inode->i_sb, inode->i_ino, bix, level);
+	block->page = page;
+
+	SetPagePrivate(page);
+	page_cache_get(page);
+	set_page_private(page, (unsigned long) block);
+
+	block->ops = &indirect_block_ops;
+}
+
+static void alloc_indirect_block(struct inode *inode, struct page *page,
+		int page_is_empty)
+{
+	struct logfs_block *block;
+	__be64 *array;
+
+	if (PagePrivate(page))
+		return;
+
+	alloc_data_block(inode, page);
+
+	block = logfs_block(page);
+	array = kmap_atomic(page);
+	initialize_block_counters(page, block, array, page_is_empty);
+	kunmap_atomic(array);
+}
+
+static void block_set_pointer(struct page *page, int index, u64 ptr)
+{
+	struct logfs_block *block = logfs_block(page);
+	__be64 *array;
+	u64 oldptr;
+
+	BUG_ON(!block);
+	array = kmap_atomic(page);
+	oldptr = be64_to_cpu(array[index]);
+	array[index] = cpu_to_be64(ptr);
+	kunmap_atomic(array);
+	SetPageUptodate(page);
+
+	block->full += !!(ptr & LOGFS_FULLY_POPULATED)
+		- !!(oldptr & LOGFS_FULLY_POPULATED);
+	block->partial += !!ptr - !!oldptr;
+}
+
+static u64 block_get_pointer(struct page *page, int index)
+{
+	__be64 *block;
+	u64 ptr;
+
+	block = kmap_atomic(page);
+	ptr = be64_to_cpu(block[index]);
+	kunmap_atomic(block);
+	return ptr;
+}
+
+static int logfs_read_empty(struct page *page)
+{
+	zero_user_segment(page, 0, PAGE_CACHE_SIZE);
+	return 0;
+}
+
+static int logfs_read_direct(struct inode *inode, struct page *page)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	pgoff_t index = page->index;
+	u64 block;
+
+	block = li->li_data[index];
+	if (!block)
+		return logfs_read_empty(page);
+
+	return logfs_segment_read(inode, page, block, index, 0);
+}
+
+static int logfs_read_loop(struct inode *inode, struct page *page,
+		int rw_context)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	u64 bix, bofs = li->li_data[INDIRECT_INDEX];
+	level_t level, target_level;
+	int ret;
+	struct page *ipage;
+
+	logfs_unpack_index(page->index, &bix, &target_level);
+	if (!bofs)
+		return logfs_read_empty(page);
+
+	if (bix >= maxbix(li->li_height))
+		return logfs_read_empty(page);
+
+	for (level = LEVEL(li->li_height);
+			(__force u8)level > (__force u8)target_level;
+			level = SUBLEVEL(level)){
+		ipage = logfs_get_page(inode, bix, level, rw_context);
+		if (!ipage)
+			return -ENOMEM;
+
+		ret = logfs_segment_read(inode, ipage, bofs, bix, level);
+		if (ret) {
+			logfs_put_read_page(ipage);
+			return ret;
+		}
+
+		bofs = block_get_pointer(ipage, get_bits(bix, SUBLEVEL(level)));
+		logfs_put_page(ipage, rw_context);
+		if (!bofs)
+			return logfs_read_empty(page);
+	}
+
+	return logfs_segment_read(inode, page, bofs, bix, 0);
+}
+
+static int logfs_read_block(struct inode *inode, struct page *page,
+		int rw_context)
+{
+	pgoff_t index = page->index;
+
+	if (index < I0_BLOCKS)
+		return logfs_read_direct(inode, page);
+	return logfs_read_loop(inode, page, rw_context);
+}
+
+static int logfs_exist_loop(struct inode *inode, u64 bix)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	u64 bofs = li->li_data[INDIRECT_INDEX];
+	level_t level;
+	int ret;
+	struct page *ipage;
+
+	if (!bofs)
+		return 0;
+	if (bix >= maxbix(li->li_height))
+		return 0;
+
+	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)) {
+		ipage = logfs_get_read_page(inode, bix, level);
+		if (!ipage)
+			return -ENOMEM;
+
+		ret = logfs_segment_read(inode, ipage, bofs, bix, level);
+		if (ret) {
+			logfs_put_read_page(ipage);
+			return ret;
+		}
+
+		bofs = block_get_pointer(ipage, get_bits(bix, SUBLEVEL(level)));
+		logfs_put_read_page(ipage);
+		if (!bofs)
+			return 0;
+	}
+
+	return 1;
+}
+
+int logfs_exist_block(struct inode *inode, u64 bix)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	if (bix < I0_BLOCKS)
+		return !!li->li_data[bix];
+	return logfs_exist_loop(inode, bix);
+}
+
+static u64 seek_holedata_direct(struct inode *inode, u64 bix, int data)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	for (; bix < I0_BLOCKS; bix++)
+		if (data ^ (li->li_data[bix] == 0))
+			return bix;
+	return I0_BLOCKS;
+}
+
+static u64 seek_holedata_loop(struct inode *inode, u64 bix, int data)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	__be64 *rblock;
+	u64 increment, bofs = li->li_data[INDIRECT_INDEX];
+	level_t level;
+	int ret, slot;
+	struct page *page;
+
+	BUG_ON(!bofs);
+
+	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)) {
+		increment = 1 << (LOGFS_BLOCK_BITS * ((__force u8)level-1));
+		page = logfs_get_read_page(inode, bix, level);
+		if (!page)
+			return bix;
+
+		ret = logfs_segment_read(inode, page, bofs, bix, level);
+		if (ret) {
+			logfs_put_read_page(page);
+			return bix;
+		}
+
+		slot = get_bits(bix, SUBLEVEL(level));
+		rblock = kmap_atomic(page);
+		while (slot < LOGFS_BLOCK_FACTOR) {
+			if (data && (rblock[slot] != 0))
+				break;
+			if (!data && !(be64_to_cpu(rblock[slot]) & LOGFS_FULLY_POPULATED))
+				break;
+			slot++;
+			bix += increment;
+			bix &= ~(increment - 1);
+		}
+		if (slot >= LOGFS_BLOCK_FACTOR) {
+			kunmap_atomic(rblock);
+			logfs_put_read_page(page);
+			return bix;
+		}
+		bofs = be64_to_cpu(rblock[slot]);
+		kunmap_atomic(rblock);
+		logfs_put_read_page(page);
+		if (!bofs) {
+			BUG_ON(data);
+			return bix;
+		}
+	}
+	return bix;
+}
+
+/**
+ * logfs_seek_hole - find next hole starting at a given block index
+ * @inode:		inode to search in
+ * @bix:		block index to start searching
+ *
+ * Returns next hole.  If the file doesn't contain any further holes, the
+ * block address next to eof is returned instead.
+ */
+u64 logfs_seek_hole(struct inode *inode, u64 bix)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	if (bix < I0_BLOCKS) {
+		bix = seek_holedata_direct(inode, bix, 0);
+		if (bix < I0_BLOCKS)
+			return bix;
+	}
+
+	if (!li->li_data[INDIRECT_INDEX])
+		return bix;
+	else if (li->li_data[INDIRECT_INDEX] & LOGFS_FULLY_POPULATED)
+		bix = maxbix(li->li_height);
+	else if (bix >= maxbix(li->li_height))
+		return bix;
+	else {
+		bix = seek_holedata_loop(inode, bix, 0);
+		if (bix < maxbix(li->li_height))
+			return bix;
+		/* Should not happen anymore.  But if some port writes semi-
+		 * corrupt images (as this one used to) we might run into it.
+		 */
+		WARN_ON_ONCE(bix == maxbix(li->li_height));
+	}
+
+	return bix;
+}
+
+static u64 __logfs_seek_data(struct inode *inode, u64 bix)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	if (bix < I0_BLOCKS) {
+		bix = seek_holedata_direct(inode, bix, 1);
+		if (bix < I0_BLOCKS)
+			return bix;
+	}
+
+	if (bix < maxbix(li->li_height)) {
+		if (!li->li_data[INDIRECT_INDEX])
+			bix = maxbix(li->li_height);
+		else
+			return seek_holedata_loop(inode, bix, 1);
+	}
+
+	return bix;
+}
+
+/**
+ * logfs_seek_data - find next data block after a given block index
+ * @inode:		inode to search in
+ * @bix:		block index to start searching
+ *
+ * Returns next data block.  If the file doesn't contain any further data
+ * blocks, the last block in the file is returned instead.
+ */
+u64 logfs_seek_data(struct inode *inode, u64 bix)
+{
+	struct super_block *sb = inode->i_sb;
+	u64 ret, end;
+
+	ret = __logfs_seek_data(inode, bix);
+	end = i_size_read(inode) >> sb->s_blocksize_bits;
+	if (ret >= end)
+		ret = max(bix, end);
+	return ret;
+}
+
+static int logfs_is_valid_direct(struct logfs_inode *li, u64 bix, u64 ofs)
+{
+	return pure_ofs(li->li_data[bix]) == ofs;
+}
+
+static int __logfs_is_valid_loop(struct inode *inode, u64 bix,
+		u64 ofs, u64 bofs)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	level_t level;
+	int ret;
+	struct page *page;
+
+	for (level = LEVEL(li->li_height); level != 0; level = SUBLEVEL(level)){
+		page = logfs_get_write_page(inode, bix, level);
+		BUG_ON(!page);
+
+		ret = logfs_segment_read(inode, page, bofs, bix, level);
+		if (ret) {
+			logfs_put_write_page(page);
+			return 0;
+		}
+
+		bofs = block_get_pointer(page, get_bits(bix, SUBLEVEL(level)));
+		logfs_put_write_page(page);
+		if (!bofs)
+			return 0;
+
+		if (pure_ofs(bofs) == ofs)
+			return 1;
+	}
+	return 0;
+}
+
+static int logfs_is_valid_loop(struct inode *inode, u64 bix, u64 ofs)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	u64 bofs = li->li_data[INDIRECT_INDEX];
+
+	if (!bofs)
+		return 0;
+
+	if (bix >= maxbix(li->li_height))
+		return 0;
+
+	if (pure_ofs(bofs) == ofs)
+		return 1;
+
+	return __logfs_is_valid_loop(inode, bix, ofs, bofs);
+}
+
+static int __logfs_is_valid_block(struct inode *inode, u64 bix, u64 ofs)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	if ((inode->i_nlink == 0) && atomic_read(&inode->i_count) == 1)
+		return 0;
+
+	if (bix < I0_BLOCKS)
+		return logfs_is_valid_direct(li, bix, ofs);
+	return logfs_is_valid_loop(inode, bix, ofs);
+}
+
+/**
+ * logfs_is_valid_block - check whether this block is still valid
+ *
+ * @sb:		superblock
+ * @ofs:	block physical offset
+ * @ino:	block inode number
+ * @bix:	block index
+ * @gc_level:	block level
+ *
+ * Returns 0 if the block is invalid, 1 if it is valid and 2 if it will
+ * become invalid once the journal is written.
+ */
+int logfs_is_valid_block(struct super_block *sb, u64 ofs, u64 ino, u64 bix,
+		gc_level_t gc_level)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *inode;
+	int ret, cookie;
+
+	/* Umount closes a segment with free blocks remaining.  Those
+	 * blocks are by definition invalid. */
+	if (ino == -1)
+		return 0;
+
+	LOGFS_BUG_ON((u64)(u_long)ino != ino, sb);
+
+	inode = logfs_safe_iget(sb, ino, &cookie);
+	if (IS_ERR(inode))
+		goto invalid;
+
+	ret = __logfs_is_valid_block(inode, bix, ofs);
+	logfs_safe_iput(inode, cookie);
+	if (ret)
+		return ret;
+
+invalid:
+	/* Block is nominally invalid, but may still sit in the shadow tree,
+	 * waiting for a journal commit.
+	 */
+	if (btree_lookup64(&super->s_shadow_tree.old, ofs))
+		return 2;
+	return 0;
+}
+
+int logfs_readpage_nolock(struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	int ret = -EIO;
+
+	ret = logfs_read_block(inode, page, READ);
+
+	if (ret) {
+		ClearPageUptodate(page);
+		SetPageError(page);
+	} else {
+		SetPageUptodate(page);
+		ClearPageError(page);
+	}
+	flush_dcache_page(page);
+
+	return ret;
+}
+
+static int logfs_reserve_bytes(struct inode *inode, int bytes)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+	u64 available = super->s_free_bytes + super->s_dirty_free_bytes
+			- super->s_dirty_used_bytes - super->s_dirty_pages;
+
+	if (!bytes)
+		return 0;
+
+	if (available < bytes)
+		return -ENOSPC;
+
+	if (available < bytes + super->s_root_reserve &&
+			!capable(CAP_SYS_RESOURCE))
+		return -ENOSPC;
+
+	return 0;
+}
+
+int get_page_reserve(struct inode *inode, struct page *page)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+	struct logfs_block *block = logfs_block(page);
+	int ret;
+
+	if (block && block->reserved_bytes)
+		return 0;
+
+	logfs_get_wblocks(inode->i_sb, page, WF_LOCK);
+	while ((ret = logfs_reserve_bytes(inode, 6 * LOGFS_MAX_OBJECTSIZE)) &&
+			!list_empty(&super->s_writeback_list)) {
+		block = list_entry(super->s_writeback_list.next,
+				struct logfs_block, alias_list);
+		block->ops->write_block(block);
+	}
+	if (!ret) {
+		alloc_data_block(inode, page);
+		block = logfs_block(page);
+		block->reserved_bytes += 6 * LOGFS_MAX_OBJECTSIZE;
+		super->s_dirty_pages += 6 * LOGFS_MAX_OBJECTSIZE;
+		list_move_tail(&block->alias_list, &super->s_writeback_list);
+	}
+	logfs_put_wblocks(inode->i_sb, page, WF_LOCK);
+	return ret;
+}
+
+/*
+ * We are protected by write lock.  Push victims up to superblock level
+ * and release transaction when appropriate.
+ */
+/* FIXME: This is currently called from the wrong spots. */
+static void logfs_handle_transaction(struct inode *inode,
+		struct logfs_transaction *ta)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+
+	if (!ta)
+		return;
+	logfs_inode(inode)->li_block->ta = NULL;
+
+	if (inode->i_ino != LOGFS_INO_MASTER) {
+		BUG(); /* FIXME: Yes, this needs more thought */
+		/* just remember the transaction until inode is written */
+		//BUG_ON(logfs_inode(inode)->li_transaction);
+		//logfs_inode(inode)->li_transaction = ta;
+		return;
+	}
+
+	switch (ta->state) {
+	case CREATE_1: /* fall through */
+	case UNLINK_1:
+		BUG_ON(super->s_victim_ino);
+		super->s_victim_ino = ta->ino;
+		break;
+	case CREATE_2: /* fall through */
+	case UNLINK_2:
+		BUG_ON(super->s_victim_ino != ta->ino);
+		super->s_victim_ino = 0;
+		/* transaction ends here - free it */
+		kfree(ta);
+		break;
+	case CROSS_RENAME_1:
+		BUG_ON(super->s_rename_dir);
+		BUG_ON(super->s_rename_pos);
+		super->s_rename_dir = ta->dir;
+		super->s_rename_pos = ta->pos;
+		break;
+	case CROSS_RENAME_2:
+		BUG_ON(super->s_rename_dir != ta->dir);
+		BUG_ON(super->s_rename_pos != ta->pos);
+		super->s_rename_dir = 0;
+		super->s_rename_pos = 0;
+		kfree(ta);
+		break;
+	case TARGET_RENAME_1:
+		BUG_ON(super->s_rename_dir);
+		BUG_ON(super->s_rename_pos);
+		BUG_ON(super->s_victim_ino);
+		super->s_rename_dir = ta->dir;
+		super->s_rename_pos = ta->pos;
+		super->s_victim_ino = ta->ino;
+		break;
+	case TARGET_RENAME_2:
+		BUG_ON(super->s_rename_dir != ta->dir);
+		BUG_ON(super->s_rename_pos != ta->pos);
+		BUG_ON(super->s_victim_ino != ta->ino);
+		super->s_rename_dir = 0;
+		super->s_rename_pos = 0;
+		break;
+	case TARGET_RENAME_3:
+		BUG_ON(super->s_rename_dir);
+		BUG_ON(super->s_rename_pos);
+		BUG_ON(super->s_victim_ino != ta->ino);
+		super->s_victim_ino = 0;
+		kfree(ta);
+		break;
+	default:
+		BUG();
+	}
+}
+
+/*
+ * Not strictly a reservation, but rather a check that we still have enough
+ * space to satisfy the write.
+ */
+static int logfs_reserve_blocks(struct inode *inode, int blocks)
+{
+	return logfs_reserve_bytes(inode, blocks * LOGFS_MAX_OBJECTSIZE);
+}
+
+struct write_control {
+	u64 ofs;
+	long flags;
+};
+
+static struct logfs_shadow *alloc_shadow(struct inode *inode, u64 bix,
+		level_t level, u64 old_ofs)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+	struct logfs_shadow *shadow;
+
+	shadow = mempool_alloc(super->s_shadow_pool, GFP_NOFS);
+	memset(shadow, 0, sizeof(*shadow));
+	shadow->ino = inode->i_ino;
+	shadow->bix = bix;
+	shadow->gc_level = expand_level(inode->i_ino, level);
+	shadow->old_ofs = old_ofs & ~LOGFS_FULLY_POPULATED;
+	return shadow;
+}
+
+static void free_shadow(struct inode *inode, struct logfs_shadow *shadow)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+
+	mempool_free(shadow, super->s_shadow_pool);
+}
+
+static void mark_segment(struct shadow_tree *tree, u32 segno)
+{
+	int err;
+
+	if (!btree_lookup32(&tree->segment_map, segno)) {
+		err = btree_insert32(&tree->segment_map, segno, (void *)1,
+				GFP_NOFS);
+		BUG_ON(err);
+		tree->no_shadowed_segments++;
+	}
+}
+
+/**
+ * fill_shadow_tree - Propagate shadow tree changes due to a write
+ * @inode:	Inode owning the page
+ * @page:	Struct page that was written
+ * @shadow:	Shadow for the current write
+ *
+ * Writes in logfs can result in two semi-valid objects.  The old object
+ * is still valid as long as it can be reached by following pointers on
+ * the medium.  Only when writes propagate all the way up to the journal
+ * has the new object safely replaced the old one.
+ *
+ * To handle this problem, a struct logfs_shadow is used to represent
+ * every single write.  It is attached to the indirect block, which is
+ * marked dirty.  When the indirect block is written, its shadows are
+ * handed up to the next indirect block (or inode).  Untimately they
+ * will reach the master inode and be freed upon journal commit.
+ *
+ * This function handles a single step in the propagation.  It adds the
+ * shadow for the current write to the tree, along with any shadows in
+ * the page's tree, in case it was an indirect block.  If a page is
+ * written, the inode parameter is left NULL, if an inode is written,
+ * the page parameter is left NULL.
+ */
+static void fill_shadow_tree(struct inode *inode, struct page *page,
+		struct logfs_shadow *shadow)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+	struct logfs_block *block = logfs_block(page);
+	struct shadow_tree *tree = &super->s_shadow_tree;
+
+	if (PagePrivate(page)) {
+		if (block->alias_map)
+			super->s_no_object_aliases -= bitmap_weight(
+					block->alias_map, LOGFS_BLOCK_FACTOR);
+		logfs_handle_transaction(inode, block->ta);
+		block->ops->free_block(inode->i_sb, block);
+	}
+	if (shadow) {
+		if (shadow->old_ofs)
+			btree_insert64(&tree->old, shadow->old_ofs, shadow,
+					GFP_NOFS);
+		else
+			btree_insert64(&tree->new, shadow->new_ofs, shadow,
+					GFP_NOFS);
+
+		super->s_dirty_used_bytes += shadow->new_len;
+		super->s_dirty_free_bytes += shadow->old_len;
+		mark_segment(tree, shadow->old_ofs >> super->s_segshift);
+		mark_segment(tree, shadow->new_ofs >> super->s_segshift);
+	}
+}
+
+static void logfs_set_alias(struct super_block *sb, struct logfs_block *block,
+		long child_no)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	if (block->inode && block->inode->i_ino == LOGFS_INO_MASTER) {
+		/* Aliases in the master inode are pointless. */
+		return;
+	}
+
+	if (!test_bit(child_no, block->alias_map)) {
+		set_bit(child_no, block->alias_map);
+		super->s_no_object_aliases++;
+	}
+	list_move_tail(&block->alias_list, &super->s_object_alias);
+}
+
+/*
+ * Object aliases can and often do change the size and occupied space of a
+ * file.  So not only do we have to change the pointers, we also have to
+ * change inode->i_size and li->li_used_bytes.  Which is done by setting
+ * another two object aliases for the inode itself.
+ */
+static void set_iused(struct inode *inode, struct logfs_shadow *shadow)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+
+	if (shadow->new_len == shadow->old_len)
+		return;
+
+	alloc_inode_block(inode);
+	li->li_used_bytes += shadow->new_len - shadow->old_len;
+	__logfs_set_blocks(inode);
+	logfs_set_alias(inode->i_sb, li->li_block, INODE_USED_OFS);
+	logfs_set_alias(inode->i_sb, li->li_block, INODE_SIZE_OFS);
+}
+
+static int logfs_write_i0(struct inode *inode, struct page *page,
+		struct write_control *wc)
+{
+	struct logfs_shadow *shadow;
+	u64 bix;
+	level_t level;
+	int full, err = 0;
+
+	logfs_unpack_index(page->index, &bix, &level);
+	if (wc->ofs == 0)
+		if (logfs_reserve_blocks(inode, 1))
+			return -ENOSPC;
+
+	shadow = alloc_shadow(inode, bix, level, wc->ofs);
+	if (wc->flags & WF_WRITE)
+		err = logfs_segment_write(inode, page, shadow);
+	if (wc->flags & WF_DELETE)
+		logfs_segment_delete(inode, shadow);
+	if (err) {
+		free_shadow(inode, shadow);
+		return err;
+	}
+
+	set_iused(inode, shadow);
+	full = 1;
+	if (level != 0) {
+		alloc_indirect_block(inode, page, 0);
+		full = logfs_block(page)->full == LOGFS_BLOCK_FACTOR;
+	}
+	fill_shadow_tree(inode, page, shadow);
+	wc->ofs = shadow->new_ofs;
+	if (wc->ofs && full)
+		wc->ofs |= LOGFS_FULLY_POPULATED;
+	return 0;
+}
+
+static int logfs_write_direct(struct inode *inode, struct page *page,
+		long flags)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct write_control wc = {
+		.ofs = li->li_data[page->index],
+		.flags = flags,
+	};
+	int err;
+
+	alloc_inode_block(inode);
+
+	err = logfs_write_i0(inode, page, &wc);
+	if (err)
+		return err;
+
+	li->li_data[page->index] = wc.ofs;
+	logfs_set_alias(inode->i_sb, li->li_block,
+			page->index + INODE_POINTER_OFS);
+	return 0;
+}
+
+static int ptr_change(u64 ofs, struct page *page)
+{
+	struct logfs_block *block = logfs_block(page);
+	int empty0, empty1, full0, full1;
+
+	empty0 = ofs == 0;
+	empty1 = block->partial == 0;
+	if (empty0 != empty1)
+		return 1;
+
+	/* The !! is necessary to shrink result to int */
+	full0 = !!(ofs & LOGFS_FULLY_POPULATED);
+	full1 = block->full == LOGFS_BLOCK_FACTOR;
+	if (full0 != full1)
+		return 1;
+	return 0;
+}
+
+static int __logfs_write_rec(struct inode *inode, struct page *page,
+		struct write_control *this_wc,
+		pgoff_t bix, level_t target_level, level_t level)
+{
+	int ret, page_empty = 0;
+	int child_no = get_bits(bix, SUBLEVEL(level));
+	struct page *ipage;
+	struct write_control child_wc = {
+		.flags = this_wc->flags,
+	};
+
+	ipage = logfs_get_write_page(inode, bix, level);
+	if (!ipage)
+		return -ENOMEM;
+
+	if (this_wc->ofs) {
+		ret = logfs_segment_read(inode, ipage, this_wc->ofs, bix, level);
+		if (ret)
+			goto out;
+	} else if (!PageUptodate(ipage)) {
+		page_empty = 1;
+		logfs_read_empty(ipage);
+	}
+
+	child_wc.ofs = block_get_pointer(ipage, child_no);
+
+	if ((__force u8)level-1 > (__force u8)target_level)
+		ret = __logfs_write_rec(inode, page, &child_wc, bix,
+				target_level, SUBLEVEL(level));
+	else
+		ret = logfs_write_i0(inode, page, &child_wc);
+
+	if (ret)
+		goto out;
+
+	alloc_indirect_block(inode, ipage, page_empty);
+	block_set_pointer(ipage, child_no, child_wc.ofs);
+	/* FIXME: first condition seems superfluous */
+	if (child_wc.ofs || logfs_block(ipage)->partial)
+		this_wc->flags |= WF_WRITE;
+	/* the condition on this_wc->ofs ensures that we won't consume extra
+	 * space for indirect blocks in the future, which we cannot reserve */
+	if (!this_wc->ofs || ptr_change(this_wc->ofs, ipage))
+		ret = logfs_write_i0(inode, ipage, this_wc);
+	else
+		logfs_set_alias(inode->i_sb, logfs_block(ipage), child_no);
+out:
+	logfs_put_write_page(ipage);
+	return ret;
+}
+
+static int logfs_write_rec(struct inode *inode, struct page *page,
+		pgoff_t bix, level_t target_level, long flags)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct write_control wc = {
+		.ofs = li->li_data[INDIRECT_INDEX],
+		.flags = flags,
+	};
+	int ret;
+
+	alloc_inode_block(inode);
+
+	if (li->li_height > (__force u8)target_level)
+		ret = __logfs_write_rec(inode, page, &wc, bix, target_level,
+				LEVEL(li->li_height));
+	else
+		ret = logfs_write_i0(inode, page, &wc);
+	if (ret)
+		return ret;
+
+	if (li->li_data[INDIRECT_INDEX] != wc.ofs) {
+		li->li_data[INDIRECT_INDEX] = wc.ofs;
+		logfs_set_alias(inode->i_sb, li->li_block,
+				INDIRECT_INDEX + INODE_POINTER_OFS);
+	}
+	return ret;
+}
+
+void logfs_add_transaction(struct inode *inode, struct logfs_transaction *ta)
+{
+	alloc_inode_block(inode);
+	logfs_inode(inode)->li_block->ta = ta;
+}
+
+void logfs_del_transaction(struct inode *inode, struct logfs_transaction *ta)
+{
+	struct logfs_block *block = logfs_inode(inode)->li_block;
+
+	if (block && block->ta)
+		block->ta = NULL;
+}
+
+static int grow_inode(struct inode *inode, u64 bix, level_t level)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	u8 height = (__force u8)level;
+	struct page *page;
+	struct write_control wc = {
+		.flags = WF_WRITE,
+	};
+	int err;
+
+	BUG_ON(height > 5 || li->li_height > 5);
+	while (height > li->li_height || bix >= maxbix(li->li_height)) {
+		page = logfs_get_write_page(inode, I0_BLOCKS + 1,
+				LEVEL(li->li_height + 1));
+		if (!page)
+			return -ENOMEM;
+		logfs_read_empty(page);
+		alloc_indirect_block(inode, page, 1);
+		block_set_pointer(page, 0, li->li_data[INDIRECT_INDEX]);
+		err = logfs_write_i0(inode, page, &wc);
+		logfs_put_write_page(page);
+		if (err)
+			return err;
+		li->li_data[INDIRECT_INDEX] = wc.ofs;
+		wc.ofs = 0;
+		li->li_height++;
+		logfs_set_alias(inode->i_sb, li->li_block, INODE_HEIGHT_OFS);
+	}
+	return 0;
+}
+
+static int __logfs_write_buf(struct inode *inode, struct page *page, long flags)
+{
+	struct logfs_super *super = logfs_super(inode->i_sb);
+	pgoff_t index = page->index;
+	u64 bix;
+	level_t level;
+	int err;
+
+	flags |= WF_WRITE | WF_DELETE;
+	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+
+	logfs_unpack_index(index, &bix, &level);
+	if (logfs_block(page) && logfs_block(page)->reserved_bytes)
+		super->s_dirty_pages -= logfs_block(page)->reserved_bytes;
+
+	if (index < I0_BLOCKS)
+		return logfs_write_direct(inode, page, flags);
+
+	bix = adjust_bix(bix, level);
+	err = grow_inode(inode, bix, level);
+	if (err)
+		return err;
+	return logfs_write_rec(inode, page, bix, level, flags);
+}
+
+int logfs_write_buf(struct inode *inode, struct page *page, long flags)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret;
+
+	logfs_get_wblocks(sb, page, flags & WF_LOCK);
+	ret = __logfs_write_buf(inode, page, flags);
+	logfs_put_wblocks(sb, page, flags & WF_LOCK);
+	return ret;
+}
+
+static int __logfs_delete(struct inode *inode, struct page *page)
+{
+	long flags = WF_DELETE;
+	int err;
+
+	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+
+	if (page->index < I0_BLOCKS)
+		return logfs_write_direct(inode, page, flags);
+	err = grow_inode(inode, page->index, 0);
+	if (err)
+		return err;
+	return logfs_write_rec(inode, page, page->index, 0, flags);
+}
+
+int logfs_delete(struct inode *inode, pgoff_t index,
+		struct shadow_tree *shadow_tree)
+{
+	struct super_block *sb = inode->i_sb;
+	struct page *page;
+	int ret;
+
+	page = logfs_get_read_page(inode, index, 0);
+	if (!page)
+		return -ENOMEM;
+
+	logfs_get_wblocks(sb, page, 1);
+	ret = __logfs_delete(inode, page);
+	logfs_put_wblocks(sb, page, 1);
+
+	logfs_put_read_page(page);
+
+	return ret;
+}
+
+int logfs_rewrite_block(struct inode *inode, u64 bix, u64 ofs,
+		gc_level_t gc_level, long flags)
+{
+	level_t level = shrink_level(gc_level);
+	struct page *page;
+	int err;
+
+	page = logfs_get_write_page(inode, bix, level);
+	if (!page)
+		return -ENOMEM;
+
+	err = logfs_segment_read(inode, page, ofs, bix, level);
+	if (!err) {
+		if (level != 0)
+			alloc_indirect_block(inode, page, 0);
+		err = logfs_write_buf(inode, page, flags);
+		if (!err && shrink_level(gc_level) == 0) {
+			/* Rewrite cannot mark the inode dirty but has to
+			 * write it immediately.
+			 * Q: Can't we just create an alias for the inode
+			 * instead?  And if not, why not?
+			 */
+			if (inode->i_ino == LOGFS_INO_MASTER)
+				logfs_write_anchor(inode->i_sb);
+			else {
+				err = __logfs_write_inode(inode, page, flags);
+			}
+		}
+	}
+	logfs_put_write_page(page);
+	return err;
+}
+
+static int truncate_data_block(struct inode *inode, struct page *page,
+		u64 ofs, struct logfs_shadow *shadow, u64 size)
+{
+	loff_t pageofs = page->index << inode->i_sb->s_blocksize_bits;
+	u64 bix;
+	level_t level;
+	int err;
+
+	/* Does truncation happen within this page? */
+	if (size <= pageofs || size - pageofs >= PAGE_SIZE)
+		return 0;
+
+	logfs_unpack_index(page->index, &bix, &level);
+	BUG_ON(level != 0);
+
+	err = logfs_segment_read(inode, page, ofs, bix, level);
+	if (err)
+		return err;
+
+	zero_user_segment(page, size - pageofs, PAGE_CACHE_SIZE);
+	return logfs_segment_write(inode, page, shadow);
+}
+
+static int logfs_truncate_i0(struct inode *inode, struct page *page,
+		struct write_control *wc, u64 size)
+{
+	struct logfs_shadow *shadow;
+	u64 bix;
+	level_t level;
+	int err = 0;
+
+	logfs_unpack_index(page->index, &bix, &level);
+	BUG_ON(level != 0);
+	shadow = alloc_shadow(inode, bix, level, wc->ofs);
+
+	err = truncate_data_block(inode, page, wc->ofs, shadow, size);
+	if (err) {
+		free_shadow(inode, shadow);
+		return err;
+	}
+
+	logfs_segment_delete(inode, shadow);
+	set_iused(inode, shadow);
+	fill_shadow_tree(inode, page, shadow);
+	wc->ofs = shadow->new_ofs;
+	return 0;
+}
+
+static int logfs_truncate_direct(struct inode *inode, u64 size)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct write_control wc;
+	struct page *page;
+	int e;
+	int err;
+
+	alloc_inode_block(inode);
+
+	for (e = I0_BLOCKS - 1; e >= 0; e--) {
+		if (size > (e+1) * LOGFS_BLOCKSIZE)
+			break;
+
+		wc.ofs = li->li_data[e];
+		if (!wc.ofs)
+			continue;
+
+		page = logfs_get_write_page(inode, e, 0);
+		if (!page)
+			return -ENOMEM;
+		err = logfs_segment_read(inode, page, wc.ofs, e, 0);
+		if (err) {
+			logfs_put_write_page(page);
+			return err;
+		}
+		err = logfs_truncate_i0(inode, page, &wc, size);
+		logfs_put_write_page(page);
+		if (err)
+			return err;
+
+		li->li_data[e] = wc.ofs;
+	}
+	return 0;
+}
+
+/* FIXME: these need to become per-sb once we support different blocksizes */
+static u64 __logfs_step[] = {
+	1,
+	I1_BLOCKS,
+	I2_BLOCKS,
+	I3_BLOCKS,
+};
+
+static u64 __logfs_start_index[] = {
+	I0_BLOCKS,
+	I1_BLOCKS,
+	I2_BLOCKS,
+	I3_BLOCKS
+};
+
+static inline u64 logfs_step(level_t level)
+{
+	return __logfs_step[(__force u8)level];
+}
+
+static inline u64 logfs_factor(u8 level)
+{
+	return __logfs_step[level] * LOGFS_BLOCKSIZE;
+}
+
+static inline u64 logfs_start_index(level_t level)
+{
+	return __logfs_start_index[(__force u8)level];
+}
+
+static void logfs_unpack_raw_index(pgoff_t index, u64 *bix, level_t *level)
+{
+	logfs_unpack_index(index, bix, level);
+	if (*bix <= logfs_start_index(SUBLEVEL(*level)))
+		*bix = 0;
+}
+
+static int __logfs_truncate_rec(struct inode *inode, struct page *ipage,
+		struct write_control *this_wc, u64 size)
+{
+	int truncate_happened = 0;
+	int e, err = 0;
+	u64 bix, child_bix, next_bix;
+	level_t level;
+	struct page *page;
+	struct write_control child_wc = { /* FIXME: flags */ };
+
+	logfs_unpack_raw_index(ipage->index, &bix, &level);
+	err = logfs_segment_read(inode, ipage, this_wc->ofs, bix, level);
+	if (err)
+		return err;
+
+	for (e = LOGFS_BLOCK_FACTOR - 1; e >= 0; e--) {
+		child_bix = bix + e * logfs_step(SUBLEVEL(level));
+		next_bix = child_bix + logfs_step(SUBLEVEL(level));
+		if (size > next_bix * LOGFS_BLOCKSIZE)
+			break;
+
+		child_wc.ofs = pure_ofs(block_get_pointer(ipage, e));
+		if (!child_wc.ofs)
+			continue;
+
+		page = logfs_get_write_page(inode, child_bix, SUBLEVEL(level));
+		if (!page)
+			return -ENOMEM;
+
+		if ((__force u8)level > 1)
+			err = __logfs_truncate_rec(inode, page, &child_wc, size);
+		else
+			err = logfs_truncate_i0(inode, page, &child_wc, size);
+		logfs_put_write_page(page);
+		if (err)
+			return err;
+
+		truncate_happened = 1;
+		alloc_indirect_block(inode, ipage, 0);
+		block_set_pointer(ipage, e, child_wc.ofs);
+	}
+
+	if (!truncate_happened) {
+		printk("ineffectual truncate (%lx, %lx, %llx)\n", inode->i_ino, ipage->index, size);
+		return 0;
+	}
+
+	this_wc->flags = WF_DELETE;
+	if (logfs_block(ipage)->partial)
+		this_wc->flags |= WF_WRITE;
+
+	return logfs_write_i0(inode, ipage, this_wc);
+}
+
+static int logfs_truncate_rec(struct inode *inode, u64 size)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct write_control wc = {
+		.ofs = li->li_data[INDIRECT_INDEX],
+	};
+	struct page *page;
+	int err;
+
+	alloc_inode_block(inode);
+
+	if (!wc.ofs)
+		return 0;
+
+	page = logfs_get_write_page(inode, 0, LEVEL(li->li_height));
+	if (!page)
+		return -ENOMEM;
+
+	err = __logfs_truncate_rec(inode, page, &wc, size);
+	logfs_put_write_page(page);
+	if (err)
+		return err;
+
+	if (li->li_data[INDIRECT_INDEX] != wc.ofs)
+		li->li_data[INDIRECT_INDEX] = wc.ofs;
+	return 0;
+}
+
+static int __logfs_truncate(struct inode *inode, u64 size)
+{
+	int ret;
+
+	if (size >= logfs_factor(logfs_inode(inode)->li_height))
+		return 0;
+
+	ret = logfs_truncate_rec(inode, size);
+	if (ret)
+		return ret;
+
+	return logfs_truncate_direct(inode, size);
+}
+
+/*
+ * Truncate, by changing the segment file, can consume a fair amount
+ * of resources.  So back off from time to time and do some GC.
+ * 8 or 2048 blocks should be well within safety limits even if
+ * every single block resided in a different segment.
+ */
+#define TRUNCATE_STEP	(8 * 1024 * 1024)
+int logfs_truncate(struct inode *inode, u64 target)
+{
+	struct super_block *sb = inode->i_sb;
+	u64 size = i_size_read(inode);
+	int err = 0;
+
+	size = ALIGN(size, TRUNCATE_STEP);
+	while (size > target) {
+		if (size > TRUNCATE_STEP)
+			size -= TRUNCATE_STEP;
+		else
+			size = 0;
+		if (size < target)
+			size = target;
+
+		logfs_get_wblocks(sb, NULL, 1);
+		err = __logfs_truncate(inode, size);
+		if (!err)
+			err = __logfs_write_inode(inode, NULL, 0);
+		logfs_put_wblocks(sb, NULL, 1);
+	}
+
+	if (!err) {
+		err = inode_newsize_ok(inode, target);
+		if (err)
+			goto out;
+
+		truncate_setsize(inode, target);
+	}
+
+ out:
+	/* I don't trust error recovery yet. */
+	WARN_ON(err);
+	return err;
+}
+
+static void move_page_to_inode(struct inode *inode, struct page *page)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct logfs_block *block = logfs_block(page);
+
+	if (!block)
+		return;
+
+	log_blockmove("move_page_to_inode(%llx, %llx, %x)\n",
+			block->ino, block->bix, block->level);
+	BUG_ON(li->li_block);
+	block->ops = &inode_block_ops;
+	block->inode = inode;
+	li->li_block = block;
+
+	block->page = NULL;
+	if (PagePrivate(page)) {
+		ClearPagePrivate(page);
+		page_cache_release(page);
+		set_page_private(page, 0);
+	}
+}
+
+static void move_inode_to_page(struct page *page, struct inode *inode)
+{
+	struct logfs_inode *li = logfs_inode(inode);
+	struct logfs_block *block = li->li_block;
+
+	if (!block)
+		return;
+
+	log_blockmove("move_inode_to_page(%llx, %llx, %x)\n",
+			block->ino, block->bix, block->level);
+	BUG_ON(PagePrivate(page));
+	block->ops = &indirect_block_ops;
+	block->page = page;
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		page_cache_get(page);
+		set_page_private(page, (unsigned long) block);
+	}
+
+	block->inode = NULL;
+	li->li_block = NULL;
+}
+
+int logfs_read_inode(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *master_inode = super->s_master_inode;
+	struct page *page;
+	struct logfs_disk_inode *di;
+	u64 ino = inode->i_ino;
+
+	if (ino << sb->s_blocksize_bits > i_size_read(master_inode))
+		return -ENODATA;
+	if (!logfs_exist_block(master_inode, ino))
+		return -ENODATA;
+
+	page = read_cache_page(master_inode->i_mapping, ino,
+			(filler_t *)logfs_readpage, NULL);
+	if (IS_ERR(page))
+		return PTR_ERR(page);
+
+	di = kmap_atomic(page);
+	logfs_disk_to_inode(di, inode);
+	kunmap_atomic(di);
+	move_page_to_inode(inode, page);
+	page_cache_release(page);
+	return 0;
+}
+
+/* Caller must logfs_put_write_page(page); */
+static struct page *inode_to_page(struct inode *inode)
+{
+	struct inode *master_inode = logfs_super(inode->i_sb)->s_master_inode;
+	struct logfs_disk_inode *di;
+	struct page *page;
+
+	BUG_ON(inode->i_ino == LOGFS_INO_MASTER);
+
+	page = logfs_get_write_page(master_inode, inode->i_ino, 0);
+	if (!page)
+		return NULL;
+
+	di = kmap_atomic(page);
+	logfs_inode_to_disk(inode, di);
+	kunmap_atomic(di);
+	move_inode_to_page(page, inode);
+	return page;
+}
+
+static int do_write_inode(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct inode *master_inode = logfs_super(sb)->s_master_inode;
+	loff_t size = (inode->i_ino + 1) << inode->i_sb->s_blocksize_bits;
+	struct page *page;
+	int err;
+
+	BUG_ON(inode->i_ino == LOGFS_INO_MASTER);
+	/* FIXME: lock inode */
+
+	if (i_size_read(master_inode) < size)
+		i_size_write(master_inode, size);
+
+	/* TODO: Tell vfs this inode is clean now */
+
+	page = inode_to_page(inode);
+	if (!page)
+		return -ENOMEM;
+
+	/* FIXME: transaction is part of logfs_block now.  Is that enough? */
+	err = logfs_write_buf(master_inode, page, 0);
+	if (err)
+		move_page_to_inode(inode, page);
+
+	logfs_put_write_page(page);
+	return err;
+}
+
+static void logfs_mod_segment_entry(struct super_block *sb, u32 segno,
+		int write,
+		void (*change_se)(struct logfs_segment_entry *, long),
+		long arg)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *inode;
+	struct page *page;
+	struct logfs_segment_entry *se;
+	pgoff_t page_no;
+	int child_no;
+
+	page_no = segno >> (sb->s_blocksize_bits - 3);
+	child_no = segno & ((sb->s_blocksize >> 3) - 1);
+
+	inode = super->s_segfile_inode;
+	page = logfs_get_write_page(inode, page_no, 0);
+	BUG_ON(!page); /* FIXME: We need some reserve page for this case */
+	if (!PageUptodate(page))
+		logfs_read_block(inode, page, WRITE);
+
+	if (write)
+		alloc_indirect_block(inode, page, 0);
+	se = kmap_atomic(page);
+	change_se(se + child_no, arg);
+	if (write) {
+		logfs_set_alias(sb, logfs_block(page), child_no);
+		BUG_ON((int)be32_to_cpu(se[child_no].valid) > super->s_segsize);
+	}
+	kunmap_atomic(se);
+
+	logfs_put_write_page(page);
+}
+
+static void __get_segment_entry(struct logfs_segment_entry *se, long _target)
+{
+	struct logfs_segment_entry *target = (void *)_target;
+
+	*target = *se;
+}
+
+void logfs_get_segment_entry(struct super_block *sb, u32 segno,
+		struct logfs_segment_entry *se)
+{
+	logfs_mod_segment_entry(sb, segno, 0, __get_segment_entry, (long)se);
+}
+
+static void __set_segment_used(struct logfs_segment_entry *se, long increment)
+{
+	u32 valid;
+
+	valid = be32_to_cpu(se->valid);
+	valid += increment;
+	se->valid = cpu_to_be32(valid);
+}
+
+void logfs_set_segment_used(struct super_block *sb, u64 ofs, int increment)
+{
+	struct logfs_super *super = logfs_super(sb);
+	u32 segno = ofs >> super->s_segshift;
+
+	if (!increment)
+		return;
+
+	logfs_mod_segment_entry(sb, segno, 1, __set_segment_used, increment);
+}
+
+static void __set_segment_erased(struct logfs_segment_entry *se, long ec_level)
+{
+	se->ec_level = cpu_to_be32(ec_level);
+}
+
+void logfs_set_segment_erased(struct super_block *sb, u32 segno, u32 ec,
+		gc_level_t gc_level)
+{
+	u32 ec_level = ec << 4 | (__force u8)gc_level;
+
+	logfs_mod_segment_entry(sb, segno, 1, __set_segment_erased, ec_level);
+}
+
+static void __set_segment_reserved(struct logfs_segment_entry *se, long ignore)
+{
+	se->valid = cpu_to_be32(RESERVED);
+}
+
+void logfs_set_segment_reserved(struct super_block *sb, u32 segno)
+{
+	logfs_mod_segment_entry(sb, segno, 1, __set_segment_reserved, 0);
+}
+
+static void __set_segment_unreserved(struct logfs_segment_entry *se,
+		long ec_level)
+{
+	se->valid = 0;
+	se->ec_level = cpu_to_be32(ec_level);
+}
+
+void logfs_set_segment_unreserved(struct super_block *sb, u32 segno, u32 ec)
+{
+	u32 ec_level = ec << 4;
+
+	logfs_mod_segment_entry(sb, segno, 1, __set_segment_unreserved,
+			ec_level);
+}
+
+int __logfs_write_inode(struct inode *inode, struct page *page, long flags)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret;
+
+	logfs_get_wblocks(sb, page, flags & WF_LOCK);
+	ret = do_write_inode(inode);
+	logfs_put_wblocks(sb, page, flags & WF_LOCK);
+	return ret;
+}
+
+static int do_delete_inode(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct inode *master_inode = logfs_super(sb)->s_master_inode;
+	struct page *page;
+	int ret;
+
+	page = logfs_get_write_page(master_inode, inode->i_ino, 0);
+	if (!page)
+		return -ENOMEM;
+
+	move_inode_to_page(page, inode);
+
+	logfs_get_wblocks(sb, page, 1);
+	ret = __logfs_delete(master_inode, page);
+	logfs_put_wblocks(sb, page, 1);
+
+	logfs_put_write_page(page);
+	return ret;
+}
+
+/*
+ * ZOMBIE inodes have already been deleted before and should remain dead,
+ * if it weren't for valid checking.  No need to kill them again here.
+ */
+void logfs_evict_inode(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct logfs_inode *li = logfs_inode(inode);
+	struct logfs_block *block = li->li_block;
+	struct page *page;
+
+	if (!inode->i_nlink) {
+		if (!(li->li_flags & LOGFS_IF_ZOMBIE)) {
+			li->li_flags |= LOGFS_IF_ZOMBIE;
+			if (i_size_read(inode) > 0)
+				logfs_truncate(inode, 0);
+			do_delete_inode(inode);
+		}
+	}
+	truncate_inode_pages_final(&inode->i_data);
+	clear_inode(inode);
+
+	/* Cheaper version of write_inode.  All changes are concealed in
+	 * aliases, which are moved back.  No write to the medium happens.
+	 */
+	/* Only deleted files may be dirty at this point */
+	BUG_ON(inode->i_state & I_DIRTY && inode->i_nlink);
+	if (!block)
+		return;
+	if ((logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN)) {
+		block->ops->free_block(inode->i_sb, block);
+		return;
+	}
+
+	page = inode_to_page(inode);
+	BUG_ON(!page); /* FIXME: Use emergency page */
+	logfs_put_write_page(page);
+}
+
+void btree_write_block(struct logfs_block *block)
+{
+	struct inode *inode;
+	struct page *page;
+	int err, cookie;
+
+	inode = logfs_safe_iget(block->sb, block->ino, &cookie);
+	page = logfs_get_write_page(inode, block->bix, block->level);
+
+	err = logfs_readpage_nolock(page);
+	BUG_ON(err);
+	BUG_ON(!PagePrivate(page));
+	BUG_ON(logfs_block(page) != block);
+	err = __logfs_write_buf(inode, page, 0);
+	BUG_ON(err);
+	BUG_ON(PagePrivate(page) || page->private);
+
+	logfs_put_write_page(page);
+	logfs_safe_iput(inode, cookie);
+}
+
+/**
+ * logfs_inode_write - write inode or dentry objects
+ *
+ * @inode:		parent inode (ifile or directory)
+ * @buf:		object to write (inode or dentry)
+ * @count:		object size
+ * @bix:		block index
+ * @flags:		write flags
+ * @shadow_tree:	shadow below this inode
+ *
+ * FIXME: All caller of this put a 200-300 byte variable on the stack,
+ * only to call here and do a memcpy from that stack variable.  A good
+ * example of wasted performance and stack space.
+ */
+int logfs_inode_write(struct inode *inode, const void *buf, size_t count,
+		loff_t bix, long flags, struct shadow_tree *shadow_tree)
+{
+	loff_t pos = bix << inode->i_sb->s_blocksize_bits;
+	int err;
+	struct page *page;
+	void *pagebuf;
+
+	BUG_ON(pos & (LOGFS_BLOCKSIZE-1));
+	BUG_ON(count > LOGFS_BLOCKSIZE);
+	page = logfs_get_write_page(inode, bix, 0);
+	if (!page)
+		return -ENOMEM;
+
+	pagebuf = kmap_atomic(page);
+	memcpy(pagebuf, buf, count);
+	flush_dcache_page(page);
+	kunmap_atomic(pagebuf);
+
+	if (i_size_read(inode) < pos + LOGFS_BLOCKSIZE)
+		i_size_write(inode, pos + LOGFS_BLOCKSIZE);
+
+	err = logfs_write_buf(inode, page, flags);
+	logfs_put_write_page(page);
+	return err;
+}
+
+int logfs_open_segfile(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *inode;
+
+	inode = logfs_read_meta_inode(sb, LOGFS_INO_SEGFILE);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+	super->s_segfile_inode = inode;
+	return 0;
+}
+
+int logfs_init_rw(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	int min_fill = 3 * super->s_no_blocks;
+
+	INIT_LIST_HEAD(&super->s_object_alias);
+	INIT_LIST_HEAD(&super->s_writeback_list);
+	mutex_init(&super->s_write_mutex);
+	super->s_block_pool = mempool_create_kmalloc_pool(min_fill,
+			sizeof(struct logfs_block));
+	super->s_shadow_pool = mempool_create_kmalloc_pool(min_fill,
+			sizeof(struct logfs_shadow));
+	return 0;
+}
+
+void logfs_cleanup_rw(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	logfs_mempool_destroy(super->s_block_pool);
+	logfs_mempool_destroy(super->s_shadow_pool);
+}