[LogFS] add new flash file system

This is a new flash file system. See
Documentation/filesystems/logfs.txt

Signed-off-by: Joern Engel <joern@logfs.org>

1 files changed, 879 insertions, 0 deletions

diff --git a/fs/logfs/journal.c b/fs/logfs/journal.c
new file mode 100644
index 000000000000..7a023dbba9f8
--- /dev/null
+++ b/fs/logfs/journal.c
@@ -0,0 +1,879 @@
+/*
+ * fs/logfs/journal.c	- journal handling code
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
+ */
+#include "logfs.h"
+
+static void logfs_calc_free(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	u64 reserve, no_segs = super->s_no_segs;
+	s64 free;
+	int i;
+
+	/* superblock segments */
+	no_segs -= 2;
+	super->s_no_journal_segs = 0;
+	/* journal */
+	journal_for_each(i)
+		if (super->s_journal_seg[i]) {
+			no_segs--;
+			super->s_no_journal_segs++;
+		}
+
+	/* open segments plus one extra per level for GC */
+	no_segs -= 2 * super->s_total_levels;
+
+	free = no_segs * (super->s_segsize - LOGFS_SEGMENT_RESERVE);
+	free -= super->s_used_bytes;
+	/* just a bit extra */
+	free -= super->s_total_levels * 4096;
+
+	/* Bad blocks are 'paid' for with speed reserve - the filesystem
+	 * simply gets slower as bad blocks accumulate.  Until the bad blocks
+	 * exceed the speed reserve - then the filesystem gets smaller.
+	 */
+	reserve = super->s_bad_segments + super->s_bad_seg_reserve;
+	reserve *= super->s_segsize - LOGFS_SEGMENT_RESERVE;
+	reserve = max(reserve, super->s_speed_reserve);
+	free -= reserve;
+	if (free < 0)
+		free = 0;
+
+	super->s_free_bytes = free;
+}
+
+static void reserve_sb_and_journal(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct btree_head32 *head = &super->s_reserved_segments;
+	int i, err;
+
+	err = btree_insert32(head, seg_no(sb, super->s_sb_ofs[0]), (void *)1,
+			GFP_KERNEL);
+	BUG_ON(err);
+
+	err = btree_insert32(head, seg_no(sb, super->s_sb_ofs[1]), (void *)1,
+			GFP_KERNEL);
+	BUG_ON(err);
+
+	journal_for_each(i) {
+		if (!super->s_journal_seg[i])
+			continue;
+		err = btree_insert32(head, super->s_journal_seg[i], (void *)1,
+				GFP_KERNEL);
+		BUG_ON(err);
+	}
+}
+
+static void read_dynsb(struct super_block *sb,
+		struct logfs_je_dynsb *dynsb)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	super->s_gec		= be64_to_cpu(dynsb->ds_gec);
+	super->s_sweeper	= be64_to_cpu(dynsb->ds_sweeper);
+	super->s_victim_ino	= be64_to_cpu(dynsb->ds_victim_ino);
+	super->s_rename_dir	= be64_to_cpu(dynsb->ds_rename_dir);
+	super->s_rename_pos	= be64_to_cpu(dynsb->ds_rename_pos);
+	super->s_used_bytes	= be64_to_cpu(dynsb->ds_used_bytes);
+	super->s_generation	= be32_to_cpu(dynsb->ds_generation);
+}
+
+static void read_anchor(struct super_block *sb,
+		struct logfs_je_anchor *da)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *inode = super->s_master_inode;
+	struct logfs_inode *li = logfs_inode(inode);
+	int i;
+
+	super->s_last_ino = be64_to_cpu(da->da_last_ino);
+	li->li_flags	= 0;
+	li->li_height	= da->da_height;
+	i_size_write(inode, be64_to_cpu(da->da_size));
+	li->li_used_bytes = be64_to_cpu(da->da_used_bytes);
+
+	for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
+		li->li_data[i] = be64_to_cpu(da->da_data[i]);
+}
+
+static void read_erasecount(struct super_block *sb,
+		struct logfs_je_journal_ec *ec)
+{
+	struct logfs_super *super = logfs_super(sb);
+	int i;
+
+	journal_for_each(i)
+		super->s_journal_ec[i] = be32_to_cpu(ec->ec[i]);
+}
+
+static int read_area(struct super_block *sb, struct logfs_je_area *a)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_area *area = super->s_area[a->gc_level];
+	u64 ofs;
+	u32 writemask = ~(super->s_writesize - 1);
+
+	if (a->gc_level >= LOGFS_NO_AREAS)
+		return -EIO;
+	if (a->vim != VIM_DEFAULT)
+		return -EIO; /* TODO: close area and continue */
+
+	area->a_used_bytes = be32_to_cpu(a->used_bytes);
+	area->a_written_bytes = area->a_used_bytes & writemask;
+	area->a_segno = be32_to_cpu(a->segno);
+	if (area->a_segno)
+		area->a_is_open = 1;
+
+	ofs = dev_ofs(sb, area->a_segno, area->a_written_bytes);
+	if (super->s_writesize > 1)
+		logfs_buf_recover(area, ofs, a + 1, super->s_writesize);
+	else
+		logfs_buf_recover(area, ofs, NULL, 0);
+	return 0;
+}
+
+static void *unpack(void *from, void *to)
+{
+	struct logfs_journal_header *jh = from;
+	void *data = from + sizeof(struct logfs_journal_header);
+	int err;
+	size_t inlen, outlen;
+
+	inlen = be16_to_cpu(jh->h_len);
+	outlen = be16_to_cpu(jh->h_datalen);
+
+	if (jh->h_compr == COMPR_NONE)
+		memcpy(to, data, inlen);
+	else {
+		err = logfs_uncompress(data, to, inlen, outlen);
+		BUG_ON(err);
+	}
+	return to;
+}
+
+static int __read_je_header(struct super_block *sb, u64 ofs,
+		struct logfs_journal_header *jh)
+{
+	struct logfs_super *super = logfs_super(sb);
+	size_t bufsize = max_t(size_t, sb->s_blocksize, super->s_writesize)
+		+ MAX_JOURNAL_HEADER;
+	u16 type, len, datalen;
+	int err;
+
+	/* read header only */
+	err = wbuf_read(sb, ofs, sizeof(*jh), jh);
+	if (err)
+		return err;
+	type = be16_to_cpu(jh->h_type);
+	len = be16_to_cpu(jh->h_len);
+	datalen = be16_to_cpu(jh->h_datalen);
+	if (len > sb->s_blocksize)
+		return -EIO;
+	if ((type < JE_FIRST) || (type > JE_LAST))
+		return -EIO;
+	if (datalen > bufsize)
+		return -EIO;
+	return 0;
+}
+
+static int __read_je_payload(struct super_block *sb, u64 ofs,
+		struct logfs_journal_header *jh)
+{
+	u16 len;
+	int err;
+
+	len = be16_to_cpu(jh->h_len);
+	err = wbuf_read(sb, ofs + sizeof(*jh), len, jh + 1);
+	if (err)
+		return err;
+	if (jh->h_crc != logfs_crc32(jh, len + sizeof(*jh), 4)) {
+		/* Old code was confused.  It forgot about the header length
+		 * and stopped calculating the crc 16 bytes before the end
+		 * of data - ick!
+		 * FIXME: Remove this hack once the old code is fixed.
+		 */
+		if (jh->h_crc == logfs_crc32(jh, len, 4))
+			WARN_ON_ONCE(1);
+		else
+			return -EIO;
+	}
+	return 0;
+}
+
+/*
+ * jh needs to be large enough to hold the complete entry, not just the header
+ */
+static int __read_je(struct super_block *sb, u64 ofs,
+		struct logfs_journal_header *jh)
+{
+	int err;
+
+	err = __read_je_header(sb, ofs, jh);
+	if (err)
+		return err;
+	return __read_je_payload(sb, ofs, jh);
+}
+
+static int read_je(struct super_block *sb, u64 ofs)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_journal_header *jh = super->s_compressed_je;
+	void *scratch = super->s_je;
+	u16 type, datalen;
+	int err;
+
+	err = __read_je(sb, ofs, jh);
+	if (err)
+		return err;
+	type = be16_to_cpu(jh->h_type);
+	datalen = be16_to_cpu(jh->h_datalen);
+
+	switch (type) {
+	case JE_DYNSB:
+		read_dynsb(sb, unpack(jh, scratch));
+		break;
+	case JE_ANCHOR:
+		read_anchor(sb, unpack(jh, scratch));
+		break;
+	case JE_ERASECOUNT:
+		read_erasecount(sb, unpack(jh, scratch));
+		break;
+	case JE_AREA:
+		read_area(sb, unpack(jh, scratch));
+		break;
+	case JE_OBJ_ALIAS:
+		err = logfs_load_object_aliases(sb, unpack(jh, scratch),
+				datalen);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return -EIO;
+	}
+	return err;
+}
+
+static int logfs_read_segment(struct super_block *sb, u32 segno)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_journal_header *jh = super->s_compressed_je;
+	u64 ofs, seg_ofs = dev_ofs(sb, segno, 0);
+	u32 h_ofs, last_ofs = 0;
+	u16 len, datalen, last_len;
+	int i, err;
+
+	/* search for most recent commit */
+	for (h_ofs = 0; h_ofs < super->s_segsize; h_ofs += sizeof(*jh)) {
+		ofs = seg_ofs + h_ofs;
+		err = __read_je_header(sb, ofs, jh);
+		if (err)
+			continue;
+		if (jh->h_type != cpu_to_be16(JE_COMMIT))
+			continue;
+		err = __read_je_payload(sb, ofs, jh);
+		if (err)
+			continue;
+		len = be16_to_cpu(jh->h_len);
+		datalen = be16_to_cpu(jh->h_datalen);
+		if ((datalen > sizeof(super->s_je_array)) ||
+				(datalen % sizeof(__be64)))
+			continue;
+		last_ofs = h_ofs;
+		last_len = datalen;
+		h_ofs += ALIGN(len, sizeof(*jh)) - sizeof(*jh);
+	}
+	/* read commit */
+	if (last_ofs == 0)
+		return -ENOENT;
+	ofs = seg_ofs + last_ofs;
+	log_journal("Read commit from %llx\n", ofs);
+	err = __read_je(sb, ofs, jh);
+	BUG_ON(err); /* We should have caught it in the scan loop already */
+	if (err)
+		return err;
+	/* uncompress */
+	unpack(jh, super->s_je_array);
+	super->s_no_je = last_len / sizeof(__be64);
+	/* iterate over array */
+	for (i = 0; i < super->s_no_je; i++) {
+		err = read_je(sb, be64_to_cpu(super->s_je_array[i]));
+		if (err)
+			return err;
+	}
+	super->s_journal_area->a_segno = segno;
+	return 0;
+}
+
+static u64 read_gec(struct super_block *sb, u32 segno)
+{
+	struct logfs_segment_header sh;
+	__be32 crc;
+	int err;
+
+	if (!segno)
+		return 0;
+	err = wbuf_read(sb, dev_ofs(sb, segno, 0), sizeof(sh), &sh);
+	if (err)
+		return 0;
+	crc = logfs_crc32(&sh, sizeof(sh), 4);
+	if (crc != sh.crc) {
+		WARN_ON(sh.gec != cpu_to_be64(0xffffffffffffffffull));
+		/* Most likely it was just erased */
+		return 0;
+	}
+	return be64_to_cpu(sh.gec);
+}
+
+static int logfs_read_journal(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	u64 gec[LOGFS_JOURNAL_SEGS], max;
+	u32 segno;
+	int i, max_i;
+
+	max = 0;
+	max_i = -1;
+	journal_for_each(i) {
+		segno = super->s_journal_seg[i];
+		gec[i] = read_gec(sb, super->s_journal_seg[i]);
+		if (gec[i] > max) {
+			max = gec[i];
+			max_i = i;
+		}
+	}
+	if (max_i == -1)
+		return -EIO;
+	/* FIXME: Try older segments in case of error */
+	return logfs_read_segment(sb, super->s_journal_seg[max_i]);
+}
+
+/*
+ * First search the current segment (outer loop), then pick the next segment
+ * in the array, skipping any zero entries (inner loop).
+ */
+static void journal_get_free_segment(struct logfs_area *area)
+{
+	struct logfs_super *super = logfs_super(area->a_sb);
+	int i;
+
+	journal_for_each(i) {
+		if (area->a_segno != super->s_journal_seg[i])
+			continue;
+
+		do {
+			i++;
+			if (i == LOGFS_JOURNAL_SEGS)
+				i = 0;
+		} while (!super->s_journal_seg[i]);
+
+		area->a_segno = super->s_journal_seg[i];
+		area->a_erase_count = ++(super->s_journal_ec[i]);
+		log_journal("Journal now at %x (ec %x)\n", area->a_segno,
+				area->a_erase_count);
+		return;
+	}
+	BUG();
+}
+
+static void journal_get_erase_count(struct logfs_area *area)
+{
+	/* erase count is stored globally and incremented in
+	 * journal_get_free_segment() - nothing to do here */
+}
+
+static int journal_erase_segment(struct logfs_area *area)
+{
+	struct super_block *sb = area->a_sb;
+	struct logfs_segment_header sh;
+	u64 ofs;
+	int err;
+
+	err = logfs_erase_segment(sb, area->a_segno);
+	if (err)
+		return err;
+
+	sh.pad = 0;
+	sh.type = SEG_JOURNAL;
+	sh.level = 0;
+	sh.segno = cpu_to_be32(area->a_segno);
+	sh.ec = cpu_to_be32(area->a_erase_count);
+	sh.gec = cpu_to_be64(logfs_super(sb)->s_gec);
+	sh.crc = logfs_crc32(&sh, sizeof(sh), 4);
+
+	/* This causes a bug in segment.c.  Not yet. */
+	//logfs_set_segment_erased(sb, area->a_segno, area->a_erase_count, 0);
+
+	ofs = dev_ofs(sb, area->a_segno, 0);
+	area->a_used_bytes = ALIGN(sizeof(sh), 16);
+	logfs_buf_write(area, ofs, &sh, sizeof(sh));
+	return 0;
+}
+
+static size_t __logfs_write_header(struct logfs_super *super,
+		struct logfs_journal_header *jh, size_t len, size_t datalen,
+		u16 type, u8 compr)
+{
+	jh->h_len	= cpu_to_be16(len);
+	jh->h_type	= cpu_to_be16(type);
+	jh->h_version	= cpu_to_be16(++super->s_last_version);
+	jh->h_datalen	= cpu_to_be16(datalen);
+	jh->h_compr	= compr;
+	jh->h_pad[0]	= 'H';
+	jh->h_pad[1]	= 'A';
+	jh->h_pad[2]	= 'T';
+	jh->h_crc	= logfs_crc32(jh, len + sizeof(*jh), 4);
+	return ALIGN(len, 16) + sizeof(*jh);
+}
+
+static size_t logfs_write_header(struct logfs_super *super,
+		struct logfs_journal_header *jh, size_t datalen, u16 type)
+{
+	size_t len = datalen;
+
+	return __logfs_write_header(super, jh, len, datalen, type, COMPR_NONE);
+}
+
+static inline size_t logfs_journal_erasecount_size(struct logfs_super *super)
+{
+	return LOGFS_JOURNAL_SEGS * sizeof(__be32);
+}
+
+static void *logfs_write_erasecount(struct super_block *sb, void *_ec,
+		u16 *type, size_t *len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_je_journal_ec *ec = _ec;
+	int i;
+
+	journal_for_each(i)
+		ec->ec[i] = cpu_to_be32(super->s_journal_ec[i]);
+	*type = JE_ERASECOUNT;
+	*len = logfs_journal_erasecount_size(super);
+	return ec;
+}
+
+static void account_shadow(void *_shadow, unsigned long _sb, u64 ignore,
+		size_t ignore2)
+{
+	struct logfs_shadow *shadow = _shadow;
+	struct super_block *sb = (void *)_sb;
+	struct logfs_super *super = logfs_super(sb);
+
+	/* consume new space */
+	super->s_free_bytes	  -= shadow->new_len;
+	super->s_used_bytes	  += shadow->new_len;
+	super->s_dirty_used_bytes -= shadow->new_len;
+
+	/* free up old space */
+	super->s_free_bytes	  += shadow->old_len;
+	super->s_used_bytes	  -= shadow->old_len;
+	super->s_dirty_free_bytes -= shadow->old_len;
+
+	logfs_set_segment_used(sb, shadow->old_ofs, -shadow->old_len);
+	logfs_set_segment_used(sb, shadow->new_ofs, shadow->new_len);
+
+	log_journal("account_shadow(%llx, %llx, %x) %llx->%llx %x->%x\n",
+			shadow->ino, shadow->bix, shadow->gc_level,
+			shadow->old_ofs, shadow->new_ofs,
+			shadow->old_len, shadow->new_len);
+	mempool_free(shadow, super->s_shadow_pool);
+}
+
+static void account_shadows(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct inode *inode = super->s_master_inode;
+	struct logfs_inode *li = logfs_inode(inode);
+	struct shadow_tree *tree = &super->s_shadow_tree;
+
+	btree_grim_visitor64(&tree->new, (unsigned long)sb, account_shadow);
+	btree_grim_visitor64(&tree->old, (unsigned long)sb, account_shadow);
+
+	if (li->li_block) {
+		/*
+		 * We never actually use the structure, when attached to the
+		 * master inode.  But it is easier to always free it here than
+		 * to have checks in several places elsewhere when allocating
+		 * it.
+		 */
+		li->li_block->ops->free_block(sb, li->li_block);
+	}
+	BUG_ON((s64)li->li_used_bytes < 0);
+}
+
+static void *__logfs_write_anchor(struct super_block *sb, void *_da,
+		u16 *type, size_t *len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_je_anchor *da = _da;
+	struct inode *inode = super->s_master_inode;
+	struct logfs_inode *li = logfs_inode(inode);
+	int i;
+
+	da->da_height	= li->li_height;
+	da->da_last_ino = cpu_to_be64(super->s_last_ino);
+	da->da_size	= cpu_to_be64(i_size_read(inode));
+	da->da_used_bytes = cpu_to_be64(li->li_used_bytes);
+	for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
+		da->da_data[i] = cpu_to_be64(li->li_data[i]);
+	*type = JE_ANCHOR;
+	*len = sizeof(*da);
+	return da;
+}
+
+static void *logfs_write_dynsb(struct super_block *sb, void *_dynsb,
+		u16 *type, size_t *len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_je_dynsb *dynsb = _dynsb;
+
+	dynsb->ds_gec		= cpu_to_be64(super->s_gec);
+	dynsb->ds_sweeper	= cpu_to_be64(super->s_sweeper);
+	dynsb->ds_victim_ino	= cpu_to_be64(super->s_victim_ino);
+	dynsb->ds_rename_dir	= cpu_to_be64(super->s_rename_dir);
+	dynsb->ds_rename_pos	= cpu_to_be64(super->s_rename_pos);
+	dynsb->ds_used_bytes	= cpu_to_be64(super->s_used_bytes);
+	dynsb->ds_generation	= cpu_to_be32(super->s_generation);
+	*type = JE_DYNSB;
+	*len = sizeof(*dynsb);
+	return dynsb;
+}
+
+static void write_wbuf(struct super_block *sb, struct logfs_area *area,
+		void *wbuf)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct address_space *mapping = super->s_mapping_inode->i_mapping;
+	u64 ofs;
+	pgoff_t index;
+	int page_ofs;
+	struct page *page;
+
+	ofs = dev_ofs(sb, area->a_segno,
+			area->a_used_bytes & ~(super->s_writesize - 1));
+	index = ofs >> PAGE_SHIFT;
+	page_ofs = ofs & (PAGE_SIZE - 1);
+
+	page = find_lock_page(mapping, index);
+	BUG_ON(!page);
+	memcpy(wbuf, page_address(page) + page_ofs, super->s_writesize);
+	unlock_page(page);
+}
+
+static void *logfs_write_area(struct super_block *sb, void *_a,
+		u16 *type, size_t *len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_area *area = super->s_area[super->s_sum_index];
+	struct logfs_je_area *a = _a;
+
+	a->vim = VIM_DEFAULT;
+	a->gc_level = super->s_sum_index;
+	a->used_bytes = cpu_to_be32(area->a_used_bytes);
+	a->segno = cpu_to_be32(area->a_segno);
+	if (super->s_writesize > 1)
+		write_wbuf(sb, area, a + 1);
+
+	*type = JE_AREA;
+	*len = sizeof(*a) + super->s_writesize;
+	return a;
+}
+
+static void *logfs_write_commit(struct super_block *sb, void *h,
+		u16 *type, size_t *len)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	*type = JE_COMMIT;
+	*len = super->s_no_je * sizeof(__be64);
+	return super->s_je_array;
+}
+
+static size_t __logfs_write_je(struct super_block *sb, void *buf, u16 type,
+		size_t len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	void *header = super->s_compressed_je;
+	void *data = header + sizeof(struct logfs_journal_header);
+	ssize_t compr_len, pad_len;
+	u8 compr = COMPR_ZLIB;
+
+	if (len == 0)
+		return logfs_write_header(super, header, 0, type);
+
+	compr_len = logfs_compress(buf, data, len, sb->s_blocksize);
+	if (compr_len < 0 || type == JE_ANCHOR) {
+		BUG_ON(len > sb->s_blocksize);
+		memcpy(data, buf, len);
+		compr_len = len;
+		compr = COMPR_NONE;
+	}
+
+	pad_len = ALIGN(compr_len, 16);
+	memset(data + compr_len, 0, pad_len - compr_len);
+
+	return __logfs_write_header(super, header, compr_len, len, type, compr);
+}
+
+static s64 logfs_get_free_bytes(struct logfs_area *area, size_t *bytes,
+		int must_pad)
+{
+	u32 writesize = logfs_super(area->a_sb)->s_writesize;
+	s32 ofs;
+	int ret;
+
+	ret = logfs_open_area(area, *bytes);
+	if (ret)
+		return -EAGAIN;
+
+	ofs = area->a_used_bytes;
+	area->a_used_bytes += *bytes;
+
+	if (must_pad) {
+		area->a_used_bytes = ALIGN(area->a_used_bytes, writesize);
+		*bytes = area->a_used_bytes - ofs;
+	}
+
+	return dev_ofs(area->a_sb, area->a_segno, ofs);
+}
+
+static int logfs_write_je_buf(struct super_block *sb, void *buf, u16 type,
+		size_t buf_len)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_area *area = super->s_journal_area;
+	struct logfs_journal_header *jh = super->s_compressed_je;
+	size_t len;
+	int must_pad = 0;
+	s64 ofs;
+
+	len = __logfs_write_je(sb, buf, type, buf_len);
+	if (jh->h_type == cpu_to_be16(JE_COMMIT))
+		must_pad = 1;
+
+	ofs = logfs_get_free_bytes(area, &len, must_pad);
+	if (ofs < 0)
+		return ofs;
+	logfs_buf_write(area, ofs, super->s_compressed_je, len);
+	super->s_je_array[super->s_no_je++] = cpu_to_be64(ofs);
+	return 0;
+}
+
+static int logfs_write_je(struct super_block *sb,
+		void* (*write)(struct super_block *sb, void *scratch,
+			u16 *type, size_t *len))
+{
+	void *buf;
+	size_t len;
+	u16 type;
+
+	buf = write(sb, logfs_super(sb)->s_je, &type, &len);
+	return logfs_write_je_buf(sb, buf, type, len);
+}
+
+int write_alias_journal(struct super_block *sb, u64 ino, u64 bix,
+		level_t level, int child_no, __be64 val)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_obj_alias *oa = super->s_je;
+	int err = 0, fill = super->s_je_fill;
+
+	log_aliases("logfs_write_obj_aliases #%x(%llx, %llx, %x, %x) %llx\n",
+			fill, ino, bix, level, child_no, be64_to_cpu(val));
+	oa[fill].ino = cpu_to_be64(ino);
+	oa[fill].bix = cpu_to_be64(bix);
+	oa[fill].val = val;
+	oa[fill].level = (__force u8)level;
+	oa[fill].child_no = cpu_to_be16(child_no);
+	fill++;
+	if (fill >= sb->s_blocksize / sizeof(*oa)) {
+		err = logfs_write_je_buf(sb, oa, JE_OBJ_ALIAS, sb->s_blocksize);
+		fill = 0;
+	}
+
+	super->s_je_fill = fill;
+	return err;
+}
+
+static int logfs_write_obj_aliases(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	int err;
+
+	log_journal("logfs_write_obj_aliases: %d aliases to write\n",
+			super->s_no_object_aliases);
+	super->s_je_fill = 0;
+	err = logfs_write_obj_aliases_pagecache(sb);
+	if (err)
+		return err;
+
+	if (super->s_je_fill)
+		err = logfs_write_je_buf(sb, super->s_je, JE_OBJ_ALIAS,
+				super->s_je_fill
+				* sizeof(struct logfs_obj_alias));
+	return err;
+}
+
+/*
+ * Write all journal entries.  The goto logic ensures that all journal entries
+ * are written whenever a new segment is used.  It is ugly and potentially a
+ * bit wasteful, but robustness is more important.  With this we can *always*
+ * erase all journal segments except the one containing the most recent commit.
+ */
+void logfs_write_anchor(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_area *area = super->s_journal_area;
+	int i, err;
+
+	BUG_ON(logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
+	mutex_lock(&super->s_journal_mutex);
+
+	/* Do this first or suffer corruption */
+	logfs_sync_segments(sb);
+	account_shadows(sb);
+
+again:
+	super->s_no_je = 0;
+	for_each_area(i) {
+		if (!super->s_area[i]->a_is_open)
+			continue;
+		super->s_sum_index = i;
+		err = logfs_write_je(sb, logfs_write_area);
+		if (err)
+			goto again;
+	}
+	err = logfs_write_obj_aliases(sb);
+	if (err)
+		goto again;
+	err = logfs_write_je(sb, logfs_write_erasecount);
+	if (err)
+		goto again;
+	err = logfs_write_je(sb, __logfs_write_anchor);
+	if (err)
+		goto again;
+	err = logfs_write_je(sb, logfs_write_dynsb);
+	if (err)
+		goto again;
+	/*
+	 * Order is imperative.  First we sync all writes, including the
+	 * non-committed journal writes.  Then we write the final commit and
+	 * sync the current journal segment.
+	 * There is a theoretical bug here.  Syncing the journal segment will
+	 * write a number of journal entries and the final commit.  All these
+	 * are written in a single operation.  If the device layer writes the
+	 * data back-to-front, the commit will precede the other journal
+	 * entries, leaving a race window.
+	 * Two fixes are possible.  Preferred is to fix the device layer to
+	 * ensure writes happen front-to-back.  Alternatively we can insert
+	 * another logfs_sync_area() super->s_devops->sync() combo before
+	 * writing the commit.
+	 */
+	/*
+	 * On another subject, super->s_devops->sync is usually not necessary.
+	 * Unless called from sys_sync or friends, a barrier would suffice.
+	 */
+	super->s_devops->sync(sb);
+	err = logfs_write_je(sb, logfs_write_commit);
+	if (err)
+		goto again;
+	log_journal("Write commit to %llx\n",
+			be64_to_cpu(super->s_je_array[super->s_no_je - 1]));
+	logfs_sync_area(area);
+	BUG_ON(area->a_used_bytes != area->a_written_bytes);
+	super->s_devops->sync(sb);
+
+	mutex_unlock(&super->s_journal_mutex);
+	return;
+}
+
+void do_logfs_journal_wl_pass(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	struct logfs_area *area = super->s_journal_area;
+	u32 segno, ec;
+	int i, err;
+
+	log_journal("Journal requires wear-leveling.\n");
+	/* Drop old segments */
+	journal_for_each(i)
+		if (super->s_journal_seg[i]) {
+			logfs_set_segment_unreserved(sb,
+					super->s_journal_seg[i],
+					super->s_journal_ec[i]);
+			super->s_journal_seg[i] = 0;
+			super->s_journal_ec[i] = 0;
+		}
+	/* Get new segments */
+	for (i = 0; i < super->s_no_journal_segs; i++) {
+		segno = get_best_cand(sb, &super->s_reserve_list, &ec);
+		super->s_journal_seg[i] = segno;
+		super->s_journal_ec[i] = ec;
+		logfs_set_segment_reserved(sb, segno);
+	}
+	/* Manually move journal_area */
+	area->a_segno = super->s_journal_seg[0];
+	area->a_is_open = 0;
+	area->a_used_bytes = 0;
+	/* Write journal */
+	logfs_write_anchor(super->s_master_inode);
+	/* Write superblocks */
+	err = logfs_write_sb(sb);
+	BUG_ON(err);
+}
+
+static const struct logfs_area_ops journal_area_ops = {
+	.get_free_segment	= journal_get_free_segment,
+	.get_erase_count	= journal_get_erase_count,
+	.erase_segment		= journal_erase_segment,
+};
+
+int logfs_init_journal(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+	size_t bufsize = max_t(size_t, sb->s_blocksize, super->s_writesize)
+		+ MAX_JOURNAL_HEADER;
+	int ret = -ENOMEM;
+
+	mutex_init(&super->s_journal_mutex);
+	btree_init_mempool32(&super->s_reserved_segments, super->s_btree_pool);
+
+	super->s_je = kzalloc(bufsize, GFP_KERNEL);
+	if (!super->s_je)
+		return ret;
+
+	super->s_compressed_je = kzalloc(bufsize, GFP_KERNEL);
+	if (!super->s_compressed_je)
+		return ret;
+
+	super->s_master_inode = logfs_new_meta_inode(sb, LOGFS_INO_MASTER);
+	if (IS_ERR(super->s_master_inode))
+		return PTR_ERR(super->s_master_inode);
+
+	ret = logfs_read_journal(sb);
+	if (ret)
+		return -EIO;
+
+	reserve_sb_and_journal(sb);
+	logfs_calc_free(sb);
+
+	super->s_journal_area->a_ops = &journal_area_ops;
+	return 0;
+}
+
+void logfs_cleanup_journal(struct super_block *sb)
+{
+	struct logfs_super *super = logfs_super(sb);
+
+	btree_grim_visitor32(&super->s_reserved_segments, 0, NULL);
+	destroy_meta_inode(super->s_master_inode);
+	super->s_master_inode = NULL;
+
+	kfree(super->s_compressed_je);
+	kfree(super->s_je);
+}