[PATCH] jbd2: initial copy of files from jbd

This is a simple copy of the files in fs/jbd to fs/jbd2 and
/usr/incude/linux/[ext4_]jbd.h to /usr/include/[ext4_]jbd2.h

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1098 insertions, 0 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
new file mode 100644
index 000000000000..fe89444b1c6f
--- /dev/null
+++ b/include/linux/jbd2.h
@@ -0,0 +1,1098 @@
+/*
+ * linux/include/linux/jbd.h
+ *
+ * Written by Stephen C. Tweedie <sct@redhat.com>
+ *
+ * Copyright 1998-2000 Red Hat, Inc --- All Rights Reserved
+ *
+ * This file is part of the Linux kernel and is made available under
+ * the terms of the GNU General Public License, version 2, or at your
+ * option, any later version, incorporated herein by reference.
+ *
+ * Definitions for transaction data structures for the buffer cache
+ * filesystem journaling support.
+ */
+
+#ifndef _LINUX_JBD_H
+#define _LINUX_JBD_H
+
+/* Allow this file to be included directly into e2fsprogs */
+#ifndef __KERNEL__
+#include "jfs_compat.h"
+#define JFS_DEBUG
+#define jfs_debug jbd_debug
+#else
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/journal-head.h>
+#include <linux/stddef.h>
+#include <linux/bit_spinlock.h>
+#include <linux/mutex.h>
+#include <linux/timer.h>
+
+#include <asm/semaphore.h>
+#endif
+
+#define journal_oom_retry 1
+
+/*
+ * Define JBD_PARANIOD_IOFAIL to cause a kernel BUG() if ext3 finds
+ * certain classes of error which can occur due to failed IOs.  Under
+ * normal use we want ext3 to continue after such errors, because
+ * hardware _can_ fail, but for debugging purposes when running tests on
+ * known-good hardware we may want to trap these errors.
+ */
+#undef JBD_PARANOID_IOFAIL
+
+/*
+ * The default maximum commit age, in seconds.
+ */
+#define JBD_DEFAULT_MAX_COMMIT_AGE 5
+
+#ifdef CONFIG_JBD_DEBUG
+/*
+ * Define JBD_EXPENSIVE_CHECKING to enable more expensive internal
+ * consistency checks.  By default we don't do this unless
+ * CONFIG_JBD_DEBUG is on.
+ */
+#define JBD_EXPENSIVE_CHECKING
+extern int journal_enable_debug;
+
+#define jbd_debug(n, f, a...)						\
+	do {								\
+		if ((n) <= journal_enable_debug) {			\
+			printk (KERN_DEBUG "(%s, %d): %s: ",		\
+				__FILE__, __LINE__, __FUNCTION__);	\
+			printk (f, ## a);				\
+		}							\
+	} while (0)
+#else
+#define jbd_debug(f, a...)	/**/
+#endif
+
+extern void * __jbd_kmalloc (const char *where, size_t size, gfp_t flags, int retry);
+extern void * jbd_slab_alloc(size_t size, gfp_t flags);
+extern void jbd_slab_free(void *ptr, size_t size);
+
+#define jbd_kmalloc(size, flags) \
+	__jbd_kmalloc(__FUNCTION__, (size), (flags), journal_oom_retry)
+#define jbd_rep_kmalloc(size, flags) \
+	__jbd_kmalloc(__FUNCTION__, (size), (flags), 1)
+
+#define JFS_MIN_JOURNAL_BLOCKS 1024
+
+#ifdef __KERNEL__
+
+/**
+ * typedef handle_t - The handle_t type represents a single atomic update being performed by some process.
+ *
+ * All filesystem modifications made by the process go
+ * through this handle.  Recursive operations (such as quota operations)
+ * are gathered into a single update.
+ *
+ * The buffer credits field is used to account for journaled buffers
+ * being modified by the running process.  To ensure that there is
+ * enough log space for all outstanding operations, we need to limit the
+ * number of outstanding buffers possible at any time.  When the
+ * operation completes, any buffer credits not used are credited back to
+ * the transaction, so that at all times we know how many buffers the
+ * outstanding updates on a transaction might possibly touch.
+ *
+ * This is an opaque datatype.
+ **/
+typedef struct handle_s		handle_t;	/* Atomic operation type */
+
+
+/**
+ * typedef journal_t - The journal_t maintains all of the journaling state information for a single filesystem.
+ *
+ * journal_t is linked to from the fs superblock structure.
+ *
+ * We use the journal_t to keep track of all outstanding transaction
+ * activity on the filesystem, and to manage the state of the log
+ * writing process.
+ *
+ * This is an opaque datatype.
+ **/
+typedef struct journal_s	journal_t;	/* Journal control structure */
+#endif
+
+/*
+ * Internal structures used by the logging mechanism:
+ */
+
+#define JFS_MAGIC_NUMBER 0xc03b3998U /* The first 4 bytes of /dev/random! */
+
+/*
+ * On-disk structures
+ */
+
+/*
+ * Descriptor block types:
+ */
+
+#define JFS_DESCRIPTOR_BLOCK	1
+#define JFS_COMMIT_BLOCK	2
+#define JFS_SUPERBLOCK_V1	3
+#define JFS_SUPERBLOCK_V2	4
+#define JFS_REVOKE_BLOCK	5
+
+/*
+ * Standard header for all descriptor blocks:
+ */
+typedef struct journal_header_s
+{
+	__be32		h_magic;
+	__be32		h_blocktype;
+	__be32		h_sequence;
+} journal_header_t;
+
+
+/*
+ * The block tag: used to describe a single buffer in the journal
+ */
+typedef struct journal_block_tag_s
+{
+	__be32		t_blocknr;	/* The on-disk block number */
+	__be32		t_flags;	/* See below */
+} journal_block_tag_t;
+
+/*
+ * The revoke descriptor: used on disk to describe a series of blocks to
+ * be revoked from the log
+ */
+typedef struct journal_revoke_header_s
+{
+	journal_header_t r_header;
+	__be32		 r_count;	/* Count of bytes used in the block */
+} journal_revoke_header_t;
+
+
+/* Definitions for the journal tag flags word: */
+#define JFS_FLAG_ESCAPE		1	/* on-disk block is escaped */
+#define JFS_FLAG_SAME_UUID	2	/* block has same uuid as previous */
+#define JFS_FLAG_DELETED	4	/* block deleted by this transaction */
+#define JFS_FLAG_LAST_TAG	8	/* last tag in this descriptor block */
+
+
+/*
+ * The journal superblock.  All fields are in big-endian byte order.
+ */
+typedef struct journal_superblock_s
+{
+/* 0x0000 */
+	journal_header_t s_header;
+
+/* 0x000C */
+	/* Static information describing the journal */
+	__be32	s_blocksize;		/* journal device blocksize */
+	__be32	s_maxlen;		/* total blocks in journal file */
+	__be32	s_first;		/* first block of log information */
+
+/* 0x0018 */
+	/* Dynamic information describing the current state of the log */
+	__be32	s_sequence;		/* first commit ID expected in log */
+	__be32	s_start;		/* blocknr of start of log */
+
+/* 0x0020 */
+	/* Error value, as set by journal_abort(). */
+	__be32	s_errno;
+
+/* 0x0024 */
+	/* Remaining fields are only valid in a version-2 superblock */
+	__be32	s_feature_compat;	/* compatible feature set */
+	__be32	s_feature_incompat;	/* incompatible feature set */
+	__be32	s_feature_ro_compat;	/* readonly-compatible feature set */
+/* 0x0030 */
+	__u8	s_uuid[16];		/* 128-bit uuid for journal */
+
+/* 0x0040 */
+	__be32	s_nr_users;		/* Nr of filesystems sharing log */
+
+	__be32	s_dynsuper;		/* Blocknr of dynamic superblock copy*/
+
+/* 0x0048 */
+	__be32	s_max_transaction;	/* Limit of journal blocks per trans.*/
+	__be32	s_max_trans_data;	/* Limit of data blocks per trans. */
+
+/* 0x0050 */
+	__u32	s_padding[44];
+
+/* 0x0100 */
+	__u8	s_users[16*48];		/* ids of all fs'es sharing the log */
+/* 0x0400 */
+} journal_superblock_t;
+
+#define JFS_HAS_COMPAT_FEATURE(j,mask)					\
+	((j)->j_format_version >= 2 &&					\
+	 ((j)->j_superblock->s_feature_compat & cpu_to_be32((mask))))
+#define JFS_HAS_RO_COMPAT_FEATURE(j,mask)				\
+	((j)->j_format_version >= 2 &&					\
+	 ((j)->j_superblock->s_feature_ro_compat & cpu_to_be32((mask))))
+#define JFS_HAS_INCOMPAT_FEATURE(j,mask)				\
+	((j)->j_format_version >= 2 &&					\
+	 ((j)->j_superblock->s_feature_incompat & cpu_to_be32((mask))))
+
+#define JFS_FEATURE_INCOMPAT_REVOKE	0x00000001
+
+/* Features known to this kernel version: */
+#define JFS_KNOWN_COMPAT_FEATURES	0
+#define JFS_KNOWN_ROCOMPAT_FEATURES	0
+#define JFS_KNOWN_INCOMPAT_FEATURES	JFS_FEATURE_INCOMPAT_REVOKE
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+#include <linux/sched.h>
+
+#define JBD_ASSERTIONS
+#ifdef JBD_ASSERTIONS
+#define J_ASSERT(assert)						\
+do {									\
+	if (!(assert)) {						\
+		printk (KERN_EMERG					\
+			"Assertion failure in %s() at %s:%d: \"%s\"\n",	\
+			__FUNCTION__, __FILE__, __LINE__, # assert);	\
+		BUG();							\
+	}								\
+} while (0)
+
+#if defined(CONFIG_BUFFER_DEBUG)
+void buffer_assertion_failure(struct buffer_head *bh);
+#define J_ASSERT_BH(bh, expr)						\
+	do {								\
+		if (!(expr))						\
+			buffer_assertion_failure(bh);			\
+		J_ASSERT(expr);						\
+	} while (0)
+#define J_ASSERT_JH(jh, expr)	J_ASSERT_BH(jh2bh(jh), expr)
+#else
+#define J_ASSERT_BH(bh, expr)	J_ASSERT(expr)
+#define J_ASSERT_JH(jh, expr)	J_ASSERT(expr)
+#endif
+
+#else
+#define J_ASSERT(assert)	do { } while (0)
+#endif		/* JBD_ASSERTIONS */
+
+#if defined(JBD_PARANOID_IOFAIL)
+#define J_EXPECT(expr, why...)		J_ASSERT(expr)
+#define J_EXPECT_BH(bh, expr, why...)	J_ASSERT_BH(bh, expr)
+#define J_EXPECT_JH(jh, expr, why...)	J_ASSERT_JH(jh, expr)
+#else
+#define __journal_expect(expr, why...)					     \
+	({								     \
+		int val = (expr);					     \
+		if (!val) {						     \
+			printk(KERN_ERR					     \
+				"EXT3-fs unexpected failure: %s;\n",# expr); \
+			printk(KERN_ERR why "\n");			     \
+		}							     \
+		val;							     \
+	})
+#define J_EXPECT(expr, why...)		__journal_expect(expr, ## why)
+#define J_EXPECT_BH(bh, expr, why...)	__journal_expect(expr, ## why)
+#define J_EXPECT_JH(jh, expr, why...)	__journal_expect(expr, ## why)
+#endif
+
+enum jbd_state_bits {
+	BH_JBD			/* Has an attached ext3 journal_head */
+	  = BH_PrivateStart,
+	BH_JWrite,		/* Being written to log (@@@ DEBUGGING) */
+	BH_Freed,		/* Has been freed (truncated) */
+	BH_Revoked,		/* Has been revoked from the log */
+	BH_RevokeValid,		/* Revoked flag is valid */
+	BH_JBDDirty,		/* Is dirty but journaled */
+	BH_State,		/* Pins most journal_head state */
+	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
+	BH_Unshadow,		/* Dummy bit, for BJ_Shadow wakeup filtering */
+};
+
+BUFFER_FNS(JBD, jbd)
+BUFFER_FNS(JWrite, jwrite)
+BUFFER_FNS(JBDDirty, jbddirty)
+TAS_BUFFER_FNS(JBDDirty, jbddirty)
+BUFFER_FNS(Revoked, revoked)
+TAS_BUFFER_FNS(Revoked, revoked)
+BUFFER_FNS(RevokeValid, revokevalid)
+TAS_BUFFER_FNS(RevokeValid, revokevalid)
+BUFFER_FNS(Freed, freed)
+
+static inline struct buffer_head *jh2bh(struct journal_head *jh)
+{
+	return jh->b_bh;
+}
+
+static inline struct journal_head *bh2jh(struct buffer_head *bh)
+{
+	return bh->b_private;
+}
+
+static inline void jbd_lock_bh_state(struct buffer_head *bh)
+{
+	bit_spin_lock(BH_State, &bh->b_state);
+}
+
+static inline int jbd_trylock_bh_state(struct buffer_head *bh)
+{
+	return bit_spin_trylock(BH_State, &bh->b_state);
+}
+
+static inline int jbd_is_locked_bh_state(struct buffer_head *bh)
+{
+	return bit_spin_is_locked(BH_State, &bh->b_state);
+}
+
+static inline void jbd_unlock_bh_state(struct buffer_head *bh)
+{
+	bit_spin_unlock(BH_State, &bh->b_state);
+}
+
+static inline void jbd_lock_bh_journal_head(struct buffer_head *bh)
+{
+	bit_spin_lock(BH_JournalHead, &bh->b_state);
+}
+
+static inline void jbd_unlock_bh_journal_head(struct buffer_head *bh)
+{
+	bit_spin_unlock(BH_JournalHead, &bh->b_state);
+}
+
+struct jbd_revoke_table_s;
+
+/**
+ * struct handle_s - The handle_s type is the concrete type associated with
+ *     handle_t.
+ * @h_transaction: Which compound transaction is this update a part of?
+ * @h_buffer_credits: Number of remaining buffers we are allowed to dirty.
+ * @h_ref: Reference count on this handle
+ * @h_err: Field for caller's use to track errors through large fs operations
+ * @h_sync: flag for sync-on-close
+ * @h_jdata: flag to force data journaling
+ * @h_aborted: flag indicating fatal error on handle
+ **/
+
+/* Docbook can't yet cope with the bit fields, but will leave the documentation
+ * in so it can be fixed later.
+ */
+
+struct handle_s
+{
+	/* Which compound transaction is this update a part of? */
+	transaction_t		*h_transaction;
+
+	/* Number of remaining buffers we are allowed to dirty: */
+	int			h_buffer_credits;
+
+	/* Reference count on this handle */
+	int			h_ref;
+
+	/* Field for caller's use to track errors through large fs */
+	/* operations */
+	int			h_err;
+
+	/* Flags [no locking] */
+	unsigned int	h_sync:		1;	/* sync-on-close */
+	unsigned int	h_jdata:	1;	/* force data journaling */
+	unsigned int	h_aborted:	1;	/* fatal error on handle */
+};
+
+
+/* The transaction_t type is the guts of the journaling mechanism.  It
+ * tracks a compound transaction through its various states:
+ *
+ * RUNNING:	accepting new updates
+ * LOCKED:	Updates still running but we don't accept new ones
+ * RUNDOWN:	Updates are tidying up but have finished requesting
+ *		new buffers to modify (state not used for now)
+ * FLUSH:       All updates complete, but we are still writing to disk
+ * COMMIT:      All data on disk, writing commit record
+ * FINISHED:	We still have to keep the transaction for checkpointing.
+ *
+ * The transaction keeps track of all of the buffers modified by a
+ * running transaction, and all of the buffers committed but not yet
+ * flushed to home for finished transactions.
+ */
+
+/*
+ * Lock ranking:
+ *
+ *    j_list_lock
+ *      ->jbd_lock_bh_journal_head()	(This is "innermost")
+ *
+ *    j_state_lock
+ *    ->jbd_lock_bh_state()
+ *
+ *    jbd_lock_bh_state()
+ *    ->j_list_lock
+ *
+ *    j_state_lock
+ *    ->t_handle_lock
+ *
+ *    j_state_lock
+ *    ->j_list_lock			(journal_unmap_buffer)
+ *
+ */
+
+struct transaction_s
+{
+	/* Pointer to the journal for this transaction. [no locking] */
+	journal_t		*t_journal;
+
+	/* Sequence number for this transaction [no locking] */
+	tid_t			t_tid;
+
+	/*
+	 * Transaction's current state
+	 * [no locking - only kjournald alters this]
+	 * FIXME: needs barriers
+	 * KLUDGE: [use j_state_lock]
+	 */
+	enum {
+		T_RUNNING,
+		T_LOCKED,
+		T_RUNDOWN,
+		T_FLUSH,
+		T_COMMIT,
+		T_FINISHED
+	}			t_state;
+
+	/*
+	 * Where in the log does this transaction's commit start? [no locking]
+	 */
+	unsigned long		t_log_start;
+
+	/* Number of buffers on the t_buffers list [j_list_lock] */
+	int			t_nr_buffers;
+
+	/*
+	 * Doubly-linked circular list of all buffers reserved but not yet
+	 * modified by this transaction [j_list_lock]
+	 */
+	struct journal_head	*t_reserved_list;
+
+	/*
+	 * Doubly-linked circular list of all buffers under writeout during
+	 * commit [j_list_lock]
+	 */
+	struct journal_head	*t_locked_list;
+
+	/*
+	 * Doubly-linked circular list of all metadata buffers owned by this
+	 * transaction [j_list_lock]
+	 */
+	struct journal_head	*t_buffers;
+
+	/*
+	 * Doubly-linked circular list of all data buffers still to be
+	 * flushed before this transaction can be committed [j_list_lock]
+	 */
+	struct journal_head	*t_sync_datalist;
+
+	/*
+	 * Doubly-linked circular list of all forget buffers (superseded
+	 * buffers which we can un-checkpoint once this transaction commits)
+	 * [j_list_lock]
+	 */
+	struct journal_head	*t_forget;
+
+	/*
+	 * Doubly-linked circular list of all buffers still to be flushed before
+	 * this transaction can be checkpointed. [j_list_lock]
+	 */
+	struct journal_head	*t_checkpoint_list;
+
+	/*
+	 * Doubly-linked circular list of all buffers submitted for IO while
+	 * checkpointing. [j_list_lock]
+	 */
+	struct journal_head	*t_checkpoint_io_list;
+
+	/*
+	 * Doubly-linked circular list of temporary buffers currently undergoing
+	 * IO in the log [j_list_lock]
+	 */
+	struct journal_head	*t_iobuf_list;
+
+	/*
+	 * Doubly-linked circular list of metadata buffers being shadowed by log
+	 * IO.  The IO buffers on the iobuf list and the shadow buffers on this
+	 * list match each other one for one at all times. [j_list_lock]
+	 */
+	struct journal_head	*t_shadow_list;
+
+	/*
+	 * Doubly-linked circular list of control buffers being written to the
+	 * log. [j_list_lock]
+	 */
+	struct journal_head	*t_log_list;
+
+	/*
+	 * Protects info related to handles
+	 */
+	spinlock_t		t_handle_lock;
+
+	/*
+	 * Number of outstanding updates running on this transaction
+	 * [t_handle_lock]
+	 */
+	int			t_updates;
+
+	/*
+	 * Number of buffers reserved for use by all handles in this transaction
+	 * handle but not yet modified. [t_handle_lock]
+	 */
+	int			t_outstanding_credits;
+
+	/*
+	 * Forward and backward links for the circular list of all transactions
+	 * awaiting checkpoint. [j_list_lock]
+	 */
+	transaction_t		*t_cpnext, *t_cpprev;
+
+	/*
+	 * When will the transaction expire (become due for commit), in jiffies?
+	 * [no locking]
+	 */
+	unsigned long		t_expires;
+
+	/*
+	 * How many handles used this transaction? [t_handle_lock]
+	 */
+	int t_handle_count;
+
+};
+
+/**
+ * struct journal_s - The journal_s type is the concrete type associated with
+ *     journal_t.
+ * @j_flags:  General journaling state flags
+ * @j_errno:  Is there an outstanding uncleared error on the journal (from a
+ *     prior abort)?
+ * @j_sb_buffer: First part of superblock buffer
+ * @j_superblock: Second part of superblock buffer
+ * @j_format_version: Version of the superblock format
+ * @j_state_lock: Protect the various scalars in the journal
+ * @j_barrier_count:  Number of processes waiting to create a barrier lock
+ * @j_barrier: The barrier lock itself
+ * @j_running_transaction: The current running transaction..
+ * @j_committing_transaction: the transaction we are pushing to disk
+ * @j_checkpoint_transactions: a linked circular list of all transactions
+ *  waiting for checkpointing
+ * @j_wait_transaction_locked: Wait queue for waiting for a locked transaction
+ *  to start committing, or for a barrier lock to be released
+ * @j_wait_logspace: Wait queue for waiting for checkpointing to complete
+ * @j_wait_done_commit: Wait queue for waiting for commit to complete
+ * @j_wait_checkpoint:  Wait queue to trigger checkpointing
+ * @j_wait_commit: Wait queue to trigger commit
+ * @j_wait_updates: Wait queue to wait for updates to complete
+ * @j_checkpoint_mutex: Mutex for locking against concurrent checkpoints
+ * @j_head: Journal head - identifies the first unused block in the journal
+ * @j_tail: Journal tail - identifies the oldest still-used block in the
+ *  journal.
+ * @j_free: Journal free - how many free blocks are there in the journal?
+ * @j_first: The block number of the first usable block
+ * @j_last: The block number one beyond the last usable block
+ * @j_dev: Device where we store the journal
+ * @j_blocksize: blocksize for the location where we store the journal.
+ * @j_blk_offset: starting block offset for into the device where we store the
+ *     journal
+ * @j_fs_dev: Device which holds the client fs.  For internal journal this will
+ *     be equal to j_dev
+ * @j_maxlen: Total maximum capacity of the journal region on disk.
+ * @j_list_lock: Protects the buffer lists and internal buffer state.
+ * @j_inode: Optional inode where we store the journal.  If present, all journal
+ *     block numbers are mapped into this inode via bmap().
+ * @j_tail_sequence:  Sequence number of the oldest transaction in the log
+ * @j_transaction_sequence: Sequence number of the next transaction to grant
+ * @j_commit_sequence: Sequence number of the most recently committed
+ *  transaction
+ * @j_commit_request: Sequence number of the most recent transaction wanting
+ *     commit
+ * @j_uuid: Uuid of client object.
+ * @j_task: Pointer to the current commit thread for this journal
+ * @j_max_transaction_buffers:  Maximum number of metadata buffers to allow in a
+ *     single compound commit transaction
+ * @j_commit_interval: What is the maximum transaction lifetime before we begin
+ *  a commit?
+ * @j_commit_timer:  The timer used to wakeup the commit thread
+ * @j_revoke_lock: Protect the revoke table
+ * @j_revoke: The revoke table - maintains the list of revoked blocks in the
+ *     current transaction.
+ * @j_revoke_table: alternate revoke tables for j_revoke
+ * @j_wbuf: array of buffer_heads for journal_commit_transaction
+ * @j_wbufsize: maximum number of buffer_heads allowed in j_wbuf, the
+ *	number that will fit in j_blocksize
+ * @j_last_sync_writer: most recent pid which did a synchronous write
+ * @j_private: An opaque pointer to fs-private information.
+ */
+
+struct journal_s
+{
+	/* General journaling state flags [j_state_lock] */
+	unsigned long		j_flags;
+
+	/*
+	 * Is there an outstanding uncleared error on the journal (from a prior
+	 * abort)? [j_state_lock]
+	 */
+	int			j_errno;
+
+	/* The superblock buffer */
+	struct buffer_head	*j_sb_buffer;
+	journal_superblock_t	*j_superblock;
+
+	/* Version of the superblock format */
+	int			j_format_version;
+
+	/*
+	 * Protect the various scalars in the journal
+	 */
+	spinlock_t		j_state_lock;
+
+	/*
+	 * Number of processes waiting to create a barrier lock [j_state_lock]
+	 */
+	int			j_barrier_count;
+
+	/* The barrier lock itself */
+	struct mutex		j_barrier;
+
+	/*
+	 * Transactions: The current running transaction...
+	 * [j_state_lock] [caller holding open handle]
+	 */
+	transaction_t		*j_running_transaction;
+
+	/*
+	 * the transaction we are pushing to disk
+	 * [j_state_lock] [caller holding open handle]
+	 */
+	transaction_t		*j_committing_transaction;
+
+	/*
+	 * ... and a linked circular list of all transactions waiting for
+	 * checkpointing. [j_list_lock]
+	 */
+	transaction_t		*j_checkpoint_transactions;
+
+	/*
+	 * Wait queue for waiting for a locked transaction to start committing,
+	 * or for a barrier lock to be released
+	 */
+	wait_queue_head_t	j_wait_transaction_locked;
+
+	/* Wait queue for waiting for checkpointing to complete */
+	wait_queue_head_t	j_wait_logspace;
+
+	/* Wait queue for waiting for commit to complete */
+	wait_queue_head_t	j_wait_done_commit;
+
+	/* Wait queue to trigger checkpointing */
+	wait_queue_head_t	j_wait_checkpoint;
+
+	/* Wait queue to trigger commit */
+	wait_queue_head_t	j_wait_commit;
+
+	/* Wait queue to wait for updates to complete */
+	wait_queue_head_t	j_wait_updates;
+
+	/* Semaphore for locking against concurrent checkpoints */
+	struct mutex		j_checkpoint_mutex;
+
+	/*
+	 * Journal head: identifies the first unused block in the journal.
+	 * [j_state_lock]
+	 */
+	unsigned long		j_head;
+
+	/*
+	 * Journal tail: identifies the oldest still-used block in the journal.
+	 * [j_state_lock]
+	 */
+	unsigned long		j_tail;
+
+	/*
+	 * Journal free: how many free blocks are there in the journal?
+	 * [j_state_lock]
+	 */
+	unsigned long		j_free;
+
+	/*
+	 * Journal start and end: the block numbers of the first usable block
+	 * and one beyond the last usable block in the journal. [j_state_lock]
+	 */
+	unsigned long		j_first;
+	unsigned long		j_last;
+
+	/*
+	 * Device, blocksize and starting block offset for the location where we
+	 * store the journal.
+	 */
+	struct block_device	*j_dev;
+	int			j_blocksize;
+	unsigned long		j_blk_offset;
+
+	/*
+	 * Device which holds the client fs.  For internal journal this will be
+	 * equal to j_dev.
+	 */
+	struct block_device	*j_fs_dev;
+
+	/* Total maximum capacity of the journal region on disk. */
+	unsigned int		j_maxlen;
+
+	/*
+	 * Protects the buffer lists and internal buffer state.
+	 */
+	spinlock_t		j_list_lock;
+
+	/* Optional inode where we store the journal.  If present, all */
+	/* journal block numbers are mapped into this inode via */
+	/* bmap(). */
+	struct inode		*j_inode;
+
+	/*
+	 * Sequence number of the oldest transaction in the log [j_state_lock]
+	 */
+	tid_t			j_tail_sequence;
+
+	/*
+	 * Sequence number of the next transaction to grant [j_state_lock]
+	 */
+	tid_t			j_transaction_sequence;
+
+	/*
+	 * Sequence number of the most recently committed transaction
+	 * [j_state_lock].
+	 */
+	tid_t			j_commit_sequence;
+
+	/*
+	 * Sequence number of the most recent transaction wanting commit
+	 * [j_state_lock]
+	 */
+	tid_t			j_commit_request;
+
+	/*
+	 * Journal uuid: identifies the object (filesystem, LVM volume etc)
+	 * backed by this journal.  This will eventually be replaced by an array
+	 * of uuids, allowing us to index multiple devices within a single
+	 * journal and to perform atomic updates across them.
+	 */
+	__u8			j_uuid[16];
+
+	/* Pointer to the current commit thread for this journal */
+	struct task_struct	*j_task;
+
+	/*
+	 * Maximum number of metadata buffers to allow in a single compound
+	 * commit transaction
+	 */
+	int			j_max_transaction_buffers;
+
+	/*
+	 * What is the maximum transaction lifetime before we begin a commit?
+	 */
+	unsigned long		j_commit_interval;
+
+	/* The timer used to wakeup the commit thread: */
+	struct timer_list	j_commit_timer;
+
+	/*
+	 * The revoke table: maintains the list of revoked blocks in the
+	 * current transaction.  [j_revoke_lock]
+	 */
+	spinlock_t		j_revoke_lock;
+	struct jbd_revoke_table_s *j_revoke;
+	struct jbd_revoke_table_s *j_revoke_table[2];
+
+	/*
+	 * array of bhs for journal_commit_transaction
+	 */
+	struct buffer_head	**j_wbuf;
+	int			j_wbufsize;
+
+	pid_t			j_last_sync_writer;
+
+	/*
+	 * An opaque pointer to fs-private information.  ext3 puts its
+	 * superblock pointer here
+	 */
+	void *j_private;
+};
+
+/*
+ * Journal flag definitions
+ */
+#define JFS_UNMOUNT	0x001	/* Journal thread is being destroyed */
+#define JFS_ABORT	0x002	/* Journaling has been aborted for errors. */
+#define JFS_ACK_ERR	0x004	/* The errno in the sb has been acked */
+#define JFS_FLUSHED	0x008	/* The journal superblock has been flushed */
+#define JFS_LOADED	0x010	/* The journal superblock has been loaded */
+#define JFS_BARRIER	0x020	/* Use IDE barriers */
+
+/*
+ * Function declarations for the journaling transaction and buffer
+ * management
+ */
+
+/* Filing buffers */
+extern void __journal_temp_unlink_buffer(struct journal_head *jh);
+extern void journal_unfile_buffer(journal_t *, struct journal_head *);
+extern void __journal_unfile_buffer(struct journal_head *);
+extern void __journal_refile_buffer(struct journal_head *);
+extern void journal_refile_buffer(journal_t *, struct journal_head *);
+extern void __journal_file_buffer(struct journal_head *, transaction_t *, int);
+extern void __journal_free_buffer(struct journal_head *bh);
+extern void journal_file_buffer(struct journal_head *, transaction_t *, int);
+extern void __journal_clean_data_list(transaction_t *transaction);
+
+/* Log buffer allocation */
+extern struct journal_head * journal_get_descriptor_buffer(journal_t *);
+int journal_next_log_block(journal_t *, unsigned long *);
+
+/* Commit management */
+extern void journal_commit_transaction(journal_t *);
+
+/* Checkpoint list management */
+int __journal_clean_checkpoint_list(journal_t *journal);
+int __journal_remove_checkpoint(struct journal_head *);
+void __journal_insert_checkpoint(struct journal_head *, transaction_t *);
+
+/* Buffer IO */
+extern int
+journal_write_metadata_buffer(transaction_t	  *transaction,
+			      struct journal_head  *jh_in,
+			      struct journal_head **jh_out,
+			      unsigned long	   blocknr);
+
+/* Transaction locking */
+extern void		__wait_on_journal (journal_t *);
+
+/*
+ * Journal locking.
+ *
+ * We need to lock the journal during transaction state changes so that nobody
+ * ever tries to take a handle on the running transaction while we are in the
+ * middle of moving it to the commit phase.  j_state_lock does this.
+ *
+ * Note that the locking is completely interrupt unsafe.  We never touch
+ * journal structures from interrupts.
+ */
+
+static inline handle_t *journal_current_handle(void)
+{
+	return current->journal_info;
+}
+
+/* The journaling code user interface:
+ *
+ * Create and destroy handles
+ * Register buffer modifications against the current transaction.
+ */
+
+extern handle_t *journal_start(journal_t *, int nblocks);
+extern int	 journal_restart (handle_t *, int nblocks);
+extern int	 journal_extend (handle_t *, int nblocks);
+extern int	 journal_get_write_access(handle_t *, struct buffer_head *);
+extern int	 journal_get_create_access (handle_t *, struct buffer_head *);
+extern int	 journal_get_undo_access(handle_t *, struct buffer_head *);
+extern int	 journal_dirty_data (handle_t *, struct buffer_head *);
+extern int	 journal_dirty_metadata (handle_t *, struct buffer_head *);
+extern void	 journal_release_buffer (handle_t *, struct buffer_head *);
+extern int	 journal_forget (handle_t *, struct buffer_head *);
+extern void	 journal_sync_buffer (struct buffer_head *);
+extern void	 journal_invalidatepage(journal_t *,
+				struct page *, unsigned long);
+extern int	 journal_try_to_free_buffers(journal_t *, struct page *, gfp_t);
+extern int	 journal_stop(handle_t *);
+extern int	 journal_flush (journal_t *);
+extern void	 journal_lock_updates (journal_t *);
+extern void	 journal_unlock_updates (journal_t *);
+
+extern journal_t * journal_init_dev(struct block_device *bdev,
+				struct block_device *fs_dev,
+				int start, int len, int bsize);
+extern journal_t * journal_init_inode (struct inode *);
+extern int	   journal_update_format (journal_t *);
+extern int	   journal_check_used_features
+		   (journal_t *, unsigned long, unsigned long, unsigned long);
+extern int	   journal_check_available_features
+		   (journal_t *, unsigned long, unsigned long, unsigned long);
+extern int	   journal_set_features
+		   (journal_t *, unsigned long, unsigned long, unsigned long);
+extern int	   journal_create     (journal_t *);
+extern int	   journal_load       (journal_t *journal);
+extern void	   journal_destroy    (journal_t *);
+extern int	   journal_recover    (journal_t *journal);
+extern int	   journal_wipe       (journal_t *, int);
+extern int	   journal_skip_recovery	(journal_t *);
+extern void	   journal_update_superblock	(journal_t *, int);
+extern void	   __journal_abort_hard	(journal_t *);
+extern void	   journal_abort      (journal_t *, int);
+extern int	   journal_errno      (journal_t *);
+extern void	   journal_ack_err    (journal_t *);
+extern int	   journal_clear_err  (journal_t *);
+extern int	   journal_bmap(journal_t *, unsigned long, unsigned long *);
+extern int	   journal_force_commit(journal_t *);
+
+/*
+ * journal_head management
+ */
+struct journal_head *journal_add_journal_head(struct buffer_head *bh);
+struct journal_head *journal_grab_journal_head(struct buffer_head *bh);
+void journal_remove_journal_head(struct buffer_head *bh);
+void journal_put_journal_head(struct journal_head *jh);
+
+/*
+ * handle management
+ */
+extern kmem_cache_t *jbd_handle_cache;
+
+static inline handle_t *jbd_alloc_handle(gfp_t gfp_flags)
+{
+	return kmem_cache_alloc(jbd_handle_cache, gfp_flags);
+}
+
+static inline void jbd_free_handle(handle_t *handle)
+{
+	kmem_cache_free(jbd_handle_cache, handle);
+}
+
+/* Primary revoke support */
+#define JOURNAL_REVOKE_DEFAULT_HASH 256
+extern int	   journal_init_revoke(journal_t *, int);
+extern void	   journal_destroy_revoke_caches(void);
+extern int	   journal_init_revoke_caches(void);
+
+extern void	   journal_destroy_revoke(journal_t *);
+extern int	   journal_revoke (handle_t *,
+				unsigned long, struct buffer_head *);
+extern int	   journal_cancel_revoke(handle_t *, struct journal_head *);
+extern void	   journal_write_revoke_records(journal_t *, transaction_t *);
+
+/* Recovery revoke support */
+extern int	journal_set_revoke(journal_t *, unsigned long, tid_t);
+extern int	journal_test_revoke(journal_t *, unsigned long, tid_t);
+extern void	journal_clear_revoke(journal_t *);
+extern void	journal_switch_revoke_table(journal_t *journal);
+
+/*
+ * The log thread user interface:
+ *
+ * Request space in the current transaction, and force transaction commit
+ * transitions on demand.
+ */
+
+int __log_space_left(journal_t *); /* Called with journal locked */
+int log_start_commit(journal_t *journal, tid_t tid);
+int __log_start_commit(journal_t *journal, tid_t tid);
+int journal_start_commit(journal_t *journal, tid_t *tid);
+int journal_force_commit_nested(journal_t *journal);
+int log_wait_commit(journal_t *journal, tid_t tid);
+int log_do_checkpoint(journal_t *journal);
+
+void __log_wait_for_space(journal_t *journal);
+extern void	__journal_drop_transaction(journal_t *, transaction_t *);
+extern int	cleanup_journal_tail(journal_t *);
+
+/* Debugging code only: */
+
+#define jbd_ENOSYS() \
+do {								           \
+	printk (KERN_ERR "JBD unimplemented function %s\n", __FUNCTION__); \
+	current->state = TASK_UNINTERRUPTIBLE;			           \
+	schedule();						           \
+} while (1)
+
+/*
+ * is_journal_abort
+ *
+ * Simple test wrapper function to test the JFS_ABORT state flag.  This
+ * bit, when set, indicates that we have had a fatal error somewhere,
+ * either inside the journaling layer or indicated to us by the client
+ * (eg. ext3), and that we and should not commit any further
+ * transactions.
+ */
+
+static inline int is_journal_aborted(journal_t *journal)
+{
+	return journal->j_flags & JFS_ABORT;
+}
+
+static inline int is_handle_aborted(handle_t *handle)
+{
+	if (handle->h_aborted)
+		return 1;
+	return is_journal_aborted(handle->h_transaction->t_journal);
+}
+
+static inline void journal_abort_handle(handle_t *handle)
+{
+	handle->h_aborted = 1;
+}
+
+#endif /* __KERNEL__   */
+
+/* Comparison functions for transaction IDs: perform comparisons using
+ * modulo arithmetic so that they work over sequence number wraps. */
+
+static inline int tid_gt(tid_t x, tid_t y)
+{
+	int difference = (x - y);
+	return (difference > 0);
+}
+
+static inline int tid_geq(tid_t x, tid_t y)
+{
+	int difference = (x - y);
+	return (difference >= 0);
+}
+
+extern int journal_blocks_per_page(struct inode *inode);
+
+/*
+ * Return the minimum number of blocks which must be free in the journal
+ * before a new transaction may be started.  Must be called under j_state_lock.
+ */
+static inline int jbd_space_needed(journal_t *journal)
+{
+	int nblocks = journal->j_max_transaction_buffers;
+	if (journal->j_committing_transaction)
+		nblocks += journal->j_committing_transaction->
+					t_outstanding_credits;
+	return nblocks;
+}
+
+/*
+ * Definitions which augment the buffer_head layer
+ */
+
+/* journaling buffer types */
+#define BJ_None		0	/* Not journaled */
+#define BJ_SyncData	1	/* Normal data: flush before commit */
+#define BJ_Metadata	2	/* Normal journaled metadata */
+#define BJ_Forget	3	/* Buffer superseded by this transaction */
+#define BJ_IO		4	/* Buffer is for temporary IO use */
+#define BJ_Shadow	5	/* Buffer contents being shadowed to the log */
+#define BJ_LogCtl	6	/* Buffer contains log descriptors */
+#define BJ_Reserved	7	/* Buffer is reserved for access by journal */
+#define BJ_Locked	8	/* Locked for I/O during commit */
+#define BJ_Types	9
+
+extern int jbd_blocks_per_page(struct inode *inode);
+
+#ifdef __KERNEL__
+
+#define buffer_trace_init(bh)	do {} while (0)
+#define print_buffer_fields(bh)	do {} while (0)
+#define print_buffer_trace(bh)	do {} while (0)
+#define BUFFER_TRACE(bh, info)	do {} while (0)
+#define BUFFER_TRACE2(bh, bh2, info)	do {} while (0)
+#define JBUFFER_TRACE(jh, info)	do {} while (0)
+
+#endif	/* __KERNEL__ */
+
+#endif	/* _LINUX_JBD_H */