[reactos.git] / reactos / drivers / filesystems / ext2 / inc / linux / jbd.h

/*
 * 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/module.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 <linux/lockdep.h>

#include <asm/semaphore.h>

#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 u8 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
#endif

static inline void *jbd_alloc(size_t size, gfp_t flags)
{
    return kmalloc(size, flags);
    /*__get_free_pages(flags, get_order(size));*/
}

static inline void jbd_free(void *ptr, size_t size)
{
    if (ptr) {
        kfree(ptr);
    }
    /* free_pages((unsigned long)ptr, get_order(size)); */
};

#define JFS_MIN_JOURNAL_BLOCKS 1024


/**
 * 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 J_ASSERT  ASSERT

#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

#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
#if 0
#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
#define __journal_expect

#define J_EXPECT
#define J_EXPECT_BH
#define J_EXPECT_JH

#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
 * @h_lockdep_map: lockdep info for debugging lock problems
 **/

/* 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 */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
    struct lockdep_map  h_lockdep_map;
#endif
};


/* 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]
     * [j_list_lock] guards transition of a transaction into T_FINISHED
     * state and subsequent call of __journal_drop_transaction()
     * 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_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 NULL;
    /* return current->journal_info; */
#ifdef _MSC_VER
#pragma message("WARNINGS: journal_current_handle NOT implemented")
#endif
}

/* 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);
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 *);

/* added by matt */
void journal_wipe_recovery(journal_t *journal);

/*
 * 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 struct kmem_cache *jbd_handle_cache;

static inline handle_t *jbd_alloc_handle(gfp_t gfp_flags)
{
    return (handle_t *)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 */