jbd2.h

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/*
 * linux/include/linux/jbd2.h
 *
 * Written by Stephen C. Tweedie <[email protected]>
 *
 * 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_JBD2_H
#define _LINUX_JBD2_H

/* Allow this file to be included directly into e2fsprogs */
#ifndef __KERNEL__
#include "jfs_compat.h"
#define JBD2_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 <linux/slab.h>
#include <crypto/hash.h>
#endif

#define journal_oom_retry 1

/*
 * Define JBD2_PARANIOD_IOFAIL to cause a kernel BUG() if ext4 finds
 * certain classes of error which can occur due to failed IOs.  Under
 * normal use we want ext4 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 JBD2_PARANOID_IOFAIL

/*
 * The default maximum commit age, in seconds.
 */
#define JBD2_DEFAULT_MAX_COMMIT_AGE 5

#ifdef CONFIG_JBD2_DEBUG
/*
 * Define JBD2_EXPENSIVE_CHECKING to enable more expensive internal
 * consistency checks.  By default we don't do this unless
 * CONFIG_JBD2_DEBUG is on.
 */
#define JBD2_EXPENSIVE_CHECKING
extern u8 jbd2_journal_enable_debug;

#define jbd_debug(n, f, a...)                       \
    do {                                \
        if ((n) <= jbd2_journal_enable_debug) {         \
            printk (KERN_DEBUG "(%s, %d): %s: ",        \
                __FILE__, __LINE__, __func__);  \
            printk (f, ## a);               \
        }                           \
    } while (0)
#else
#define jbd_debug(f, a...)  
#endif

extern void *jbd2_alloc(size_t size, gfp_t flags);
extern void jbd2_free(void *ptr, size_t size);

#define JBD2_MIN_JOURNAL_BLOCKS 1024

#ifdef __KERNEL__

typedef struct jbd2_journal_handle handle_t;    /* Atomic operation type */


typedef struct journal_s    journal_t;  /* Journal control structure */
#endif

/*
 * Internal structures used by the logging mechanism:
 */

#define JBD2_MAGIC_NUMBER 0xc03b3998U /* The first 4 bytes of /dev/random! */

/*
 * On-disk structures
 */

/*
 * Descriptor block types:
 */

#define JBD2_DESCRIPTOR_BLOCK   1
#define JBD2_COMMIT_BLOCK   2
#define JBD2_SUPERBLOCK_V1  3
#define JBD2_SUPERBLOCK_V2  4
#define JBD2_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;

/*
 * Checksum types.
 */
#define JBD2_CRC32_CHKSUM   1
#define JBD2_MD5_CHKSUM     2
#define JBD2_SHA1_CHKSUM    3
#define JBD2_CRC32C_CHKSUM  4

#define JBD2_CRC32_CHKSUM_SIZE 4

#define JBD2_CHECKSUM_BYTES (32 / sizeof(u32))
/*
 * Commit block header for storing transactional checksums:
 *
 * NOTE: If FEATURE_COMPAT_CHECKSUM (checksum v1) is set, the h_chksum*
 * fields are used to store a checksum of the descriptor and data blocks.
 *
 * If FEATURE_INCOMPAT_CSUM_V2 (checksum v2) is set, then the h_chksum
 * field is used to store crc32c(uuid+commit_block).  Each journal metadata
 * block gets its own checksum, and data block checksums are stored in
 * journal_block_tag (in the descriptor).  The other h_chksum* fields are
 * not used.
 *
 * Checksum v1 and v2 are mutually exclusive features.
 */
struct commit_header {
    __be32      h_magic;
    __be32          h_blocktype;
    __be32          h_sequence;
    unsigned char   h_chksum_type;
    unsigned char   h_chksum_size;
    unsigned char   h_padding[2];
    __be32      h_chksum[JBD2_CHECKSUM_BYTES];
    __be64      h_commit_sec;
    __be32      h_commit_nsec;
};

/*
 * The block tag: used to describe a single buffer in the journal.
 * t_blocknr_high is only used if INCOMPAT_64BIT is set, so this
 * raw struct shouldn't be used for pointer math or sizeof() - use
 * journal_tag_bytes(journal) instead to compute this.
 */
typedef struct journal_block_tag_s
{
    __be32      t_blocknr;  /* The on-disk block number */
    __be16      t_checksum; /* truncated crc32c(uuid+seq+block) */
    __be16      t_flags;    /* See below */
    __be32      t_blocknr_high; /* most-significant high 32bits. */
} journal_block_tag_t;

#define JBD2_TAG_SIZE32 (offsetof(journal_block_tag_t, t_blocknr_high))
#define JBD2_TAG_SIZE64 (sizeof(journal_block_tag_t))

/* Tail of descriptor block, for checksumming */
struct jbd2_journal_block_tail {
    __be32      t_checksum; /* crc32c(uuid+descr_block) */
};

/*
 * The revoke descriptor: used on disk to describe a series of blocks to
 * be revoked from the log
 */
typedef struct jbd2_journal_revoke_header_s
{
    journal_header_t r_header;
    __be32       r_count;   /* Count of bytes used in the block */
} jbd2_journal_revoke_header_t;

/* Tail of revoke block, for checksumming */
struct jbd2_journal_revoke_tail {
    __be32      r_checksum; /* crc32c(uuid+revoke_block) */
};

/* Definitions for the journal tag flags word: */
#define JBD2_FLAG_ESCAPE        1   /* on-disk block is escaped */
#define JBD2_FLAG_SAME_UUID 2   /* block has same uuid as previous */
#define JBD2_FLAG_DELETED   4   /* block deleted by this transaction */
#define JBD2_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 jbd2_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 */
    __u8    s_checksum_type;    /* checksum type */
    __u8    s_padding2[3];
    __u32   s_padding[42];
    __be32  s_checksum;     /* crc32c(superblock) */

/* 0x0100 */
    __u8    s_users[16*48];     /* ids of all fs'es sharing the log */
/* 0x0400 */
} journal_superblock_t;

#define JBD2_HAS_COMPAT_FEATURE(j,mask)                 \
    ((j)->j_format_version >= 2 &&                  \
     ((j)->j_superblock->s_feature_compat & cpu_to_be32((mask))))
#define JBD2_HAS_RO_COMPAT_FEATURE(j,mask)              \
    ((j)->j_format_version >= 2 &&                  \
     ((j)->j_superblock->s_feature_ro_compat & cpu_to_be32((mask))))
#define JBD2_HAS_INCOMPAT_FEATURE(j,mask)               \
    ((j)->j_format_version >= 2 &&                  \
     ((j)->j_superblock->s_feature_incompat & cpu_to_be32((mask))))

#define JBD2_FEATURE_COMPAT_CHECKSUM    0x00000001

#define JBD2_FEATURE_INCOMPAT_REVOKE        0x00000001
#define JBD2_FEATURE_INCOMPAT_64BIT     0x00000002
#define JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT  0x00000004
#define JBD2_FEATURE_INCOMPAT_CSUM_V2       0x00000008

/* Features known to this kernel version: */
#define JBD2_KNOWN_COMPAT_FEATURES  JBD2_FEATURE_COMPAT_CHECKSUM
#define JBD2_KNOWN_ROCOMPAT_FEATURES    0
#define JBD2_KNOWN_INCOMPAT_FEATURES    (JBD2_FEATURE_INCOMPAT_REVOKE | \
                    JBD2_FEATURE_INCOMPAT_64BIT | \
                    JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT | \
                    JBD2_FEATURE_INCOMPAT_CSUM_V2)

#ifdef __KERNEL__

#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/jbd_common.h>

#define J_ASSERT(assert)    BUG_ON(!(assert))

#define J_ASSERT_BH(bh, expr)   J_ASSERT(expr)
#define J_ASSERT_JH(jh, expr)   J_ASSERT(expr)

#if defined(JBD2_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                      \
                   "JBD2 unexpected failure: %s: %s;\n",         \
                   __func__, #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

/* Flags in jbd_inode->i_flags */
#define __JI_COMMIT_RUNNING 0
/* Commit of the inode data in progress. We use this flag to protect us from
 * concurrent deletion of inode. We cannot use reference to inode for this
 * since we cannot afford doing last iput() on behalf of kjournald
 */
#define JI_COMMIT_RUNNING (1 << __JI_COMMIT_RUNNING)

struct jbd2_inode {
    /* Which transaction does this inode belong to? Either the running
     * transaction or the committing one. [j_list_lock] */
    transaction_t *i_transaction;

    /* Pointer to the running transaction modifying inode's data in case
     * there is already a committing transaction touching it. [j_list_lock] */
    transaction_t *i_next_transaction;

    /* List of inodes in the i_transaction [j_list_lock] */
    struct list_head i_list;

    /* VFS inode this inode belongs to [constant during the lifetime
     * of the structure] */
    struct inode *i_vfs_inode;

    /* Flags of inode [j_list_lock] */
    unsigned long i_flags;
};

struct jbd2_revoke_table_s;

/* Docbook can't yet cope with the bit fields, but will leave the documentation
 * in so it can be fixed later.
 */

struct jbd2_journal_handle
{
    /* 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 */
    unsigned int    h_cowing:1; /* COWing block to snapshot */

    /* Number of buffers requested by user:
     * (before adding the COW credits factor) */
    unsigned int    h_base_credits:14;

    /* Number of buffers the user is allowed to dirty:
     * (counts only buffers dirtied when !h_cowing) */
    unsigned int    h_user_credits:14;


#ifdef CONFIG_DEBUG_LOCK_ALLOC
    struct lockdep_map  h_lockdep_map;
#endif

#ifdef CONFIG_JBD2_DEBUG
    /* COW debugging counters: */
    unsigned int h_cow_moved; /* blocks moved to snapshot */
    unsigned int h_cow_copied; /* blocks copied to snapshot */
    unsigned int h_cow_ok_jh; /* blocks already COWed during current
                     transaction */
    unsigned int h_cow_ok_bitmap; /* blocks not set in COW bitmap */
    unsigned int h_cow_ok_mapped;/* blocks already mapped in snapshot */
    unsigned int h_cow_bitmaps; /* COW bitmaps created */
    unsigned int h_cow_excluded; /* blocks set in exclude bitmap */
#endif
};


/*
 * Some stats for checkpoint phase
 */
struct transaction_chp_stats_s {
    unsigned long       cs_chp_time;
    __u32           cs_forced_to_close;
    __u32           cs_written;
    __u32           cs_dropped;
};

/* 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 kjournald2 alters this]
     * [j_list_lock] guards transition of a transaction into T_FINISHED
     * state and subsequent call of __jbd2_journal_drop_transaction()
     * FIXME: needs barriers
     * KLUDGE: [use j_state_lock]
     */
    enum {
        T_RUNNING,
        T_LOCKED,
        T_FLUSH,
        T_COMMIT,
        T_COMMIT_DFLUSH,
        T_COMMIT_JFLUSH,
        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 metadata buffers owned by this
     * transaction [j_list_lock]
     */
    struct journal_head *t_buffers;

    /*
     * 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;

    /*
     * List of inodes whose data we've modified in data=ordered mode.
     * [j_list_lock]
     */
    struct list_head    t_inode_list;

    /*
     * Protects info related to handles
     */
    spinlock_t      t_handle_lock;

    /*
     * Longest time some handle had to wait for running transaction
     */
    unsigned long       t_max_wait;

    /*
     * When transaction started
     */
    unsigned long       t_start;

    /*
     * Checkpointing stats [j_checkpoint_sem]
     */
    struct transaction_chp_stats_s t_chp_stats;

    /*
     * Number of outstanding updates running on this transaction
     * [t_handle_lock]
     */
    atomic_t        t_updates;

    /*
     * Number of buffers reserved for use by all handles in this transaction
     * handle but not yet modified. [t_handle_lock]
     */
    atomic_t        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;

    /*
     * When this transaction started, in nanoseconds [no locking]
     */
    ktime_t         t_start_time;

    /*
     * How many handles used this transaction? [t_handle_lock]
     */
    atomic_t        t_handle_count;

    /*
     * This transaction is being forced and some process is
     * waiting for it to finish.
     */
    unsigned int t_synchronous_commit:1;

    /* Disk flush needs to be sent to fs partition [no locking] */
    int         t_need_data_flush;

    /*
     * For use by the filesystem to store fs-specific data
     * structures associated with the transaction
     */
    struct list_head    t_private_list;
};

struct transaction_run_stats_s {
    unsigned long       rs_wait;
    unsigned long       rs_running;
    unsigned long       rs_locked;
    unsigned long       rs_flushing;
    unsigned long       rs_logging;

    __u32           rs_handle_count;
    __u32           rs_blocks;
    __u32           rs_blocks_logged;
};

struct transaction_stats_s {
    unsigned long       ts_tid;
    struct transaction_run_stats_s run;
};

static inline unsigned long
jbd2_time_diff(unsigned long start, unsigned long end)
{
    if (end >= start)
        return end - start;

    return end + (MAX_JIFFY_OFFSET - start);
}

#define JBD2_NR_BATCH   64

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
     */
    rwlock_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;

    /*
     * List of buffer heads used by the checkpoint routine.  This
     * was moved from jbd2_log_do_checkpoint() to reduce stack
     * usage.  Access to this array is controlled by the
     * j_checkpoint_mutex.  [j_checkpoint_mutex]
     */
    struct buffer_head  *j_chkpt_bhs[JBD2_NR_BATCH];
    
    /*
     * 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 long  j_blk_offset;
    char            j_devname[BDEVNAME_SIZE+24];

    /*
     * 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 jbd2_revoke_table_s *j_revoke;
    struct jbd2_revoke_table_s *j_revoke_table[2];

    /*
     * array of bhs for jbd2_journal_commit_transaction
     */
    struct buffer_head  **j_wbuf;
    int         j_wbufsize;

    /*
     * this is the pid of hte last person to run a synchronous operation
     * through the journal
     */
    pid_t           j_last_sync_writer;

    /*
     * the average amount of time in nanoseconds it takes to commit a
     * transaction to disk. [j_state_lock]
     */
    u64         j_average_commit_time;

    /*
     * minimum and maximum times that we should wait for
     * additional filesystem operations to get batched into a
     * synchronous handle in microseconds
     */
    u32         j_min_batch_time;
    u32         j_max_batch_time;

    /* This function is called when a transaction is closed */
    void            (*j_commit_callback)(journal_t *,
                             transaction_t *);

    /*
     * Journal statistics
     */
    spinlock_t      j_history_lock;
    struct proc_dir_entry   *j_proc_entry;
    struct transaction_stats_s j_stats;

    /* Failed journal commit ID */
    unsigned int        j_failed_commit;

    /*
     * An opaque pointer to fs-private information.  ext3 puts its
     * superblock pointer here
     */
    void *j_private;

    /* Reference to checksum algorithm driver via cryptoapi */
    struct crypto_shash *j_chksum_driver;

    /* Precomputed journal UUID checksum for seeding other checksums */
    __u32 j_csum_seed;
};

/*
 * Journal flag definitions
 */
#define JBD2_UNMOUNT    0x001   /* Journal thread is being destroyed */
#define JBD2_ABORT  0x002   /* Journaling has been aborted for errors. */
#define JBD2_ACK_ERR    0x004   /* The errno in the sb has been acked */
#define JBD2_FLUSHED    0x008   /* The journal superblock has been flushed */
#define JBD2_LOADED 0x010   /* The journal superblock has been loaded */
#define JBD2_BARRIER    0x020   /* Use IDE barriers */
#define JBD2_ABORT_ON_SYNCDATA_ERR  0x040   /* Abort the journal on file
                         * data write error in ordered
                         * mode */

/*
 * Function declarations for the journaling transaction and buffer
 * management
 */

/* Filing buffers */
extern void jbd2_journal_unfile_buffer(journal_t *, struct journal_head *);
extern void __jbd2_journal_refile_buffer(struct journal_head *);
extern void jbd2_journal_refile_buffer(journal_t *, struct journal_head *);
extern void __jbd2_journal_file_buffer(struct journal_head *, transaction_t *, int);
extern void __journal_free_buffer(struct journal_head *bh);
extern void jbd2_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 * jbd2_journal_get_descriptor_buffer(journal_t *);
int jbd2_journal_next_log_block(journal_t *, unsigned long long *);
int jbd2_journal_get_log_tail(journal_t *journal, tid_t *tid,
                  unsigned long *block);
void __jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block);
void jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block);

/* Commit management */
extern void jbd2_journal_commit_transaction(journal_t *);

/* Checkpoint list management */
int __jbd2_journal_clean_checkpoint_list(journal_t *journal);
int __jbd2_journal_remove_checkpoint(struct journal_head *);
void __jbd2_journal_insert_checkpoint(struct journal_head *, transaction_t *);


/*
 * Triggers
 */

struct jbd2_buffer_trigger_type {
    /*
     * Fired a the moment data to write to the journal are known to be
     * stable - so either at the moment b_frozen_data is created or just
     * before a buffer is written to the journal.  mapped_data is a mapped
     * buffer that is the frozen data for commit.
     */
    void (*t_frozen)(struct jbd2_buffer_trigger_type *type,
             struct buffer_head *bh, void *mapped_data,
             size_t size);

    /*
     * Fired during journal abort for dirty buffers that will not be
     * committed.
     */
    void (*t_abort)(struct jbd2_buffer_trigger_type *type,
            struct buffer_head *bh);
};

extern void jbd2_buffer_frozen_trigger(struct journal_head *jh,
                       void *mapped_data,
                       struct jbd2_buffer_trigger_type *triggers);
extern void jbd2_buffer_abort_trigger(struct journal_head *jh,
                      struct jbd2_buffer_trigger_type *triggers);

/* Buffer IO */
extern int
jbd2_journal_write_metadata_buffer(transaction_t      *transaction,
                  struct journal_head  *jh_in,
                  struct journal_head **jh_out,
                  unsigned long long   blocknr);

/* Transaction locking */
extern void     __wait_on_journal (journal_t *);

/* Transaction cache support */
extern void jbd2_journal_destroy_transaction_cache(void);
extern int  jbd2_journal_init_transaction_cache(void);
extern void jbd2_journal_free_transaction(transaction_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 *jbd2_journal_start(journal_t *, int nblocks);
extern handle_t *jbd2__journal_start(journal_t *, int nblocks, gfp_t gfp_mask);
extern int   jbd2_journal_restart(handle_t *, int nblocks);
extern int   jbd2__journal_restart(handle_t *, int nblocks, gfp_t gfp_mask);
extern int   jbd2_journal_extend (handle_t *, int nblocks);
extern int   jbd2_journal_get_write_access(handle_t *, struct buffer_head *);
extern int   jbd2_journal_get_create_access (handle_t *, struct buffer_head *);
extern int   jbd2_journal_get_undo_access(handle_t *, struct buffer_head *);
void         jbd2_journal_set_triggers(struct buffer_head *,
                       struct jbd2_buffer_trigger_type *type);
extern int   jbd2_journal_dirty_metadata (handle_t *, struct buffer_head *);
extern void  jbd2_journal_release_buffer (handle_t *, struct buffer_head *);
extern int   jbd2_journal_forget (handle_t *, struct buffer_head *);
extern void  journal_sync_buffer (struct buffer_head *);
extern void  jbd2_journal_invalidatepage(journal_t *,
                struct page *, unsigned long);
extern int   jbd2_journal_try_to_free_buffers(journal_t *, struct page *, gfp_t);
extern int   jbd2_journal_stop(handle_t *);
extern int   jbd2_journal_flush (journal_t *);
extern void  jbd2_journal_lock_updates (journal_t *);
extern void  jbd2_journal_unlock_updates (journal_t *);

extern journal_t * jbd2_journal_init_dev(struct block_device *bdev,
                struct block_device *fs_dev,
                unsigned long long start, int len, int bsize);
extern journal_t * jbd2_journal_init_inode (struct inode *);
extern int     jbd2_journal_update_format (journal_t *);
extern int     jbd2_journal_check_used_features
           (journal_t *, unsigned long, unsigned long, unsigned long);
extern int     jbd2_journal_check_available_features
           (journal_t *, unsigned long, unsigned long, unsigned long);
extern int     jbd2_journal_set_features
           (journal_t *, unsigned long, unsigned long, unsigned long);
extern void    jbd2_journal_clear_features
           (journal_t *, unsigned long, unsigned long, unsigned long);
extern int     jbd2_journal_load       (journal_t *journal);
extern int     jbd2_journal_destroy    (journal_t *);
extern int     jbd2_journal_recover    (journal_t *journal);
extern int     jbd2_journal_wipe       (journal_t *, int);
extern int     jbd2_journal_skip_recovery   (journal_t *);
extern void    jbd2_journal_update_sb_errno(journal_t *);
extern void    jbd2_journal_update_sb_log_tail  (journal_t *, tid_t,
                unsigned long, int);
extern void    __jbd2_journal_abort_hard    (journal_t *);
extern void    jbd2_journal_abort      (journal_t *, int);
extern int     jbd2_journal_errno      (journal_t *);
extern void    jbd2_journal_ack_err    (journal_t *);
extern int     jbd2_journal_clear_err  (journal_t *);
extern int     jbd2_journal_bmap(journal_t *, unsigned long, unsigned long long *);
extern int     jbd2_journal_force_commit(journal_t *);
extern int     jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *inode);
extern int     jbd2_journal_begin_ordered_truncate(journal_t *journal,
                struct jbd2_inode *inode, loff_t new_size);
extern void    jbd2_journal_init_jbd_inode(struct jbd2_inode *jinode, struct inode *inode);
extern void    jbd2_journal_release_jbd_inode(journal_t *journal, struct jbd2_inode *jinode);

/*
 * journal_head management
 */
struct journal_head *jbd2_journal_add_journal_head(struct buffer_head *bh);
struct journal_head *jbd2_journal_grab_journal_head(struct buffer_head *bh);
void jbd2_journal_put_journal_head(struct journal_head *jh);

/*
 * handle management
 */
extern struct kmem_cache *jbd2_handle_cache;

static inline handle_t *jbd2_alloc_handle(gfp_t gfp_flags)
{
    return kmem_cache_alloc(jbd2_handle_cache, gfp_flags);
}

static inline void jbd2_free_handle(handle_t *handle)
{
    kmem_cache_free(jbd2_handle_cache, handle);
}

/*
 * jbd2_inode management (optional, for those file systems that want to use
 * dynamically allocated jbd2_inode structures)
 */
extern struct kmem_cache *jbd2_inode_cache;

static inline struct jbd2_inode *jbd2_alloc_inode(gfp_t gfp_flags)
{
    return kmem_cache_alloc(jbd2_inode_cache, gfp_flags);
}

static inline void jbd2_free_inode(struct jbd2_inode *jinode)
{
    kmem_cache_free(jbd2_inode_cache, jinode);
}

/* Primary revoke support */
#define JOURNAL_REVOKE_DEFAULT_HASH 256
extern int     jbd2_journal_init_revoke(journal_t *, int);
extern void    jbd2_journal_destroy_revoke_caches(void);
extern int     jbd2_journal_init_revoke_caches(void);

extern void    jbd2_journal_destroy_revoke(journal_t *);
extern int     jbd2_journal_revoke (handle_t *, unsigned long long, struct buffer_head *);
extern int     jbd2_journal_cancel_revoke(handle_t *, struct journal_head *);
extern void    jbd2_journal_write_revoke_records(journal_t *,
                             transaction_t *, int);

/* Recovery revoke support */
extern int  jbd2_journal_set_revoke(journal_t *, unsigned long long, tid_t);
extern int  jbd2_journal_test_revoke(journal_t *, unsigned long long, tid_t);
extern void jbd2_journal_clear_revoke(journal_t *);
extern void jbd2_journal_switch_revoke_table(journal_t *journal);
extern void jbd2_clear_buffer_revoked_flags(journal_t *journal);

/*
 * The log thread user interface:
 *
 * Request space in the current transaction, and force transaction commit
 * transitions on demand.
 */

int __jbd2_log_space_left(journal_t *); /* Called with journal locked */
int jbd2_log_start_commit(journal_t *journal, tid_t tid);
int __jbd2_log_start_commit(journal_t *journal, tid_t tid);
int jbd2_journal_start_commit(journal_t *journal, tid_t *tid);
int jbd2_journal_force_commit_nested(journal_t *journal);
int jbd2_log_wait_commit(journal_t *journal, tid_t tid);
int jbd2_log_do_checkpoint(journal_t *journal);
int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid);

void __jbd2_log_wait_for_space(journal_t *journal);
extern void __jbd2_journal_drop_transaction(journal_t *, transaction_t *);
extern int jbd2_cleanup_journal_tail(journal_t *);

/* Debugging code only: */

#define jbd_ENOSYS() \
do {                                           \
    printk (KERN_ERR "JBD unimplemented function %s\n", __func__); \
    current->state = TASK_UNINTERRUPTIBLE;                     \
    schedule();                                \
} while (1)

/*
 * is_journal_abort
 *
 * Simple test wrapper function to test the JBD2_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 & JBD2_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 jbd2_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 jbd2_journal_blocks_per_page(struct inode *inode);
extern size_t journal_tag_bytes(journal_t *journal);

/*
 * 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 += atomic_read(&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_Metadata 1   /* Normal journaled metadata */
#define BJ_Forget   2   /* Buffer superseded by this transaction */
#define BJ_IO       3   /* Buffer is for temporary IO use */
#define BJ_Shadow   4   /* Buffer contents being shadowed to the log */
#define BJ_LogCtl   5   /* Buffer contains log descriptors */
#define BJ_Reserved 6   /* Buffer is reserved for access by journal */
#define BJ_Types    7

extern int jbd_blocks_per_page(struct inode *inode);

static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
                  const void *address, unsigned int length)
{
    struct {
        struct shash_desc shash;
        char ctx[crypto_shash_descsize(journal->j_chksum_driver)];
    } desc;
    int err;

    desc.shash.tfm = journal->j_chksum_driver;
    desc.shash.flags = 0;
    *(u32 *)desc.ctx = crc;

    err = crypto_shash_update(&desc.shash, address, length);
    BUG_ON(err);

    return *(u32 *)desc.ctx;
}

#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_JBD2_H */