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 /* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  * linux/include/linux/jbd2.h
  *
  * Written by Stephen C. Tweedie <sct@redhat.com>
  *
  * Copyright 1998-2000 Red Hat, Inc --- All Rights Reserved
  *
  * 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
 #else
 
 #include <linux/types.h>
 #include <linux/buffer_head.h>
 #include <linux/journal-head.h>
 #include <linux/stddef.h>
 #include <linux/mutex.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
 #include <linux/bit_spinlock.h>
 #include <linux/blkdev.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
 void __jbd2_debug(int level, const char *file, const char *func,
           unsigned int line, const char *fmt, ...);
 
 #define jbd2_debug(n, fmt, a...) \
     __jbd2_debug((n), __FILE__, __func__, __LINE__, (fmt), ##a)
 #else
 #define jbd2_debug(n, fmt, a...)  no_printk(fmt, ##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
 #define JBD2_DEFAULT_FAST_COMMIT_BLOCKS 256
 
 #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 jbd2_journal_handle 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 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.
  *
  * If FEATURE_INCOMPAT_CSUM_V3 is set, the descriptor block uses
  * journal_block_tag3_t to store a full 32-bit checksum.  Everything else
  * is the same as v2.
  *
  * Checksum v1, v2, and v3 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_tag3_s
 {
     __be32      t_blocknr;  /* The on-disk block number */
     __be32      t_flags;    /* See below */
     __be32      t_blocknr_high; /* most-significant high 32bits. */
     __be32      t_checksum; /* crc32c(uuid+seq+block) */
 } journal_block_tag3_t;
 
 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;
 
 /* Tail of descriptor or revoke 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;
 
 /* 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];
 /* 0x0054 */
     __be32  s_num_fc_blks;      /* Number of fast commit blocks */
 /* 0x0058 */
     __u32   s_padding[41];
     __be32  s_checksum;     /* crc32c(superblock) */
 
 /* 0x0100 */
     __u8    s_users[16*48];     /* ids of all fs'es sharing the log */
 /* 0x0400 */
 } journal_superblock_t;
 
 /* Use the jbd2_{has,set,clear}_feature_* helpers; these will be removed */
 #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
 #define JBD2_FEATURE_INCOMPAT_CSUM_V3       0x00000010
 #define JBD2_FEATURE_INCOMPAT_FAST_COMMIT   0x00000020
 
 /* See "journal feature predicate functions" below */
 
 /* 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 | \
                     JBD2_FEATURE_INCOMPAT_CSUM_V3 | \
                     JBD2_FEATURE_INCOMPAT_FAST_COMMIT)
 
 #ifdef __KERNEL__
 
 #include <linux/fs.h>
 #include <linux/sched.h>
 
 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_JournalHead,     /* Pins bh->b_private and jh->b_bh */
     BH_Shadow,      /* IO on shadow buffer is running */
     BH_Verified,        /* Metadata block has been verified ok */
     BH_JBDPrivateStart, /* First bit available for private use by FS */
 };
 
 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)
 BUFFER_FNS(Shadow, shadow)
 BUFFER_FNS(Verified, verified)
 
 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_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);
 }
 
 #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
 #define __JI_WRITE_DATA 1
 #define __JI_WAIT_DATA 2
 
 /*
  * 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)
 /* Write allocated dirty buffers in this inode before commit */
 #define JI_WRITE_DATA (1 << __JI_WRITE_DATA)
 /* Wait for outstanding data writes for this inode before commit */
 #define JI_WAIT_DATA (1 << __JI_WAIT_DATA)
 
 /**
  * struct jbd2_inode - The jbd_inode type is the structure linking inodes in
  * ordered mode present in a transaction so that we can sync them during commit.
  */
 struct jbd2_inode {
     /**
      * @i_transaction:
      *
      * Which transaction does this inode belong to? Either the running
      * transaction or the committing one. [j_list_lock]
      */
     transaction_t *i_transaction;
 
     /**
      * @i_next_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;
 
     /**
      * @i_list: List of inodes in the i_transaction [j_list_lock]
      */
     struct list_head i_list;
 
     /**
      * @i_vfs_inode:
      *
      * VFS inode this inode belongs to [constant for lifetime of structure]
      */
     struct inode *i_vfs_inode;
 
     /**
      * @i_flags: Flags of inode [j_list_lock]
      */
     unsigned long i_flags;
 
     /**
      * @i_dirty_start:
      *
      * Offset in bytes where the dirty range for this inode starts.
      * [j_list_lock]
      */
     loff_t i_dirty_start;
 
     /**
      * @i_dirty_end:
      *
      * Inclusive offset in bytes where the dirty range for this inode
      * ends. [j_list_lock]
      */
     loff_t i_dirty_end;
 };
 
 struct jbd2_revoke_table_s;
 
 /**
  * struct jbd2_journal_handle - The jbd2_journal_handle type is the concrete
  *     type associated with handle_t.
  * @h_transaction: Which compound transaction is this update a part of?
  * @h_journal: Which journal handle belongs to - used iff h_reserved set.
  * @h_rsv_handle: Handle reserved for finishing the logical operation.
  * @h_total_credits: Number of remaining buffers we are allowed to add to
  *  journal. These are dirty buffers and revoke descriptor blocks.
  * @h_revoke_credits: Number of remaining revoke records available for handle
  * @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_reserved: Flag for handle for reserved credits.
  * @h_aborted: Flag indicating fatal error on handle.
  * @h_type: For handle statistics.
  * @h_line_no: For handle statistics.
  * @h_start_jiffies: Handle Start time.
  * @h_requested_credits: Holds @h_total_credits after handle is started.
  * @h_revoke_credits_requested: Holds @h_revoke_credits after handle is started.
  * @saved_alloc_context: Saved context while transaction is open.
  **/
 
 /* 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
 {
     union {
         transaction_t   *h_transaction;
         /* Which journal handle belongs to - used iff h_reserved set */
         journal_t   *h_journal;
     };
 
     handle_t        *h_rsv_handle;
     int         h_total_credits;
     int         h_revoke_credits;
     int         h_revoke_credits_requested;
     int         h_ref;
     int         h_err;
 
     /* Flags [no locking] */
     unsigned int    h_sync:     1;
     unsigned int    h_jdata:    1;
     unsigned int    h_reserved: 1;
     unsigned int    h_aborted:  1;
     unsigned int    h_type:     8;
     unsigned int    h_line_no:  16;
 
     unsigned long       h_start_jiffies;
     unsigned int        h_requested_credits;
 
     unsigned int        saved_alloc_context;
 };
 
 
 /*
  * 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.
  * (Locking Documentation improved by LockDoc)
  */
 
 /*
  * Lock ranking:
  *
  *    j_list_lock
  *      ->jbd_lock_bh_journal_head()    (This is "innermost")
  *
  *    j_state_lock
  *    ->b_state_lock
  *
  *    b_state_lock
  *    ->j_list_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_SWITCH,
         T_FLUSH,
         T_COMMIT,
         T_COMMIT_DFLUSH,
         T_COMMIT_JFLUSH,
         T_COMMIT_CALLBACK,
         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, no locks
      * needed for jbd2 thread]
      */
     int         t_nr_buffers;
 
     /*
      * Doubly-linked circular list of all buffers reserved but not yet
      * modified by this transaction [j_list_lock, no locks needed fo
      * jbd2 thread]
      */
     struct journal_head *t_reserved_list;
 
     /*
      * Doubly-linked circular list of all metadata buffers owned by this
      * transaction [j_list_lock, no locks needed for jbd2 thread]
      */
     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 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, no locks needed for jbd2
      * thread]
      */
     struct journal_head *t_shadow_list;
 
     /*
      * List of inodes associated with the transaction; e.g., ext4 uses
      * this to track inodes in data=ordered and data=journal mode that
      * need special handling on transaction commit; also used by ocfs2.
      * [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;
 
     /*
      * When commit was requested [j_state_lock]
      */
     unsigned long       t_requested;
 
     /*
      * Checkpointing stats [j_list_lock]
      */
     struct transaction_chp_stats_s t_chp_stats;
 
     /*
      * Number of outstanding updates running on this transaction
      * [none]
      */
     atomic_t        t_updates;
 
     /*
      * Number of blocks reserved for this transaction in the journal.
      * This is including all credits reserved when starting transaction
      * handles as well as all journal descriptor blocks needed for this
      * transaction. [none]
      */
     atomic_t        t_outstanding_credits;
 
     /*
      * Number of revoke records for this transaction added by already
      * stopped handles. [none]
      */
     atomic_t        t_outstanding_revokes;
 
     /*
      * How many handles used this transaction? [none]
      */
     atomic_t        t_handle_count;
 
     /*
      * 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;
 
     /*
      * 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_request_delay;
     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;
     unsigned long       ts_requested;
     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
 
 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
 
 #define JBD2_FC_REPLAY_STOP 0
 #define JBD2_FC_REPLAY_CONTINUE 1
 
 /**
  * struct journal_s - The journal_s type is the concrete type associated with
  *     journal_t.
  */
 struct journal_s
 {
     /**
      * @j_flags: General journaling state flags [j_state_lock,
      * no lock for quick racy checks]
      */
     unsigned long       j_flags;
 
     /**
      * @j_atomic_flags: Atomic journaling state flags.
      */
     unsigned long       j_atomic_flags;
 
     /**
      * @j_errno:
      *
      * Is there an outstanding uncleared error on the journal (from a prior
      * abort)? [j_state_lock]
      */
     int         j_errno;
 
     /**
      * @j_abort_mutex: Lock the whole aborting procedure.
      */
     struct mutex        j_abort_mutex;
 
     /**
      * @j_sb_buffer: The first part of the superblock buffer.
      */
     struct buffer_head  *j_sb_buffer;
 
     /**
      * @j_superblock: The second part of the superblock buffer.
      */
     journal_superblock_t    *j_superblock;
 
     /**
      * @j_format_version: Version of the superblock format.
      */
     int         j_format_version;
 
     /**
      * @j_state_lock: Protect the various scalars in the journal.
      */
     rwlock_t        j_state_lock;
 
     /**
      * @j_barrier_count:
      *
      * Number of processes waiting to create a barrier lock [j_state_lock,
      * no lock for quick racy checks]
      */
     int         j_barrier_count;
 
     /**
      * @j_barrier: The barrier lock itself.
      */
     struct mutex        j_barrier;
 
     /**
      * @j_running_transaction:
      *
      * Transactions: The current running transaction...
      * [j_state_lock, no lock for quick racy checks] [caller holding
      * open handle]
      */
     transaction_t       *j_running_transaction;
 
     /**
      * @j_committing_transaction:
      *
      * the transaction we are pushing to disk
      * [j_state_lock] [caller holding open handle]
      */
     transaction_t       *j_committing_transaction;
 
     /**
      * @j_checkpoint_transactions:
      *
      * ... and a linked circular list of all transactions waiting for
      * checkpointing. [j_list_lock]
      */
     transaction_t       *j_checkpoint_transactions;
 
     /**
      * @j_wait_transaction_locked:
      *
      * 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;
 
     /**
      * @j_wait_done_commit: Wait queue for waiting for commit to complete.
      */
     wait_queue_head_t   j_wait_done_commit;
 
     /**
      * @j_wait_commit: Wait queue to trigger commit.
      */
     wait_queue_head_t   j_wait_commit;
 
     /**
      * @j_wait_updates: Wait queue to wait for updates to complete.
      */
     wait_queue_head_t   j_wait_updates;
 
     /**
      * @j_wait_reserved:
      *
      * Wait queue to wait for reserved buffer credits to drop.
      */
     wait_queue_head_t   j_wait_reserved;
 
     /**
      * @j_fc_wait:
      *
      * Wait queue to wait for completion of async fast commits.
      */
     wait_queue_head_t   j_fc_wait;
 
     /**
      * @j_checkpoint_mutex:
      *
      * Semaphore for locking against concurrent checkpoints.
      */
     struct mutex        j_checkpoint_mutex;
 
     /**
      * @j_chkpt_bhs:
      *
      * 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];
 
     /**
      * @j_shrinker:
      *
      * Journal head shrinker, reclaim buffer's journal head which
      * has been written back.
      */
     struct shrinker     j_shrinker;
 
     /**
      * @j_checkpoint_jh_count:
      *
      * Number of journal buffers on the checkpoint list. [j_list_lock]
      */
     struct percpu_counter   j_checkpoint_jh_count;
 
     /**
      * @j_shrink_transaction:
      *
      * Record next transaction will shrink on the checkpoint list.
      * [j_list_lock]
      */
     transaction_t       *j_shrink_transaction;
 
     /**
      * @j_head:
      *
      * Journal head: identifies the first unused block in the journal.
      * [j_state_lock]
      */
     unsigned long       j_head;
 
     /**
      * @j_tail:
      *
      * Journal tail: identifies the oldest still-used block in the journal.
      * [j_state_lock]
      */
     unsigned long       j_tail;
 
     /**
      * @j_free:
      *
      * Journal free: how many free blocks are there in the journal?
      * [j_state_lock]
      */
     unsigned long       j_free;
 
     /**
      * @j_first:
      *
      * The block number of the first usable block in the journal
      * [j_state_lock].
      */
     unsigned long       j_first;
 
     /**
      * @j_last:
      *
      * The block number one beyond the last usable block in the journal
      * [j_state_lock].
      */
     unsigned long       j_last;
 
     /**
      * @j_fc_first:
      *
      * The block number of the first fast commit block in the journal
      * [j_state_lock].
      */
     unsigned long       j_fc_first;
 
     /**
      * @j_fc_off:
      *
      * Number of fast commit blocks currently allocated. Accessed only
      * during fast commit. Currently only process can do fast commit, so
      * this field is not protected by any lock.
      */
     unsigned long       j_fc_off;
 
     /**
      * @j_fc_last:
      *
      * The block number one beyond the last fast commit block in the journal
      * [j_state_lock].
      */
     unsigned long       j_fc_last;
 
     /**
      * @j_dev: Device where we store the journal.
      */
     struct block_device *j_dev;
 
     /**
      * @j_blocksize: Block size for the location where we store the journal.
      */
     int         j_blocksize;
 
     /**
      * @j_blk_offset:
      *
      * Starting block offset into the device where we store the journal.
      */
     unsigned long long  j_blk_offset;
 
     /**
      * @j_devname: Journal device name.
      */
     char            j_devname[BDEVNAME_SIZE+24];
 
     /**
      * @j_fs_dev:
      *
      * Device which holds the client fs.  For internal journal this will be
      * equal to j_dev.
      */
     struct block_device *j_fs_dev;
 
     /**
      * @j_total_len: Total maximum capacity of the journal region on disk.
      */
     unsigned int        j_total_len;
 
     /**
      * @j_reserved_credits:
      *
      * Number of buffers reserved from the running transaction.
      */
     atomic_t        j_reserved_credits;
 
     /**
      * @j_list_lock: Protects the buffer lists and internal buffer state.
      */
     spinlock_t      j_list_lock;
 
     /**
      * @j_inode:
      *
      * Optional inode where we store the journal.  If present, all
      * journal block numbers are mapped into this inode via bmap().
      */
     struct inode        *j_inode;
 
     /**
      * @j_tail_sequence:
      *
      * Sequence number of the oldest transaction in the log [j_state_lock]
      */
     tid_t           j_tail_sequence;
 
     /**
      * @j_transaction_sequence:
      *
      * Sequence number of the next transaction to grant [j_state_lock]
      */
     tid_t           j_transaction_sequence;
 
     /**
      * @j_commit_sequence:
      *
      * Sequence number of the most recently committed transaction
      * [j_state_lock, no lock for quick racy checks]
      */
     tid_t           j_commit_sequence;
 
     /**
      * @j_commit_request:
      *
      * Sequence number of the most recent transaction wanting commit
      * [j_state_lock, no lock for quick racy checks]
      */
     tid_t           j_commit_request;
 
     /**
      * @j_uuid:
      *
      * 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];
 
     /**
      * @j_task: Pointer to the current commit thread for this journal.
      */
     struct task_struct  *j_task;
 
     /**
      * @j_max_transaction_buffers:
      *
      * Maximum number of metadata buffers to allow in a single compound
      * commit transaction.
      */
     int         j_max_transaction_buffers;
 
     /**
      * @j_revoke_records_per_block:
      *
      * Number of revoke records that fit in one descriptor block.
      */
     int         j_revoke_records_per_block;
 
     /**
      * @j_commit_interval:
      *
      * What is the maximum transaction lifetime before we begin a commit?
      */
     unsigned long       j_commit_interval;
 
     /**
      * @j_commit_timer: The timer used to wakeup the commit thread.
      */
     struct timer_list   j_commit_timer;
 
     /**
      * @j_revoke_lock: Protect the revoke table.
      */
     spinlock_t      j_revoke_lock;
 
     /**
      * @j_revoke:
      *
      * The revoke table - maintains the list of revoked blocks in the
      * current transaction.
      */
     struct jbd2_revoke_table_s *j_revoke;
 
     /**
      * @j_revoke_table: Alternate revoke tables for j_revoke.
      */
     struct jbd2_revoke_table_s *j_revoke_table[2];
 
     /**
      * @j_wbuf: Array of bhs for jbd2_journal_commit_transaction.
      */
     struct buffer_head  **j_wbuf;
 
     /**
      * @j_fc_wbuf: Array of fast commit bhs for fast commit. Accessed only
      * during a fast commit. Currently only process can do fast commit, so
      * this field is not protected by any lock.
      */
     struct buffer_head  **j_fc_wbuf;
 
     /**
      * @j_wbufsize:
      *
      * Size of @j_wbuf array.
      */
     int         j_wbufsize;
 
     /**
      * @j_fc_wbufsize:
      *
      * Size of @j_fc_wbuf array.
      */
     int         j_fc_wbufsize;
 
     /**
      * @j_last_sync_writer:
      *
      * The pid of the last person to run a synchronous operation
      * through the journal.
      */
     pid_t           j_last_sync_writer;
 
     /**
      * @j_average_commit_time:
      *
      * The average amount of time in nanoseconds it takes to commit a
      * transaction to disk. [j_state_lock]
      */
     u64         j_average_commit_time;
 
     /**
      * @j_min_batch_time:
      *
      * Minimum time that we should wait for additional filesystem operations
      * to get batched into a synchronous handle in microseconds.
      */
     u32         j_min_batch_time;
 
     /**
      * @j_max_batch_time:
      *
      * Maximum time that we should wait for additional filesystem operations
      * to get batched into a synchronous handle in microseconds.
      */
     u32         j_max_batch_time;
 
     /**
      * @j_commit_callback:
      *
      * This function is called when a transaction is closed.
      */
     void            (*j_commit_callback)(journal_t *,
                              transaction_t *);
 
     /**
      * @j_submit_inode_data_buffers:
      *
      * This function is called for all inodes associated with the
      * committing transaction marked with JI_WRITE_DATA flag
      * before we start to write out the transaction to the journal.
      */
     int         (*j_submit_inode_data_buffers)
                     (struct jbd2_inode *);
 
     /**
      * @j_finish_inode_data_buffers:
      *
      * This function is called for all inodes associated with the
      * committing transaction marked with JI_WAIT_DATA flag
      * after we have written the transaction to the journal
      * but before we write out the commit block.
      */
     int         (*j_finish_inode_data_buffers)
                     (struct jbd2_inode *);
 
     /*
      * Journal statistics
      */
 
     /**
      * @j_history_lock: Protect the transactions statistics history.
      */
     spinlock_t      j_history_lock;
 
     /**
      * @j_proc_entry: procfs entry for the jbd statistics directory.
      */
     struct proc_dir_entry   *j_proc_entry;
 
     /**
      * @j_stats: Overall statistics.
      */
     struct transaction_stats_s j_stats;
 
     /**
      * @j_failed_commit: Failed journal commit ID.
      */
     unsigned int        j_failed_commit;
 
     /**
      * @j_private:
      *
      * An opaque pointer to fs-private information.  ext3 puts its
      * superblock pointer here.
      */
     void *j_private;
 
     /**
      * @j_chksum_driver:
      *
      * Reference to checksum algorithm driver via cryptoapi.
      */
     struct crypto_shash *j_chksum_driver;
 
     /**
      * @j_csum_seed:
      *
      * Precomputed journal UUID checksum for seeding other checksums.
      */
     __u32 j_csum_seed;
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
     /**
      * @j_trans_commit_map:
      *
      * Lockdep entity to track transaction commit dependencies. Handles
      * hold this "lock" for read, when we wait for commit, we acquire the
      * "lock" for writing. This matches the properties of jbd2 journalling
      * where the running transaction has to wait for all handles to be
      * dropped to commit that transaction and also acquiring a handle may
      * require transaction commit to finish.
      */
     struct lockdep_map  j_trans_commit_map;
 #endif
 
     /**
      * @j_fc_cleanup_callback:
      *
      * Clean-up after fast commit or full commit. JBD2 calls this function
      * after every commit operation.
      */
     void (*j_fc_cleanup_callback)(struct journal_s *journal, int full, tid_t tid);
 
     /**
      * @j_fc_replay_callback:
      *
      * File-system specific function that performs replay of a fast
      * commit. JBD2 calls this function for each fast commit block found in
      * the journal. This function should return JBD2_FC_REPLAY_CONTINUE
      * to indicate that the block was processed correctly and more fast
      * commit replay should continue. Return value of JBD2_FC_REPLAY_STOP
      * indicates the end of replay (no more blocks remaining). A negative
      * return value indicates error.
      */
     int (*j_fc_replay_callback)(struct journal_s *journal,
                     struct buffer_head *bh,
                     enum passtype pass, int off,
                     tid_t expected_commit_id);
 };
 
 #define jbd2_might_wait_for_commit(j) \
     do { \
         rwsem_acquire(&j->j_trans_commit_map, 0, 0, _THIS_IP_); \
         rwsem_release(&j->j_trans_commit_map, _THIS_IP_); \
     } while (0)
 
 /* journal feature predicate functions */
 #define JBD2_FEATURE_COMPAT_FUNCS(name, flagname) \
 static inline bool jbd2_has_feature_##name(journal_t *j) \
 { \
     return ((j)->j_format_version >= 2 && \
         ((j)->j_superblock->s_feature_compat & \
          cpu_to_be32(JBD2_FEATURE_COMPAT_##flagname)) != 0); \
 } \
 static inline void jbd2_set_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_compat |= \
         cpu_to_be32(JBD2_FEATURE_COMPAT_##flagname); \
 } \
 static inline void jbd2_clear_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_compat &= \
         ~cpu_to_be32(JBD2_FEATURE_COMPAT_##flagname); \
 }
 
 #define JBD2_FEATURE_RO_COMPAT_FUNCS(name, flagname) \
 static inline bool jbd2_has_feature_##name(journal_t *j) \
 { \
     return ((j)->j_format_version >= 2 && \
         ((j)->j_superblock->s_feature_ro_compat & \
          cpu_to_be32(JBD2_FEATURE_RO_COMPAT_##flagname)) != 0); \
 } \
 static inline void jbd2_set_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_ro_compat |= \
         cpu_to_be32(JBD2_FEATURE_RO_COMPAT_##flagname); \
 } \
 static inline void jbd2_clear_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_ro_compat &= \
         ~cpu_to_be32(JBD2_FEATURE_RO_COMPAT_##flagname); \
 }
 
 #define JBD2_FEATURE_INCOMPAT_FUNCS(name, flagname) \
 static inline bool jbd2_has_feature_##name(journal_t *j) \
 { \
     return ((j)->j_format_version >= 2 && \
         ((j)->j_superblock->s_feature_incompat & \
          cpu_to_be32(JBD2_FEATURE_INCOMPAT_##flagname)) != 0); \
 } \
 static inline void jbd2_set_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_incompat |= \
         cpu_to_be32(JBD2_FEATURE_INCOMPAT_##flagname); \
 } \
 static inline void jbd2_clear_feature_##name(journal_t *j) \
 { \
     (j)->j_superblock->s_feature_incompat &= \
         ~cpu_to_be32(JBD2_FEATURE_INCOMPAT_##flagname); \
 }
 
 JBD2_FEATURE_COMPAT_FUNCS(checksum,     CHECKSUM)
 
 JBD2_FEATURE_INCOMPAT_FUNCS(revoke,     REVOKE)
 JBD2_FEATURE_INCOMPAT_FUNCS(64bit,      64BIT)
 JBD2_FEATURE_INCOMPAT_FUNCS(async_commit,   ASYNC_COMMIT)
 JBD2_FEATURE_INCOMPAT_FUNCS(csum2,      CSUM_V2)
 JBD2_FEATURE_INCOMPAT_FUNCS(csum3,      CSUM_V3)
 JBD2_FEATURE_INCOMPAT_FUNCS(fast_commit,    FAST_COMMIT)
 
 /*
  * 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 */
 #define JBD2_FAST_COMMIT_ONGOING    0x100   /* Fast commit is ongoing */
 #define JBD2_FULL_COMMIT_ONGOING    0x200   /* Full commit is ongoing */
 #define JBD2_JOURNAL_FLUSH_DISCARD  0x0001
 #define JBD2_JOURNAL_FLUSH_ZEROOUT  0x0002
 #define JBD2_JOURNAL_FLUSH_VALID    (JBD2_JOURNAL_FLUSH_DISCARD | \
                     JBD2_JOURNAL_FLUSH_ZEROOUT)
 
 /*
  * Journal atomic flag definitions
  */
 #define JBD2_CHECKPOINT_IO_ERROR    0x001   /* Detect io error while writing
                          * buffer back to disk */
 
 /*
  * Function declarations for the journaling transaction and buffer
  * management
  */
 
 /* Filing buffers */
 extern void jbd2_journal_unfile_buffer(journal_t *, struct journal_head *);
 extern bool __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 jbd2_journal_file_buffer(struct journal_head *, transaction_t *, int);
 static inline void jbd2_file_log_bh(struct list_head *head, struct buffer_head *bh)
 {
     list_add_tail(&bh->b_assoc_buffers, head);
 }
 static inline void jbd2_unfile_log_bh(struct buffer_head *bh)
 {
     list_del_init(&bh->b_assoc_buffers);
 }
 
 /* Log buffer allocation */
 struct buffer_head *jbd2_journal_get_descriptor_buffer(transaction_t *, int);
 void jbd2_descriptor_block_csum_set(journal_t *, struct buffer_head *);
 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);
 int __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 */
 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy);
 unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal, unsigned long *nr_to_scan);
 int __jbd2_journal_remove_checkpoint(struct journal_head *);
 void jbd2_journal_destroy_checkpoint(journal_t *journal);
 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 buffer_head **bh_out,
                           sector_t blocknr);
 
 /* Transaction cache support */
 extern void jbd2_journal_destroy_transaction_cache(void);
 extern int __init 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 blocks, int rsv_blocks,
                      int revoke_records, gfp_t gfp_mask,
                      unsigned int type, unsigned int line_no);
 extern int   jbd2_journal_restart(handle_t *, int nblocks);
 extern int   jbd2__journal_restart(handle_t *, int nblocks,
                        int revoke_records, gfp_t gfp_mask);
 extern int   jbd2_journal_start_reserved(handle_t *handle,
                 unsigned int type, unsigned int line_no);
 extern void  jbd2_journal_free_reserved(handle_t *handle);
 extern int   jbd2_journal_extend(handle_t *handle, int nblocks,
                      int revoke_records);
 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 int   jbd2_journal_forget (handle_t *, struct buffer_head *);
 int jbd2_journal_invalidate_folio(journal_t *, struct folio *,
                     size_t offset, size_t length);
 bool jbd2_journal_try_to_free_buffers(journal_t *journal, struct folio *folio);
 extern int   jbd2_journal_stop(handle_t *);
 extern int   jbd2_journal_flush(journal_t *journal, unsigned int flags);
 extern void  jbd2_journal_lock_updates (journal_t *);
 extern void  jbd2_journal_unlock_updates (journal_t *);
 
 void jbd2_journal_wait_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 int     jbd2_journal_update_sb_log_tail  (journal_t *, tid_t,
                 unsigned long, blk_opf_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_force_commit_nested(journal_t *);
 extern int     jbd2_journal_inode_ranged_write(handle_t *handle,
             struct jbd2_inode *inode, loff_t start_byte,
             loff_t length);
 extern int     jbd2_journal_inode_ranged_wait(handle_t *handle,
             struct jbd2_inode *inode, loff_t start_byte,
             loff_t length);
 extern int     jbd2_journal_submit_inode_data_buffers(
             struct jbd2_inode *jinode);
 extern int     jbd2_journal_finish_inode_data_buffers(
             struct jbd2_inode *jinode);
 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_zalloc(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_record_cache(void);
 extern void    jbd2_journal_destroy_revoke_table_cache(void);
 extern int __init jbd2_journal_init_revoke_record_cache(void);
 extern int __init jbd2_journal_init_revoke_table_cache(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(transaction_t *transaction,
                              struct list_head *log_bufs);
 
 /* 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_start_commit(journal_t *journal, tid_t tid);
 int jbd2_journal_start_commit(journal_t *journal, tid_t *tid);
 int jbd2_log_wait_commit(journal_t *journal, tid_t tid);
 int jbd2_transaction_committed(journal_t *journal, tid_t tid);
 int jbd2_complete_transaction(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 *);
 
 /* Fast commit related APIs */
 int jbd2_fc_begin_commit(journal_t *journal, tid_t tid);
 int jbd2_fc_end_commit(journal_t *journal);
 int jbd2_fc_end_commit_fallback(journal_t *journal);
 int jbd2_fc_get_buf(journal_t *journal, struct buffer_head **bh_out);
 int jbd2_submit_inode_data(struct jbd2_inode *jinode);
 int jbd2_wait_inode_data(journal_t *journal, struct jbd2_inode *jinode);
 int jbd2_fc_wait_bufs(journal_t *journal, int num_blks);
 int jbd2_fc_release_bufs(journal_t *journal);
 
 static inline int jbd2_journal_get_max_txn_bufs(journal_t *journal)
 {
     return (journal->j_total_len - journal->j_fc_wbufsize) / 4;
 }
 
 /*
  * 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 || !handle->h_transaction)
         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);
 
 static inline bool jbd2_journal_has_csum_v2or3_feature(journal_t *j)
 {
     return jbd2_has_feature_csum2(j) || jbd2_has_feature_csum3(j);
 }
 
 static inline int jbd2_journal_has_csum_v2or3(journal_t *journal)
 {
     WARN_ON_ONCE(jbd2_journal_has_csum_v2or3_feature(journal) &&
              journal->j_chksum_driver == NULL);
 
     return journal->j_chksum_driver != NULL;
 }
 
 static inline int jbd2_journal_get_num_fc_blks(journal_superblock_t *jsb)
 {
     int num_fc_blocks = be32_to_cpu(jsb->s_num_fc_blks);
 
     return num_fc_blocks ? num_fc_blocks : JBD2_DEFAULT_FAST_COMMIT_BLOCKS;
 }
 
 /*
  * Return number of free blocks in the log. Must be called under j_state_lock.
  */
 static inline unsigned long jbd2_log_space_left(journal_t *journal)
 {
     /* Allow for rounding errors */
     long free = journal->j_free - 32;
 
     if (journal->j_committing_transaction) {
         free -= atomic_read(&journal->
                         j_committing_transaction->t_outstanding_credits);
     }
     return max_t(long, free, 0);
 }
 
 /*
  * 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_Shadow   3   /* Buffer contents being shadowed to the log */
 #define BJ_Reserved 4   /* Buffer is reserved for access by journal */
 #define BJ_Types    5
 
 /* JBD uses a CRC32 checksum */
 #define JBD_MAX_CHECKSUM_SIZE 4
 
 static inline u32 jbd2_chksum(journal_t *journal, u32 crc,
                   const void *address, unsigned int length)
 {
     struct {
         struct shash_desc shash;
         char ctx[JBD_MAX_CHECKSUM_SIZE];
     } desc;
     int err;
 
     BUG_ON(crypto_shash_descsize(journal->j_chksum_driver) >
         JBD_MAX_CHECKSUM_SIZE);
 
     desc.shash.tfm = journal->j_chksum_driver;
     *(u32 *)desc.ctx = crc;
 
     err = crypto_shash_update(&desc.shash, address, length);
     BUG_ON(err);
 
     return *(u32 *)desc.ctx;
 }
 
 /* Return most recent uncommitted transaction */
 static inline tid_t  jbd2_get_latest_transaction(journal_t *journal)
 {
     tid_t tid;
 
     read_lock(&journal->j_state_lock);
     tid = journal->j_commit_request;
     if (journal->j_running_transaction)
         tid = journal->j_running_transaction->t_tid;
     read_unlock(&journal->j_state_lock);
     return tid;
 }
 
 static inline int jbd2_handle_buffer_credits(handle_t *handle)
 {
     journal_t *journal;
 
     if (!handle->h_reserved)
         journal = handle->h_transaction->t_journal;
     else
         journal = handle->h_journal;
 
     return handle->h_total_credits -
         DIV_ROUND_UP(handle->h_revoke_credits_requested,
                  journal->j_revoke_records_per_block);
 }
 
 #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__ */
 
 #define EFSBADCRC   EBADMSG     /* Bad CRC detected */
 #define EFSCORRUPTED    EUCLEAN     /* Filesystem is corrupted */
 
 #endif  /* _LINUX_JBD2_H */

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