LU-3534 osp: send updates by separate thread

[fs/lustre-release.git] / lustre / include / dt_object.h

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
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/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2014, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */

#ifndef __LUSTRE_DT_OBJECT_H
#define __LUSTRE_DT_OBJECT_H

/** \defgroup dt dt
 * Sub-class of lu_object with methods common for "data" objects in OST stack.
 *
 * Data objects behave like regular files: you can read/write them, get and
 * set their attributes. Implementation of dt interface is supposed to
 * implement some form of garbage collection, normally reference counting
 * (nlink) based one.
 *
 * Examples: osd (lustre/osd) is an implementation of dt interface.
 * @{
 */

#include <obd_support.h>
/*
 * super-class definitions.
 */
#include <lu_object.h>

#include <libcfs/libcfs.h>

struct seq_file;
struct proc_dir_entry;
struct lustre_cfg;

struct thandle;
struct dt_device;
struct dt_object;
struct dt_index_features;
struct niobuf_local;
struct niobuf_remote;
struct ldlm_enqueue_info;

typedef enum {
        MNTOPT_USERXATTR        = 0x00000001,
        MNTOPT_ACL              = 0x00000002,
} mntopt_t;

struct dt_device_param {
        unsigned           ddp_max_name_len;
        unsigned           ddp_max_nlink;
        unsigned           ddp_block_shift;
        mntopt_t           ddp_mntopts;
        unsigned           ddp_max_ea_size;
        int                ddp_mount_type;
        unsigned long long ddp_maxbytes;
        /* percentage of available space to reserve for grant error margin */
        int                ddp_grant_reserved;
        /* per-inode space consumption */
        short              ddp_inodespace;
        /* per-fragment grant overhead to be used by client for grant
         * calculation */
        int                ddp_grant_frag;
};

/**
 * Per-transaction commit callback function
 */
struct dt_txn_commit_cb;
typedef void (*dt_cb_t)(struct lu_env *env, struct thandle *th,
                        struct dt_txn_commit_cb *cb, int err);
/**
 * Special per-transaction callback for cases when just commit callback
 * is needed and per-device callback are not convenient to use
 */
#define TRANS_COMMIT_CB_MAGIC   0xa0a00a0a
#define MAX_COMMIT_CB_STR_LEN   32

#define DCB_TRANS_STOP          0x1
struct dt_txn_commit_cb {
        struct list_head        dcb_linkage;
        dt_cb_t                 dcb_func;
        void                    *dcb_data;
        __u32                   dcb_magic;
        __u32                   dcb_flags;
        char                    dcb_name[MAX_COMMIT_CB_STR_LEN];
};

/**
 * Operations on dt device.
 */
struct dt_device_operations {
        /**
         * Return device-wide statistics.
         *
         * Return device-wide stats including block size, total and
         * free blocks, total and free objects, etc. See struct obd_statfs
         * for the details.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         * \param[out] osfs     stats information
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_statfs)(const struct lu_env *env,
                           struct dt_device *dev,
                           struct obd_statfs *osfs);

        /**
         * Create transaction.
         *
         * Create in-memory structure representing the transaction for the
         * caller. The structure returned will be used by the calling thread
         * to specify the transaction the updates belong to. Once created
         * successfully ->dt_trans_stop() must be called in any case (with
         * ->dt_trans_start() and updates or not) so that the transaction
         * handle and other resources can be released by the layers below.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         *
         * \retval pointer to handle    if creation succeeds
         * \retval ERR_PTR(errno)       if creation fails
         */
        struct thandle *(*dt_trans_create)(const struct lu_env *env,
                                           struct dt_device *dev);

        /**
         * Start transaction.
         *
         * Start the transaction. The transaction described by \a th can be
         * started only once. Another start is considered as an error.
         * A thread is not supposed to start a transaction while another
         * transaction isn't closed by the thread (though multiple handles
         * can be created). The caller should start the transaction once
         * all possible updates are declared (see the ->do_declare_* methods
         * below) and all the needed resources are reserved.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_trans_start)(const struct lu_env *env,
                                struct dt_device *dev,
                                struct thandle *th);

        /**
         * Stop transaction.
         *
         * Once stopped the transaction described by \a th is complete (all
         * the needed updates are applied) and further processing such as
         * flushing to disk, sending to another target, etc, is handled by
         * lower layers. The caller can't access this transaction by the
         * handle anymore (except from the commit callbacks, see below).
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_trans_stop)(const struct lu_env *env,
                               struct dt_device *dev,
                               struct thandle *th);

        /**
         * Add commit callback to the transaction.
         *
         * Add a commit callback to the given transaction handle. The callback
         * will be called when the associated transaction is stored. I.e. the
         * transaction will survive an event like power off if the callback did
         * run. The number of callbacks isn't limited, but you should note that
         * some disk filesystems do handle the commit callbacks in the thread
         * handling commit/flush of all the transactions, meaning that new
         * transactions are blocked from commit and flush until all the
         * callbacks are done. Also, note multiple callbacks can be running
         * concurrently using multiple CPU cores. The callbacks will be running
         * in a special environment which can not be used to pass data around.
         *
         * \param[in] th        transaction handle
         * \param[in] dcb       commit callback description
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_trans_cb_add)(struct thandle *th,
                                 struct dt_txn_commit_cb *dcb);

        /**
         * Return FID of root index object.
         *
         * Return the FID of the root object in the filesystem. This object
         * is usually provided as a bootstrap point by a disk filesystem.
         * This is up to the implementation which FID to use, though
         * [FID_SEQ_ROOT:1:0] is reserved for this purpose.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         * \param[out] fid      FID of the root object
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_root_get)(const struct lu_env *env,
                             struct dt_device *dev,
                             struct lu_fid *f);

        /**
         * Return device configuration data.
         *
         * Return device (disk fs, actually) specific configuration.
         * The configuration isn't subject to change at runtime.
         * See struct dt_device_param for the details.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         * \param[out] param    configuration parameters
         */
        void  (*dt_conf_get)(const struct lu_env *env,
                             const struct dt_device *dev,
                             struct dt_device_param *param);

        /**
         * Sync the device.
         *
         * Sync all the cached state (dirty buffers, pages, etc) to the
         * persistent storage. The method returns control once the sync is
         * complete. This operation may incur significant I/O to disk and
         * should be reserved for cases where a global sync is strictly
         * necessary.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_sync)(const struct lu_env *env,
                         struct dt_device *dev);

        /**
         * Make device read-only.
         *
         * Prevent new modifications to the device. This is a very specific
         * state where all the changes are accepted successfully and the
         * commit callbacks are called, but persistent state never changes.
         * Used only in the tests to simulate power-off scenario.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dt_ro)(const struct lu_env *env,
                       struct dt_device *dev);

        /**
         * Start transaction commit asynchronously.
         *

         * Provide a hint to the underlying filesystem that it should start
         * committing soon. The control returns immediately. It's up to the
         * layer implementing the method how soon to start committing. Usually
         * this should be throttled to some extent, otherwise the number of
         * aggregated transaction goes too high causing performance drop.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dev       dt device
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
         int   (*dt_commit_async)(const struct lu_env *env,
                                  struct dt_device *dev);
};

struct dt_index_features {
        /** required feature flags from enum dt_index_flags */
        __u32 dif_flags;
        /** minimal required key size */
        size_t dif_keysize_min;
        /** maximal required key size, 0 if no limit */
        size_t dif_keysize_max;
        /** minimal required record size */
        size_t dif_recsize_min;
        /** maximal required record size, 0 if no limit */
        size_t dif_recsize_max;
        /** pointer size for record */
        size_t dif_ptrsize;
};

enum dt_index_flags {
        /** index supports variable sized keys */
        DT_IND_VARKEY = 1 << 0,
        /** index supports variable sized records */
        DT_IND_VARREC = 1 << 1,
        /** index can be modified */
        DT_IND_UPDATE = 1 << 2,
        /** index supports records with non-unique (duplicate) keys */
        DT_IND_NONUNQ = 1 << 3,
        /**
         * index support fixed-size keys sorted with natural numerical way
         * and is able to return left-side value if no exact value found
         */
        DT_IND_RANGE = 1 << 4,
};

/**
 * Features, required from index to support file system directories (mapping
 * names to fids).
 */
extern const struct dt_index_features dt_directory_features;
extern const struct dt_index_features dt_otable_features;
extern const struct dt_index_features dt_lfsck_orphan_features;
extern const struct dt_index_features dt_lfsck_features;

/* index features supported by the accounting objects */
extern const struct dt_index_features dt_acct_features;

/* index features supported by the quota global indexes */
extern const struct dt_index_features dt_quota_glb_features;

/* index features supported by the quota slave indexes */
extern const struct dt_index_features dt_quota_slv_features;

/**
 * This is a general purpose dt allocation hint.
 * It now contains the parent object.
 * It can contain any allocation hint in the future.
 */
struct dt_allocation_hint {
        struct dt_object        *dah_parent;
        const void              *dah_eadata;
        int                     dah_eadata_len;
        __u32                   dah_mode;
};

/**
 * object type specifier.
 */

enum dt_format_type {
        DFT_REGULAR,
        DFT_DIR,
        /** for mknod */
        DFT_NODE,
        /** for special index */
        DFT_INDEX,
        /** for symbolic link */
        DFT_SYM,
};

/**
 * object format specifier.
 */
struct dt_object_format {
        /** type for dt object */
        enum dt_format_type dof_type;
        union {
                struct dof_regular {
                        int striped;
                } dof_reg;
                struct dof_dir {
                } dof_dir;
                struct dof_node {
                } dof_node;
                /**
                 * special index need feature as parameter to create
                 * special idx
                 */
                struct dof_index {
                        const struct dt_index_features *di_feat;
                } dof_idx;
        } u;
};

enum dt_format_type dt_mode_to_dft(__u32 mode);

typedef __u64 dt_obj_version_t;

union ldlm_policy_data;

/**
 * A dt_object provides common operations to create and destroy
 * objects and to manage regular and extended attributes.
 */
struct dt_object_operations {
        /**
         * Get read lock on object.
         *
         * Read lock is compatible with other read locks, so it's shared.
         * Read lock is not compatible with write lock which is exclusive.
         * The lock is blocking and can't be used from an interrupt context.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object to lock for reading
         * \param[in] role      a hint to debug locks (see kernel's mutexes)
         */
        void  (*do_read_lock)(const struct lu_env *env,
                              struct dt_object *dt,
                              unsigned role);

        /*
         * Get write lock on object.
         *
         * Write lock is exclusive and cannot be shared. The lock is blocking
         * and can't be used from an interrupt context.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object to lock for writing
         * \param[in] role      a hint to debug locks (see kernel's mutexes)
         *
         */
        void  (*do_write_lock)(const struct lu_env *env,
                               struct dt_object *dt,
                               unsigned role);

        /**
         * Release read lock.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         */
        void  (*do_read_unlock)(const struct lu_env *env,
                                struct dt_object *dt);

        /**
         * Release write lock.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         */
        void  (*do_write_unlock)(const struct lu_env *env,
                                 struct dt_object *dt);

        /**
         * Check whether write lock is held.
         *
         * The caller can learn whether write lock is held on the object
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         *
         * \retval 0            no write lock
         * \retval 1            write lock is held
         */
        int  (*do_write_locked)(const struct lu_env *env,
                                struct dt_object *dt);

        /**
         * Declare intention to request reqular attributes.
         *
         * Notity the underlying filesystem that the caller may request regular
         * attributes with ->do_attr_get() soon. This allows OSD to implement
         * prefetching logic in an object-oriented manner. The implementation
         * can be noop. This method should avoid expensive delays such as
         * waiting on disk I/O, otherwise the goal of enabling a performance
         * optimization would be defeated.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_attr_get)(const struct lu_env *env,
                                     struct dt_object *dt);

        /**
         * Return regular attributes.
         *
         * The object must exist. Currently all the attributes should be
         * returned, but in the future this can be improved so that only
         * a selected set is returned. This can improve performance as in
         * some cases attributes are stored in different places and
         * getting them all can be an iterative and expensive process.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] attr     attributes to fill
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_attr_get)(const struct lu_env *env,
                             struct dt_object *dt,
                             struct lu_attr *attr);

        /**
         * Declare intention to change regular object's attributes.
         *
         * Notify the underlying filesystem that the regular attributes may
         * change in this transaction. This enables the layer below to prepare
         * resources (e.g. journal credits in ext4).  This method should be
         * called between creating the transaction and starting it. Note that
         * the la_valid field of \a attr specifies which attributes will change.
         * The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] attr      attributes to change specified in attr.la_valid
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_attr_set)(const struct lu_env *env,
                                     struct dt_object *dt,
                                     const struct lu_attr *attr,
                                     struct thandle *th);

        /**
         * Change regular attributes.
         *
         * Change regular attributes in the given transaction. Note only
         * attributes flagged by attr.la_valid change. The object must
         * exist. If the layer implementing this method is responsible for
         * quota, then the method should maintain object accounting for the
         * given credentials when la_uid/la_gid changes.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] attr      new attributes to apply
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_attr_set)(const struct lu_env *env,
                             struct dt_object *dt,
                             const struct lu_attr *attr,
                             struct thandle *th);

        /**
         * Declare intention to request extented attribute.
         *
         * Notify the underlying filesystem that the caller may request extended
         * attribute with ->do_xattr_get() soon. This allows OSD to implement
         * prefetching logic in an object-oriented manner. The implementation
         * can be noop. This method should avoid expensive delays such as
         * waiting on disk I/O, otherwise the goal of enabling a performance
         * optimization would be defeated.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] buf       unused, may be removed in the future
         * \param[in] name      name of the extended attribute
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_xattr_get)(const struct lu_env *env,
                                      struct dt_object *dt,
                                      struct lu_buf *buf,
                                      const char *name);

        /**
         * Return a value of an extended attribute.
         *
         * The object must exist. If the buffer is NULL, then the method
         * must return the size of the value.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] buf      buffer in which to store the value
         * \param[in] name      name of the extended attribute
         *
         * \retval 0            on success
         * \retval -ERANGE      if \a buf is too small
         * \retval negative     negated errno on error
         * \retval positive     value's size if \a buf is NULL or has zero size
         */
        int   (*do_xattr_get)(const struct lu_env *env,
                              struct dt_object *dt,
                              struct lu_buf *buf,
                              const char *name);

        /**
         * Declare intention to change an extended attribute.
         *
         * Notify the underlying filesystem that the extended attribute may
         * change in this transaction.  This enables the layer below to prepare
         * resources (e.g. journal credits in ext4).  This method should be
         * called between creating the transaction and starting it. The object
         * need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] buf       buffer storing new value of the attribute
         * \param[in] name      name of the attribute
         * \param[in] fl        LU_XATTR_CREATE - fail if EA exists
         *                      LU_XATTR_REPLACE - fail if EA doesn't exist
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_xattr_set)(const struct lu_env *env,
                                      struct dt_object *dt,
                                      const struct lu_buf *buf,
                                      const char *name,
                                      int fl,
                                      struct thandle *th);

        /**
         * Set an extended attribute.
         *
         * Change or replace the specified extended attribute (EA).
         * The flags passed in \a fl dictate whether the EA is to be
         * created or replaced, as follows.
         *   LU_XATTR_CREATE - fail if EA exists
         *   LU_XATTR_REPLACE - fail if EA doesn't exist
         * The object must exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] buf       buffer storing new value of the attribute
         * \param[in] name      name of the attribute
         * \param[in] fl        flags indicating EA creation or replacement
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_xattr_set)(const struct lu_env *env,
                              struct dt_object *dt,
                              const struct lu_buf *buf,
                              const char *name,
                              int fl,
                              struct thandle *th);

        /**
         * Declare intention to delete an extended attribute.
         *
         * Notify the underlying filesystem that the extended attribute may
         * be deleted in this transaction. This enables the layer below to
         * prepare resources (e.g. journal credits in ext4).  This method
         * should be called between creating the transaction and starting it.
         * The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] name      name of the attribute
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_xattr_del)(const struct lu_env *env,
                                      struct dt_object *dt,
                                      const char *name,
                                      struct thandle *th);

        /**
         * Delete an extended attribute.
         *
         * This method deletes the specified extended attribute. The object
         * must exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] name      name of the attribute
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_xattr_del)(const struct lu_env *env,
                              struct dt_object *dt,
                              const char *name,
                              struct thandle *th);

        /**
         * Return a list of the extended attributes.
         *
         * Fills the passed buffer with a list of the extended attributes
         * found in the object. The names are separated with '\0'.
         * The object must exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] buf      buffer to put the list in
         *
         * \retval positive     bytes used/required in the buffer
         * \retval negative     negated errno on error
         */
        int   (*do_xattr_list)(const struct lu_env *env,
                               struct dt_object *dt,
                               const struct lu_buf *buf);

        /**
         * Prepare allocation hint for a new object.
         *
         * This method is used by the caller to inform OSD of the parent-child
         * relationship between two objects and enable efficient object
         * allocation. Filled allocation hint will be passed to ->do_create()
         * later.
         *
         * \param[in] env       execution environment for this thread
         * \param[out] ah       allocation hint
         * \param[in] parent    parent object (can be NULL)
         * \param[in] child     child object
         * \param[in] _mode     type of the child object
         */
        void  (*do_ah_init)(const struct lu_env *env,
                            struct dt_allocation_hint *ah,
                            struct dt_object *parent,
                            struct dt_object *child,
                            umode_t mode);

        /**
         * Declare intention to create a new object.
         *
         * Notify the underlying filesystem that the object may be created
         * in this transaction. This enables the layer below to prepare
         * resources (e.g. journal credits in ext4).  This method should be
         * called between creating the transaction and starting it.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should reserve an object for the given credentials
         * and return an error if quota is over. If object creation later
         * fails for some reason, then the reservation should be released
         * properly (usually in ->dt_trans_stop()).
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] attr      attributes of the new object
         * \param[in] hint      allocation hint
         * \param[in] dof       object format
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_create)(const struct lu_env *env,
                                   struct dt_object *dt,
                                   struct lu_attr *attr,
                                   struct dt_allocation_hint *hint,
                                   struct dt_object_format *dof,
                                   struct thandle *th);

        /**
         * Create new object.
         *
         * The method creates the object passed with the specified attributes
         * and object format. Object allocation procedure can use information
         * stored in the allocation hint. Different object formats are supported
         * (see enum dt_format_type and struct dt_object_format) depending on
         * the device. If creation succeeds, then LOHA_EXISTS flag must be set
         * in the LU-object header attributes.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should maintain object accounting for the given
         * credentials.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] attr      attributes of the new object
         * \param[in] hint      allocation hint
         * \param[in] dof       object format
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_create)(const struct lu_env *env,
                           struct dt_object *dt,
                           struct lu_attr *attr,
                           struct dt_allocation_hint *hint,
                           struct dt_object_format *dof,
                           struct thandle *th);

        /**
         * Declare intention to destroy an object.
         *
         * Notify the underlying filesystem that the object may be destroyed
         * in this transaction. This enables the layer below to prepare
         * resources (e.g. journal credits in ext4).  This method should be
         * called between creating the transaction and starting it. The object
         * need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_destroy)(const struct lu_env *env,
                                    struct dt_object *dt,
                                    struct thandle *th);

        /**
         * Destroy an object.
         *
         * This method destroys the object and all the resources associated
         * with the object (data, key/value pairs, extended attributes, etc).
         * The object must exist. If destroy is successful, then flag
         * LU_OBJECT_HEARD_BANSHEE should be set to forbid access to this
         * instance of in-core object. Any subsequent access to the same FID
         * should get another instance with no LOHA_EXIST flag set.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should maintain object accounting for the given
         * credentials.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_destroy)(const struct lu_env *env,
                            struct dt_object *dt,
                            struct thandle *th);

        /**
         * Try object as an index.
         *
         * Announce that this object is going to be used as an index. This
         * operation checks that object supports indexing operations and
         * installs appropriate dt_index_operations vector on success.
         * Also probes for features. Operation is successful if all required
         * features are supported. It's not possible to access the object
         * with index methods before ->do_index_try() returns success.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] feat      index features
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_index_try)(const struct lu_env *env,
                              struct dt_object *dt,
                              const struct dt_index_features *feat);

        /**
         * Declare intention to increment nlink count.
         *
         * Notify the underlying filesystem that the nlink regular attribute
         * be changed in this transaction. This enables the layer below to
         * prepare resources (e.g. journal credits in ext4).  This method
         * should be called between creating the transaction and starting it.
         * The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_ref_add)(const struct lu_env *env,
                                    struct dt_object *dt,
                                    struct thandle *th);

        /**
         * Increment nlink.
         *
         * Increment nlink (from the regular attributes set) in the given
         * transaction. Note the absolute limit for nlink should be learnt
         * from struct dt_device_param::ddp_max_nlink. The object must exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_ref_add)(const struct lu_env *env,
                            struct dt_object *dt, struct thandle *th);

        /**
         * Declare intention to decrement nlink count.
         *
         * Notify the underlying filesystem that the nlink regular attribute
         * be changed in this transaction. This enables the layer below to
         * prepare resources (e.g. journal credits in ext4).  This method
         * should be called between creating the transaction and starting it.
         * The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_declare_ref_del)(const struct lu_env *env,
                                    struct dt_object *dt,
                                    struct thandle *th);

        /**
         * Decrement nlink.
         *
         * Decrement nlink (from the regular attributes set) in the given
         * transaction. The object must exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*do_ref_del)(const struct lu_env *env,
                            struct dt_object *dt,
                            struct thandle *th);

        /**
         * Sync obect.
         *
         * The method is called to sync specified range of the object to a
         * persistent storage. The control is returned once the operation is
         * complete. The difference from ->do_sync() is that the object can
         * be in-sync with the persistent storage (nothing to flush), then
         * the method returns quickly with no I/O overhead. So, this method
         * should be preferred over ->do_sync() where possible. Also note that
         * if the object isn't clean, then some disk filesystems will call
         * ->do_sync() to maintain overall consistency, in which case it's
         * still very expensive.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] start     start of the range to sync
         * \param[in] end       end of the range to sync
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*do_object_sync)(const struct lu_env *env,
                              struct dt_object *obj,
                              __u64 start,
                              __u64 end);

        /**
         * Lock object.
         *
         * Lock object(s) using Distributed Lock Manager (LDLM).
         *
         * Get LDLM locks for the object. Currently used to lock "remote"
         * objects in DNE configuration - a service running on MDTx needs
         * to lock an object on MDTy.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] lh       lock handle, sometimes used, sometimes not
         * \param[in] einfo     ldlm callbacks, locking type and mode
         * \param[out] einfo    private data to be passed to unlock later
         * \param[in] policy    inodebits data
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*do_object_lock)(const struct lu_env *env, struct dt_object *dt,
                              struct lustre_handle *lh,
                              struct ldlm_enqueue_info *einfo,
                              union ldlm_policy_data *policy);

        /**
         * Unlock object.
         *
         * Release LDLM lock(s) granted with ->do_object_lock().
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] einfo     lock handles, from ->do_object_lock()
         * \param[in] policy    inodebits data
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*do_object_unlock)(const struct lu_env *env,
                                struct dt_object *dt,
                                struct ldlm_enqueue_info *einfo,
                                union ldlm_policy_data *policy);
};

/**
 * Per-dt-object operations on "file body" - unstructure raw data.
 */
struct dt_body_operations {
        /**
         * Read data.
         *
         * Read unstructured data from an existing regular object.
         * Only data before attr.la_size is returned.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] buf      buffer (including size) to copy data in
         * \param[in] pos       position in the object to start
         * \param[out] pos      original value of \a pos + bytes returned
         *
         * \retval positive     bytes read on success
         * \retval negative     negated errno on error
         */
        ssize_t (*dbo_read)(const struct lu_env *env,
                            struct dt_object *dt,
                            struct lu_buf *buf,
                            loff_t *pos);

        /**
         * Declare intention to write data to object.
         *
         * Notify the underlying filesystem that data may be written in
         * this transaction. This enables the layer below to prepare resources
         * (e.g. journal credits in ext4).  This method should be called
         * between creating the transaction and starting it. The object need
         * not exist. If the layer implementing this method is responsible for
         * quota, then the method should reserve space for the given credentials
         * and return an error if quota is over. If the write later fails
         * for some reason, then the reserve should be released properly
         * (usually in ->dt_trans_stop()).
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] buf       buffer (including size) to copy data from
         * \param[in] pos       position in the object to start
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        ssize_t (*dbo_declare_write)(const struct lu_env *env,
                                     struct dt_object *dt,
                                     const struct lu_buf *buf,
                                     loff_t pos,
                                     struct thandle *th);

        /**
         * Write unstructured data to regular existing object.
         *
         * The method allocates space and puts data in. Also, the method should
         * maintain attr.la_size properly. Partial writes are possible.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should maintain space accounting for the given
         * credentials.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] buf       buffer (including size) to copy data from
         * \param[in] pos       position in the object to start
         * \param[out] pos      \a pos + bytes written
         * \param[in] th        transaction handle
         * \param[in] ignore    unused (was used to request quota ignorance)
         *
         * \retval positive     bytes written on success
         * \retval negative     negated errno on error
         */
        ssize_t (*dbo_write)(const struct lu_env *env,
                             struct dt_object *dt,
                             const struct lu_buf *buf,
                             loff_t *pos,
                             struct thandle *th,
                             int ignore);

        /**
         * Return buffers for data.
         *
         * This method is used to access data with no copying. It's so-called
         * zero-copy I/O. The method returns the descriptors for the internal
         * buffers where data are managed by the disk filesystem. For example,
         * pagecache in case of ext4 or ARC with ZFS. Then other components
         * (e.g. networking) can transfer data from or to the buffers with no
         * additional copying.
         *
         * The method should fill an array of struct niobuf_local, where
         * each element describes a full or partial page for data at specific
         * offset. The caller should use page/lnb_page_offset/len to find data
         * at object's offset lnb_file_offset.
         *
         * The memory referenced by the descriptors can't change its purpose
         * until the complementary ->dbo_bufs_put() is called. The caller should
         * specify if the buffers are used to read or modify data so that OSD
         * can decide how to initialize the buffers: bring all the data for
         * reads or just bring partial buffers for write. Note: the method does
         * not check whether output array is large enough.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] pos       position in the object to start
         * \param[in] len       size of region in bytes
         * \param[out] lb       array of descriptors to fill
         * \param[in] rw        0 if used to read, 1 if used for write
         *
         * \retval positive     number of descriptors on success
         * \retval negative     negated errno on error
         */
        int (*dbo_bufs_get)(const struct lu_env *env,
                            struct dt_object *dt,
                            loff_t pos,
                            ssize_t len,
                            struct niobuf_local *lb,
                            int rw);

        /**
         * Release reference granted by ->dbo_bufs_get().
         *
         * Release the reference granted by the previous ->dbo_bufs_get().
         * Note the references are counted.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] lb       array of descriptors to fill
         * \param[in] nr        size of the array
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_bufs_put)(const struct lu_env *env,
                            struct dt_object *dt,
                            struct niobuf_local *lb,
                            int nr);

        /**
         * Prepare buffers for reading.
         *
         * The method is called on the given buffers to fill them with data
         * if that wasn't done in ->dbo_bufs_get(). The idea is that the
         * caller should be able to get few buffers for discontiguous regions
         * using few calls to ->dbo_bufs_get() and then request them all for
         * the preparation with a single call, so that OSD can fire many I/Os
         * to run concurrently. It's up to the specific OSD whether to implement
         * this logic in ->dbo_read_prep() or just use ->dbo_bufs_get() to
         * prepare data for every requested region individually.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] lnb       array of buffer descriptors
         * \param[in] nr        size of the array
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_read_prep)(const struct lu_env *env,
                             struct dt_object *dt,
                             struct niobuf_local *lnb,
                             int nr);

        /**
         * Prepare buffers for write.
         *
         * This method is called on the given buffers to ensure the partial
         * buffers contain correct data. The underlying idea is the same as
         * in ->db_read_prep().
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] lb        array of buffer descriptors
         * \param[in] nr        size of the array
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_write_prep)(const struct lu_env *env,
                              struct dt_object *dt,
                              struct niobuf_local *lb,
                              int nr);

        /**
         * Declare intention to write data stored in the buffers.
         *
         * Notify the underlying filesystem that data may be written in
         * this transaction. This enables the layer below to prepare resources
         * (e.g. journal credits in ext4).  This method should be called
         * between creating the transaction and starting it.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should be reserving a space for the given
         * credentials and return an error if quota is exceeded. If the write
         * later fails for some reason, then the reserve should be released
         * properly (usually in ->dt_trans_stop()).
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] lb        array of descriptors
         * \param[in] nr        size of the array
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_declare_write_commit)(const struct lu_env *env,
                                        struct dt_object *dt,
                                        struct niobuf_local *lb,
                                        int nr,
                                        struct thandle *th);

        /**
         * Write to existing object.
         *
         * This method is used to write data to a persistent storage using
         * the buffers returned by ->dbo_bufs_get(). The caller puts new
         * data into the buffers using own mechanisms (e.g. direct transfer
         * from a NIC). The method should maintain attr.la_size. Also,
         * attr.la_blocks should be maintained but this can be done in lazy
         * manner, when actual allocation happens.
         *
         * If the layer implementing this method is responsible for quota,
         * then the method should maintain space accounting for the given
         * credentials.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] lb        array of descriptors for the buffers
         * \param[in] nr        size of the array
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_write_commit)(const struct lu_env *env,
                                struct dt_object *dt,
                                struct niobuf_local *lb,
                                int nr,
                                struct thandle *th);

        /**
         * Return logical to physical block mapping for a given extent
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] fm        describe the region to map and the output buffer
         *                      see the details in include/linux/fiemap.h
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dbo_fiemap_get)(const struct lu_env *env,
                              struct dt_object *dt,
                              struct fiemap *fm);

        /**
         * Declare intention to deallocate space from an object.
         *
         * Notify the underlying filesystem that space may be deallocated in
         * this transactions. This enables the layer below to prepare resources
         * (e.g. journal credits in ext4).  This method should be called between
         * creating the transaction and starting it. The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] start     the start of the region to deallocate
         * \param[in] end       the end of the region to deallocate
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dbo_declare_punch)(const struct lu_env *env,
                                   struct dt_object *dt,
                                   __u64 start,
                                   __u64 end,
                                   struct thandle *th);

        /**
         * Deallocate specified region in an object.
         *
         * This method is used to deallocate (release) space possibly consumed
         * by the given region of the object. If the layer implementing this
         * method is responsible for quota, then the method should maintain
         * space accounting for the given credentials.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] start     the start of the region to deallocate
         * \param[in] end       the end of the region to deallocate
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int   (*dbo_punch)(const struct lu_env *env,
                           struct dt_object *dt,
                           __u64 start,
                           __u64 end,
                           struct thandle *th);
};

/**
 * Incomplete type of index record.
 */
struct dt_rec;

/**
 * Incomplete type of index key.
 */
struct dt_key;

/**
 * Incomplete type of dt iterator.
 */
struct dt_it;

/**
 * Per-dt-object operations on object as index. Index is a set of key/value
 * pairs abstracted from an on-disk representation. An index supports the
 * number of operations including lookup by key, insert and delete. Also,
 * an index can be iterated to find the pairs one by one, from a beginning
 * or specified point.
 */
struct dt_index_operations {
        /**
         * Lookup in an index by key.
         *
         * The method returns a value for the given key. Key/value format
         * and size should have been negotiated with ->do_index_try() before.
         * Thus it's the caller's responsibility to provide the method with
         * proper key and big enough buffer. No external locking is required,
         * all the internal consistency should be implemented by the method
         * or lower layers. The object should should have been created with
         * type DFT_INDEX or DFT_DIR.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[out] rec      buffer where value will be stored
         * \param[in] key       key
         *
         * \retval 0            on success
         * \retval -ENOENT      if key isn't found
         * \retval negative     negated errno on error
         */
        int (*dio_lookup)(const struct lu_env *env,
                          struct dt_object *dt,
                          struct dt_rec *rec,
                          const struct dt_key *key);

        /**
         * Declare intention to insert a key/value into an index.
         *
         * Notify the underlying filesystem that new key/value may be inserted
         * in this transaction. This enables the layer below to prepare
         * resources (e.g. journal credits in ext4). This method should be
         * called between creating the transaction and starting it. key/value
         * format and size is subject to ->do_index_try().
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] rec       buffer storing value
         * \param[in] key       key
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dio_declare_insert)(const struct lu_env *env,
                                  struct dt_object *dt,
                                  const struct dt_rec *rec,
                                  const struct dt_key *key,
                                  struct thandle *th);

        /**
         * Insert a new key/value pair into an index.
         *
         * The method inserts specified key/value pair into the given index
         * object. The internal consistency is maintained by the method or
         * the functionality below. The format and size of key/value should
         * have been negotiated before using ->do_index_try(), no additional
         * information can be specified to the method. The keys are unique
         * in a given index.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] rec       buffer storing value
         * \param[in] key       key
         * \param[in] th        transaction handle
         * \param[in] ignore    unused (was used to request quota ignorance)
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dio_insert)(const struct lu_env *env,
                          struct dt_object *dt,
                          const struct dt_rec *rec,
                          const struct dt_key *key,
                          struct thandle *th,
                          int ignore);

        /**
         * Declare intention to delete a key/value from an index.
         *
         * Notify the underlying filesystem that key/value may be deleted in
         * this transaction. This enables the layer below to prepare resources
         * (e.g. journal credits in ext4).  This method should be called
         * between creating the transaction and starting it. Key/value format
         * and size is subject to ->do_index_try(). The object need not exist.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] key       key
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dio_declare_delete)(const struct lu_env *env,
                                  struct dt_object *dt,
                                  const struct dt_key *key,
                                  struct thandle *th);

        /**
         * Delete key/value pair from an index.
         *
         * The method deletes specified key and corresponding value from the
         * given index object. The internal consistency is maintained by the
         * method or the functionality below. The format and size of the key
         * should have been negotiated before using ->do_index_try(), no
         * additional information can be specified to the method.
         *
         * \param[in] env       execution environment for this thread
         * \param[in] dt        object
         * \param[in] key       key
         * \param[in] th        transaction handle
         *
         * \retval 0            on success
         * \retval negative     negated errno on error
         */
        int (*dio_delete)(const struct lu_env *env,
                          struct dt_object *dt,
                          const struct dt_key *key,
                          struct thandle *th);

        /**
         * Iterator interface.
         *
         * Methods to iterate over an existing index, list the keys stored and
         * associated values, get key/value size, etc.
         */
        struct dt_it_ops {
                /**
                 * Allocate and initialize new iterator.
                 *
                 * The iterator is a handler to be used in the subsequent
                 * methods to access index's content. Note the position is
                 * not defined at this point and should be initialized with
                 * ->get() or ->load() method.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] dt        object
                 * \param[in] attr      ask the iterator to return part of
                                        the records, see LUDA_* for details
                 *
                 * \retval pointer      iterator pointer on success
                 * \retval ERR_PTR(errno)       on error
                 */
                struct dt_it *(*init)(const struct lu_env *env,
                                      struct dt_object *dt,
                                      __u32 attr);

                /**
                 * Release iterator.
                 *
                 * Release the specified iterator and all the resources
                 * associated (e.g. the object, index cache, etc).
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator to release
                 */
                void          (*fini)(const struct lu_env *env,
                                      struct dt_it *di);

                /**
                 * Move position of iterator.
                 *
                 * Move the position of the specified iterator to the specified
                 * key.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 * \param[in] key       key to position to
                 *
                 * \retval 0            if exact key is found
                 * \retval 1            if at the record with least key
                 *                      not larger than the key
                 * \retval negative     negated errno on error
                 */
                int            (*get)(const struct lu_env *env,
                                      struct dt_it *di,
                                      const struct dt_key *key);

                /**
                 * Release position
                 *
                 * Complimentary method for dt_it_ops::get() above. Some
                 * implementation can increase a reference on the iterator in
                 * dt_it_ops::get(). So the caller should be able to release
                 * with dt_it_ops::put().
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 */
                void           (*put)(const struct lu_env *env,
                                      struct dt_it *di);

                /**
                 * Move to next record.
                 *
                 * Moves the position of the iterator to a next record
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 *
                 * \retval 1            if no more records
                 * \retval 0            on success, the next record is found
                 * \retval negative     negated errno on error
                 */
                int           (*next)(const struct lu_env *env,
                                      struct dt_it *di);

                /**
                 * Return key.
                 *
                 * Returns a pointer to a buffer containing the key of the
                 * record at the current position. The pointer is valid and
                 * retains data until ->get(), ->load() and ->fini() methods
                 * are called.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 *
                 * \retval pointer to key       on success
                 * \retval ERR_PTR(errno)       on error
                 */
                struct dt_key *(*key)(const struct lu_env *env,
                                      const struct dt_it *di);

                /**
                 * Return key size.
                 *
                 * Returns size of the key at the current position.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 *
                 * \retval key's size   on success
                 * \retval negative     negated errno on error
                 */
                int       (*key_size)(const struct lu_env *env,
                                      const struct dt_it *di);

                /**
                 * Return record.
                 *
                 * Stores the value of the record at the current position. The
                 * buffer must be big enough (as negotiated with
                 * ->do_index_try() or ->rec_size()). The caller can specify
                 * she is interested only in part of the record, using attr
                 * argument (see LUDA_* definitions for the details).
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 * \param[out] rec      buffer to store value in
                 * \param[in] attr      specify part of the value to copy
                 *
                 * \retval 0            on success
                 * \retval negative     negated errno on error
                 */
                int            (*rec)(const struct lu_env *env,
                                      const struct dt_it *di,
                                      struct dt_rec *rec,
                                      __u32 attr);

                /**
                 * Return record size.
                 *
                 * Returns size of the record at the current position. The
                 * \a attr can be used to specify only the parts of the record
                 * needed to be returned. (see LUDA_* definitions for the
                 * details).
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 * \param[in] attr      part of the record to return
                 *
                 * \retval record's size        on success
                 * \retval negative             negated errno on error
                 */
                int        (*rec_size)(const struct lu_env *env,
                                       const struct dt_it *di,
                                      __u32 attr);

                /**
                 * Return a cookie (hash).
                 *
                 * Returns the cookie (usually hash) of the key at the current
                 * position. This allows the caller to resume iteration at this
                 * position later. The exact value is specific to implementation
                 * and should not be interpreted by the caller.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 *
                 * \retval cookie/hash of the key
                 */
                __u64        (*store)(const struct lu_env *env,
                                      const struct dt_it *di);

                /**
                 * Initialize position using cookie/hash.
                 *
                 * Initializes the current position of the iterator to one
                 * described by the cookie/hash as returned by ->store()
                 * previously.
                 *
                 * \param[in] env       execution environment for this thread
                 * \param[in] di        iterator
                 * \param[in] hash      cookie/hash value
                 *
                 * \retval positive     if current position points to
                 *                      record with least cookie not larger
                 *                      than cookie
                 * \retval 0            if current position matches cookie
                 * \retval negative     negated errno on error
                 */
                int           (*load)(const struct lu_env *env,
                                      const struct dt_it *di,
                                      __u64 hash);

                /**
                 * Not used
                 */
                int        (*key_rec)(const struct lu_env *env,
                                      const struct dt_it *di,
                                      void *key_rec);
        } dio_it;
};

enum dt_otable_it_valid {
        DOIV_ERROR_HANDLE       = 0x0001,
        DOIV_DRYRUN             = 0x0002,
};

enum dt_otable_it_flags {
        /* Exit when fail. */
        DOIF_FAILOUT    = 0x0001,

        /* Reset iteration position to the device beginning. */
        DOIF_RESET      = 0x0002,

        /* There is up layer component uses the iteration. */
        DOIF_OUTUSED    = 0x0004,

        /* Check only without repairing. */
        DOIF_DRYRUN     = 0x0008,
};

/* otable based iteration needs to use the common DT iteration APIs.
 * To initialize the iteration, it needs call dio_it::init() firstly.
 * Here is how the otable based iteration should prepare arguments to
 * call dt_it_ops::init().
 *
 * For otable based iteration, the 32-bits 'attr' for dt_it_ops::init()
 * is composed of two parts:
 * low 16-bits is for valid bits, high 16-bits is for flags bits. */
#define DT_OTABLE_IT_FLAGS_SHIFT        16
#define DT_OTABLE_IT_FLAGS_MASK         0xffff0000

struct dt_device {
        struct lu_device                   dd_lu_dev;
        const struct dt_device_operations *dd_ops;

        /**
         * List of dt_txn_callback (see below). This is not protected in any
         * way, because callbacks are supposed to be added/deleted only during
         * single-threaded start-up shut-down procedures.
         */
        struct list_head                   dd_txn_callbacks;
        unsigned int                       dd_record_fid_accessed:1;
};

int  dt_device_init(struct dt_device *dev, struct lu_device_type *t);
void dt_device_fini(struct dt_device *dev);

static inline int lu_device_is_dt(const struct lu_device *d)
{
        return ergo(d != NULL, d->ld_type->ldt_tags & LU_DEVICE_DT);
}

static inline struct dt_device * lu2dt_dev(struct lu_device *l)
{
        LASSERT(lu_device_is_dt(l));
        return container_of0(l, struct dt_device, dd_lu_dev);
}

struct dt_object {
        struct lu_object                   do_lu;
        const struct dt_object_operations *do_ops;
        const struct dt_body_operations   *do_body_ops;
        const struct dt_index_operations  *do_index_ops;
};

/*
 * In-core representation of per-device local object OID storage
 */
struct local_oid_storage {
        /* all initialized llog systems on this node linked by this */
        struct list_head  los_list;

        /* how many handle's reference this los has */
        atomic_t          los_refcount;
        struct dt_device *los_dev;
        struct dt_object *los_obj;

        /* data used to generate new fids */
        struct mutex      los_id_lock;
        __u64             los_seq;
        __u32             los_last_oid;
};

static inline struct lu_device *dt2lu_dev(struct dt_device *d)
{
        return &d->dd_lu_dev;
}

static inline struct dt_object *lu2dt(struct lu_object *l)
{
        LASSERT(l == NULL || IS_ERR(l) || lu_device_is_dt(l->lo_dev));
        return container_of0(l, struct dt_object, do_lu);
}

int  dt_object_init(struct dt_object *obj,
                    struct lu_object_header *h, struct lu_device *d);

void dt_object_fini(struct dt_object *obj);

static inline int dt_object_exists(const struct dt_object *dt)
{
        return lu_object_exists(&dt->do_lu);
}

static inline int dt_object_remote(const struct dt_object *dt)
{
        return lu_object_remote(&dt->do_lu);
}

static inline struct dt_object *lu2dt_obj(struct lu_object *o)
{
        LASSERT(ergo(o != NULL, lu_device_is_dt(o->lo_dev)));
        return container_of0(o, struct dt_object, do_lu);
}

static inline struct dt_object *dt_object_child(struct dt_object *o)
{
        return container_of0(lu_object_next(&(o)->do_lu),
                             struct dt_object, do_lu);
}

/**
 * This is the general purpose transaction handle.
 * 1. Transaction Life Cycle
 *      This transaction handle is allocated upon starting a new transaction,
 *      and deallocated after this transaction is committed.
 * 2. Transaction Nesting
 *      We do _NOT_ support nested transaction. So, every thread should only
 *      have one active transaction, and a transaction only belongs to one
 *      thread. Due to this, transaction handle need no reference count.
 * 3. Transaction & dt_object locking
 *      dt_object locks should be taken inside transaction.
 * 4. Transaction & RPC
 *      No RPC request should be issued inside transaction.
 */
struct thandle {
        /** the dt device on which the transactions are executed */
        struct dt_device *th_dev;

        /* point to the top thandle, XXX this is a bit hacky right now,
         * but normal device trans callback triggered by the bottom
         * device (OSP/OSD == sub thandle layer) needs to get the
         * top_thandle (see dt_txn_hook_start/stop()), so we put the
         * top thandle here for now, will fix it when we have better
         * callback mechanism */
        struct thandle  *th_top;
        /** context for this transaction, tag is LCT_TX_HANDLE */
        struct lu_context th_ctx;

        /** additional tags (layers can add in declare) */
        __u32             th_tags;

        /** the last operation result in this transaction.
         * this value is used in recovery */
        __s32             th_result;

        /** whether we need sync commit */
        unsigned int            th_sync:1,
        /* local transation, no need to inform other layers */
                                th_local:1,
        /* Whether we need wait the transaction to be submitted */
                                th_wait_submit:1;
};

/**
 * Transaction call-backs.
 *
 * These are invoked by osd (or underlying transaction engine) when
 * transaction changes state.
 *
 * Call-backs are used by upper layers to modify transaction parameters and to
 * perform some actions on for each transaction state transition. Typical
 * example is mdt registering call-back to write into last-received file
 * before each transaction commit.
 */
struct dt_txn_callback {
        int (*dtc_txn_start)(const struct lu_env *env,
                             struct thandle *txn, void *cookie);
        int (*dtc_txn_stop)(const struct lu_env *env,
                            struct thandle *txn, void *cookie);
        void (*dtc_txn_commit)(struct thandle *txn, void *cookie);
        void                    *dtc_cookie;
        __u32                   dtc_tag;
        struct list_head        dtc_linkage;
};

void dt_txn_callback_add(struct dt_device *dev, struct dt_txn_callback *cb);
void dt_txn_callback_del(struct dt_device *dev, struct dt_txn_callback *cb);

int dt_txn_hook_start(const struct lu_env *env,
                      struct dt_device *dev, struct thandle *txn);
int dt_txn_hook_stop(const struct lu_env *env, struct thandle *txn);
void dt_txn_hook_commit(struct thandle *txn);

int dt_try_as_dir(const struct lu_env *env, struct dt_object *obj);

/**
 * Callback function used for parsing path.
 * \see llo_store_resolve
 */
typedef int (*dt_entry_func_t)(const struct lu_env *env,
                            const char *name,
                            void *pvt);

#define DT_MAX_PATH 1024

int dt_path_parser(const struct lu_env *env,
                   char *local, dt_entry_func_t entry_func,
                   void *data);

struct dt_object *
dt_store_resolve(const struct lu_env *env, struct dt_device *dt,
                 const char *path, struct lu_fid *fid);

struct dt_object *dt_store_open(const struct lu_env *env,
                                struct dt_device *dt,
                                const char *dirname,
                                const char *filename,
                                struct lu_fid *fid);

struct dt_object *dt_find_or_create(const struct lu_env *env,
                                    struct dt_device *dt,
                                    const struct lu_fid *fid,
                                    struct dt_object_format *dof,
                                    struct lu_attr *attr);

struct dt_object *dt_locate_at(const struct lu_env *env,
                               struct dt_device *dev,
                               const struct lu_fid *fid,
                               struct lu_device *top_dev,
                               const struct lu_object_conf *conf);

static inline struct dt_object *
dt_locate(const struct lu_env *env, struct dt_device *dev,
          const struct lu_fid *fid)
{
        return dt_locate_at(env, dev, fid,
                            dev->dd_lu_dev.ld_site->ls_top_dev, NULL);
}

static inline struct dt_object *
dt_object_locate(struct dt_object *dto, struct dt_device *dt_dev)
{
        struct lu_object *lo;

        list_for_each_entry(lo, &dto->do_lu.lo_header->loh_layers, lo_linkage) {
                if (lo->lo_dev == &dt_dev->dd_lu_dev)
                        return container_of(lo, struct dt_object, do_lu);
        }
        return NULL;
}

int local_oid_storage_init(const struct lu_env *env, struct dt_device *dev,
                           const struct lu_fid *first_fid,
                           struct local_oid_storage **los);
void local_oid_storage_fini(const struct lu_env *env,
                            struct local_oid_storage *los);
int local_object_fid_generate(const struct lu_env *env,
                              struct local_oid_storage *los,
                              struct lu_fid *fid);
int local_object_declare_create(const struct lu_env *env,
                                struct local_oid_storage *los,
                                struct dt_object *o,
                                struct lu_attr *attr,
                                struct dt_object_format *dof,
                                struct thandle *th);
int local_object_create(const struct lu_env *env,
                        struct local_oid_storage *los,
                        struct dt_object *o,
                        struct lu_attr *attr, struct dt_object_format *dof,
                        struct thandle *th);
struct dt_object *local_file_find_or_create(const struct lu_env *env,
                                            struct local_oid_storage *los,
                                            struct dt_object *parent,
                                            const char *name, __u32 mode);
struct dt_object *local_file_find_or_create_with_fid(const struct lu_env *env,
                                                     struct dt_device *dt,
                                                     const struct lu_fid *fid,
                                                     struct dt_object *parent,
                                                     const char *name,
                                                     __u32 mode);
struct dt_object *
local_index_find_or_create(const struct lu_env *env,
                           struct local_oid_storage *los,
                           struct dt_object *parent,
                           const char *name, __u32 mode,
                           const struct dt_index_features *ft);
struct dt_object *
local_index_find_or_create_with_fid(const struct lu_env *env,
                                    struct dt_device *dt,
                                    const struct lu_fid *fid,
                                    struct dt_object *parent,
                                    const char *name, __u32 mode,
                                    const struct dt_index_features *ft);
int local_object_unlink(const struct lu_env *env, struct dt_device *dt,
                        struct dt_object *parent, const char *name);

static inline int dt_object_lock(const struct lu_env *env,
                                 struct dt_object *o, struct lustre_handle *lh,
                                 struct ldlm_enqueue_info *einfo,
                                 union ldlm_policy_data *policy)
{
        LASSERT(o != NULL);
        LASSERT(o->do_ops != NULL);
        LASSERT(o->do_ops->do_object_lock != NULL);
        return o->do_ops->do_object_lock(env, o, lh, einfo, policy);
}

static inline int dt_object_unlock(const struct lu_env *env,
                                   struct dt_object *o,
                                   struct ldlm_enqueue_info *einfo,
                                   union ldlm_policy_data *policy)
{
        LASSERT(o != NULL);
        LASSERT(o->do_ops != NULL);
        LASSERT(o->do_ops->do_object_unlock != NULL);
        return o->do_ops->do_object_unlock(env, o, einfo, policy);
}

int dt_lookup_dir(const struct lu_env *env, struct dt_object *dir,
                  const char *name, struct lu_fid *fid);

static inline int dt_object_sync(const struct lu_env *env, struct dt_object *o,
                                 __u64 start, __u64 end)
{
        LASSERT(o);
        LASSERT(o->do_ops);
        LASSERT(o->do_ops->do_object_sync);
        return o->do_ops->do_object_sync(env, o, start, end);
}

int dt_declare_version_set(const struct lu_env *env, struct dt_object *o,
                           struct thandle *th);
void dt_version_set(const struct lu_env *env, struct dt_object *o,
                    dt_obj_version_t version, struct thandle *th);
dt_obj_version_t dt_version_get(const struct lu_env *env, struct dt_object *o);


int dt_read(const struct lu_env *env, struct dt_object *dt,
            struct lu_buf *buf, loff_t *pos);
int dt_record_read(const struct lu_env *env, struct dt_object *dt,
                   struct lu_buf *buf, loff_t *pos);
int dt_record_write(const struct lu_env *env, struct dt_object *dt,
                    const struct lu_buf *buf, loff_t *pos, struct thandle *th);
typedef int (*dt_index_page_build_t)(const struct lu_env *env,
                                     union lu_page *lp, size_t nob,
                                     const struct dt_it_ops *iops,
                                     struct dt_it *it, __u32 attr, void *arg);
int dt_index_walk(const struct lu_env *env, struct dt_object *obj,
                  const struct lu_rdpg *rdpg, dt_index_page_build_t filler,
                  void *arg);
int dt_index_read(const struct lu_env *env, struct dt_device *dev,
                  struct idx_info *ii, const struct lu_rdpg *rdpg);

static inline struct thandle *dt_trans_create(const struct lu_env *env,
                                              struct dt_device *d)
{
        LASSERT(d->dd_ops->dt_trans_create);
        return d->dd_ops->dt_trans_create(env, d);
}

static inline int dt_trans_start(const struct lu_env *env,
                                 struct dt_device *d, struct thandle *th)
{
        LASSERT(d->dd_ops->dt_trans_start);
        return d->dd_ops->dt_trans_start(env, d, th);
}

/* for this transaction hooks shouldn't be called */
static inline int dt_trans_start_local(const struct lu_env *env,
                                       struct dt_device *d, struct thandle *th)
{
        LASSERT(d->dd_ops->dt_trans_start);
        th->th_local = 1;
        return d->dd_ops->dt_trans_start(env, d, th);
}

static inline int dt_trans_stop(const struct lu_env *env,
                                struct dt_device *d, struct thandle *th)
{
        LASSERT(d->dd_ops->dt_trans_stop);
        return d->dd_ops->dt_trans_stop(env, d, th);
}

static inline int dt_trans_cb_add(struct thandle *th,
                                  struct dt_txn_commit_cb *dcb)
{
        LASSERT(th->th_dev->dd_ops->dt_trans_cb_add);
        dcb->dcb_magic = TRANS_COMMIT_CB_MAGIC;
        return th->th_dev->dd_ops->dt_trans_cb_add(th, dcb);
}
/** @} dt */


static inline int dt_declare_record_write(const struct lu_env *env,
                                          struct dt_object *dt,
                                          const struct lu_buf *buf,
                                          loff_t pos,
                                          struct thandle *th)
{
        int rc;

        LASSERTF(dt != NULL, "dt is NULL when we want to write record\n");
        LASSERT(th != NULL);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_declare_write);
        rc = dt->do_body_ops->dbo_declare_write(env, dt, buf, pos, th);
        return rc;
}

static inline int dt_declare_create(const struct lu_env *env,
                                    struct dt_object *dt,
                                    struct lu_attr *attr,
                                    struct dt_allocation_hint *hint,
                                    struct dt_object_format *dof,
                                    struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_create);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_CREATE))
                return cfs_fail_err;

        return dt->do_ops->do_declare_create(env, dt, attr, hint, dof, th);
}

static inline int dt_create(const struct lu_env *env,
                                    struct dt_object *dt,
                                    struct lu_attr *attr,
                                    struct dt_allocation_hint *hint,
                                    struct dt_object_format *dof,
                                    struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_create);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_CREATE))
                return cfs_fail_err;

        return dt->do_ops->do_create(env, dt, attr, hint, dof, th);
}

static inline int dt_declare_destroy(const struct lu_env *env,
                                     struct dt_object *dt,
                                     struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_destroy);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_DESTROY))
                return cfs_fail_err;

        return dt->do_ops->do_declare_destroy(env, dt, th);
}

static inline int dt_destroy(const struct lu_env *env,
                             struct dt_object *dt,
                             struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_destroy);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DESTROY))
                return cfs_fail_err;

        return dt->do_ops->do_destroy(env, dt, th);
}

static inline void dt_read_lock(const struct lu_env *env,
                                struct dt_object *dt,
                                unsigned role)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_read_lock);
        dt->do_ops->do_read_lock(env, dt, role);
}

static inline void dt_write_lock(const struct lu_env *env,
                                struct dt_object *dt,
                                unsigned role)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_write_lock);
        dt->do_ops->do_write_lock(env, dt, role);
}

static inline void dt_read_unlock(const struct lu_env *env,
                                struct dt_object *dt)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_read_unlock);
        dt->do_ops->do_read_unlock(env, dt);
}

static inline void dt_write_unlock(const struct lu_env *env,
                                struct dt_object *dt)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_write_unlock);
        dt->do_ops->do_write_unlock(env, dt);
}

static inline int dt_write_locked(const struct lu_env *env,
                                  struct dt_object *dt)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_write_locked);
        return dt->do_ops->do_write_locked(env, dt);
}

static inline int dt_declare_attr_get(const struct lu_env *env,
                                      struct dt_object *dt)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_attr_get);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_ATTR_GET))
                return cfs_fail_err;

        return dt->do_ops->do_declare_attr_get(env, dt);
}

static inline int dt_attr_get(const struct lu_env *env, struct dt_object *dt,
                              struct lu_attr *la)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_attr_get);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_ATTR_GET))
                return cfs_fail_err;

        return dt->do_ops->do_attr_get(env, dt, la);
}

static inline int dt_declare_attr_set(const struct lu_env *env,
                                      struct dt_object *dt,
                                      const struct lu_attr *la,
                                      struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_attr_set);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_ATTR_SET))
                return cfs_fail_err;

        return dt->do_ops->do_declare_attr_set(env, dt, la, th);
}

static inline int dt_attr_set(const struct lu_env *env, struct dt_object *dt,
                              const struct lu_attr *la, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_attr_set);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_ATTR_SET))
                return cfs_fail_err;

        return dt->do_ops->do_attr_set(env, dt, la, th);
}

static inline int dt_declare_ref_add(const struct lu_env *env,
                                     struct dt_object *dt, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_ref_add);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_REF_ADD))
                return cfs_fail_err;

        return dt->do_ops->do_declare_ref_add(env, dt, th);
}

static inline int dt_ref_add(const struct lu_env *env,
                             struct dt_object *dt, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_ref_add);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_REF_ADD))
                return cfs_fail_err;

        return dt->do_ops->do_ref_add(env, dt, th);
}

static inline int dt_declare_ref_del(const struct lu_env *env,
                                     struct dt_object *dt, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_ref_del);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_REF_DEL))
                return cfs_fail_err;

        return dt->do_ops->do_declare_ref_del(env, dt, th);
}

static inline int dt_ref_del(const struct lu_env *env,
                             struct dt_object *dt, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_ref_del);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_REF_DEL))
                return cfs_fail_err;

        return dt->do_ops->do_ref_del(env, dt, th);
}

static inline int dt_bufs_get(const struct lu_env *env, struct dt_object *d,
                              struct niobuf_remote *rnb,
                              struct niobuf_local *lnb, int rw)
{
        LASSERT(d);
        LASSERT(d->do_body_ops);
        LASSERT(d->do_body_ops->dbo_bufs_get);
        return d->do_body_ops->dbo_bufs_get(env, d, rnb->rnb_offset,
                                            rnb->rnb_len, lnb, rw);
}

static inline int dt_bufs_put(const struct lu_env *env, struct dt_object *d,
                              struct niobuf_local *lnb, int n)
{
        LASSERT(d);
        LASSERT(d->do_body_ops);
        LASSERT(d->do_body_ops->dbo_bufs_put);
        return d->do_body_ops->dbo_bufs_put(env, d, lnb, n);
}

static inline int dt_write_prep(const struct lu_env *env, struct dt_object *d,
                                struct niobuf_local *lnb, int n)
{
        LASSERT(d);
        LASSERT(d->do_body_ops);
        LASSERT(d->do_body_ops->dbo_write_prep);
        return d->do_body_ops->dbo_write_prep(env, d, lnb, n);
}

static inline int dt_declare_write_commit(const struct lu_env *env,
                                          struct dt_object *d,
                                          struct niobuf_local *lnb,
                                          int n, struct thandle *th)
{
        LASSERTF(d != NULL, "dt is NULL when we want to declare write\n");
        LASSERT(th != NULL);
        return d->do_body_ops->dbo_declare_write_commit(env, d, lnb, n, th);
}


static inline int dt_write_commit(const struct lu_env *env,
                                  struct dt_object *d, struct niobuf_local *lnb,
                                  int n, struct thandle *th)
{
        LASSERT(d);
        LASSERT(d->do_body_ops);
        LASSERT(d->do_body_ops->dbo_write_commit);
        return d->do_body_ops->dbo_write_commit(env, d, lnb, n, th);
}

static inline int dt_read_prep(const struct lu_env *env, struct dt_object *d,
                               struct niobuf_local *lnb, int n)
{
        LASSERT(d);
        LASSERT(d->do_body_ops);
        LASSERT(d->do_body_ops->dbo_read_prep);
        return d->do_body_ops->dbo_read_prep(env, d, lnb, n);
}

static inline int dt_declare_write(const struct lu_env *env,
                                   struct dt_object *dt,
                                   const struct lu_buf *buf, loff_t pos,
                                   struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_declare_write);
        return dt->do_body_ops->dbo_declare_write(env, dt, buf, pos, th);
}

static inline ssize_t dt_write(const struct lu_env *env, struct dt_object *dt,
                               const struct lu_buf *buf, loff_t *pos,
                               struct thandle *th, int rq)
{
        LASSERT(dt);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_write);
        return dt->do_body_ops->dbo_write(env, dt, buf, pos, th, rq);
}

static inline int dt_declare_punch(const struct lu_env *env,
                                   struct dt_object *dt, __u64 start,
                                   __u64 end, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_declare_punch);
        return dt->do_body_ops->dbo_declare_punch(env, dt, start, end, th);
}

static inline int dt_punch(const struct lu_env *env, struct dt_object *dt,
                           __u64 start, __u64 end, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_body_ops);
        LASSERT(dt->do_body_ops->dbo_punch);
        return dt->do_body_ops->dbo_punch(env, dt, start, end, th);
}

static inline int dt_fiemap_get(const struct lu_env *env, struct dt_object *d,
                                struct fiemap *fm)
{
        LASSERT(d);
        if (d->do_body_ops == NULL)
                return -EPROTO;
        if (d->do_body_ops->dbo_fiemap_get == NULL)
                return -EOPNOTSUPP;
        return d->do_body_ops->dbo_fiemap_get(env, d, fm);
}

static inline int dt_statfs(const struct lu_env *env, struct dt_device *dev,
                            struct obd_statfs *osfs)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_statfs);
        return dev->dd_ops->dt_statfs(env, dev, osfs);
}

static inline int dt_root_get(const struct lu_env *env, struct dt_device *dev,
                              struct lu_fid *f)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_root_get);
        return dev->dd_ops->dt_root_get(env, dev, f);
}

static inline void dt_conf_get(const struct lu_env *env,
                               const struct dt_device *dev,
                               struct dt_device_param *param)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_conf_get);
        return dev->dd_ops->dt_conf_get(env, dev, param);
}

static inline int dt_sync(const struct lu_env *env, struct dt_device *dev)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_sync);
        return dev->dd_ops->dt_sync(env, dev);
}

static inline int dt_ro(const struct lu_env *env, struct dt_device *dev)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_ro);
        return dev->dd_ops->dt_ro(env, dev);
}

static inline int dt_declare_insert(const struct lu_env *env,
                                    struct dt_object *dt,
                                    const struct dt_rec *rec,
                                    const struct dt_key *key,
                                    struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_index_ops);
        LASSERT(dt->do_index_ops->dio_declare_insert);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_INSERT))
                return cfs_fail_err;

        return dt->do_index_ops->dio_declare_insert(env, dt, rec, key, th);
}

static inline int dt_insert(const struct lu_env *env,
                                    struct dt_object *dt,
                                    const struct dt_rec *rec,
                                    const struct dt_key *key,
                                    struct thandle *th,
                                    int noquota)
{
        LASSERT(dt);
        LASSERT(dt->do_index_ops);
        LASSERT(dt->do_index_ops->dio_insert);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_INSERT))
                return cfs_fail_err;

        return dt->do_index_ops->dio_insert(env, dt, rec, key, th, noquota);
}

static inline int dt_declare_xattr_del(const struct lu_env *env,
                                       struct dt_object *dt,
                                       const char *name,
                                       struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_xattr_del);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_XATTR_DEL))
                return cfs_fail_err;

        return dt->do_ops->do_declare_xattr_del(env, dt, name, th);
}

static inline int dt_xattr_del(const struct lu_env *env,
                               struct dt_object *dt, const char *name,
                               struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_xattr_del);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_XATTR_DEL))
                return cfs_fail_err;

        return dt->do_ops->do_xattr_del(env, dt, name, th);
}

static inline int dt_declare_xattr_set(const struct lu_env *env,
                                      struct dt_object *dt,
                                      const struct lu_buf *buf,
                                      const char *name, int fl,
                                      struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_xattr_set);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_XATTR_SET))
                return cfs_fail_err;

        return dt->do_ops->do_declare_xattr_set(env, dt, buf, name, fl, th);
}

static inline int dt_xattr_set(const struct lu_env *env,
                               struct dt_object *dt, const struct lu_buf *buf,
                               const char *name, int fl, struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_xattr_set);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_XATTR_SET))
                return cfs_fail_err;

        return dt->do_ops->do_xattr_set(env, dt, buf, name, fl, th);
}

static inline int dt_declare_xattr_get(const struct lu_env *env,
                                       struct dt_object *dt,
                                       struct lu_buf *buf,
                                       const char *name)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_declare_xattr_get);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_XATTR_GET))
                return cfs_fail_err;

        return dt->do_ops->do_declare_xattr_get(env, dt, buf, name);
}

static inline int dt_xattr_get(const struct lu_env *env,
                               struct dt_object *dt, struct lu_buf *buf,
                               const char *name)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_xattr_get);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_XATTR_GET))
                return cfs_fail_err;

        return dt->do_ops->do_xattr_get(env, dt, buf, name);
}

static inline int dt_xattr_list(const struct lu_env *env, struct dt_object *dt,
                                const struct lu_buf *buf)
{
        LASSERT(dt);
        LASSERT(dt->do_ops);
        LASSERT(dt->do_ops->do_xattr_list);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_XATTR_LIST))
                return cfs_fail_err;

        return dt->do_ops->do_xattr_list(env, dt, buf);
}

static inline int dt_declare_delete(const struct lu_env *env,
                                    struct dt_object *dt,
                                    const struct dt_key *key,
                                    struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_index_ops);
        LASSERT(dt->do_index_ops->dio_declare_delete);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DECLARE_DELETE))
                return cfs_fail_err;

        return dt->do_index_ops->dio_declare_delete(env, dt, key, th);
}

static inline int dt_delete(const struct lu_env *env,
                            struct dt_object *dt,
                            const struct dt_key *key,
                            struct thandle *th)
{
        LASSERT(dt);
        LASSERT(dt->do_index_ops);
        LASSERT(dt->do_index_ops->dio_delete);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_DELETE))
                return cfs_fail_err;

        return dt->do_index_ops->dio_delete(env, dt, key, th);
}

static inline int dt_commit_async(const struct lu_env *env,
                                  struct dt_device *dev)
{
        LASSERT(dev);
        LASSERT(dev->dd_ops);
        LASSERT(dev->dd_ops->dt_commit_async);
        return dev->dd_ops->dt_commit_async(env, dev);
}

static inline int dt_lookup(const struct lu_env *env,
                            struct dt_object *dt,
                            struct dt_rec *rec,
                            const struct dt_key *key)
{
        int ret;

        LASSERT(dt);
        LASSERT(dt->do_index_ops);
        LASSERT(dt->do_index_ops->dio_lookup);

        if (CFS_FAULT_CHECK(OBD_FAIL_DT_LOOKUP))
                return cfs_fail_err;

        ret = dt->do_index_ops->dio_lookup(env, dt, rec, key);
        if (ret > 0)
                ret = 0;
        else if (ret == 0)
                ret = -ENOENT;
        return ret;
}

#define LU221_BAD_TIME (0x80000000U + 24 * 3600)

struct dt_find_hint {
        struct lu_fid        *dfh_fid;
        struct dt_device     *dfh_dt;
        struct dt_object     *dfh_o;
};

struct dt_insert_rec {
        union {
                const struct lu_fid     *rec_fid;
                void                    *rec_data;
        };
        union {
                struct {
                        __u32            rec_type;
                        __u32            rec_padding;
                };
                __u64                    rec_misc;
        };
};

struct dt_thread_info {
        char                     dti_buf[DT_MAX_PATH];
        struct dt_find_hint      dti_dfh;
        struct lu_attr           dti_attr;
        struct lu_fid            dti_fid;
        struct dt_object_format  dti_dof;
        struct lustre_mdt_attrs  dti_lma;
        struct lu_buf            dti_lb;
        struct lu_object_conf    dti_conf;
        loff_t                   dti_off;
        struct dt_insert_rec     dti_dt_rec;
};

extern struct lu_context_key dt_key;

static inline struct dt_thread_info *dt_info(const struct lu_env *env)
{
        struct dt_thread_info *dti;

        dti = lu_context_key_get(&env->le_ctx, &dt_key);
        LASSERT(dti);
        return dti;
}

int dt_global_init(void);
void dt_global_fini(void);

# ifdef CONFIG_PROC_FS
int lprocfs_dt_blksize_seq_show(struct seq_file *m, void *v);
int lprocfs_dt_kbytestotal_seq_show(struct seq_file *m, void *v);
int lprocfs_dt_kbytesfree_seq_show(struct seq_file *m, void *v);
int lprocfs_dt_kbytesavail_seq_show(struct seq_file *m, void *v);
int lprocfs_dt_filestotal_seq_show(struct seq_file *m, void *v);
int lprocfs_dt_filesfree_seq_show(struct seq_file *m, void *v);
# endif /* CONFIG_PROC_FS */

#endif /* __LUSTRE_DT_OBJECT_H */