lustre/lov/lov_cl_internal.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
 */
/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Internal interfaces of LOV layer.
 *
 *   Author: Nikita Danilov <nikita.danilov@sun.com>
 *   Author: Jinshan Xiong <jinshan.xiong@intel.com>
 */

#ifndef LOV_CL_INTERNAL_H
#define LOV_CL_INTERNAL_H

#include "../../include/linux/libcfs/libcfs.h"

#include "../include/obd.h"
#include "../include/cl_object.h"
#include "lov_internal.h"

/** \defgroup lov lov
 * Logical object volume layer. This layer implements data striping (raid0).
 *
 * At the lov layer top-entity (object, page, lock, io) is connected to one or
 * more sub-entities: top-object, representing a file is connected to a set of
 * sub-objects, each representing a stripe, file-level top-lock is connected
 * to a set of per-stripe sub-locks, top-page is connected to a (single)
 * sub-page, and a top-level IO is connected to a set of (potentially
 * concurrent) sub-IO's.
 *
 * Sub-object, sub-page, and sub-io have well-defined top-object and top-page
 * respectively, while a single sub-lock can be part of multiple top-locks.
 *
 * Reference counting models are different for different types of entities:
 *
 *     - top-object keeps a reference to its sub-objects, and destroys them
 *       when it is destroyed.
 *
 *     - top-page keeps a reference to its sub-page, and destroys it when it
 *       is destroyed.
 *
 *     - sub-lock keep a reference to its top-locks. Top-lock keeps a
 *       reference (and a hold, see cl_lock_hold()) on its sub-locks when it
 *       actively using them (that is, in cl_lock_state::CLS_QUEUING,
 *       cl_lock_state::CLS_ENQUEUED, cl_lock_state::CLS_HELD states). When
 *       moving into cl_lock_state::CLS_CACHED state, top-lock releases a
 *       hold. From this moment top-lock has only a 'weak' reference to its
 *       sub-locks. This reference is protected by top-lock
 *       cl_lock::cll_guard, and will be automatically cleared by the sub-lock
 *       when the latter is destroyed. When a sub-lock is canceled, a
 *       reference to it is removed from the top-lock array, and top-lock is
 *       moved into CLS_NEW state. It is guaranteed that all sub-locks exist
 *       while their top-lock is in CLS_HELD or CLS_CACHED states.
 *
 *     - IO's are not reference counted.
 *
 * To implement a connection between top and sub entities, lov layer is split
 * into two pieces: lov ("upper half"), and lovsub ("bottom half"), both
 * implementing full set of cl-interfaces. For example, top-object has vvp and
 * lov layers, and it's sub-object has lovsub and osc layers. lovsub layer is
 * used to track child-parent relationship.
 *
 * @{
 */

struct lovsub_device;
struct lovsub_object;
struct lovsub_lock;

enum lov_device_flags {
	LOV_DEV_INITIALIZED = 1 << 0
};

/*
 * Upper half.
 */

/**
 * Resources that are used in memory-cleaning path, and whose allocation
 * cannot fail even when memory is tight. They are preallocated in sufficient
 * quantities in lov_device::ld_emerg[], and access to them is serialized
 * lov_device::ld_mutex.
 */
struct lov_device_emerg {
	/**
	 * Page list used to submit IO when memory is in pressure.
	 */
	struct cl_page_list emrg_page_list;
	/**
	 * sub-io's shared by all threads accessing this device when memory is
	 * too low to allocate sub-io's dynamically.
	 */
	struct cl_io	emrg_subio;
	/**
	 * Environments used by sub-io's in
	 * lov_device_emerg::emrg_subio.
	 */
	struct lu_env      *emrg_env;
	/**
	 * Refchecks for lov_device_emerg::emrg_env.
	 *
	 * \see cl_env_get()
	 */
	int		 emrg_refcheck;
};

struct lov_device {
	/*
	 * XXX Locking of lov-private data is missing.
	 */
	struct cl_device	  ld_cl;
	struct lov_obd	   *ld_lov;
	/** size of lov_device::ld_target[] array */
	__u32		     ld_target_nr;
	struct lovsub_device    **ld_target;
	__u32		     ld_flags;

	/** Emergency resources used in memory-cleansing paths. */
	struct lov_device_emerg **ld_emrg;
	/**
	 * Serializes access to lov_device::ld_emrg in low-memory
	 * conditions.
	 */
	struct mutex		  ld_mutex;
};

/**
 * Layout type.
 */
enum lov_layout_type {
	LLT_EMPTY,	/** empty file without body (mknod + truncate) */
	LLT_RAID0,	/** striped file */
	LLT_RELEASED,	/** file with no objects (data in HSM) */
	LLT_NR
};

static inline char *llt2str(enum lov_layout_type llt)
{
	switch (llt) {
	case LLT_EMPTY:
		return "EMPTY";
	case LLT_RAID0:
		return "RAID0";
	case LLT_RELEASED:
		return "RELEASED";
	case LLT_NR:
		LBUG();
	}
	LBUG();
	return "";
}

/**
 * lov-specific file state.
 *
 * lov object has particular layout type, determining how top-object is built
 * on top of sub-objects. Layout type can change dynamically. When this
 * happens, lov_object::lo_type_guard semaphore is taken in exclusive mode,
 * all state pertaining to the old layout type is destroyed, and new state is
 * constructed. All object methods take said semaphore in the shared mode,
 * providing serialization against transition between layout types.
 *
 * To avoid multiple `if' or `switch' statements, selecting behavior for the
 * current layout type, object methods perform double-dispatch, invoking
 * function corresponding to the current layout type.
 */
struct lov_object {
	struct cl_object       lo_cl;
	/**
	 * Serializes object operations with transitions between layout types.
	 *
	 * This semaphore is taken in shared mode by all object methods, and
	 * is taken in exclusive mode when object type is changed.
	 *
	 * \see lov_object::lo_type
	 */
	struct rw_semaphore	lo_type_guard;
	/**
	 * Type of an object. Protected by lov_object::lo_type_guard.
	 */
	enum lov_layout_type	lo_type;
	/**
	 * True if layout is invalid. This bit is cleared when layout lock
	 * is lost.
	 */
	bool			lo_layout_invalid;
	/**
	 * How many IOs are on going on this object. Layout can be changed
	 * only if there is no active IO.
	 */
	atomic_t	       lo_active_ios;
	/**
	 * Waitq - wait for no one else is using lo_lsm
	 */
	wait_queue_head_t	       lo_waitq;
	/**
	 * Layout metadata. NULL if empty layout.
	 */
	struct lov_stripe_md  *lo_lsm;

	union lov_layout_state {
		struct lov_layout_raid0 {
			unsigned	       lo_nr;
			/**
			 * When this is true, lov_object::lo_attr contains
			 * valid up to date attributes for a top-level
			 * object. This field is reset to 0 when attributes of
			 * any sub-object change.
			 */
			int		       lo_attr_valid;
			/**
			 * Array of sub-objects. Allocated when top-object is
			 * created (lov_init_raid0()).
			 *
			 * Top-object is a strict master of its sub-objects:
			 * it is created before them, and outlives its
			 * children (this later is necessary so that basic
			 * functions like cl_object_top() always
			 * work). Top-object keeps a reference on every
			 * sub-object.
			 *
			 * When top-object is destroyed (lov_delete_raid0())
			 * it releases its reference to a sub-object and waits
			 * until the latter is finally destroyed.
			 */
			struct lovsub_object **lo_sub;
			/**
			 * protect lo_sub
			 */
			spinlock_t		lo_sub_lock;
			/**
			 * Cached object attribute, built from sub-object
			 * attributes.
			 */
			struct cl_attr	 lo_attr;
		} raid0;
		struct lov_layout_state_empty {
		} empty;
		struct lov_layout_state_released {
		} released;
	} u;
	/**
	 * Thread that acquired lov_object::lo_type_guard in an exclusive
	 * mode.
	 */
	struct task_struct	*lo_owner;
};

/**
 * Flags that top-lock can set on each of its sub-locks.
 */
enum lov_sub_flags {
	/** Top-lock acquired a hold (cl_lock_hold()) on a sub-lock. */
	LSF_HELD = 1 << 0
};

/**
 * State lov_lock keeps for each sub-lock.
 */
struct lov_lock_sub {
	/** sub-lock itself */
	struct lovsub_lock  *sub_lock;
	/** An array of per-sub-lock flags, taken from enum lov_sub_flags */
	unsigned	     sub_flags;
	int		  sub_stripe;
	struct cl_lock_descr sub_descr;
	struct cl_lock_descr sub_got;
};

/**
 * lov-specific lock state.
 */
struct lov_lock {
	struct cl_lock_slice   lls_cl;
	/** Number of sub-locks in this lock */
	int		    lls_nr;
	/**
	 * Number of existing sub-locks.
	 */
	unsigned	       lls_nr_filled;
	/**
	 * Set when sub-lock was canceled, while top-lock was being
	 * used, or unused.
	 */
	unsigned int	       lls_cancel_race:1;
	/**
	 * An array of sub-locks
	 *
	 * There are two issues with managing sub-locks:
	 *
	 *     - sub-locks are concurrently canceled, and
	 *
	 *     - sub-locks are shared with other top-locks.
	 *
	 * To manage cancellation, top-lock acquires a hold on a sublock
	 * (lov_sublock_adopt()) when the latter is inserted into
	 * lov_lock::lls_sub[]. This hold is released (lov_sublock_release())
	 * when top-lock is going into CLS_CACHED state or destroyed. Hold
	 * prevents sub-lock from cancellation.
	 *
	 * Sub-lock sharing means, among other things, that top-lock that is
	 * in the process of creation (i.e., not yet inserted into lock list)
	 * is already accessible to other threads once at least one of its
	 * sub-locks is created, see lov_lock_sub_init().
	 *
	 * Sub-lock can be in one of the following states:
	 *
	 *     - doesn't exist, lov_lock::lls_sub[]::sub_lock == NULL. Such
	 *       sub-lock was either never created (top-lock is in CLS_NEW
	 *       state), or it was created, then canceled, then destroyed
	 *       (lov_lock_unlink() cleared sub-lock pointer in the top-lock).
	 *
	 *     - sub-lock exists and is on
	 *       hold. (lov_lock::lls_sub[]::sub_flags & LSF_HELD). This is a
	 *       normal state of a sub-lock in CLS_HELD and CLS_CACHED states
	 *       of a top-lock.
	 *
	 *     - sub-lock exists, but is not held by the top-lock. This
	 *       happens after top-lock released a hold on sub-locks before
	 *       going into cache (lov_lock_unuse()).
	 *
	 * \todo To support wide-striping, array has to be replaced with a set
	 * of queues to avoid scanning.
	 */
	struct lov_lock_sub   *lls_sub;
	/**
	 * Original description with which lock was enqueued.
	 */
	struct cl_lock_descr   lls_orig;
};

struct lov_page {
	struct cl_page_slice lps_cl;
	int		  lps_invalid;
};

/*
 * Bottom half.
 */

struct lovsub_device {
	struct cl_device   acid_cl;
	struct lov_device *acid_super;
	int		acid_idx;
	struct cl_device  *acid_next;
};

struct lovsub_object {
	struct cl_object_header lso_header;
	struct cl_object	lso_cl;
	struct lov_object      *lso_super;
	int		     lso_index;
};

/**
 * A link between a top-lock and a sub-lock. Separate data-structure is
 * necessary, because top-locks and sub-locks are in M:N relationship.
 *
 * \todo This can be optimized for a (by far) most frequent case of a single
 * top-lock per sub-lock.
 */
struct lov_lock_link {
	struct lov_lock *lll_super;
	/** An index within parent lock. */
	int	      lll_idx;
	/**
	 * A linkage into per sub-lock list of all corresponding top-locks,
	 * hanging off lovsub_lock::lss_parents.
	 */
	struct list_head       lll_list;
};

/**
 * Lock state at lovsub layer.
 */
struct lovsub_lock {
	struct cl_lock_slice  lss_cl;
	/**
	 * List of top-locks that have given sub-lock as their part. Protected
	 * by cl_lock::cll_guard mutex.
	 */
	struct list_head	    lss_parents;
	/**
	 * Top-lock that initiated current operation on this sub-lock. This is
	 * only set during top-to-bottom lock operations like enqueue, and is
	 * used to optimize state change notification. Protected by
	 * cl_lock::cll_guard mutex.
	 *
	 * \see lovsub_lock_state_one().
	 */
	struct cl_lock       *lss_active;
};

/**
 * Describe the environment settings for sublocks.
 */
struct lov_sublock_env {
	const struct lu_env *lse_env;
	struct cl_io	*lse_io;
	struct lov_io_sub   *lse_sub;
};

struct lovsub_page {
	struct cl_page_slice lsb_cl;
};


struct lov_thread_info {
	struct cl_object_conf   lti_stripe_conf;
	struct lu_fid	   lti_fid;
	struct cl_lock_descr    lti_ldescr;
	struct ost_lvb	  lti_lvb;
	struct cl_2queue	lti_cl2q;
	struct cl_lock_closure  lti_closure;
	wait_queue_t	  lti_waiter;
};

/**
 * State that lov_io maintains for every sub-io.
 */
struct lov_io_sub {
	int		  sub_stripe;
	/**
	 * sub-io for a stripe. Ideally sub-io's can be stopped and resumed
	 * independently, with lov acting as a scheduler to maximize overall
	 * throughput.
	 */
	struct cl_io	*sub_io;
	/**
	 * Linkage into a list (hanging off lov_io::lis_active) of all
	 * sub-io's active for the current IO iteration.
	 */
	struct list_head	   sub_linkage;
	/**
	 * true, iff cl_io_init() was successfully executed against
	 * lov_io_sub::sub_io.
	 */
	int		  sub_io_initialized;
	/**
	 * True, iff lov_io_sub::sub_io and lov_io_sub::sub_env weren't
	 * allocated, but borrowed from a per-device emergency pool.
	 */
	int		  sub_borrowed;
	/**
	 * environment, in which sub-io executes.
	 */
	struct lu_env *sub_env;
	/**
	 * environment's refcheck.
	 *
	 * \see cl_env_get()
	 */
	int		  sub_refcheck;
	int		  sub_refcheck2;
	int		  sub_reenter;
	void		*sub_cookie;
};

/**
 * IO state private for LOV.
 */
struct lov_io {
	/** super-class */
	struct cl_io_slice lis_cl;
	/**
	 * Pointer to the object slice. This is a duplicate of
	 * lov_io::lis_cl::cis_object.
	 */
	struct lov_object *lis_object;
	/**
	 * Original end-of-io position for this IO, set by the upper layer as
	 * cl_io::u::ci_rw::pos + cl_io::u::ci_rw::count. lov remembers this,
	 * changes pos and count to fit IO into a single stripe and uses saved
	 * value to determine when IO iterations have to stop.
	 *
	 * This is used only for CIT_READ and CIT_WRITE io's.
	 */
	loff_t	     lis_io_endpos;

	/**
	 * starting position within a file, for the current io loop iteration
	 * (stripe), used by ci_io_loop().
	 */
	u64	    lis_pos;
	/**
	 * end position with in a file, for the current stripe io. This is
	 * exclusive (i.e., next offset after last byte affected by io).
	 */
	u64	    lis_endpos;

	int		lis_mem_frozen;
	int		lis_stripe_count;
	int		lis_active_subios;

	/**
	 * the index of ls_single_subio in ls_subios array
	 */
	int		lis_single_subio_index;
	struct cl_io       lis_single_subio;

	/**
	 * size of ls_subios array, actually the highest stripe #
	 */
	int		lis_nr_subios;
	struct lov_io_sub *lis_subs;
	/**
	 * List of active sub-io's.
	 */
	struct list_head	 lis_active;
};

struct lov_session {
	struct lov_io	  ls_io;
	struct lov_sublock_env ls_subenv;
};

/**
 * State of transfer for lov.
 */
struct lov_req {
	struct cl_req_slice lr_cl;
};

/**
 * State of transfer for lovsub.
 */
struct lovsub_req {
	struct cl_req_slice lsrq_cl;
};

extern struct lu_device_type lov_device_type;
extern struct lu_device_type lovsub_device_type;

extern struct lu_context_key lov_key;
extern struct lu_context_key lov_session_key;

extern struct kmem_cache *lov_lock_kmem;
extern struct kmem_cache *lov_object_kmem;
extern struct kmem_cache *lov_thread_kmem;
extern struct kmem_cache *lov_session_kmem;
extern struct kmem_cache *lov_req_kmem;

extern struct kmem_cache *lovsub_lock_kmem;
extern struct kmem_cache *lovsub_object_kmem;
extern struct kmem_cache *lovsub_req_kmem;

extern struct kmem_cache *lov_lock_link_kmem;

int   lov_object_init(const struct lu_env *env, struct lu_object *obj,
			   const struct lu_object_conf *conf);
int   lovsub_object_init(const struct lu_env *env, struct lu_object *obj,
			   const struct lu_object_conf *conf);
int   lov_lock_init(const struct lu_env *env, struct cl_object *obj,
			   struct cl_lock *lock, const struct cl_io *io);
int   lov_io_init(const struct lu_env *env, struct cl_object *obj,
			   struct cl_io *io);
int   lovsub_lock_init(const struct lu_env *env, struct cl_object *obj,
			   struct cl_lock *lock, const struct cl_io *io);

int   lov_lock_init_raid0(const struct lu_env *env, struct cl_object *obj,
			   struct cl_lock *lock, const struct cl_io *io);
int   lov_lock_init_empty(const struct lu_env *env, struct cl_object *obj,
			   struct cl_lock *lock, const struct cl_io *io);
int   lov_io_init_raid0(const struct lu_env *env, struct cl_object *obj,
			   struct cl_io *io);
int   lov_io_init_empty(const struct lu_env *env, struct cl_object *obj,
			   struct cl_io *io);
int   lov_io_init_released(const struct lu_env *env, struct cl_object *obj,
			   struct cl_io *io);
void  lov_lock_unlink(const struct lu_env *env, struct lov_lock_link *link,
			   struct lovsub_lock *sub);

struct lov_io_sub *lov_sub_get(const struct lu_env *env, struct lov_io *lio,
			       int stripe);
void  lov_sub_put(struct lov_io_sub *sub);
int   lov_sublock_modify(const struct lu_env *env, struct lov_lock *lov,
			   struct lovsub_lock *sublock,
			   const struct cl_lock_descr *d, int idx);


int   lov_page_init(const struct lu_env *env, struct cl_object *ob,
			   struct cl_page *page, struct page *vmpage);
int   lovsub_page_init(const struct lu_env *env, struct cl_object *ob,
			   struct cl_page *page, struct page *vmpage);

int   lov_page_init_empty(const struct lu_env *env,
			   struct cl_object *obj,
			   struct cl_page *page, struct page *vmpage);
int   lov_page_init_raid0(const struct lu_env *env,
			   struct cl_object *obj,
			   struct cl_page *page, struct page *vmpage);
struct lu_object *lov_object_alloc(const struct lu_env *env,
				      const struct lu_object_header *hdr,
				      struct lu_device *dev);
struct lu_object *lovsub_object_alloc(const struct lu_env *env,
				      const struct lu_object_header *hdr,
				      struct lu_device *dev);

struct lov_lock_link *lov_lock_link_find(const struct lu_env *env,
					 struct lov_lock *lck,
					 struct lovsub_lock *sub);
struct lov_io_sub    *lov_page_subio(const struct lu_env *env,
					 struct lov_io *lio,
					 const struct cl_page_slice *slice);

void lov_lsm_decref(struct lov_object *lov, struct lov_stripe_md *lsm);
struct lov_stripe_md *lov_lsm_addref(struct lov_object *lov);

#define lov_foreach_target(lov, var)		    \
	for (var = 0; var < lov_targets_nr(lov); ++var)

/*****************************************************************************
 *
 * Type conversions.
 *
 * Accessors.
 *
 */

static inline struct lov_session *lov_env_session(const struct lu_env *env)
{
	struct lov_session *ses;

	ses = lu_context_key_get(env->le_ses, &lov_session_key);
	LASSERT(ses != NULL);
	return ses;
}

static inline struct lov_io *lov_env_io(const struct lu_env *env)
{
	return &lov_env_session(env)->ls_io;
}

static inline int lov_is_object(const struct lu_object *obj)
{
	return obj->lo_dev->ld_type == &lov_device_type;
}

static inline int lovsub_is_object(const struct lu_object *obj)
{
	return obj->lo_dev->ld_type == &lovsub_device_type;
}

static inline struct lu_device *lov2lu_dev(struct lov_device *lov)
{
	return &lov->ld_cl.cd_lu_dev;
}

static inline struct lov_device *lu2lov_dev(const struct lu_device *d)
{
	LINVRNT(d->ld_type == &lov_device_type);
	return container_of0(d, struct lov_device, ld_cl.cd_lu_dev);
}

static inline struct cl_device *lovsub2cl_dev(struct lovsub_device *lovsub)
{
	return &lovsub->acid_cl;
}

static inline struct lu_device *lovsub2lu_dev(struct lovsub_device *lovsub)
{
	return &lovsub2cl_dev(lovsub)->cd_lu_dev;
}

static inline struct lovsub_device *lu2lovsub_dev(const struct lu_device *d)
{
	LINVRNT(d->ld_type == &lovsub_device_type);
	return container_of0(d, struct lovsub_device, acid_cl.cd_lu_dev);
}

static inline struct lovsub_device *cl2lovsub_dev(const struct cl_device *d)
{
	LINVRNT(d->cd_lu_dev.ld_type == &lovsub_device_type);
	return container_of0(d, struct lovsub_device, acid_cl);
}

static inline struct lu_object *lov2lu(struct lov_object *lov)
{
	return &lov->lo_cl.co_lu;
}

static inline struct cl_object *lov2cl(struct lov_object *lov)
{
	return &lov->lo_cl;
}

static inline struct lov_object *lu2lov(const struct lu_object *obj)
{
	LINVRNT(lov_is_object(obj));
	return container_of0(obj, struct lov_object, lo_cl.co_lu);
}

static inline struct lov_object *cl2lov(const struct cl_object *obj)
{
	LINVRNT(lov_is_object(&obj->co_lu));
	return container_of0(obj, struct lov_object, lo_cl);
}

static inline struct lu_object *lovsub2lu(struct lovsub_object *los)
{
	return &los->lso_cl.co_lu;
}

static inline struct cl_object *lovsub2cl(struct lovsub_object *los)
{
	return &los->lso_cl;
}

static inline struct lovsub_object *cl2lovsub(const struct cl_object *obj)
{
	LINVRNT(lovsub_is_object(&obj->co_lu));
	return container_of0(obj, struct lovsub_object, lso_cl);
}

static inline struct lovsub_object *lu2lovsub(const struct lu_object *obj)
{
	LINVRNT(lovsub_is_object(obj));
	return container_of0(obj, struct lovsub_object, lso_cl.co_lu);
}

static inline struct lovsub_lock *
cl2lovsub_lock(const struct cl_lock_slice *slice)
{
	LINVRNT(lovsub_is_object(&slice->cls_obj->co_lu));
	return container_of(slice, struct lovsub_lock, lss_cl);
}

static inline struct lovsub_lock *cl2sub_lock(const struct cl_lock *lock)
{
	const struct cl_lock_slice *slice;

	slice = cl_lock_at(lock, &lovsub_device_type);
	LASSERT(slice != NULL);
	return cl2lovsub_lock(slice);
}

static inline struct lov_lock *cl2lov_lock(const struct cl_lock_slice *slice)
{
	LINVRNT(lov_is_object(&slice->cls_obj->co_lu));
	return container_of(slice, struct lov_lock, lls_cl);
}

static inline struct lov_page *cl2lov_page(const struct cl_page_slice *slice)
{
	LINVRNT(lov_is_object(&slice->cpl_obj->co_lu));
	return container_of0(slice, struct lov_page, lps_cl);
}

static inline struct lov_req *cl2lov_req(const struct cl_req_slice *slice)
{
	return container_of0(slice, struct lov_req, lr_cl);
}

static inline struct lovsub_page *
cl2lovsub_page(const struct cl_page_slice *slice)
{
	LINVRNT(lovsub_is_object(&slice->cpl_obj->co_lu));
	return container_of0(slice, struct lovsub_page, lsb_cl);
}

static inline struct lovsub_req *cl2lovsub_req(const struct cl_req_slice *slice)
{
	return container_of0(slice, struct lovsub_req, lsrq_cl);
}

static inline struct cl_page *lov_sub_page(const struct cl_page_slice *slice)
{
	return slice->cpl_page->cp_child;
}

static inline struct lov_io *cl2lov_io(const struct lu_env *env,
				const struct cl_io_slice *ios)
{
	struct lov_io *lio;

	lio = container_of(ios, struct lov_io, lis_cl);
	LASSERT(lio == lov_env_io(env));
	return lio;
}

static inline int lov_targets_nr(const struct lov_device *lov)
{
	return lov->ld_lov->desc.ld_tgt_count;
}

static inline struct lov_thread_info *lov_env_info(const struct lu_env *env)
{
	struct lov_thread_info *info;

	info = lu_context_key_get(&env->le_ctx, &lov_key);
	LASSERT(info != NULL);
	return info;
}

static inline struct lov_layout_raid0 *lov_r0(struct lov_object *lov)
{
	LASSERT(lov->lo_type == LLT_RAID0);
	LASSERT(lov->lo_lsm->lsm_wire.lw_magic == LOV_MAGIC ||
		lov->lo_lsm->lsm_wire.lw_magic == LOV_MAGIC_V3);
	return &lov->u.raid0;
}

/** @} lov */

#endif