text: // SPDX-License-Identifier: GPL-2.0
  /*
   * 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.gnu.org/licenses/gpl-2.0.html
   *
   * GPL HEADER END
   */
  /*
   * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
   * Use is subject to license terms.
   *
   * Copyright (c) 2011, 2015, Intel Corporation.
   */
  /*
   * This file is part of Lustre, http://www.lustre.org/
   * Lustre is a trademark of Sun Microsystems, Inc.
   */
  
  #ifndef __LUSTRE_LU_OBJECT_H
  #define __LUSTRE_LU_OBJECT_H
  
  #include <stdarg.h>
  #include <linux/percpu_counter.h>
  #include <linux/libcfs/libcfs.h>
  #include <uapi/linux/lustre/lustre_idl.h>
  #include <lu_ref.h>
  
  struct seq_file;
  struct lustre_cfg;
  struct lprocfs_stats;
  
  /** \defgroup lu lu
   * lu_* data-types represent server-side entities shared by data and meta-data
   * stacks.
   *
   * Design goals:
   *
   * -# support for layering.
   *
   *     Server side object is split into layers, one per device in the
   *     corresponding device stack. Individual layer is represented by struct
   *     lu_object. Compound layered object --- by struct lu_object_header. Most
   *     interface functions take lu_object as an argument and operate on the
   *     whole compound object. This decision was made due to the following
   *     reasons:
   *
   *	- it's envisaged that lu_object will be used much more often than
   *	lu_object_header;
   *
   *	- we want lower (non-top) layers to be able to initiate operations
   *	on the whole object.
   *
   *     Generic code supports layering more complex than simple stacking, e.g.,
   *     it is possible that at some layer object "spawns" multiple sub-objects
   *     on the lower layer.
   *
   * -# fid-based identification.
   *
   *     Compound object is uniquely identified by its fid. Objects are indexed
   *     by their fids (hash table is used for index).
   *
   * -# caching and life-cycle management.
   *
   *     Object's life-time is controlled by reference counting. When reference
   *     count drops to 0, object is returned to cache. Cached objects still
   *     retain their identity (i.e., fid), and can be recovered from cache.
   *
   *     Objects are kept in the global LRU list, and lu_site_purge() function
   *     can be used to reclaim given number of unused objects from the tail of
   *     the LRU.
   *
   * -# avoiding recursion.
   *
   *     Generic code tries to replace recursion through layers by iterations
   *     where possible. Additionally to the end of reducing stack consumption,
   *     data, when practically possible, are allocated through lu_context_key
   *     interface rather than on stack.
   * @{
   */
  
  struct lu_site;
  struct lu_object;
  struct lu_device;
  struct lu_object_header;
  struct lu_context;
  struct lu_env;
  
  /**
   * Operations common for data and meta-data devices.
   */
  struct lu_device_operations {
  	/**
  	 * Allocate object for the given device (without lower-layer
  	 * parts). This is called by lu_object_operations::loo_object_init()
  	 * from the parent layer, and should setup at least lu_object::lo_dev
  	 * and lu_object::lo_ops fields of resulting lu_object.
  	 *
  	 * Object creation protocol.
  	 *
  	 * Due to design goal of avoiding recursion, object creation (see
  	 * lu_object_alloc()) is somewhat involved:
  	 *
  	 *  - first, lu_device_operations::ldo_object_alloc() method of the
  	 *  top-level device in the stack is called. It should allocate top
  	 *  level object (including lu_object_header), but without any
  	 *  lower-layer sub-object(s).
  	 *
  	 *  - then lu_object_alloc() sets fid in the header of newly created
  	 *  object.
  	 *
  	 *  - then lu_object_operations::loo_object_init() is called. It has
  	 *  to allocate lower-layer object(s). To do this,
  	 *  lu_object_operations::loo_object_init() calls ldo_object_alloc()
  	 *  of the lower-layer device(s).
  	 *
  	 *  - for all new objects allocated by
  	 *  lu_object_operations::loo_object_init() (and inserted into object
  	 *  stack), lu_object_operations::loo_object_init() is called again
  	 *  repeatedly, until no new objects are created.
  	 *
  	 * \post ergo(!IS_ERR(result), result->lo_dev == d &&
  	 *			     result->lo_ops != NULL);
  	 */
  	struct lu_object *(*ldo_object_alloc)(const struct lu_env *env,
  					      const struct lu_object_header *h,
  					      struct lu_device *d);
  	/**
  	 * process config specific for device.
  	 */
  	int (*ldo_process_config)(const struct lu_env *env,
  				  struct lu_device *, struct lustre_cfg *);
  	int (*ldo_recovery_complete)(const struct lu_env *,
  				     struct lu_device *);
  
  	/**
  	 * initialize local objects for device. this method called after layer
  	 * has been initialized (after LCFG_SETUP stage) and before it starts
  	 * serving user requests.
  	 */
  
  	int (*ldo_prepare)(const struct lu_env *,
  			   struct lu_device *parent,
  			   struct lu_device *dev);
  
  };
  
  /**
   * For lu_object_conf flags
   */
  enum loc_flags {
  	/* This is a new object to be allocated, or the file
  	 * corresponding to the object does not exists.
  	 */
  	LOC_F_NEW	= 0x00000001,
  };
  
  /**
   * Object configuration, describing particulars of object being created. On
   * server this is not used, as server objects are full identified by fid. On
   * client configuration contains struct lustre_md.
   */
  struct lu_object_conf {
  	/**
  	 * Some hints for obj find and alloc.
  	 */
  	enum loc_flags     loc_flags;
  };
  
  /**
   * Type of "printer" function used by lu_object_operations::loo_object_print()
   * method.
   *
   * Printer function is needed to provide some flexibility in (semi-)debugging
   * output: possible implementations: printk, CDEBUG, sysfs/seq_file
   */
  typedef int (*lu_printer_t)(const struct lu_env *env,
  			    void *cookie, const char *format, ...)
  	__printf(3, 4);
  
  /**
   * Operations specific for particular lu_object.
   */
  struct lu_object_operations {
  	/**
  	 * Allocate lower-layer parts of the object by calling
  	 * lu_device_operations::ldo_object_alloc() of the corresponding
  	 * underlying device.
  	 *
  	 * This method is called once for each object inserted into object
  	 * stack. It's responsibility of this method to insert lower-layer
  	 * object(s) it create into appropriate places of object stack.
  	 */
  	int (*loo_object_init)(const struct lu_env *env,
  			       struct lu_object *o,
  			       const struct lu_object_conf *conf);
  	/**
  	 * Called (in top-to-bottom order) during object allocation after all
  	 * layers were allocated and initialized. Can be used to perform
  	 * initialization depending on lower layers.
  	 */
  	int (*loo_object_start)(const struct lu_env *env,
  				struct lu_object *o);
  	/**
  	 * Called before lu_object_operations::loo_object_free() to signal
  	 * that object is being destroyed. Dual to
  	 * lu_object_operations::loo_object_init().
  	 */
  	void (*loo_object_delete)(const struct lu_env *env,
  				  struct lu_object *o);
  	/**
  	 * Dual to lu_device_operations::ldo_object_alloc(). Called when
  	 * object is removed from memory.
  	 */
  	void (*loo_object_free)(const struct lu_env *env,
  				struct lu_object *o);
  	/**
  	 * Called when last active reference to the object is released (and
  	 * object returns to the cache). This method is optional.
  	 */
  	void (*loo_object_release)(const struct lu_env *env,
  				   struct lu_object *o);
  	/**
  	 * Optional debugging helper. Print given object.
  	 */
  	int (*loo_object_print)(const struct lu_env *env, void *cookie,
  				lu_printer_t p, const struct lu_object *o);
  	/**
  	 * Optional debugging method. Returns true iff method is internally
  	 * consistent.
  	 */
  	int (*loo_object_invariant)(const struct lu_object *o);
  };
  
  /**
   * Type of lu_device.
   */
  struct lu_device_type;
  
  /**
   * Device: a layer in the server side abstraction stacking.
   */
  struct lu_device {
  	/**
  	 * reference count. This is incremented, in particular, on each object
  	 * created at this layer.
  	 *
  	 * \todo XXX which means that atomic_t is probably too small.
  	 */
  	atomic_t		       ld_ref;
  	/**
  	 * Pointer to device type. Never modified once set.
  	 */
  	struct lu_device_type       *ld_type;
  	/**
  	 * Operation vector for this device.
  	 */
  	const struct lu_device_operations *ld_ops;
  	/**
  	 * Stack this device belongs to.
  	 */
  	struct lu_site		    *ld_site;
  
  	/** \todo XXX: temporary back pointer into obd. */
  	struct obd_device		 *ld_obd;
  	/**
  	 * A list of references to this object, for debugging.
  	 */
  	struct lu_ref		      ld_reference;
  	/**
  	 * Link the device to the site.
  	 **/
  	struct list_head			 ld_linkage;
  };
  
  struct lu_device_type_operations;
  
  /**
   * Tag bits for device type. They are used to distinguish certain groups of
   * device types.
   */
  enum lu_device_tag {
  	/** this is meta-data device */
  	LU_DEVICE_MD = (1 << 0),
  	/** this is data device */
  	LU_DEVICE_DT = (1 << 1),
  	/** data device in the client stack */
  	LU_DEVICE_CL = (1 << 2)
  };
  
  /**
   * Type of device.
   */
  struct lu_device_type {
  	/**
  	 * Tag bits. Taken from enum lu_device_tag. Never modified once set.
  	 */
  	__u32				   ldt_tags;
  	/**
  	 * Name of this class. Unique system-wide. Never modified once set.
  	 */
  	char				   *ldt_name;
  	/**
  	 * Operations for this type.
  	 */
  	const struct lu_device_type_operations *ldt_ops;
  	/**
  	 * \todo XXX: temporary pointer to associated obd_type.
  	 */
  	struct obd_type			*ldt_obd_type;
  	/**
  	 * \todo XXX: temporary: context tags used by obd_*() calls.
  	 */
  	__u32				   ldt_ctx_tags;
  	/**
  	 * Number of existing device type instances.
  	 */
  	atomic_t				ldt_device_nr;
  	/**
  	 * Linkage into a global list of all device types.
  	 *
  	 * \see lu_device_types.
  	 */
  	struct list_head			      ldt_linkage;
  };
  
  /**
   * Operations on a device type.
   */
  struct lu_device_type_operations {
  	/**
  	 * Allocate new device.
  	 */
  	struct lu_device *(*ldto_device_alloc)(const struct lu_env *env,
  					       struct lu_device_type *t,
  					       struct lustre_cfg *lcfg);
  	/**
  	 * Free device. Dual to
  	 * lu_device_type_operations::ldto_device_alloc(). Returns pointer to
  	 * the next device in the stack.
  	 */
  	struct lu_device *(*ldto_device_free)(const struct lu_env *,
  					      struct lu_device *);
  
  	/**
  	 * Initialize the devices after allocation
  	 */
  	int  (*ldto_device_init)(const struct lu_env *env,
  				 struct lu_device *, const char *,
  				 struct lu_device *);
  	/**
  	 * Finalize device. Dual to
  	 * lu_device_type_operations::ldto_device_init(). Returns pointer to
  	 * the next device in the stack.
  	 */
  	struct lu_device *(*ldto_device_fini)(const struct lu_env *env,
  					      struct lu_device *);
  	/**
  	 * Initialize device type. This is called on module load.
  	 */
  	int  (*ldto_init)(struct lu_device_type *t);
  	/**
  	 * Finalize device type. Dual to
  	 * lu_device_type_operations::ldto_init(). Called on module unload.
  	 */
  	void (*ldto_fini)(struct lu_device_type *t);
  	/**
  	 * Called when the first device is created.
  	 */
  	void (*ldto_start)(struct lu_device_type *t);
  	/**
  	 * Called when number of devices drops to 0.
  	 */
  	void (*ldto_stop)(struct lu_device_type *t);
  };
  
  static inline int lu_device_is_md(const struct lu_device *d)
  {
  	return ergo(d, d->ld_type->ldt_tags & LU_DEVICE_MD);
  }
  
  /**
   * Common object attributes.
   */
  struct lu_attr {
  	/** size in bytes */
  	__u64	  la_size;
  	/** modification time in seconds since Epoch */
  	s64	  la_mtime;
  	/** access time in seconds since Epoch */
  	s64	  la_atime;
  	/** change time in seconds since Epoch */
  	s64	  la_ctime;
  	/** 512-byte blocks allocated to object */
  	__u64	  la_blocks;
  	/** permission bits and file type */
  	__u32	  la_mode;
  	/** owner id */
  	__u32	  la_uid;
  	/** group id */
  	__u32	  la_gid;
  	/** object flags */
  	__u32	  la_flags;
  	/** number of persistent references to this object */
  	__u32	  la_nlink;
  	/** blk bits of the object*/
  	__u32	  la_blkbits;
  	/** blk size of the object*/
  	__u32	  la_blksize;
  	/** real device */
  	__u32	  la_rdev;
  	/**
  	 * valid bits
  	 *
  	 * \see enum la_valid
  	 */
  	__u64	  la_valid;
  };
  
  /** Bit-mask of valid attributes */
  enum la_valid {
  	LA_ATIME = 1 << 0,
  	LA_MTIME = 1 << 1,
  	LA_CTIME = 1 << 2,
  	LA_SIZE  = 1 << 3,
  	LA_MODE  = 1 << 4,
  	LA_UID   = 1 << 5,
  	LA_GID   = 1 << 6,
  	LA_BLOCKS = 1 << 7,
  	LA_TYPE   = 1 << 8,
  	LA_FLAGS  = 1 << 9,
  	LA_NLINK  = 1 << 10,
  	LA_RDEV   = 1 << 11,
  	LA_BLKSIZE = 1 << 12,
  	LA_KILL_SUID = 1 << 13,
  	LA_KILL_SGID = 1 << 14,
  };
  
  /**
   * Layer in the layered object.
   */
  struct lu_object {
  	/**
  	 * Header for this object.
  	 */
  	struct lu_object_header	   *lo_header;
  	/**
  	 * Device for this layer.
  	 */
  	struct lu_device		  *lo_dev;
  	/**
  	 * Operations for this object.
  	 */
  	const struct lu_object_operations *lo_ops;
  	/**
  	 * Linkage into list of all layers.
  	 */
  	struct list_head			 lo_linkage;
  	/**
  	 * Link to the device, for debugging.
  	 */
  	struct lu_ref_link                 lo_dev_ref;
  };
  
  enum lu_object_header_flags {
  	/**
  	 * Don't keep this object in cache. Object will be destroyed as soon
  	 * as last reference to it is released. This flag cannot be cleared
  	 * once set.
  	 */
  	LU_OBJECT_HEARD_BANSHEE = 0,
  	/**
  	 * Mark this object has already been taken out of cache.
  	 */
  	LU_OBJECT_UNHASHED = 1,
  };
  
  enum lu_object_header_attr {
  	LOHA_EXISTS   = 1 << 0,
  	LOHA_REMOTE   = 1 << 1,
  	/**
  	 * UNIX file type is stored in S_IFMT bits.
  	 */
  	LOHA_FT_START = 001 << 12, /**< S_IFIFO */
  	LOHA_FT_END   = 017 << 12, /**< S_IFMT */
  };
  
  /**
   * "Compound" object, consisting of multiple layers.
   *
   * Compound object with given fid is unique with given lu_site.
   *
   * Note, that object does *not* necessary correspond to the real object in the
   * persistent storage: object is an anchor for locking and method calling, so
   * it is created for things like not-yet-existing child created by mkdir or
   * create calls. lu_object_operations::loo_exists() can be used to check
   * whether object is backed by persistent storage entity.
   */
  struct lu_object_header {
  	/**
  	 * Fid, uniquely identifying this object.
  	 */
  	struct lu_fid		loh_fid;
  	/**
  	 * Object flags from enum lu_object_header_flags. Set and checked
  	 * atomically.
  	 */
  	unsigned long	  loh_flags;
  	/**
  	 * Object reference count. Protected by lu_site::ls_guard.
  	 */
  	atomic_t	   loh_ref;
  	/**
  	 * Common object attributes, cached for efficiency. From enum
  	 * lu_object_header_attr.
  	 */
  	__u32		  loh_attr;
  	/**
  	 * Linkage into per-site hash table. Protected by lu_site::ls_guard.
  	 */
  	struct hlist_node       loh_hash;
  	/**
  	 * Linkage into per-site LRU list. Protected by lu_site::ls_guard.
  	 */
  	struct list_head	     loh_lru;
  	/**
  	 * Linkage into list of layers. Never modified once set (except lately
  	 * during object destruction). No locking is necessary.
  	 */
  	struct list_head	     loh_layers;
  	/**
  	 * A list of references to this object, for debugging.
  	 */
  	struct lu_ref	  loh_reference;
  };
  
  struct fld;
  
  struct lu_site_bkt_data {
  	/**
  	 * number of object in this bucket on the lsb_lru list.
  	 */
  	long			lsb_lru_len;
  	/**
  	 * LRU list, updated on each access to object. Protected by
  	 * bucket lock of lu_site::ls_obj_hash.
  	 *
  	 * "Cold" end of LRU is lu_site::ls_lru.next. Accessed object are
  	 * moved to the lu_site::ls_lru.prev (this is due to the non-existence
  	 * of list_for_each_entry_safe_reverse()).
  	 */
  	struct list_head		lsb_lru;
  	/**
  	 * Wait-queue signaled when an object in this site is ultimately
  	 * destroyed (lu_object_free()). It is used by lu_object_find() to
  	 * wait before re-trying when object in the process of destruction is
  	 * found in the hash table.
  	 *
  	 * \see htable_lookup().
  	 */
  	wait_queue_head_t	       lsb_marche_funebre;
  };
  
  enum {
  	LU_SS_CREATED	 = 0,
  	LU_SS_CACHE_HIT,
  	LU_SS_CACHE_MISS,
  	LU_SS_CACHE_RACE,
  	LU_SS_CACHE_DEATH_RACE,
  	LU_SS_LRU_PURGED,
  	LU_SS_LAST_STAT
  };
  
  /**
   * lu_site is a "compartment" within which objects are unique, and LRU
   * discipline is maintained.
   *
   * lu_site exists so that multiple layered stacks can co-exist in the same
   * address space.
   *
   * lu_site has the same relation to lu_device as lu_object_header to
   * lu_object.
   */
  struct lu_site {
  	/**
  	 * objects hash table
  	 */
  	struct cfs_hash	       *ls_obj_hash;
  	/**
  	 * index of bucket on hash table while purging
  	 */
  	unsigned int		ls_purge_start;
  	/**
  	 * Top-level device for this stack.
  	 */
  	struct lu_device	 *ls_top_dev;
  	/**
  	 * Bottom-level device for this stack
  	 */
  	struct lu_device	*ls_bottom_dev;
  	/**
  	 * Linkage into global list of sites.
  	 */
  	struct list_head		ls_linkage;
  	/**
  	 * List for lu device for this site, protected
  	 * by ls_ld_lock.
  	 **/
  	struct list_head		ls_ld_linkage;
  	spinlock_t		ls_ld_lock;
  
  	/**
  	 * Lock to serialize site purge.
  	 */
  	struct mutex		ls_purge_mutex;
  
  	/**
  	 * lu_site stats
  	 */
  	struct lprocfs_stats	*ls_stats;
  	/**
  	 * XXX: a hack! fld has to find md_site via site, remove when possible
  	 */
  	struct seq_server_site	*ld_seq_site;
  	/**
  	 * Number of objects in lsb_lru_lists - used for shrinking
  	 */
  	struct percpu_counter	 ls_lru_len_counter;
  };
  
  static inline struct lu_site_bkt_data *
  lu_site_bkt_from_fid(struct lu_site *site, struct lu_fid *fid)
  {
  	struct cfs_hash_bd bd;
  
  	cfs_hash_bd_get(site->ls_obj_hash, fid, &bd);
  	return cfs_hash_bd_extra_get(site->ls_obj_hash, &bd);
  }
  
  static inline struct seq_server_site *lu_site2seq(const struct lu_site *s)
  {
  	return s->ld_seq_site;
  }
  
  /** \name ctors
   * Constructors/destructors.
   * @{
   */
  
  int lu_site_init(struct lu_site *s, struct lu_device *d);
  void lu_site_fini(struct lu_site *s);
  int lu_site_init_finish(struct lu_site *s);
  void lu_stack_fini(const struct lu_env *env, struct lu_device *top);
  void lu_device_get(struct lu_device *d);
  void lu_device_put(struct lu_device *d);
  int lu_device_init(struct lu_device *d, struct lu_device_type *t);
  void lu_device_fini(struct lu_device *d);
  int lu_object_header_init(struct lu_object_header *h);
  void lu_object_header_fini(struct lu_object_header *h);
  int lu_object_init(struct lu_object *o,
  		   struct lu_object_header *h, struct lu_device *d);
  void lu_object_fini(struct lu_object *o);
  void lu_object_add_top(struct lu_object_header *h, struct lu_object *o);
  void lu_object_add(struct lu_object *before, struct lu_object *o);
  
  /**
   * Helpers to initialize and finalize device types.
   */
  
  int  lu_device_type_init(struct lu_device_type *ldt);
  void lu_device_type_fini(struct lu_device_type *ldt);
  
  /** @} ctors */
  
  /** \name caching
   * Caching and reference counting.
   * @{
   */
  
  /**
   * Acquire additional reference to the given object. This function is used to
   * attain additional reference. To acquire initial reference use
   * lu_object_find().
   */
  static inline void lu_object_get(struct lu_object *o)
  {
  	LASSERT(atomic_read(&o->lo_header->loh_ref) > 0);
  	atomic_inc(&o->lo_header->loh_ref);
  }
  
  /**
   * Return true of object will not be cached after last reference to it is
   * released.
   */
  static inline int lu_object_is_dying(const struct lu_object_header *h)
  {
  	return test_bit(LU_OBJECT_HEARD_BANSHEE, &h->loh_flags);
  }
  
  void lu_object_put(const struct lu_env *env, struct lu_object *o);
  void lu_object_unhash(const struct lu_env *env, struct lu_object *o);
  int lu_site_purge_objects(const struct lu_env *env, struct lu_site *s, int nr,
  			  bool canblock);
  
  static inline int lu_site_purge(const struct lu_env *env, struct lu_site *s,
  				int nr)
  {
  	return lu_site_purge_objects(env, s, nr, true);
  }
  
  void lu_site_print(const struct lu_env *env, struct lu_site *s, void *cookie,
  		   lu_printer_t printer);
  struct lu_object *lu_object_find_at(const struct lu_env *env,
  				    struct lu_device *dev,
  				    const struct lu_fid *f,
  				    const struct lu_object_conf *conf);
  struct lu_object *lu_object_find_slice(const struct lu_env *env,
  				       struct lu_device *dev,
  				       const struct lu_fid *f,
  				       const struct lu_object_conf *conf);
  /** @} caching */
  
  /** \name helpers
   * Helpers.
   * @{
   */
  
  /**
   * First (topmost) sub-object of given compound object
   */
  static inline struct lu_object *lu_object_top(struct lu_object_header *h)
  {
  	LASSERT(!list_empty(&h->loh_layers));
  	return container_of0(h->loh_layers.next, struct lu_object, lo_linkage);
  }
  
  /**
   * Next sub-object in the layering
   */
  static inline struct lu_object *lu_object_next(const struct lu_object *o)
  {
  	return container_of0(o->lo_linkage.next, struct lu_object, lo_linkage);
  }
  
  /**
   * Pointer to the fid of this object.
   */
  static inline const struct lu_fid *lu_object_fid(const struct lu_object *o)
  {
  	return &o->lo_header->loh_fid;
  }
  
  /**
   * return device operations vector for this object
   */
  static inline const struct lu_device_operations *
  lu_object_ops(const struct lu_object *o)
  {
  	return o->lo_dev->ld_ops;
  }
  
  /**
   * Given a compound object, find its slice, corresponding to the device type
   * \a dtype.
   */
  struct lu_object *lu_object_locate(struct lu_object_header *h,
  				   const struct lu_device_type *dtype);
  
  /**
   * Printer function emitting messages through libcfs_debug_msg().
   */
  int lu_cdebug_printer(const struct lu_env *env,
  		      void *cookie, const char *format, ...);
  
  /**
   * Print object description followed by a user-supplied message.
   */
  #define LU_OBJECT_DEBUG(mask, env, object, format, ...)		   \
  do {								      \
  	if (cfs_cdebug_show(mask, DEBUG_SUBSYSTEM)) {		     \
  		LIBCFS_DEBUG_MSG_DATA_DECL(msgdata, mask, NULL);	\
  		lu_object_print(env, &msgdata, lu_cdebug_printer, object);\
  		CDEBUG(mask, format "\n", ## __VA_ARGS__);		    \
  	}								 \
  } while (0)
  
  /**
   * Print short object description followed by a user-supplied message.
   */
  #define LU_OBJECT_HEADER(mask, env, object, format, ...)		\
  do {								    \
  	if (cfs_cdebug_show(mask, DEBUG_SUBSYSTEM)) {		   \
  		LIBCFS_DEBUG_MSG_DATA_DECL(msgdata, mask, NULL);	\
  		lu_object_header_print(env, &msgdata, lu_cdebug_printer,\
  				       (object)->lo_header);	    \
  		lu_cdebug_printer(env, &msgdata, "\n");		 \
  		CDEBUG(mask, format, ## __VA_ARGS__);		  \
  	}							       \
  } while (0)
  
  void lu_object_print       (const struct lu_env *env, void *cookie,
  			    lu_printer_t printer, const struct lu_object *o);
  void lu_object_header_print(const struct lu_env *env, void *cookie,
  			    lu_printer_t printer,
  			    const struct lu_object_header *hdr);
  
  /**
   * Check object consistency.
   */
  int lu_object_invariant(const struct lu_object *o);
  
  /**
   * Check whether object exists, no matter on local or remote storage.
   * Note: LOHA_EXISTS will be set once some one created the object,
   * and it does not needs to be committed to storage.
   */
  #define lu_object_exists(o) ((o)->lo_header->loh_attr & LOHA_EXISTS)
  
  /**
   * Check whether object on the remote storage.
   */
  #define lu_object_remote(o) unlikely((o)->lo_header->loh_attr & LOHA_REMOTE)
  
  static inline int lu_object_assert_exists(const struct lu_object *o)
  {
  	return lu_object_exists(o);
  }
  
  static inline int lu_object_assert_not_exists(const struct lu_object *o)
  {
  	return !lu_object_exists(o);
  }
  
  /**
   * Attr of this object.
   */
  static inline __u32 lu_object_attr(const struct lu_object *o)
  {
  	LASSERT(lu_object_exists(o) != 0);
  	return o->lo_header->loh_attr;
  }
  
  static inline void lu_object_ref_add(struct lu_object *o,
  				     const char *scope,
  				     const void *source)
  {
  	lu_ref_add(&o->lo_header->loh_reference, scope, source);
  }
  
  static inline void lu_object_ref_add_at(struct lu_object *o,
  					struct lu_ref_link *link,
  					const char *scope,
  					const void *source)
  {
  	lu_ref_add_at(&o->lo_header->loh_reference, link, scope, source);
  }
  
  static inline void lu_object_ref_del(struct lu_object *o,
  				     const char *scope, const void *source)
  {
  	lu_ref_del(&o->lo_header->loh_reference, scope, source);
  }
  
  static inline void lu_object_ref_del_at(struct lu_object *o,
  					struct lu_ref_link *link,
  					const char *scope, const void *source)
  {
  	lu_ref_del_at(&o->lo_header->loh_reference, link, scope, source);
  }
  
  /** input params, should be filled out by mdt */
  struct lu_rdpg {
  	/** hash */
  	__u64		   rp_hash;
  	/** count in bytes */
  	unsigned int	    rp_count;
  	/** number of pages */
  	unsigned int	    rp_npages;
  	/** requested attr */
  	__u32		   rp_attrs;
  	/** pointers to pages */
  	struct page	   **rp_pages;
  };
  
  enum lu_xattr_flags {
  	LU_XATTR_REPLACE = (1 << 0),
  	LU_XATTR_CREATE  = (1 << 1)
  };
  
  /** @} helpers */
  
  /** \name lu_context
   * @{
   */
  
  /** For lu_context health-checks */
  enum lu_context_state {
  	LCS_INITIALIZED = 1,
  	LCS_ENTERED,
  	LCS_LEFT,
  	LCS_FINALIZED
  };
  
  /**
   * lu_context. Execution context for lu_object methods. Currently associated
   * with thread.
   *
   * All lu_object methods, except device and device type methods (called during
   * system initialization and shutdown) are executed "within" some
   * lu_context. This means, that pointer to some "current" lu_context is passed
   * as an argument to all methods.
   *
   * All service ptlrpc threads create lu_context as part of their
   * initialization. It is possible to create "stand-alone" context for other
   * execution environments (like system calls).
   *
   * lu_object methods mainly use lu_context through lu_context_key interface
   * that allows each layer to associate arbitrary pieces of data with each
   * context (see pthread_key_create(3) for similar interface).
   *
   * On a client, lu_context is bound to a thread, see cl_env_get().
   *
   * \see lu_context_key
   */
  struct lu_context {
  	/**
  	 * lu_context is used on the client side too. Yet we don't want to
  	 * allocate values of server-side keys for the client contexts and
  	 * vice versa.
  	 *
  	 * To achieve this, set of tags in introduced. Contexts and keys are
  	 * marked with tags. Key value are created only for context whose set
  	 * of tags has non-empty intersection with one for key. Tags are taken
  	 * from enum lu_context_tag.
  	 */
  	__u32		  lc_tags;
  	enum lu_context_state  lc_state;
  	/**
  	 * Pointer to the home service thread. NULL for other execution
  	 * contexts.
  	 */
  	struct ptlrpc_thread  *lc_thread;
  	/**
  	 * Pointer to an array with key values. Internal implementation
  	 * detail.
  	 */
  	void		 **lc_value;
  	/**
  	 * Linkage into a list of all remembered contexts. Only
  	 * `non-transient' contexts, i.e., ones created for service threads
  	 * are placed here.
  	 */
  	struct list_head	     lc_remember;
  	/**
  	 * Version counter used to skip calls to lu_context_refill() when no
  	 * keys were registered.
  	 */
  	unsigned int		lc_version;
  	/**
  	 * Debugging cookie.
  	 */
  	unsigned int		lc_cookie;
  };
  
  /**
   * lu_context_key interface. Similar to pthread_key.
   */
  
  enum lu_context_tag {
  	/**
  	 * Thread on md server
  	 */
  	LCT_MD_THREAD = 1 << 0,
  	/**
  	 * Thread on dt server
  	 */
  	LCT_DT_THREAD = 1 << 1,
  	/**
  	 * Context for transaction handle
  	 */
  	LCT_TX_HANDLE = 1 << 2,
  	/**
  	 * Thread on client
  	 */
  	LCT_CL_THREAD = 1 << 3,
  	/**
  	 * A per-request session on a server, and a per-system-call session on
  	 * a client.
  	 */
  	LCT_SESSION   = 1 << 4,
  	/**
  	 * A per-request data on OSP device
  	 */
  	LCT_OSP_THREAD = 1 << 5,
  	/**
  	 * MGS device thread
  	 */
  	LCT_MG_THREAD = 1 << 6,
  	/**
  	 * Context for local operations
  	 */
  	LCT_LOCAL = 1 << 7,
  	/**
  	 * session for server thread
  	 **/
  	LCT_SERVER_SESSION = BIT(8),
  	/**
  	 * Set when at least one of keys, having values in this context has
  	 * non-NULL lu_context_key::lct_exit() method. This is used to
  	 * optimize lu_context_exit() call.
  	 */
  	LCT_HAS_EXIT  = 1 << 28,
  	/**
  	 * Don't add references for modules creating key values in that context.
  	 * This is only for contexts used internally by lu_object framework.
  	 */
  	LCT_NOREF     = 1 << 29,
  	/**
  	 * Key is being prepared for retiring, don't create new values for it.
  	 */
  	LCT_QUIESCENT = 1 << 30,
  	/**
  	 * Context should be remembered.
  	 */
  	LCT_REMEMBER  = 1 << 31,
  	/**
  	 * Contexts usable in cache shrinker thread.
  	 */
  	LCT_SHRINKER  = LCT_MD_THREAD | LCT_DT_THREAD | LCT_CL_THREAD |
  			LCT_NOREF
  };
  
  /**
   * Key. Represents per-context value slot.
   *
   * Keys are usually registered when module owning the key is initialized, and
   * de-registered when module is unloaded. Once key is registered, all new
   * contexts with matching tags, will get key value. "Old" contexts, already
   * initialized at the time of key registration, can be forced to get key value
   * by calling lu_context_refill().
   *
   * Every key value is counted in lu_context_key::lct_used and acquires a
   * reference on an owning module. This means, that all key values have to be
   * destroyed before module can be unloaded. This is usually achieved by
   * stopping threads started by the module, that created contexts in their
   * entry functions. Situation is complicated by the threads shared by multiple
   * modules, like ptlrpcd daemon on a client. To work around this problem,
   * contexts, created in such threads, are `remembered' (see
   * LCT_REMEMBER)---i.e., added into a global list. When module is preparing
   * for unloading it does the following:
   *
   *     - marks its keys as `quiescent' (lu_context_tag::LCT_QUIESCENT)
   *       preventing new key values from being allocated in the new contexts,
   *       and
   *
   *     - scans a list of remembered contexts, destroying values of module
   *       keys, thus releasing references to the module.
   *
   * This is done by lu_context_key_quiesce(). If module is re-activated
   * before key has been de-registered, lu_context_key_revive() call clears
   * `quiescent' marker.
   *
   * lu_context code doesn't provide any internal synchronization for these
   * activities---it's assumed that startup (including threads start-up) and
   * shutdown are serialized by some external means.
   *
   * \see lu_context
   */
  struct lu_context_key {
  	/**
  	 * Set of tags for which values of this key are to be instantiated.
  	 */
  	__u32 lct_tags;
  	/**
  	 * Value constructor. This is called when new value is created for a
  	 * context. Returns pointer to new value of error pointer.
  	 */
  	void  *(*lct_init)(const struct lu_context *ctx,
  			   struct lu_context_key *key);
  	/**
  	 * Value destructor. Called when context with previously allocated
  	 * value of this slot is destroyed. \a data is a value that was returned
  	 * by a matching call to lu_context_key::lct_init().
  	 */
  	void   (*lct_fini)(const struct lu_context *ctx,
  			   struct lu_context_key *key, void *data);
  	/**
  	 * Optional method called on lu_context_exit() for all allocated
  	 * keys. Can be used by debugging code checking that locks are
  	 * released, etc.
  	 */
  	void   (*lct_exit)(const struct lu_context *ctx,
  			   struct lu_context_key *key, void *data);
  	/**
  	 * Internal implementation detail: index within lu_context::lc_value[]
  	 * reserved for this key.
  	 */
  	int      lct_index;
  	/**
  	 * Internal implementation detail: number of values created for this
  	 * key.
  	 */
  	atomic_t lct_used;
  	/**
  	 * Internal implementation detail: module for this key.
  	 */
  	struct module *lct_owner;
  	/**
  	 * References to this key. For debugging.
  	 */
  	struct lu_ref  lct_reference;
  };
  
  #define LU_KEY_INIT(mod, type)				    \
  	static void *mod##_key_init(const struct lu_context *ctx, \
  				    struct lu_context_key *key)   \
  	{							 \
  		type *value;				      \
  								  \
  		BUILD_BUG_ON(sizeof(*value) > PAGE_SIZE);        \
  								  \
  		value = kzalloc(sizeof(*value), GFP_NOFS);	\
  		if (!value)				\
  			value = ERR_PTR(-ENOMEM);		 \
  								  \
  		return value;				     \
  	}							 \
  	struct __##mod##__dummy_init {; } /* semicolon catcher */
  
  #define LU_KEY_FINI(mod, type)					      \
  	static void mod##_key_fini(const struct lu_context *ctx,	    \
  				    struct lu_context_key *key, void *data) \
  	{								   \
  		type *info = data;					  \
  									    \
  		kfree(info);					 \
  	}								   \
  	struct __##mod##__dummy_fini {; } /* semicolon catcher */
  
  #define LU_KEY_INIT_FINI(mod, type)   \
  	LU_KEY_INIT(mod, type);	\
  	LU_KEY_FINI(mod, type)
  
  #define LU_CONTEXT_KEY_DEFINE(mod, tags)		\
  	struct lu_context_key mod##_thread_key = {      \
  		.lct_tags = tags,		       \
  		.lct_init = mod##_key_init,	     \
  		.lct_fini = mod##_key_fini	      \
  	}
  
  #define LU_CONTEXT_KEY_INIT(key)			\
  do {						    \
  	(key)->lct_owner = THIS_MODULE;		 \
  } while (0)
  
  int lu_context_key_register(struct lu_context_key *key);
  void lu_context_key_degister(struct lu_context_key *key);
  void *lu_context_key_get(const struct lu_context *ctx,
  			 const struct lu_context_key *key);
  void lu_context_key_quiesce(struct lu_context_key *key);
  void lu_context_key_revive(struct lu_context_key *key);
  
  /*
   * LU_KEY_INIT_GENERIC() has to be a macro to correctly determine an
   * owning module.
   */
  
  #define LU_KEY_INIT_GENERIC(mod)					\
  	static void mod##_key_init_generic(struct lu_context_key *k, ...) \
  	{							       \
  		struct lu_context_key *key = k;			 \
  		va_list args;					   \
  									\
  		va_start(args, k);				      \
  		do {						    \
  			LU_CONTEXT_KEY_INIT(key);		       \
  			key = va_arg(args, struct lu_context_key *);    \
  		} while (key);				  \
  		va_end(args);					   \
  	}
  
  #define LU_TYPE_INIT(mod, ...)					  \
  	LU_KEY_INIT_GENERIC(mod)					\
  	static int mod##_type_init(struct lu_device_type *t)	    \
  	{							       \
  		mod##_key_init_generic(__VA_ARGS__, NULL);	      \
  		return lu_context_key_register_many(__VA_ARGS__, NULL); \
  	}							       \
  	struct __##mod##_dummy_type_init {; }
  
  #define LU_TYPE_FINI(mod, ...)					  \
  	static void mod##_type_fini(struct lu_device_type *t)	   \
  	{							       \
  		lu_context_key_degister_many(__VA_ARGS__, NULL);	\
  	}							       \
  	struct __##mod##_dummy_type_fini {; }
  
  #define LU_TYPE_START(mod, ...)				 \
  	static void mod##_type_start(struct lu_device_type *t)  \
  	{						       \
  		lu_context_key_revive_many(__VA_ARGS__, NULL);  \
  	}						       \
  	struct __##mod##_dummy_type_start {; }
  
  #define LU_TYPE_STOP(mod, ...)				  \
  	static void mod##_type_stop(struct lu_device_type *t)   \
  	{						       \
  		lu_context_key_quiesce_many(__VA_ARGS__, NULL); \
  	}						       \
  	struct __##mod##_dummy_type_stop {; }
  
  #define LU_TYPE_INIT_FINI(mod, ...)	     \
  	LU_TYPE_INIT(mod, __VA_ARGS__);	 \
  	LU_TYPE_FINI(mod, __VA_ARGS__);	 \
  	LU_TYPE_START(mod, __VA_ARGS__);	\
  	LU_TYPE_STOP(mod, __VA_ARGS__)
  
  int lu_context_init(struct lu_context *ctx, __u32 tags);
  void lu_context_fini(struct lu_context *ctx);
  void lu_context_enter(struct lu_context *ctx);
  void lu_context_exit(struct lu_context *ctx);
  int lu_context_refill(struct lu_context *ctx);
  
  /*
   * Helper functions to operate on multiple keys. These are used by the default
   * device type operations, defined by LU_TYPE_INIT_FINI().
   */
  
  int lu_context_key_register_many(struct lu_context_key *k, ...);
  void lu_context_key_degister_many(struct lu_context_key *k, ...);
  void lu_context_key_revive_many(struct lu_context_key *k, ...);
  void lu_context_key_quiesce_many(struct lu_context_key *k, ...);
  
  /**
   * Environment.
   */
  struct lu_env {
  	/**
  	 * "Local" context, used to store data instead of stack.
  	 */
  	struct lu_context  le_ctx;
  	/**
  	 * "Session" context for per-request data.
  	 */
  	struct lu_context *le_ses;
  };
  
  int lu_env_init(struct lu_env *env, __u32 tags);
  void lu_env_fini(struct lu_env *env);
  int lu_env_refill(struct lu_env *env);
  
  /** @} lu_context */
  
  /**
   * Output site statistical counters into a buffer. Suitable for
   * ll_rd_*()-style functions.
   */
  int lu_site_stats_print(const struct lu_site *s, struct seq_file *m);
  
  /**
   * Common name structure to be passed around for various name related methods.
   */
  struct lu_name {
  	const char    *ln_name;
  	int	    ln_namelen;
  };
  
  /**
   * Validate names (path components)
   *
   * To be valid \a name must be non-empty, '\0' terminated of length \a
   * name_len, and not contain '/'. The maximum length of a name (before
   * say -ENAMETOOLONG will be returned) is really controlled by llite
   * and the server. We only check for something insane coming from bad
   * integer handling here.
   */
  static inline bool lu_name_is_valid_2(const char *name, size_t name_len)
  {
  	return name && name_len > 0 && name_len < INT_MAX &&
  	       name[name_len] == '\0' && strlen(name) == name_len &&
  	       !memchr(name, '/', name_len);
  }
  
  /**
   * Common buffer structure to be passed around for various xattr_{s,g}et()
   * methods.
   */
  struct lu_buf {
  	void   *lb_buf;
  	size_t	lb_len;
  };
  
  /**
   * One-time initializers, called at obdclass module initialization, not
   * exported.
   */
  
  /**
   * Initialization of global lu_* data.
   */
  int lu_global_init(void);
  
  /**
   * Dual to lu_global_init().
   */
  void lu_global_fini(void);
  
  struct lu_kmem_descr {
  	struct kmem_cache **ckd_cache;
  	const char       *ckd_name;
  	const size_t      ckd_size;
  };
  
  int  lu_kmem_init(struct lu_kmem_descr *caches);
  void lu_kmem_fini(struct lu_kmem_descr *caches);
  
  extern __u32 lu_context_tags_default;
  extern __u32 lu_session_tags_default;
  
  /** @} lu */
  #endif /* __LUSTRE_LU_OBJECT_H */
  