freebsd-nq/include/sys/dnode.h

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
 */

#ifndef	_SYS_DNODE_H
#define	_SYS_DNODE_H

#include <sys/zfs_context.h>
#include <sys/avl.h>
#include <sys/spa.h>
#include <sys/txg.h>
#include <sys/zio.h>
#include <sys/refcount.h>
#include <sys/dmu_zfetch.h>
#include <sys/zrlock.h>
#include <sys/multilist.h>

#ifdef	__cplusplus
extern "C" {
#endif

/*
 * dnode_hold() flags.
 */
#define	DNODE_MUST_BE_ALLOCATED	1
#define	DNODE_MUST_BE_FREE	2

/*
 * dnode_next_offset() flags.
 */
#define	DNODE_FIND_HOLE		1
#define	DNODE_FIND_BACKWARDS	2
#define	DNODE_FIND_HAVELOCK	4

/*
 * Fixed constants.
 */
#define	DNODE_SHIFT		9	/* 512 bytes */
#define	DN_MIN_INDBLKSHIFT	12	/* 4k */
/*
 * If we ever increase this value beyond 20, we need to revisit all logic that
 * does x << level * ebps to handle overflow.  With a 1M indirect block size,
 * 4 levels of indirect blocks would not be able to guarantee addressing an
 * entire object, so 5 levels will be used, but 5 * (20 - 7) = 65.
 */
#define	DN_MAX_INDBLKSHIFT	17	/* 128k */
#define	DNODE_BLOCK_SHIFT	14	/* 16k */
#define	DNODE_CORE_SIZE		64	/* 64 bytes for dnode sans blkptrs */
#define	DN_MAX_OBJECT_SHIFT	48	/* 256 trillion (zfs_fid_t limit) */
#define	DN_MAX_OFFSET_SHIFT	64	/* 2^64 bytes in a dnode */

/*
 * dnode id flags
 *
 * Note: a file will never ever have its ids moved from bonus->spill
 */
#define	DN_ID_CHKED_BONUS	0x1
#define	DN_ID_CHKED_SPILL	0x2
#define	DN_ID_OLD_EXIST		0x4
#define	DN_ID_NEW_EXIST		0x8

/*
 * Derived constants.
 */
#define	DNODE_MIN_SIZE		(1 << DNODE_SHIFT)
#define	DNODE_MAX_SIZE		(1 << DNODE_BLOCK_SHIFT)
#define	DNODE_BLOCK_SIZE	(1 << DNODE_BLOCK_SHIFT)
#define	DNODE_MIN_SLOTS		(DNODE_MIN_SIZE >> DNODE_SHIFT)
#define	DNODE_MAX_SLOTS		(DNODE_MAX_SIZE >> DNODE_SHIFT)
#define	DN_BONUS_SIZE(dnsize)	((dnsize) - DNODE_CORE_SIZE - \
	(1 << SPA_BLKPTRSHIFT))
#define	DN_SLOTS_TO_BONUSLEN(slots)	DN_BONUS_SIZE((slots) << DNODE_SHIFT)
#define	DN_OLD_MAX_BONUSLEN	(DN_BONUS_SIZE(DNODE_MIN_SIZE))
#define	DN_MAX_NBLKPTR	((DNODE_MIN_SIZE - DNODE_CORE_SIZE) >> SPA_BLKPTRSHIFT)
#define	DN_MAX_OBJECT	(1ULL << DN_MAX_OBJECT_SHIFT)
#define	DN_ZERO_BONUSLEN	(DN_BONUS_SIZE(DNODE_MAX_SIZE) + 1)
#define	DN_KILL_SPILLBLK (1)

#define	DN_SLOT_UNINIT		((void *)NULL)	/* Uninitialized */
#define	DN_SLOT_FREE		((void *)1UL)	/* Free slot */
#define	DN_SLOT_ALLOCATED	((void *)2UL)	/* Allocated slot */
#define	DN_SLOT_INTERIOR	((void *)3UL)	/* Interior allocated slot */
#define	DN_SLOT_IS_PTR(dn)	((void *)dn > DN_SLOT_INTERIOR)
#define	DN_SLOT_IS_VALID(dn)	((void *)dn != NULL)

#define	DNODES_PER_BLOCK_SHIFT	(DNODE_BLOCK_SHIFT - DNODE_SHIFT)
#define	DNODES_PER_BLOCK	(1ULL << DNODES_PER_BLOCK_SHIFT)

/*
 * This is inaccurate if the indblkshift of the particular object is not the
 * max.  But it's only used by userland to calculate the zvol reservation.
 */
#define	DNODES_PER_LEVEL_SHIFT	(DN_MAX_INDBLKSHIFT - SPA_BLKPTRSHIFT)
#define	DNODES_PER_LEVEL	(1ULL << DNODES_PER_LEVEL_SHIFT)

#define	DN_MAX_LEVELS	(DIV_ROUND_UP(DN_MAX_OFFSET_SHIFT - SPA_MINBLOCKSHIFT, \
	DN_MIN_INDBLKSHIFT - SPA_BLKPTRSHIFT) + 1)

#define	DN_BONUS(dnp)	((void*)((dnp)->dn_bonus + \
	(((dnp)->dn_nblkptr - 1) * sizeof (blkptr_t))))
#define	DN_MAX_BONUS_LEN(dnp) \
	((dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) ? \
	(uint8_t *)DN_SPILL_BLKPTR(dnp) - (uint8_t *)DN_BONUS(dnp) : \
	(uint8_t *)(dnp + (dnp->dn_extra_slots + 1)) - (uint8_t *)DN_BONUS(dnp))

#define	DN_USED_BYTES(dnp) (((dnp)->dn_flags & DNODE_FLAG_USED_BYTES) ? \
	(dnp)->dn_used : (dnp)->dn_used << SPA_MINBLOCKSHIFT)

#define	EPB(blkshift, typeshift)	(1 << (blkshift - typeshift))

struct dmu_buf_impl;
struct objset;
struct zio;

enum dnode_dirtycontext {
	DN_UNDIRTIED,
	DN_DIRTY_OPEN,
	DN_DIRTY_SYNC
};

/* Is dn_used in bytes?  if not, it's in multiples of SPA_MINBLOCKSIZE */
#define	DNODE_FLAG_USED_BYTES			(1 << 0)
#define	DNODE_FLAG_USERUSED_ACCOUNTED		(1 << 1)

/* Does dnode have a SA spill blkptr in bonus? */
#define	DNODE_FLAG_SPILL_BLKPTR			(1 << 2)

/* User/Group/Project dnode accounting */
#define	DNODE_FLAG_USEROBJUSED_ACCOUNTED	(1 << 3)

/*
 * This mask defines the set of flags which are "portable", meaning
 * that they can be preserved when doing a raw encrypted zfs send.
 * Flags included in this mask will be protected by AAD when the block
 * of dnodes is encrypted.
 */
#define	DNODE_CRYPT_PORTABLE_FLAGS_MASK		(DNODE_FLAG_SPILL_BLKPTR)

/*
 * VARIABLE-LENGTH (LARGE) DNODES
 *
 * The motivation for variable-length dnodes is to eliminate the overhead
 * associated with using spill blocks.  Spill blocks are used to store
 * system attribute data (i.e. file metadata) that does not fit in the
 * dnode's bonus buffer. By allowing a larger bonus buffer area the use of
 * a spill block can be avoided.  Spill blocks potentially incur an
 * additional read I/O for every dnode in a dnode block. As a worst case
 * example, reading 32 dnodes from a 16k dnode block and all of the spill
 * blocks could issue 33 separate reads. Now suppose those dnodes have size
 * 1024 and therefore don't need spill blocks. Then the worst case number
 * of blocks read is reduced to from 33 to two--one per dnode block.
 *
 * ZFS-on-Linux systems that make heavy use of extended attributes benefit
 * from this feature. In particular, ZFS-on-Linux supports the xattr=sa
 * dataset property which allows file extended attribute data to be stored
 * in the dnode bonus buffer as an alternative to the traditional
 * directory-based format. Workloads such as SELinux and the Lustre
 * distributed filesystem often store enough xattr data to force spill
 * blocks when xattr=sa is in effect. Large dnodes may therefore provide a
 * performance benefit to such systems. Other use cases that benefit from
 * this feature include files with large ACLs and symbolic links with long
 * target names.
 *
 * The size of a dnode may be a multiple of 512 bytes up to the size of a
 * dnode block (currently 16384 bytes). The dn_extra_slots field of the
 * on-disk dnode_phys_t structure describes the size of the physical dnode
 * on disk. The field represents how many "extra" dnode_phys_t slots a
 * dnode consumes in its dnode block. This convention results in a value of
 * 0 for 512 byte dnodes which preserves on-disk format compatibility with
 * older software which doesn't support large dnodes.
 *
 * Similarly, the in-memory dnode_t structure has a dn_num_slots field
 * to represent the total number of dnode_phys_t slots consumed on disk.
 * Thus dn->dn_num_slots is 1 greater than the corresponding
 * dnp->dn_extra_slots. This difference in convention was adopted
 * because, unlike on-disk structures, backward compatibility is not a
 * concern for in-memory objects, so we used a more natural way to
 * represent size for a dnode_t.
 *
 * The default size for newly created dnodes is determined by the value of
 * the "dnodesize" dataset property. By default the property is set to
 * "legacy" which is compatible with older software. Setting the property
 * to "auto" will allow the filesystem to choose the most suitable dnode
 * size. Currently this just sets the default dnode size to 1k, but future
 * code improvements could dynamically choose a size based on observed
 * workload patterns. Dnodes of varying sizes can coexist within the same
 * dataset and even within the same dnode block.
 */

typedef struct dnode_phys {
	uint8_t dn_type;		/* dmu_object_type_t */
	uint8_t dn_indblkshift;		/* ln2(indirect block size) */
	uint8_t dn_nlevels;		/* 1=dn_blkptr->data blocks */
	uint8_t dn_nblkptr;		/* length of dn_blkptr */
	uint8_t dn_bonustype;		/* type of data in bonus buffer */
	uint8_t	dn_checksum;		/* ZIO_CHECKSUM type */
	uint8_t	dn_compress;		/* ZIO_COMPRESS type */
	uint8_t dn_flags;		/* DNODE_FLAG_* */
	uint16_t dn_datablkszsec;	/* data block size in 512b sectors */
	uint16_t dn_bonuslen;		/* length of dn_bonus */
	uint8_t dn_extra_slots;		/* # of subsequent slots consumed */
	uint8_t dn_pad2[3];

	/* accounting is protected by dn_dirty_mtx */
	uint64_t dn_maxblkid;		/* largest allocated block ID */
	uint64_t dn_used;		/* bytes (or sectors) of disk space */

	/*
	 * Both dn_pad2 and dn_pad3 are protected by the block's MAC. This
	 * allows us to protect any fields that might be added here in the
	 * future. In either case, developers will want to check
	 * zio_crypt_init_uios_dnode() to ensure the new field is being
	 * protected properly.
	 */
	uint64_t dn_pad3[4];

	/*
	 * The tail region is 448 bytes for a 512 byte dnode, and
	 * correspondingly larger for larger dnode sizes. The spill
	 * block pointer, when present, is always at the end of the tail
	 * region. There are three ways this space may be used, using
	 * a 512 byte dnode for this diagram:
	 *
	 * 0       64      128     192     256     320     384     448 (offset)
	 * +---------------+---------------+---------------+-------+
	 * | dn_blkptr[0]  | dn_blkptr[1]  | dn_blkptr[2]  | /     |
	 * +---------------+---------------+---------------+-------+
	 * | dn_blkptr[0]  | dn_bonus[0..319]                      |
	 * +---------------+-----------------------+---------------+
	 * | dn_blkptr[0]  | dn_bonus[0..191]      | dn_spill      |
	 * +---------------+-----------------------+---------------+
	 */
	union {
		blkptr_t dn_blkptr[1+DN_OLD_MAX_BONUSLEN/sizeof (blkptr_t)];
		struct {
			blkptr_t __dn_ignore1;
			uint8_t dn_bonus[DN_OLD_MAX_BONUSLEN];
		};
		struct {
			blkptr_t __dn_ignore2;
			uint8_t __dn_ignore3[DN_OLD_MAX_BONUSLEN -
			    sizeof (blkptr_t)];
			blkptr_t dn_spill;
		};
	};
} dnode_phys_t;

#define	DN_SPILL_BLKPTR(dnp)	(blkptr_t *)((char *)(dnp) + \
	(((dnp)->dn_extra_slots + 1) << DNODE_SHIFT) - (1 << SPA_BLKPTRSHIFT))

struct dnode {
	/*
	 * Protects the structure of the dnode, including the number of levels
	 * of indirection (dn_nlevels), dn_maxblkid, and dn_next_*
	 */
	krwlock_t dn_struct_rwlock;

	/* Our link on dn_objset->os_dnodes list; protected by os_lock.  */
	list_node_t dn_link;

	/* immutable: */
	struct objset *dn_objset;
	uint64_t dn_object;
	struct dmu_buf_impl *dn_dbuf;
	struct dnode_handle *dn_handle;
	dnode_phys_t *dn_phys; /* pointer into dn->dn_dbuf->db.db_data */

	/*
	 * Copies of stuff in dn_phys.  They're valid in the open
	 * context (eg. even before the dnode is first synced).
	 * Where necessary, these are protected by dn_struct_rwlock.
	 */
	dmu_object_type_t dn_type;	/* object type */
	uint16_t dn_bonuslen;		/* bonus length */
	uint8_t dn_bonustype;		/* bonus type */
	uint8_t dn_nblkptr;		/* number of blkptrs (immutable) */
	uint8_t dn_checksum;		/* ZIO_CHECKSUM type */
	uint8_t dn_compress;		/* ZIO_COMPRESS type */
	uint8_t dn_nlevels;
	uint8_t dn_indblkshift;
	uint8_t dn_datablkshift;	/* zero if blksz not power of 2! */
	uint8_t dn_moved;		/* Has this dnode been moved? */
	uint16_t dn_datablkszsec;	/* in 512b sectors */
	uint32_t dn_datablksz;		/* in bytes */
	uint64_t dn_maxblkid;
	uint8_t dn_next_type[TXG_SIZE];
	uint8_t dn_num_slots;		/* metadnode slots consumed on disk */
	uint8_t dn_next_nblkptr[TXG_SIZE];
	uint8_t dn_next_nlevels[TXG_SIZE];
	uint8_t dn_next_indblkshift[TXG_SIZE];
	uint8_t dn_next_bonustype[TXG_SIZE];
	uint8_t dn_rm_spillblk[TXG_SIZE];	/* for removing spill blk */
	uint16_t dn_next_bonuslen[TXG_SIZE];
	uint32_t dn_next_blksz[TXG_SIZE];	/* next block size in bytes */
	uint64_t dn_next_maxblkid[TXG_SIZE];	/* next maxblkid in bytes */

	/* protected by dn_dbufs_mtx; declared here to fill 32-bit hole */
	uint32_t dn_dbufs_count;	/* count of dn_dbufs */

	/* protected by os_lock: */
	multilist_node_t dn_dirty_link[TXG_SIZE]; /* next on dataset's dirty */

	/* protected by dn_mtx: */
	kmutex_t dn_mtx;
	list_t dn_dirty_records[TXG_SIZE];
	struct range_tree *dn_free_ranges[TXG_SIZE];
	uint64_t dn_allocated_txg;
	uint64_t dn_free_txg;
	uint64_t dn_assigned_txg;
	uint64_t dn_dirty_txg;			/* txg dnode was last dirtied */
	kcondvar_t dn_notxholds;
	enum dnode_dirtycontext dn_dirtyctx;
	uint8_t *dn_dirtyctx_firstset;		/* dbg: contents meaningless */

	/* protected by own devices */
	zfs_refcount_t dn_tx_holds;
	zfs_refcount_t dn_holds;

	kmutex_t dn_dbufs_mtx;
	/*
	 * Descendent dbufs, ordered by dbuf_compare. Note that dn_dbufs
	 * can contain multiple dbufs of the same (level, blkid) when a
	 * dbuf is marked DB_EVICTING without being removed from
	 * dn_dbufs. To maintain the avl invariant that there cannot be
	 * duplicate entries, we order the dbufs by an arbitrary value -
	 * their address in memory. This means that dn_dbufs cannot be used to
	 * directly look up a dbuf. Instead, callers must use avl_walk, have
	 * a reference to the dbuf, or look up a non-existent node with
	 * db_state = DB_SEARCH (see dbuf_free_range for an example).
	 */
	avl_tree_t dn_dbufs;

	/* protected by dn_struct_rwlock */
	struct dmu_buf_impl *dn_bonus;	/* bonus buffer dbuf */

	boolean_t dn_have_spill;	/* have spill or are spilling */

	/* parent IO for current sync write */
	zio_t *dn_zio;

	/* used in syncing context */
	uint64_t dn_oldused;	/* old phys used bytes */
	uint64_t dn_oldflags;	/* old phys dn_flags */
	uint64_t dn_olduid, dn_oldgid, dn_oldprojid;
	uint64_t dn_newuid, dn_newgid, dn_newprojid;
	int dn_id_flags;

	/* holds prefetch structure */
	struct zfetch	dn_zfetch;
};

/*
 * We use this (otherwise unused) bit to indicate if the value of
 * dn_next_maxblkid[txgoff] is valid to use in dnode_sync().
 */
#define	DMU_NEXT_MAXBLKID_SET		(1ULL << 63)

/*
 * Adds a level of indirection between the dbuf and the dnode to avoid
 * iterating descendent dbufs in dnode_move(). Handles are not allocated
 * individually, but as an array of child dnodes in dnode_hold_impl().
 */
typedef struct dnode_handle {
	/* Protects dnh_dnode from modification by dnode_move(). */
	zrlock_t dnh_zrlock;
	dnode_t *dnh_dnode;
} dnode_handle_t;

typedef struct dnode_children {
	dmu_buf_user_t dnc_dbu;		/* User evict data */
	size_t dnc_count;		/* number of children */
	dnode_handle_t dnc_children[];	/* sized dynamically */
} dnode_children_t;

typedef struct free_range {
	avl_node_t fr_node;
	uint64_t fr_blkid;
	uint64_t fr_nblks;
} free_range_t;

void dnode_special_open(struct objset *dd, dnode_phys_t *dnp,
    uint64_t object, dnode_handle_t *dnh);
void dnode_special_close(dnode_handle_t *dnh);

void dnode_setbonuslen(dnode_t *dn, int newsize, dmu_tx_t *tx);
void dnode_setbonus_type(dnode_t *dn, dmu_object_type_t, dmu_tx_t *tx);
void dnode_rm_spill(dnode_t *dn, dmu_tx_t *tx);

int dnode_hold(struct objset *dd, uint64_t object,
    void *ref, dnode_t **dnp);
int dnode_hold_impl(struct objset *dd, uint64_t object, int flag, int dn_slots,
    void *ref, dnode_t **dnp);
boolean_t dnode_add_ref(dnode_t *dn, void *ref);
void dnode_rele(dnode_t *dn, void *ref);
void dnode_rele_and_unlock(dnode_t *dn, void *tag, boolean_t evicting);
void dnode_setdirty(dnode_t *dn, dmu_tx_t *tx);
void dnode_sync(dnode_t *dn, dmu_tx_t *tx);
void dnode_allocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, int ibs,
    dmu_object_type_t bonustype, int bonuslen, int dn_slots, dmu_tx_t *tx);
void dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize,
    dmu_object_type_t bonustype, int bonuslen, int dn_slots, dmu_tx_t *tx);
void dnode_free(dnode_t *dn, dmu_tx_t *tx);
void dnode_byteswap(dnode_phys_t *dnp);
void dnode_buf_byteswap(void *buf, size_t size);
void dnode_verify(dnode_t *dn);
int dnode_set_nlevels(dnode_t *dn, int nlevels, dmu_tx_t *tx);
int dnode_set_blksz(dnode_t *dn, uint64_t size, int ibs, dmu_tx_t *tx);
void dnode_free_range(dnode_t *dn, uint64_t off, uint64_t len, dmu_tx_t *tx);
void dnode_diduse_space(dnode_t *dn, int64_t space);
void dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx,
    boolean_t have_read, boolean_t force);
uint64_t dnode_block_freed(dnode_t *dn, uint64_t blkid);
void dnode_init(void);
void dnode_fini(void);
int dnode_next_offset(dnode_t *dn, int flags, uint64_t *off,
    int minlvl, uint64_t blkfill, uint64_t txg);
void dnode_evict_dbufs(dnode_t *dn);
void dnode_evict_bonus(dnode_t *dn);
void dnode_free_interior_slots(dnode_t *dn);
boolean_t dnode_needs_remap(const dnode_t *dn);

#define	DNODE_IS_DIRTY(_dn)						\
	((_dn)->dn_dirty_txg >= spa_syncing_txg((_dn)->dn_objset->os_spa))

#define	DNODE_IS_CACHEABLE(_dn)						\
	((_dn)->dn_objset->os_primary_cache == ZFS_CACHE_ALL ||		\
	(DMU_OT_IS_METADATA((_dn)->dn_type) &&				\
	(_dn)->dn_objset->os_primary_cache == ZFS_CACHE_METADATA))

#define	DNODE_META_IS_CACHEABLE(_dn)					\
	((_dn)->dn_objset->os_primary_cache == ZFS_CACHE_ALL ||		\
	(_dn)->dn_objset->os_primary_cache == ZFS_CACHE_METADATA)

/*
 * Used for dnodestats kstat.
 */
typedef struct dnode_stats {
	/*
	 * Number of failed attempts to hold a meta dnode dbuf.
	 */
	kstat_named_t dnode_hold_dbuf_hold;
	/*
	 * Number of failed attempts to read a meta dnode dbuf.
	 */
	kstat_named_t dnode_hold_dbuf_read;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) was able
	 * to hold the requested object number which was allocated.  This is
	 * the common case when looking up any allocated object number.
	 */
	kstat_named_t dnode_hold_alloc_hits;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) was not
	 * able to hold the request object number because it was not allocated.
	 */
	kstat_named_t dnode_hold_alloc_misses;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) was not
	 * able to hold the request object number because the object number
	 * refers to an interior large dnode slot.
	 */
	kstat_named_t dnode_hold_alloc_interior;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) needed
	 * to retry acquiring slot zrl locks due to contention.
	 */
	kstat_named_t dnode_hold_alloc_lock_retry;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) did not
	 * need to create the dnode because another thread did so after
	 * dropping the read lock but before acquiring the write lock.
	 */
	kstat_named_t dnode_hold_alloc_lock_misses;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_ALLOCATED) found
	 * a free dnode instantiated by dnode_create() but not yet allocated
	 * by dnode_allocate().
	 */
	kstat_named_t dnode_hold_alloc_type_none;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) was able
	 * to hold the requested range of free dnode slots.
	 */
	kstat_named_t dnode_hold_free_hits;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) was not
	 * able to hold the requested range of free dnode slots because
	 * at least one slot was allocated.
	 */
	kstat_named_t dnode_hold_free_misses;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) was not
	 * able to hold the requested range of free dnode slots because
	 * after acquiring the zrl lock at least one slot was allocated.
	 */
	kstat_named_t dnode_hold_free_lock_misses;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) needed
	 * to retry acquiring slot zrl locks due to contention.
	 */
	kstat_named_t dnode_hold_free_lock_retry;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) requested
	 * a range of dnode slots which were held by another thread.
	 */
	kstat_named_t dnode_hold_free_refcount;
	/*
	 * Number of times dnode_hold(..., DNODE_MUST_BE_FREE) requested
	 * a range of dnode slots which would overflow the dnode_phys_t.
	 */
	kstat_named_t dnode_hold_free_overflow;
	/*
	 * Number of times a dnode_hold(...) was attempted on a dnode
	 * which had already been unlinked in an earlier txg.
	 */
	kstat_named_t dnode_hold_free_txg;
	/*
	 * Number of times dnode_free_interior_slots() needed to retry
	 * acquiring a slot zrl lock due to contention.
	 */
	kstat_named_t dnode_free_interior_lock_retry;
	/*
	 * Number of new dnodes allocated by dnode_allocate().
	 */
	kstat_named_t dnode_allocate;
	/*
	 * Number of dnodes re-allocated by dnode_reallocate().
	 */
	kstat_named_t dnode_reallocate;
	/*
	 * Number of meta dnode dbufs evicted.
	 */
	kstat_named_t dnode_buf_evict;
	/*
	 * Number of times dmu_object_alloc*() reached the end of the existing
	 * object ID chunk and advanced to a new one.
	 */
	kstat_named_t dnode_alloc_next_chunk;
	/*
	 * Number of times multiple threads attempted to allocate a dnode
	 * from the same block of free dnodes.
	 */
	kstat_named_t dnode_alloc_race;
	/*
	 * Number of times dmu_object_alloc*() was forced to advance to the
	 * next meta dnode dbuf due to an error from  dmu_object_next().
	 */
	kstat_named_t dnode_alloc_next_block;
	/*
	 * Statistics for tracking dnodes which have been moved.
	 */
	kstat_named_t dnode_move_invalid;
	kstat_named_t dnode_move_recheck1;
	kstat_named_t dnode_move_recheck2;
	kstat_named_t dnode_move_special;
	kstat_named_t dnode_move_handle;
	kstat_named_t dnode_move_rwlock;
	kstat_named_t dnode_move_active;
} dnode_stats_t;

extern dnode_stats_t dnode_stats;

#define	DNODE_STAT_INCR(stat, val) \
    atomic_add_64(&dnode_stats.stat.value.ui64, (val));
#define	DNODE_STAT_BUMP(stat) \
    DNODE_STAT_INCR(stat, 1);

#ifdef ZFS_DEBUG

/*
 * There should be a ## between the string literal and fmt, to make it
 * clear that we're joining two strings together, but that piece of shit
 * gcc doesn't support that preprocessor token.
 */
#define	dprintf_dnode(dn, fmt, ...) do { \
	if (zfs_flags & ZFS_DEBUG_DPRINTF) { \
	char __db_buf[32]; \
	uint64_t __db_obj = (dn)->dn_object; \
	if (__db_obj == DMU_META_DNODE_OBJECT) \
		(void) strcpy(__db_buf, "mdn"); \
	else \
		(void) snprintf(__db_buf, sizeof (__db_buf), "%lld", \
		    (u_longlong_t)__db_obj);\
	dprintf_ds((dn)->dn_objset->os_dsl_dataset, "obj=%s " fmt, \
	    __db_buf, __VA_ARGS__); \
	} \
_NOTE(CONSTCOND) } while (0)

#define	DNODE_VERIFY(dn)		dnode_verify(dn)
#define	FREE_VERIFY(db, start, end, tx)	free_verify(db, start, end, tx)

#else

#define	dprintf_dnode(db, fmt, ...)
#define	DNODE_VERIFY(dn)
#define	FREE_VERIFY(db, start, end, tx)

#endif

#ifdef	__cplusplus
}
#endif

#endif	/* _SYS_DNODE_H */