zfs/sys/dbuf.h

	dbuf.h revision fa9e4066f08beec538e775443c5be79dd423fcab
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#ifndef _SYS_DBUF_H
#define _SYS_DBUF_H

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/dmu.h>
#include <sys/spa.h>
#include <sys/txg.h>
#include <sys/zio.h>
#include <sys/arc.h>
#include <sys/zfs_context.h>
#include <sys/refcount.h>

#ifdef  __cplusplus
extern "C" {
#endif

#define DB_BONUS_BLKID (-1ULL)
#define IN_DMU_SYNC ((blkptr_t *)-1)

/*
 * define flags for dbuf_read and friends
 */

#define DB_RF_MUST_SUCCEED  0
#define DB_RF_CANFAIL       (1 << 1)
#define DB_RF_HAVESTRUCT    (1 << 2)
#define DB_RF_NOPREFETCH    (1 << 3)

/*
 * The state transition diagram for dbufs looks like:
 *
 *      +----> READ ----+
 *      |       |
 *      |       V
 *   (alloc)-->UNCACHED      CACHED-->(free)
 *      |       ^
 *      |       |
 *      +----> FILL ----+
 */
typedef enum dbuf_states {
    DB_UNCACHED,
    DB_FILL,
    DB_READ,
    DB_CACHED
} dbuf_states_t;

struct objset_impl;
struct dnode;
struct dmu_tx;

/*
 * level = 0 means the user data
 * level = 1 means the single indirect block
 * etc.
 */

#define LIST_LINK_INACTIVE(link) \
    ((link)->list_next == NULL && (link)->list_prev == NULL)

typedef struct dmu_buf_impl {
    /*
     * The following members are immutable, with the exception of
     * db.db_data, which is protected by db_mtx.
     */

    /* the publicly visible structure */
    dmu_buf_t db;

    /* the objset we belong to */
    struct objset_impl *db_objset;

    /*
     * the dnode we belong to (NULL when evicted)
     */
    struct dnode *db_dnode;

    /*
     * our parent buffer; if the dnode points to us directly,
     * db_parent == db_dnode->dn_dbuf
     * only accessed by sync thread ???
     * (NULL when evicted)
     */
    struct dmu_buf_impl *db_parent;

    /*
     * link for hash table of all dmu_buf_impl_t's
     */
    struct dmu_buf_impl *db_hash_next;

    /* our block number */
    uint64_t db_blkid;

    /*
     * Pointer to the blkptr_t which points to us. May be NULL if we
     * don't have one yet. (NULL when evicted)
     */
    blkptr_t *db_blkptr;

    /*
     * Our indirection level.  Data buffers have db_level==0.
     * Indirect buffers which point to data buffers have
     * db_level==1. etc.  Buffers which contain dnodes have
     * db_level==0, since the dnodes are stored in a file.
     */
    uint8_t db_level;

    /* db_mtx protects the members below */
    kmutex_t db_mtx;

    /*
     * Current state of the buffer
     */
    dbuf_states_t db_state;

    /*
     * Refcount accessed by dmu_buf_{hold,rele}.
     * If nonzero, the buffer can't be destroyed.
     * Protected by db_mtx.
     */
    refcount_t db_holds;

    /* buffer holding our data */
    arc_buf_t *db_buf;

    kcondvar_t db_changed;
    arc_buf_t *db_data_pending;

    /*
     * Last time (transaction group) this buffer was dirtied.
     */
    uint64_t db_dirtied;

    /*
     * If dd_dnode != NULL, our link on the owner dnodes's dn_dbufs list.
     * Protected by its dn_mtx.
     */
    list_node_t db_link;

    /* Our link on dn_dirty_dbufs[txg] */
    list_node_t db_dirty_node[TXG_SIZE];
    uint8_t db_dirtycnt;

    /*
     * Data which is unique to data (leaf) blocks:
     */
    struct {
        /* stuff we store for the user (see dmu_buf_set_user) */
        void *db_user_ptr;
        void **db_user_data_ptr_ptr;
        dmu_buf_evict_func_t *db_evict_func;
        uint8_t db_immediate_evict;
        uint8_t db_freed_in_flight;

        /*
         * db_data_old[txg&TXG_MASK] is set when we
         * dirty the buffer, so that we can retain the
         * pointer even if it gets COW'd in a subsequent
         * transaction group.
         *
         * If the buffer is dirty in any txg, it can't
         * be destroyed.
         */
        /*
         * XXX Protected by db_mtx and dn_dirty_mtx.
         * db_mtx must be held to read db_dirty[], and
         * both db_mtx and dn_dirty_mtx must be held to
         * modify (dirty or clean). db_mtx must be held
         * before dn_dirty_mtx.
         */
        arc_buf_t *db_data_old[TXG_SIZE];
        blkptr_t *db_overridden_by[TXG_SIZE];
    } db_d;
} dmu_buf_impl_t;

/* Note: the dbuf hash table is exposed only for the mdb module */
#define DBUF_MUTEXES 256
#define DBUF_HASH_MUTEX(h, idx) (&(h)->hash_mutexes[(idx) & (DBUF_MUTEXES-1)])
typedef struct dbuf_hash_table {
    uint64_t hash_table_mask;
    dmu_buf_impl_t **hash_table;
    kmutex_t hash_mutexes[DBUF_MUTEXES];
} dbuf_hash_table_t;


uint64_t dbuf_whichblock(struct dnode *di, uint64_t offset);

dmu_buf_impl_t *dbuf_create_tlib(struct dnode *dn, char *data);

dmu_buf_impl_t *dbuf_hold(struct dnode *dn, uint64_t blkid);
dmu_buf_impl_t *dbuf_hold_level(struct dnode *dn, int level, uint64_t blkid,
    void *tag);
dmu_buf_impl_t *dbuf_hold_bonus(struct dnode *dn, void *tag);
int dbuf_hold_impl(struct dnode *dn, uint8_t level, uint64_t blkid, int create,
    void *tag, dmu_buf_impl_t **dbp);

void dbuf_prefetch(struct dnode *dn, uint64_t blkid);

void dbuf_add_ref(dmu_buf_impl_t *db, void *tag);
void dbuf_remove_ref(dmu_buf_impl_t *db, void *tag);
uint64_t dbuf_refcount(dmu_buf_impl_t *db);

void dbuf_rele(dmu_buf_impl_t *db);

dmu_buf_impl_t *dbuf_find(struct dnode *dn, uint8_t level, uint64_t blkid);

void dbuf_read(dmu_buf_impl_t *db);
int dbuf_read_canfail(dmu_buf_impl_t *db);
void dbuf_read_havestruct(dmu_buf_impl_t *db);
void dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags);
void dbuf_will_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx);
void dbuf_will_fill(dmu_buf_impl_t *db, dmu_tx_t *tx);
void dbuf_fill_done(dmu_buf_impl_t *db, dmu_tx_t *tx);
void dmu_buf_will_fill(dmu_buf_t *db, dmu_tx_t *tx);
void dmu_buf_fill_done(dmu_buf_t *db, dmu_tx_t *tx);
void dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx);

void dbuf_evict(dmu_buf_impl_t *db);

void dbuf_setdirty(dmu_buf_impl_t *db, dmu_tx_t *tx);
void dbuf_sync(dmu_buf_impl_t *db, zio_t *zio, dmu_tx_t *tx);
void dbuf_unoverride(dmu_buf_impl_t *db, uint64_t txg);

void dbuf_free_range(struct dnode *dn, uint64_t blkid, uint64_t nblks,
    struct dmu_tx *);

void dbuf_downgrade(dmu_buf_impl_t *db, int evicting);
void dbuf_new_size(dmu_buf_impl_t *db, int size, dmu_tx_t *tx);

void dbuf_init(void);
void dbuf_fini(void);

#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_dbuf(dbuf, fmt, ...) do { \
    if (zfs_flags & ZFS_DEBUG_DPRINTF) { \
    char __db_buf[32]; \
    uint64_t __db_obj = (dbuf)->db.db_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((dbuf)->db_objset->os_dsl_dataset, \
        "obj=%s lvl=%u blkid=%lld " fmt, \
        __db_buf, (dbuf)->db_level, \
        (u_longlong_t)(dbuf)->db_blkid, __VA_ARGS__); \
    } \
_NOTE(CONSTCOND) } while (0)

#define dprintf_dbuf_bp(db, bp, fmt, ...) do {          \
    if (zfs_flags & ZFS_DEBUG_DPRINTF) { \
    char __blkbuf[200];                 \
    sprintf_blkptr(__blkbuf, bp);               \
    dprintf_dbuf(db, fmt " %s\n", __VA_ARGS__, __blkbuf);   \
    } \
_NOTE(CONSTCOND) } while (0)

#else

#define dprintf_dbuf(db, fmt, ...)
#define dprintf_dbuf_bp(db, bp, fmt, ...)

#endif


#ifdef  __cplusplus
}
#endif

#endif /* _SYS_DBUF_H */