path: root/xlators/storage/bdb/src/bdb-ll.c

/*
  Copyright (c) 2008-2009 Z RESEARCH, Inc. <http://www.zresearch.com>
  This file is part of GlusterFS.

  GlusterFS is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published
  by the Free Software Foundation; either version 3 of the License,
  or (at your option) any later version.

  GlusterFS 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 for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see
  <http://www.gnu.org/licenses/>.
*/

#include <libgen.h>
#include "bdb.h"
#include <list.h>
/*
 * implement the procedures to interact with bdb */

/****************************************************************
 *
 * General wrappers and utility procedures for bdb xlator
 *
 ****************************************************************/

ino_t
bdb_inode_transform (ino_t parent,
                     bctx_t *bctx)
{
        struct bdb_private *private = NULL;
        ino_t               ino = -1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);

        private = bctx->table->this->private;

        LOCK (&private->ino_lock);
        ino = ++private->next_ino;
        UNLOCK (&private->ino_lock);
out:
        return ino;
}


/***********************************************************
 *
 *  bdb storage database utilities
 *
 **********************************************************/

/*
 * bdb_db_open - opens a storage db.
 *
 * @ctx: context specific to the directory for which we are supposed to open db
 *
 * see, if we have empty slots to open a db.
 *      if (no-empty-slots), then prune open dbs and close as many as possible
 *      if (empty-slot-available), tika muchkonDu db open maaDu
 *
 * NOTE: illi baro munche lock hiDkobEku
 */
static DB *
bdb_db_open (bctx_t *bctx)
{
        DB *storage_dbp = NULL;
        int32_t op_ret = -1;
        bctx_table_t *table = NULL;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);

        table = bctx->table;
        GF_VALIDATE_OR_GOTO ("bdb-ll", table, out);

        /* we have to do the following, we can't deny someone of db_open ;) */
        op_ret = db_create (&storage_dbp, table->dbenv, 0);
        if (op_ret != 0) {
                gf_log ("bdb-ll", GF_LOG_ERROR,
                        "failed to do db_create for directory %s (%s)",
                        bctx->directory, db_strerror (op_ret));
                storage_dbp = NULL;
                goto out;
        }

        if (table->page_size) {
                op_ret = storage_dbp->set_pagesize (storage_dbp,
                                                    table->page_size);
                if (op_ret != 0) {
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "failed to set the page_size (%"PRIu64") for "
                                "directory %s (%s)",
                                table->page_size, bctx->directory,
                                db_strerror (op_ret));
                } else {
                        gf_log ("bdb-ll", GF_LOG_DEBUG,
                                "page-size (%"PRIu64") set on DB",
                                table->page_size);
                }
        }

        op_ret = storage_dbp->open (storage_dbp,
                                    NULL,
                                    bctx->db_path,
                                    NULL,
                                    table->access_mode,
                                    table->dbflags,
                                    0);
        if (op_ret != 0 ) {
                gf_log ("bdb-ll",
                        GF_LOG_ERROR,
                        "failed to open storage-db for directory %s (%s)",
                        bctx->db_path, db_strerror (op_ret));
                storage_dbp = NULL;
        }

out:
        return storage_dbp;
}



int32_t
bdb_cursor_close (bctx_t *bctx,
                  DBC *cursorp)
{
        int32_t ret = -1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", cursorp, out);

        LOCK (&bctx->lock);
        {
#ifdef HAVE_BDB_CURSOR_GET
                ret = cursorp->close (cursorp);
#else
                ret = cursorp->c_close (cursorp);
#endif
                if ((ret != 0)) {
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "failed to close db cursor for directory "
                                "%s (%s)",
                                bctx->directory, db_strerror (ret));
                }
        }
        UNLOCK (&bctx->lock);

out:
        return ret;
}


int32_t
bdb_cursor_open (bctx_t *bctx,
                 DBC **cursorpp)
{
        int32_t ret = -1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", cursorpp, out);

        LOCK (&bctx->lock);
        {
                if (bctx->dbp) {
                        /* do nothing, just continue */
                        ret = 0;
                } else {
                        bctx->dbp = bdb_db_open (bctx);
                        if (!bctx->dbp) {
                                gf_log ("bdb-ll", GF_LOG_ERROR,
                                        "failed to open storage db for %s",
                                        bctx->directory);
                                ret = -1;
                        } else {
                                ret = 0;
                        }
                }

                if (ret == 0) {
                        /* all set, lets open cursor */
                        ret = bctx->dbp->cursor (bctx->dbp, NULL, cursorpp, 0);
                        if (ret != 0) {
                                gf_log ("bdb-ll", GF_LOG_ERROR,
                                        "failed to create a cursor for %s (%s)",
                                        bctx->directory, db_strerror (ret));
                        }
                }
        }
        UNLOCK (&bctx->lock);

out:
        return ret;
}


/* cache related */
static bdb_cache_t *
bdb_cache_lookup (bctx_t *bctx,
                  char *path)
{
        bdb_cache_t *bcache = NULL;
        bdb_cache_t *trav   = NULL;
        char        *key    = NULL;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", path, out);

        MAKE_KEY_FROM_PATH (key, path);

        LOCK (&bctx->lock);
        {
                list_for_each_entry (trav, &bctx->c_list, c_list) {
                        if (!strcmp (trav->key, key)){
                                bcache = trav;
                                break;
                        }
                }
        }
        UNLOCK (&bctx->lock);

out:
        return bcache;
}

static int32_t
bdb_cache_insert (bctx_t *bctx,
                  DBT *key,
                  DBT *data)
{
        bdb_cache_t *bcache = NULL;
        int32_t ret = -1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", key, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", data, out);

        LOCK (&bctx->lock);
        {
                if (bctx->c_count > 5) {
                        /* most of the times, we enter here */
                        /* FIXME: ugly, not supposed to disect any of the
                         * 'struct list_head' directly */
                        if (!list_empty (&bctx->c_list)) {
                                bcache = list_entry (bctx->c_list.prev, bdb_cache_t, c_list);
                                list_del_init (&bcache->c_list);
                        }
                        if (bcache->key) {
                                free (bcache->key);
                                bcache->key = strdup ((char *)key->data);
                                GF_VALIDATE_OR_GOTO ("bdb-ll", bcache->key, unlock);
                        } else {
                                /* should never come here */
                                gf_log ("bdb-ll", GF_LOG_CRITICAL,
                                        "bcache->key (null)");
                        } /* if(bcache->key)...else */
                        if (bcache->data) {
                                free (bcache->data);
                                bcache->data = memdup (data->data, data->size);
                                GF_VALIDATE_OR_GOTO ("bdb-ll", bcache->data, unlock);
                                bcache->size = data->size;
                        } else {
                                /* should never come here */
                                gf_log ("bdb-ll", GF_LOG_CRITICAL,
                                        "bcache->data (null)");
                        } /* if(bcache->data)...else */
                        list_add (&bcache->c_list, &bctx->c_list);
                        ret = 0;
                } else {
                        /* we will be entering here very rarely */
                        bcache = CALLOC (1, sizeof (*bcache));
                        GF_VALIDATE_OR_GOTO ("bdb-ll", bcache, unlock);
                        bcache->key = strdup ((char *)(key->data));
                        GF_VALIDATE_OR_GOTO ("bdb-ll", bcache->key, unlock);
                        bcache->data = memdup (data->data, data->size);
                        GF_VALIDATE_OR_GOTO ("bdb-ll", bcache->data, unlock);
                        bcache->size = data->size;
                        list_add (&bcache->c_list, &bctx->c_list);
                        bctx->c_count++;
                        ret = 0;
                } /* if(private->c_count < 5)...else */
        }
unlock:
        UNLOCK (&bctx->lock);
out:
        return ret;
}

static int32_t
bdb_cache_delete (bctx_t *bctx,
                  char *key)
{
        bdb_cache_t *bcache = NULL;
        bdb_cache_t *trav   = NULL;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", key, out);

        LOCK (&bctx->lock);
        {
                list_for_each_entry (trav, &bctx->c_list, c_list) {
                        if (!strcmp (trav->key, key)){
                                bctx->c_count--;
                                bcache = trav;
                                break;
                        }
                }

                if (bcache) {
                        list_del_init (&bcache->c_list);
                        free (bcache->key);
                        free (bcache->data);
                        free (bcache);
                }
        }
        UNLOCK (&bctx->lock);

out:
        return 0;
}

void *
bdb_db_stat (bctx_t *bctx,
             DB_TXN *txnid,
             uint32_t flags)
{
        DB     *storage = NULL;
        void   *stat    = NULL;
        int32_t ret     = -1;

        LOCK (&bctx->lock);
        {
                if (bctx->dbp == NULL) {
                        bctx->dbp = bdb_db_open (bctx);
                        storage = bctx->dbp;
                } else {
                        /* we are just fine, lets continue */
                        storage = bctx->dbp;
                } /* if(bctx->dbp==NULL)...else */
        }
        UNLOCK (&bctx->lock);

        GF_VALIDATE_OR_GOTO ("bdb-ll", storage, out);

        ret = storage->stat (storage, txnid, &stat, flags);

        if (ret != 0) {
                gf_log ("bdb-ll", GF_LOG_ERROR,
                        "failed to do DB->stat() on db file %s: %s",
                        bctx->db_path, db_strerror (ret));
        } else {
                gf_log ("bdb-ll", GF_LOG_DEBUG,
                        "successfully called DB->stat() on db file %s",
                        bctx->db_path);
        }
out:
        return stat;

}

/* bdb_storage_get - retrieve a key/value pair corresponding to @path from the corresponding
 *                   db file.
 *
 * @bctx: bctx_t * corresponding to the parent directory of @path. (should always be a valid
 *        bctx).  bdb_storage_get should never be called if @bctx = NULL.
 * @txnid: NULL if bdb_storage_get is not embedded in an explicit transaction or a valid
 *         DB_TXN *, when embedded in an explicit transaction.
 * @path: path of the file to read from (translated to a database key using MAKE_KEY_FROM_PATH)
 * @buf: char ** - pointer to a pointer to char. a read buffer is created in this procedure
 *       and pointer to the buffer is passed through @buf to the caller.
 * @size: size of the file content to be read.
 * @offset: offset from which the file content to be read.
 *
 * NOTE: bdb_storage_get tries to open DB, if @bctx->dbp == NULL (@bctx->dbp == NULL,
 *      nobody has opened DB till now or DB was closed by bdb_table_prune()).
 *
 * NOTE: if private->cache is set (bdb xlator's internal caching enabled), then bdb_storage_get
 *      first looks up the cache for key/value pair. if bdb_lookup_cache fails, then only
 *      DB->get() is called. also,  inserts a newly read key/value pair to cache through
 *      bdb_insert_to_cache.
 *
 * return: 'number of bytes read' on success or -1 on error.
 *
 * also see: bdb_lookup_cache, bdb_insert_to_cache for details about bdb xlator's internal cache.
 */
int32_t
bdb_db_get (bctx_t *bctx,
            DB_TXN *txnid,
            const char *path,
            char **buf,
            size_t size,
            off_t offset)
{
        DB          *storage    = NULL;
        DBT          key        = {0,};
        DBT          value      = {0,};
        int32_t      ret        = -1;
        char        *key_string = NULL;
        bdb_cache_t *bcache     = NULL;
        int32_t      db_flags   = 0;
        uint8_t      need_break = 0;
        int32_t      retries    = 1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", bctx, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", path, out);

        MAKE_KEY_FROM_PATH (key_string, path);

        if (bctx->cache &&
            ((bcache = bdb_cache_lookup (bctx, key_string)) != NULL)) {
                if (buf) {
                        *buf = CALLOC (1, bcache->size);
                        GF_VALIDATE_OR_GOTO ("bdb-ll", buf, out);
                        memcpy (*buf, (bcache->data + offset), bcache->size);
                }
                ret = bcache->size;
        } else {
                LOCK (&bctx->lock);
                {
                        if (bctx->dbp == NULL) {
                                bctx->dbp = bdb_db_open (bctx);
                                storage = bctx->dbp;
                        } else {
                                /* we are just fine, lets continue */
                                storage = bctx->dbp;
                        } /* if(bctx->dbp==NULL)...else */
                }
                UNLOCK (&bctx->lock);

                GF_VALIDATE_OR_GOTO ("bdb-ll", storage, out);

                key.data = (char *)key_string;
                key.size = strlen (key_string);
                key.flags = DB_DBT_USERMEM;

                if (bctx->cache){
                        /* we are called to return the size of the file */
                        value.flags = DB_DBT_MALLOC;
                } else {
                        if (size) {
                                value.flags = DB_DBT_MALLOC | DB_DBT_PARTIAL;
                        } else {
                                value.flags = DB_DBT_MALLOC;
                        }
                        value.dlen = size;
                        value.doff = offset;
                }

                do {
                        /* TODO: we prefer to give our own buffer to value.data
                         * and ask bdb to fill in it */
                        ret = storage->get (storage, txnid, &key, &value,
                                            db_flags);

                        if (ret == DB_NOTFOUND) {
                                gf_log ("bdb-ll", GF_LOG_DEBUG,
                                        "failed to do DB->get() for key: %s."
                                        " key not found in storage DB",
                                        key_string);
                                ret = -1;
                                need_break = 1;
                        } else if (ret == DB_LOCK_DEADLOCK) {
                                retries++;
                                gf_log ("bdb-ll", GF_LOG_ERROR,
                                        "deadlock detected in DB->put. retrying"
                                        " DB->put (%d)", retries);
                        }else if (ret == 0) {
                                /* successfully read data, lets set everything
                                 * in place and return */
                                if (buf) {
                                        *buf = CALLOC (1, value.size);
                                        ERR_ABORT (*buf);
                                        memcpy (*buf, value.data, value.size);
                                }
                                ret = value.size;
                                if (bctx->cache)
                                        bdb_cache_insert (bctx, &key, &value);
                                free (value.data);
                                need_break = 1;
                        } else {
                                gf_log ("bdb-ll",
                                        GF_LOG_ERROR,
                                        "failed to do DB->get() for key %s: %s",
                                        key_string, db_strerror (ret));
                                ret = -1;
                                need_break = 1;
                        }
                } while (!need_break);
        }
out:
        return ret;
}/* bdb_db_get */

/* bdb_storage_put - insert a key/value specified to the corresponding DB.
 *
 * @bctx: bctx_t * corresponding to the parent directory of @path.
 *        (should always be a valid bctx). bdb_storage_put should never be
 *         called if @bctx = NULL.
 * @txnid: NULL if bdb_storage_put is not embedded in an explicit transaction
 *         or a valid DB_TXN *, when embedded in an explicit transaction.
 * @key_string: key of the database entry.
 * @buf: pointer to the buffer data to be written as data for @key_string.
 * @size: size of @buf.
 * @offset: offset in the key's data to be modified with provided data.
 * @flags: valid flags are BDB_TRUNCATE_RECORD (to reduce the data of
 *         @key_string to 0 size).
 *
 * NOTE: bdb_storage_put tries to open DB, if @bctx->dbp == NULL
 *      (@bctx->dbp == NULL, nobody has opened DB till now or DB was closed by
 *       bdb_table_prune()).
 *
 * NOTE: bdb_storage_put deletes the key/value from bdb xlator's internal cache.
 *
 * return: 0 on success or -1 on error.
 *
 * also see: bdb_cache_delete for details on how a cached key/value pair is
 * removed.
 */
int32_t
bdb_db_put (bctx_t *bctx,
            DB_TXN *txnid,
            const char *key_string,
            const char *buf,
            size_t size,
            off_t offset,
            int32_t flags)
{
        DB     *storage = NULL;
        DBT     key = {0,}, value = {0,};
        int32_t ret = -1;
        int32_t db_flags = DB_AUTO_COMMIT;
        uint8_t need_break = 0;
        int32_t retries = 1;

        LOCK (&bctx->lock);
        {
                if (bctx->dbp == NULL) {
                        bctx->dbp = bdb_db_open (bctx);
                        storage = bctx->dbp;
                } else {
                        /* we are just fine, lets continue */
                        storage = bctx->dbp;
                }
        }
        UNLOCK (&bctx->lock);

        GF_VALIDATE_OR_GOTO ("bdb-ll", storage, out);

        if (bctx->cache) {
                ret = bdb_cache_delete (bctx, (char *)key_string);
                GF_VALIDATE_OR_GOTO ("bdb-ll", (ret == 0), out);
        }

        key.data = (void *)key_string;
        key.size = strlen (key_string);

        /* NOTE: bdb lets us expand the file, suppose value.size > value.len,
         * then value.len bytes from value.doff offset and value.size bytes
         * will be written from value.doff and data from
         * value.doff + value.dlen will be pushed value.doff + value.size
         */
        value.data = (void *)buf;

        if (flags & BDB_TRUNCATE_RECORD) {
                value.size = size;
                value.doff = 0;
                value.dlen = offset;
        } else {
                value.size = size;
                value.dlen = size;
                value.doff = offset;
        }
        value.flags = DB_DBT_PARTIAL;
        if (buf == NULL && size == 0)
                /* truncate called us */
                value.flags = 0;

        do {
                ret = storage->put (storage, txnid, &key, &value, db_flags);
                if (ret == DB_LOCK_DEADLOCK) {
                        retries++;
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "deadlock detected in DB->put. "
                                "retrying DB->put (%d)",
                                retries);
                } else if (ret) {
                        /* write failed */
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "failed to do DB->put() for key %s: %s",
                                key_string, db_strerror (ret));
                        need_break = 1;
                } else {
                        /* successfully wrote */
                        ret = 0;
                        need_break = 1;
                }
        } while (!need_break);
out:
        return ret;
}/* bdb_db_put */


/* bdb_storage_del - delete a key/value pair corresponding to @path from corresponding db file.
 *
 * @bctx: bctx_t * corresponding to the parent directory of @path.
 *       (should always be a valid bctx). bdb_storage_del should never be called
 *       if @bctx = NULL.
 * @txnid: NULL if bdb_storage_del is not embedded in an explicit transaction or a
 *         valid DB_TXN *, when embedded in an explicit transaction.
 * @path: path to the file, whose key/value pair has to be deleted.
 *
 * NOTE: bdb_storage_del tries to open DB, if @bctx->dbp == NULL (@bctx->dbp == NULL,
 *      nobody has opened DB till now or DB was closed by bdb_table_prune()).
 *
 * return: 0 on success or -1 on error.
 */
int32_t
bdb_db_del (bctx_t *bctx,
            DB_TXN *txnid,
            const char *path)
{
        DB     *storage    = NULL;
        DBT     key        = {0,};
        char   *key_string = NULL;
        int32_t ret        = -1;
        int32_t db_flags   = 0;
        uint8_t need_break = 0;
        int32_t retries    = 1;

        MAKE_KEY_FROM_PATH (key_string, path);

        LOCK (&bctx->lock);
        {
                if (bctx->dbp == NULL) {
                        bctx->dbp = bdb_db_open (bctx);
                        storage = bctx->dbp;
                } else {
                        /* we are just fine, lets continue */
                        storage = bctx->dbp;
                }
        }
        UNLOCK (&bctx->lock);

        GF_VALIDATE_OR_GOTO ("bdb-ll", storage, out);

        ret = bdb_cache_delete (bctx, key_string);
        GF_VALIDATE_OR_GOTO ("bdb-ll", (ret == 0), out);

        key.data = key_string;
        key.size = strlen (key_string);
        key.flags = DB_DBT_USERMEM;

        do {
                ret = storage->del (storage, txnid, &key, db_flags);

                if (ret == DB_NOTFOUND) {
                        gf_log ("bdb-ll", GF_LOG_DEBUG,
                                "failed to delete %s from storage db, "
                                "doesn't exist in storage DB",
                                path);
                        need_break = 1;
                } else if (ret == DB_LOCK_DEADLOCK) {
                        retries++;
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "deadlock detected in DB->put. "
                                "retrying DB->put (%d)",
                                retries);
                }else if (ret == 0) {
                        /* successfully deleted the entry */
                        gf_log ("bdb-ll", GF_LOG_DEBUG,
                                "deleted %s from storage db", path);
                        ret = 0;
                        need_break = 1;
                } else {
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "failed to delete %s from storage db: %s",
                                path, db_strerror (ret));
                        ret = -1;
                        need_break = 1;
                }
        } while (!need_break);
out:
        return ret;
}

/* NOTE: bdb version compatibility wrapper */
int32_t
bdb_cursor_get (DBC *cursorp,
                DBT *key,
                DBT *value,
                int32_t flags)
{
        int32_t ret = -1;

        GF_VALIDATE_OR_GOTO ("bdb-ll", cursorp, out);

#ifdef HAVE_BDB_CURSOR_GET
        ret = cursorp->get (cursorp, key, value, flags);
#else
        ret = cursorp->c_get (cursorp, key, value, flags);
#endif
        if ((ret != 0)  && (ret != DB_NOTFOUND)) {
                gf_log ("bdb-ll", GF_LOG_ERROR,
                        "failed to CURSOR->get() for key %s (%s)",
                        (char *)key->data, db_strerror (ret));
        }

out:
        return ret;
}/* bdb_cursor_get */


int32_t
bdb_dirent_size (DBT *key)
{
        return ALIGN (24 /* FIX MEEEE!!! */ + key->size);
}


/* bdb_extract_bfd - translate a fd_t to a bfd (either a 'struct bdb_bfd' or 'struct bdb_dir')
 *
 * @fd->ctx is with bdb specific file handle during a successful bdb_open (also bdb_create)
 *  or bdb_opendir.
 *
 * return: 'struct bdb_bfd *' or 'struct bdb_dir *' on success, or NULL on failure.
 */
inline void *
bdb_extract_bfd (fd_t *fd,
                 xlator_t *this)
{
        uint64_t tmp_bfd = 0;
        void    *bfd     = NULL;

        GF_VALIDATE_OR_GOTO ("bdb-ll", fd, out);
        GF_VALIDATE_OR_GOTO ("bdb-ll", this, out);

        fd_ctx_get (fd, this, &tmp_bfd);
        bfd = (void *)(long)bfd;

out:
        return bfd;
}

/* bdb_dbenv_init - initialize DB_ENV
 *
 *  initialization includes:
 *   1. opening DB_ENV (db_env_create(), DB_ENV->open()).
 *      NOTE: see private->envflags for flags used.
 *   2. DB_ENV->set_lg_dir - set log directory to be used for storing log files
 *     (log files are the files in which transaction logs are written by db).
 *   3. DB_ENV->set_flags (DB_LOG_AUTOREMOVE) - set DB_ENV to automatically clear
 *      the unwanted log files (flushed at each checkpoint).
 *   4. DB_ENV->set_errfile - set errfile to be used by db to report detailed error logs.
 *     used only for debbuging purpose.
 *
 * return: returns a valid DB_ENV * on success or NULL on error.
 *
 */
static DB_ENV *
bdb_dbenv_init (xlator_t *this,
                char *directory)
{
        /* Create a DB environment */
        DB_ENV        *dbenv       = NULL;
        int32_t        ret         = 0;
        bdb_private_t *private     = NULL;
        int32_t        fatal_flags = 0;

        VALIDATE_OR_GOTO (this, out);
        VALIDATE_OR_GOTO (directory, out);

        private = this->private;
        VALIDATE_OR_GOTO (private, out);

        ret = db_env_create (&dbenv, 0);
        VALIDATE_OR_GOTO ((ret == 0), out);

        /* NOTE: set_errpfx returns 'void' */
        dbenv->set_errpfx(dbenv, this->name);

        ret = dbenv->set_lk_detect (dbenv, DB_LOCK_DEFAULT);
        VALIDATE_OR_GOTO ((ret == 0), out);

        ret = dbenv->open(dbenv, directory,
                          private->envflags,
                          S_IRUSR | S_IWUSR);
        if ((ret != 0) && (ret != DB_RUNRECOVERY)) {
                gf_log (this->name, GF_LOG_CRITICAL,
                        "failed to open DB environment (%s)",
                        db_strerror (ret));
                dbenv = NULL;
                goto out;
        } else if (ret == DB_RUNRECOVERY) {
                fatal_flags = ((private->envflags & (~DB_RECOVER))
                               | DB_RECOVER_FATAL);
                ret = dbenv->open(dbenv, directory, fatal_flags,
                                  S_IRUSR | S_IWUSR);
                if (ret != 0) {
                        gf_log (this->name, GF_LOG_ERROR,
                                "failed to open DB environment (%s) with "
                                "DB_REOVER_FATAL",
                                db_strerror (ret));
                        dbenv = NULL;
                        goto out;
                } else {
                        gf_log (this->name, GF_LOG_WARNING,
                                "opened DB environment after DB_RECOVER_FATAL:"
                                " %s", db_strerror (ret));
                }
        } else {
                gf_log (this->name, GF_LOG_DEBUG,
                        "DB environment successfull opened: %s",
                        db_strerror (ret));
        }



#if (DB_VERSION_MAJOR == 4 &&                   \
     DB_VERSION_MINOR == 7)
        if (private->log_auto_remove) {
                ret = dbenv->log_set_config (dbenv, DB_LOG_AUTO_REMOVE, 1);
        } else {
                ret = dbenv->log_set_config (dbenv, DB_LOG_AUTO_REMOVE, 0);
        }
#else
        if (private->log_auto_remove) {
                ret = dbenv->set_flags (dbenv, DB_LOG_AUTOREMOVE, 1);
        } else {
                ret = dbenv->set_flags (dbenv, DB_LOG_AUTOREMOVE, 0);
        }
#endif
        if (ret != 0) {
                gf_log ("bctx", GF_LOG_ERROR,
                        "failed to set DB_LOG_AUTOREMOVE on dbenv: %s",
                        db_strerror (ret));
        } else {
                gf_log ("bctx", GF_LOG_DEBUG,
                        "DB_LOG_AUTOREMOVE set on dbenv");
        }

        if (private->transaction) {
                ret = dbenv->set_flags(dbenv, DB_AUTO_COMMIT, 1);

                if (ret != 0) {
                        gf_log ("bctx", GF_LOG_ERROR,
                                "failed to set DB_AUTO_COMMIT on dbenv: %s",
                                db_strerror (ret));
                } else {
                        gf_log ("bctx", GF_LOG_DEBUG,
                                "DB_AUTO_COMMIT set on dbenv");
                }

                if (private->txn_timeout) {
                        ret = dbenv->set_timeout (dbenv,
                                                  private->txn_timeout,
                                                  DB_SET_TXN_TIMEOUT);
                        if (ret != 0) {
                                gf_log ("bctx", GF_LOG_ERROR,
                                        "failed to set TXN_TIMEOUT to %d "
                                        "milliseconds on dbenv: %s",
                                        private->txn_timeout,
                                        db_strerror (ret));
                        } else {
                                gf_log ("bctx", GF_LOG_DEBUG,
                                        "TXN_TIMEOUT set to %d milliseconds",
                                        private->txn_timeout);
                        }
                }

                if (private->lock_timeout) {
                        ret = dbenv->set_timeout(dbenv,
                                                 private->txn_timeout,
                                                 DB_SET_LOCK_TIMEOUT);

                        if (ret != 0) {
                                gf_log ("bctx", GF_LOG_ERROR,
                                        "failed to set LOCK_TIMEOUT to %d "
                                        "milliseconds on dbenv: %s",
                                        private->lock_timeout,
                                        db_strerror (ret));
                        } else {
                                gf_log ("bctx", GF_LOG_DEBUG,
                                        "LOCK_TIMEOUT set to %d milliseconds",
                                        private->lock_timeout);
                        }
                }

                ret = dbenv->set_lg_dir (dbenv, private->logdir);

                if (ret != 0) {
                        gf_log ("bctx", GF_LOG_ERROR,
                                "failed to set log directory for dbenv: %s",
                                db_strerror (ret));
                } else {
                        gf_log ("bctx", GF_LOG_DEBUG,
                                "set dbenv log dir to %s",
                                private->logdir);
                }

        }

        if (private->errfile) {
                private->errfp = fopen (private->errfile, "a+");
                if (private->errfp) {
                        dbenv->set_errfile (dbenv, private->errfp);
                } else {
                        gf_log ("bctx", GF_LOG_ERROR,
                                "failed to open errfile: %s",
                                strerror (errno));
                }
        }

out:
        return dbenv;
}

#define BDB_ENV(this) ((((struct bdb_private *)this->private)->b_table)->dbenv)

/* bdb_checkpoint - during transactional usage, db does not directly write the data to db
 *                  files, instead db writes a 'log' (similar to a journal entry) into a
 *                  log file. db normally clears the log files during opening of an
 *                  environment. since we expect a filesystem server to run for a pretty
 *                  long duration and flushing 'log's during dbenv->open would prove very
 *                  costly, if we accumulate the log entries for one complete run of
 *                  glusterfs server. to flush the logs frequently, db provides a mechanism
 *                  called 'checkpointing'. when we do a checkpoint, db flushes the logs to
 *                  disk (writes changes to db files) and we can also clear the accumulated
 *                  log files after checkpointing. NOTE: removing unwanted log files is not
 *                  part of dbenv->txn_checkpoint() call.
 *
 * @data: xlator_t of the current instance of bdb xlator.
 *
 *  bdb_checkpoint is called in a different thread from the main glusterfs thread. bdb
 *  xlator creates the checkpoint thread after successfully opening the db environment.
 *  NOTE: bdb_checkpoint thread shares the DB_ENV handle with the filesystem thread.
 *
 *  db environment checkpointing frequency is controlled by
 *  'option checkpoint-timeout <time-in-seconds>' in volfile.
 *
 * NOTE: checkpointing thread is started only if 'option transaction on' specified in
 *      volfile. checkpointing is not valid for non-transactional environments.
 *
 */
static void *
bdb_checkpoint (void *data)
{
        xlator_t *this = NULL;
        struct bdb_private *private = NULL;
        DB_ENV *dbenv = NULL;
        int32_t ret = 0;
        uint32_t active = 0;

        this = (xlator_t *) data;
        dbenv = BDB_ENV(this);
        private = this->private;

        for (;;sleep (private->checkpoint_interval)) {
                LOCK (&private->active_lock);
                active = private->active;
                UNLOCK (&private->active_lock);

                if (active) {
                        ret = dbenv->txn_checkpoint (dbenv, 1024, 0, 0);
                        if (ret) {
                                gf_log ("bctx", GF_LOG_ERROR,
                                        "failed to checkpoint environment: %s",
                                        db_strerror (ret));
                        } else {
                                gf_log ("bctx", GF_LOG_DEBUG,
                                        "checkpointing successful");
                        }
                } else {
                        ret = dbenv->txn_checkpoint (dbenv, 1024, 0, 0);
                        if (ret) {
                                gf_log ("bctx", GF_LOG_ERROR,
                                        "failed to do final checkpoint "
                                        "environment: %s",
                                        db_strerror (ret));
                        } else {
                                gf_log ("bctx", GF_LOG_DEBUG,
                                        "final checkpointing successful");
                        }
                        break;
                }
        }

        return NULL;
}

static inline void
bdb_cache_init (xlator_t *this,
                dict_t *options,
                struct bdb_private *private)
{
        /* cache is always on */
        private->cache = ON;
}

static inline void
bdb_log_remove_init (xlator_t *this,
                     dict_t *options,
                     struct bdb_private *private)
{
        private->log_auto_remove = 1;
        gf_log (this->name, GF_LOG_DEBUG,
                "DB_ENV will use DB_LOG_AUTO_REMOVE");
}

static inline void
bdb_errfile_init (xlator_t *this,
                  dict_t *options,
                  struct bdb_private *private)
{
        int ret = -1;
        char *errfile = NULL;

        ret = dict_get_str (options, "errfile", &errfile);
        if (ret == 0) {
                private->errfile = strdup (errfile);
                gf_log (this->name, GF_LOG_DEBUG,
                        "using errfile: %s", private->errfile);
        }
}

static inline void
bdb_table_init (xlator_t *this,
                dict_t *options,
                struct bdb_private *private)
{
        bctx_table_t *table = NULL;
        int32_t       idx   = 0;

        int ret = -1;
        char *lru_limit_str = NULL;
        char *page_size_str = NULL;

        table = CALLOC (1, sizeof (*table));
        if (table) {
                INIT_LIST_HEAD(&(table->b_lru));
                INIT_LIST_HEAD(&(table->active));
                INIT_LIST_HEAD(&(table->purge));

                LOCK_INIT (&table->lock);
                LOCK_INIT (&table->checkpoint_lock);

                table->transaction = private->transaction;
                table->access_mode = private->access_mode;
                table->dbflags = private->dbflags;
                table->this    = this;

                {
                        ret = dict_get_str (options, "lru-limit",
                                            &lru_limit_str);

                        /* TODO: set max lockers and max txns to accomodate
                         * for more than lru_limit */
                        if (ret == 0) {
                                ret = gf_string2uint32 (lru_limit_str,
                                                        &table->lru_limit);
                                gf_log ("bdb-ll", GF_LOG_DEBUG,
                                        "setting bctx lru limit to %d",
                                        table->lru_limit);
                        } else {
                                table->lru_limit = BDB_DEFAULT_LRU_LIMIT;
                        }
                }

                {
                        ret = dict_get_str (options, "page-size",
                                            &page_size_str);

                        if (ret == 0) {
                                ret = gf_string2bytesize (page_size_str,
                                                          &table->page_size);
                                if (ret != 0) {
                                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                                "invalid number format \"%s\""
                                                " of \"option page-size\"",
                                                page_size_str);
                                }

                                if (!PAGE_SIZE_IN_RANGE(table->page_size)) {
                                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                                "pagesize %s is out of range."
                                                "Allowed pagesize is between "
                                                "%d and %d",
                                                page_size_str,
                                                BDB_LL_PAGE_SIZE_MIN,
                                                BDB_LL_PAGE_SIZE_MAX);
                                }
                        }
                        else {
                                table->page_size = BDB_LL_PAGE_SIZE_DEFAULT;
                        }
                        gf_log ("bdb-ll",
                                GF_LOG_DEBUG, "using page-size %"PRIu64,
                                table->page_size);
                }

                table->hash_size = BDB_DEFAULT_HASH_SIZE;
                table->b_hash = CALLOC (BDB_DEFAULT_HASH_SIZE,
                                        sizeof (struct list_head));

                for (idx = 0; idx < table->hash_size; idx++)
                        INIT_LIST_HEAD(&(table->b_hash[idx]));

                private->b_table = table;
        } else {
                gf_log ("bdb-ll", GF_LOG_CRITICAL,
                        "failed to allocate bctx table: out of memory");
        }
}

static inline void
bdb_directory_init (xlator_t *this,
                    dict_t *options,
                    struct bdb_private *private)
{
        int ret = -1;
        char *directory = NULL;
        char *logdir = NULL;
        int32_t op_ret = -1;
        struct stat stbuf = {0};

        ret = dict_get_str (options, "directory", &directory);

        if (ret == 0) {
                ret = dict_get_str (options, "logdir", &logdir);

                if (ret != 0) {
                        gf_log ("bdb-ll", GF_LOG_DEBUG,
                                "using default logdir as database home");
                        private->logdir = strdup (directory);

                } else {
                        private->logdir = strdup (logdir);
                        gf_log ("bdb-ll", GF_LOG_DEBUG,
                                "using logdir: %s",
                                private->logdir);
                        umask (000);
                        if (mkdir (private->logdir, 0777) == 0) {
                                gf_log ("bdb-ll", GF_LOG_WARNING,
                                        "logdir specified (%s) not exists, "
                                        "created",
                                        private->logdir);
                        }

                        op_ret = stat (private->logdir, &stbuf);
                        if ((op_ret != 0)
                            || (!S_ISDIR (stbuf.st_mode))) {
                                gf_log ("bdb-ll", GF_LOG_ERROR,
                                        "specified logdir doesn't exist, "
                                        "using default "
                                        "(environment home directory: %s)",
                                        directory);
                                private->logdir = strdup (directory);
                        }
                }

                private->b_table->dbenv = bdb_dbenv_init (this, directory);

                if (!private->b_table->dbenv) {
                        gf_log ("bdb-ll", GF_LOG_ERROR,
                                "failed to initialize db environment");
                        FREE (private);
                        op_ret = -1;
                } else {
                        if (private->transaction) {
                                /* all well, start the checkpointing thread */
                                LOCK_INIT (&private->active_lock);

                                LOCK (&private->active_lock);
                                {
                                        private->active = 1;
                                }
                                UNLOCK (&private->active_lock);
                                pthread_create (&private->checkpoint_thread,
                                                NULL, bdb_checkpoint, this);
                        }
                }
        }
}

static inline void
bdb_dir_mode_init (xlator_t *this,
                   dict_t *options,
                   struct bdb_private *private)
{
        int ret = -1;
        char *mode_str = NULL;
        char *endptr = NULL;

        ret = dict_get_str (options, "dir-mode", &mode_str);

        if (ret == 0) {
                private->dir_mode = strtol (mode_str, &endptr, 8);
                if ((*endptr) ||
                    (!IS_VALID_FILE_MODE(private->dir_mode))) {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "invalid dir-mode %o. setting to default %o",
                                private->dir_mode,
                                DEFAULT_DIR_MODE);
                        private->dir_mode = DEFAULT_DIR_MODE;
                } else {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "setting dir-mode to %o",
                                private->dir_mode);
                }
        } else {
                private->dir_mode = DEFAULT_DIR_MODE;
        }

        private->dir_mode = private->dir_mode | S_IFDIR;
}

static inline void
bdb_file_mode_init (xlator_t *this,
                    dict_t *options,
                    struct bdb_private *private)
{
        int ret = -1;
        char *mode_str = NULL;
        char *endptr = NULL;

        ret = dict_get_str (options, "file-mode", &mode_str);

        if (ret == 0) {
                private->file_mode = strtol (mode_str, &endptr, 8);

                if ((*endptr) ||
                    (!IS_VALID_FILE_MODE(private->file_mode))) {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "invalid file-mode %o. setting to default %o",
                                private->file_mode, DEFAULT_FILE_MODE);
                        private->file_mode = DEFAULT_FILE_MODE;
                } else {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "setting file-mode to %o",
                                private->file_mode);
                        private->file_mode = private->file_mode;
                }
        } else {
                private->file_mode = DEFAULT_FILE_MODE;
        }

        private->symlink_mode = private->file_mode | S_IFLNK;
        private->file_mode = private->file_mode | S_IFREG;
}

static inline void
bdb_checkpoint_interval_init (xlator_t *this,
                              dict_t *options,
                              struct bdb_private *private)
{
        int   ret = -1;
        char *checkpoint_interval_str = NULL;

        private->checkpoint_interval = BDB_DEFAULT_CHECKPOINT_INTERVAL;

        ret = dict_get_str (options, "checkpoint-interval",
                            &checkpoint_interval_str);

        if (ret == 0) {
                ret = gf_string2time (checkpoint_interval_str,
                                      &private->checkpoint_interval);

                if (ret == 0) {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "setting checkpoint-interval to %"PRIu32" seconds",
                                private->checkpoint_interval);
                }
        } else {
                gf_log (this->name, GF_LOG_DEBUG,
                        "setting checkpoint-interval to default: %"PRIu32" seconds",
                        private->checkpoint_interval);
        }
}

static inline void
bdb_lock_timeout_init (xlator_t *this,
                       dict_t *options,
                       struct bdb_private *private)
{
        int   ret = -1;
        char *timeout_str = NULL;

        ret = dict_get_str (options, "lock-timeout", &timeout_str);

        if (ret == 0) {
                ret = gf_string2time (timeout_str, &private->lock_timeout);

                if (private->lock_timeout > 4260000) {
                        /* db allows us to DB_SET_LOCK_TIMEOUT to be set to a
                         * maximum of 71 mins (4260000 milliseconds) */
                        gf_log (this->name, GF_LOG_DEBUG,
                                "lock-timeout %d, out of range",
                                private->lock_timeout);
                        private->lock_timeout = 0;
                } else {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "setting lock-timeout to %d milliseconds",
                                private->lock_timeout);
                }
        }
}

static inline void
bdb_transaction_timeout_init (xlator_t *this,
                              dict_t *options,
                              struct bdb_private *private)
{
        int   ret = -1;
        char *timeout_str = NULL;

        ret = dict_get_str (options, "transaction-timeout", &timeout_str);

        if (ret == 0) {
                ret = gf_string2time (timeout_str, &private->txn_timeout);

                if (private->txn_timeout > 4260000) {
                        /* db allows us to DB_SET_TXN_TIMEOUT to be set to
                         * a maximum of 71 mins (4260000 milliseconds) */
                        gf_log (this->name, GF_LOG_DEBUG,
                                "transaction-timeout %d, out of range",
                                private->txn_timeout);
                        private->txn_timeout = 0;
                } else {
                        gf_log (this->name, GF_LOG_DEBUG,
                                "setting transaction-timeout to %d "
                                "milliseconds",
                                private->txn_timeout);
                }
        }
}

static inline void
bdb_transaction_init (xlator_t *this,
                      dict_t *options,
                      struct bdb_private *private)
{
        int   ret = -1;
        char *mode = NULL;

        ret = dict_get_str (options, "mode", &mode);

        if ((ret == 0)
            && (!strcmp (mode, "cache"))) {
                gf_log (this->name, GF_LOG_DEBUG,
                        "cache mode selected");
                private->envflags = DB_CREATE | DB_INIT_LOG |
                        DB_INIT_MPOOL | DB_THREAD;
                private->dbflags = DB_CREATE | DB_THREAD;
                private->transaction = OFF;
        } else {
                gf_log (this->name, GF_LOG_DEBUG,
                        "persistant mode selected");
                private->transaction = ON;
                private->envflags = DB_CREATE | DB_INIT_LOCK | DB_INIT_LOG |
                        DB_INIT_MPOOL | DB_INIT_TXN | DB_RECOVER | DB_THREAD;
                private->dbflags = DB_CREATE | DB_THREAD;

                bdb_lock_timeout_init (this, options, private);

                bdb_transaction_timeout_init (this, options, private);

                bdb_log_remove_init (this, options, private);

                bdb_checkpoint_interval_init (this, options, private);
        }
}

static inline void
bdb_access_mode_init (xlator_t *this,
                      dict_t *options,
                      struct bdb_private *private)
{
        int   ret = -1;
        char *access_mode = NULL;

        ret = dict_get_str (options, "access-mode", &access_mode);

        if ((ret == 0)
            && (!strcmp (access_mode, "btree"))) {
                gf_log (this->name, GF_LOG_DEBUG,
                        "using access mode BTREE");
                private->access_mode = DB_BTREE;
        } else {
                gf_log (this->name, GF_LOG_DEBUG,
                        "using access mode HASH");
                private->access_mode = DB_HASH;
        }
}


/* bdb_db_init - initialize bdb xlator
 *
 * reads the options from @options dictionary and sets appropriate values in
 * @this->private. also initializes DB_ENV.
 *
 * return: 0 on success or -1 on error
 * (with logging the error through gf_log()).
 */
int
bdb_db_init (xlator_t *this,
             dict_t *options)
{
        /* create a db entry for root */
        int32_t        op_ret             = 0;
        bdb_private_t *private            = NULL;

        private = this->private;

        bdb_cache_init (this, options, private);

        bdb_access_mode_init (this, options, private);

        bdb_transaction_init (this, options, private);

        {
                LOCK_INIT (&private->ino_lock);
                private->next_ino = 2;
        }

        bdb_file_mode_init (this, options, private);

        bdb_dir_mode_init (this, options, private);

        bdb_table_init (this, options, private);

        bdb_errfile_init (this, options, private);

        bdb_directory_init (this, options, private);

        return op_ret;
}