dbreg.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: dbreg.c,v 12.12 2005/10/14 14:40:41 bostic Exp $
 */

#include "db_config.h"

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <string.h>
#endif

#include "db_int.h"
#include "dbinc/db_page.h"
#include "dbinc/log.h"
#include "dbinc/txn.h"
#include "dbinc/db_am.h"

static int __dbreg_push_id __P((DB_ENV *, DB *, int32_t));
static int __dbreg_pop_id __P((DB_ENV *, int32_t *));
static int __dbreg_pluck_id __P((DB_ENV *, int32_t));

/*
 * The dbreg subsystem, as its name implies, registers database handles so
 * that we can associate log messages with them without logging a filename
 * or a full, unique DB ID.  Instead, we assign each dbp an int32_t which is
 * easy and cheap to log, and use this subsystem to map back and forth.
 *
 * Overview of how dbreg ids are managed:
 *
 * OPEN
 *      dbreg_setup (Creates FNAME struct.)
 *      dbreg_new_id (Assigns new ID to dbp and logs it.  May be postponed
 *      until we attempt to log something else using that dbp, if the dbp
 *      was opened on a replication client.)
 *
 * CLOSE
 *      dbreg_close_id  (Logs closure of dbp/revocation of ID.)
 *      dbreg_revoke_id (As name implies, revokes ID.)
 *      dbreg_teardown (Destroys FNAME.)
 *
 * RECOVERY
 *      dbreg_setup
 *      dbreg_assign_id (Assigns a particular ID we have in the log to a dbp.)
 *
 *      sometimes: dbreg_revoke_id; dbreg_teardown
 *      other times: normal close path
 *
 * A note about locking:
 *
 *      FNAME structures are referenced only by their corresponding dbp's
 *      until they have a valid id.
 *
 *      Once they have a valid id, they must get linked into the log
 *      region list so they can get logged on checkpoints.
 *
 *      An FNAME that may/does have a valid id must be accessed under
 *      protection of the mtx_filelist, with the following exception:
 *
 *      We don't want to have to grab the mtx_filelist on every log
 *      record, and it should be safe not to do so when we're just
 *      looking at the id, because once allocated, the id should
 *      not change under a handle until the handle is closed.
 *
 *      If a handle is closed during an attempt by another thread to
 *      log with it, well, the application doing the close deserves to
 *      go down in flames and a lot else is about to fail anyway.
 *
 *      When in the course of logging we encounter an invalid id
 *      and go to allocate it lazily, we *do* need to check again
 *      after grabbing the mutex, because it's possible to race with
 *      another thread that has also decided that it needs to allocate
 *      a id lazily.
 *
 * See SR #5623 for further discussion of the new dbreg design.
 */

/*
 * __dbreg_setup --
 *      Allocate and initialize an FNAME structure.  The FNAME structures
 * live in the log shared region and map one-to-one with open database handles.
 * When the handle needs to be logged, the FNAME should have a valid fid
 * allocated.  If the handle currently isn't logged, it still has an FNAME
 * entry.  If we later discover that the handle needs to be logged, we can
 * allocate a id for it later.  (This happens when the handle is on a
 * replication client that later becomes a master.)
 *
 * PUBLIC: int __dbreg_setup __P((DB *, const char *, u_int32_t));
 */
int
__dbreg_setup(dbp, name, create_txnid)
        DB *dbp;
        const char *name;
        u_int32_t create_txnid;
{
        DB_ENV *dbenv;
        DB_LOG *dblp;
        FNAME *fnp;
        REGINFO *infop;
        int ret;
        size_t len;
        void *namep;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        infop = &dblp->reginfo;

        fnp = NULL;
        namep = NULL;

        /* Allocate an FNAME and, if necessary, a buffer for the name itself. */
        LOG_SYSTEM_LOCK(dbenv);
        if ((ret = __db_shalloc(infop, sizeof(FNAME), 0, &fnp)) != 0)
                goto err;
        memset(fnp, 0, sizeof(FNAME));
        if (name != NULL) {
                len = strlen(name) + 1;
                if ((ret = __db_shalloc(infop, len, 0, &namep)) != 0)
                        goto err;
                fnp->name_off = R_OFFSET(infop, namep);
                memcpy(namep, name, len);
        } else
                fnp->name_off = INVALID_ROFF;

        LOG_SYSTEM_UNLOCK(dbenv);

        /*
         * Fill in all the remaining info that we'll need later to register
         * the file, if we use it for logging.
         */
        fnp->id = DB_LOGFILEID_INVALID;
        fnp->s_type = dbp->type;
        memcpy(fnp->ufid, dbp->fileid, DB_FILE_ID_LEN);
        fnp->meta_pgno = dbp->meta_pgno;
        fnp->create_txnid = create_txnid;

        dbp->log_filename = fnp;

        return (0);

err:    LOG_SYSTEM_UNLOCK(dbenv);
        if (ret == ENOMEM)
                __db_err(dbenv,
    "Logging region out of memory; you may need to increase its size");

        return (ret);
}

/*
 * __dbreg_teardown --
 *      Destroy a DB handle's FNAME struct.
 *
 * PUBLIC: int __dbreg_teardown __P((DB *));
 */
int
__dbreg_teardown(dbp)
        DB *dbp;
{
        DB_ENV *dbenv;
        DB_LOG *dblp;
        REGINFO *infop;
        FNAME *fnp;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        infop = &dblp->reginfo;
        fnp = dbp->log_filename;

        /*
         * We may not have an FNAME if we were never opened.  This is not an
         * error.
         */
        if (fnp == NULL || F_ISSET(fnp, DB_FNAME_NOTLOGGED))
                return (0);

        DB_ASSERT(fnp->id == DB_LOGFILEID_INVALID);

        LOG_SYSTEM_LOCK(dbenv);
        if (fnp->name_off != INVALID_ROFF)
                __db_shalloc_free(infop, R_ADDR(infop, fnp->name_off));
        __db_shalloc_free(infop, fnp);
        LOG_SYSTEM_UNLOCK(dbenv);

        dbp->log_filename = NULL;

        return (0);
}

/*
 * __dbreg_new_id --
 *      Get an unused dbreg id to this database handle.
 *      Used as a wrapper to acquire the mutex and
 *      only set the id on success.
 *
 * PUBLIC: int __dbreg_new_id __P((DB *, DB_TXN *));
 */
int
__dbreg_new_id(dbp, txn)
        DB *dbp;
        DB_TXN *txn;
{
        DB_ENV *dbenv;
        DB_LOG *dblp;
        FNAME *fnp;
        LOG *lp;
        int32_t id;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        /* The mtx_filelist protects the FNAME list and id management. */
        MUTEX_LOCK(dbenv, lp->mtx_filelist);
        if (fnp->id != DB_LOGFILEID_INVALID) {
                MUTEX_UNLOCK(dbenv, lp->mtx_filelist);
                return (0);
        }
        if ((ret = __dbreg_get_id(dbp, txn, &id)) == 0)
                fnp->id = id;
        MUTEX_UNLOCK(dbenv, lp->mtx_filelist);
        return (ret);
}

/*
 * __dbreg_get_id --
 *      Assign an unused dbreg id to this database handle.
 *      Assume the caller holds the mtx_filelist locked.  Assume the
 *      caller will set the fnp->id field with the id we return.
 *
 * PUBLIC: int __dbreg_get_id __P((DB *, DB_TXN *, int32_t *));
 */
int
__dbreg_get_id(dbp, txn, idp)
        DB *dbp;
        DB_TXN *txn;
        int32_t *idp;
{
        DB_ENV *dbenv;
        DB_LOG *dblp;
        FNAME *fnp;
        LOG *lp;
        int32_t id;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        /*
         * It's possible that after deciding we needed to call this function,
         * someone else allocated an ID before we grabbed the lock.  Check
         * to make sure there was no race and we have something useful to do.
         */
        /* Get an unused ID from the free list. */
        if ((ret = __dbreg_pop_id(dbenv, &id)) != 0)
                goto err;

        /* If no ID was found, allocate a new one. */
        if (id == DB_LOGFILEID_INVALID)
                id = lp->fid_max++;

        /* If the file is durable (i.e., not, not-durable), mark it as such. */
        if (!F_ISSET(dbp, DB_AM_NOT_DURABLE))
                F_SET(fnp, DB_FNAME_DURABLE);

        /* Hook the FNAME into the list of open files. */
        SH_TAILQ_INSERT_HEAD(&lp->fq, fnp, q, __fname);

        /*
         * Log the registry.  We should only request a new ID in situations
         * where logging is reasonable.
         */
        DB_ASSERT(!F_ISSET(dbp, DB_AM_RECOVER));

        if ((ret = __dbreg_log_id(dbp, txn, id, 0)) != 0)
                goto err;

        /*
         * Once we log the create_txnid, we need to make sure we never
         * log it again (as might happen if this is a replication client
         * that later upgrades to a master).
         */
        fnp->create_txnid = TXN_INVALID;

        DB_ASSERT(dbp->type == fnp->s_type);
        DB_ASSERT(dbp->meta_pgno == fnp->meta_pgno);

        if ((ret = __dbreg_add_dbentry(dbenv, dblp, dbp, id)) != 0)
                goto err;
        /*
         * If we have a successful call, set the ID.  Otherwise
         * we have to revoke it and remove it from all the lists
         * it has been added to, and return an invalid id.
         */
err:
        if (ret != 0 && id != DB_LOGFILEID_INVALID) {
                (void)__dbreg_revoke_id(dbp, 1, id);
                id = DB_LOGFILEID_INVALID;
        }
        *idp = id;
        return (ret);
}

/*
 * __dbreg_assign_id --
 *      Assign a particular dbreg id to this database handle.
 *
 * PUBLIC: int __dbreg_assign_id __P((DB *, int32_t));
 */
int
__dbreg_assign_id(dbp, id)
        DB *dbp;
        int32_t id;
{
        DB *close_dbp;
        DB_ENV *dbenv;
        DB_LOG *dblp;
        FNAME *close_fnp, *fnp;
        LOG *lp;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        close_dbp = NULL;
        close_fnp = NULL;

        /* The mtx_filelist protects the FNAME list and id management. */
        MUTEX_LOCK(dbenv, lp->mtx_filelist);

        /* We should only call this on DB handles that have no ID. */
        DB_ASSERT(fnp->id == DB_LOGFILEID_INVALID);

        /*
         * Make sure there isn't already a file open with this ID. There can
         * be in recovery, if we're recovering across a point where an ID got
         * reused.
         */
        if (__dbreg_id_to_fname(dblp, id, 1, &close_fnp) == 0) {
                /*
                 * We want to save off any dbp we have open with this id.  We
                 * can't safely close it now, because we hold the mtx_filelist,
                 * but we should be able to rely on it being open in this
                 * process, and we're running recovery, so no other thread
                 * should muck with it if we just put off closing it until
                 * we're ready to return.
                 *
                 * Once we have the dbp, revoke its id;  we're about to
                 * reuse it.
                 */
                ret = __dbreg_id_to_db_int(dbenv, NULL, &close_dbp, id, 0, 0);
                if (ret == ENOENT) {
                        ret = 0;
                        goto cont;
                } else if (ret != 0)
                        goto err;

                if ((ret = __dbreg_revoke_id(close_dbp, 1,
                    DB_LOGFILEID_INVALID)) != 0)
                        goto err;
        }

        /*
         * Remove this ID from the free list, if it's there, and make sure
         * we don't allocate it anew.
         */
cont:   if ((ret = __dbreg_pluck_id(dbenv, id)) != 0)
                goto err;
        if (id >= lp->fid_max)
                lp->fid_max = id + 1;

        /* Now go ahead and assign the id to our dbp. */
        fnp->id = id;
        /* If the file is durable (i.e., not, not-durable), mark it as such. */
        if (!F_ISSET(dbp, DB_AM_NOT_DURABLE))
                F_SET(fnp, DB_FNAME_DURABLE);
        SH_TAILQ_INSERT_HEAD(&lp->fq, fnp, q, __fname);

        /*
         * If we get an error adding the dbentry, revoke the id.
         * We void the return value since we want to retain and
         * return the original error in ret anyway.
         */
        if ((ret = __dbreg_add_dbentry(dbenv, dblp, dbp, id)) != 0)
                (void)__dbreg_revoke_id(dbp, 1, id);

err:    MUTEX_UNLOCK(dbenv, lp->mtx_filelist);

        /* There's nothing useful that our caller can do if this close fails. */
        if (close_dbp != NULL)
                (void)__db_close(close_dbp, NULL, DB_NOSYNC);

        return (ret);
}

/*
 * __dbreg_revoke_id --
 *      Take a log id away from a dbp, in preparation for closing it,
 *      but without logging the close.
 *
 * PUBLIC: int __dbreg_revoke_id __P((DB *, int, int32_t));
 */
int
__dbreg_revoke_id(dbp, have_lock, force_id)
        DB *dbp;
        int have_lock;
        int32_t force_id;
{
        DB_ENV *dbenv;
        DB_LOG *dblp;
        FNAME *fnp;
        LOG *lp;
        int32_t id;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        /* If we lack an ID, this is a null-op. */
        if (fnp == NULL)
                return (0);

        /*
         * If we have a force_id, we had an error after allocating
         * the id, and putting it on the fq list, but before we
         * finished setting up fnp.  So, if we have a force_id use it.
         */
        if (force_id != DB_LOGFILEID_INVALID)
                id = force_id;
        else if (fnp->id == DB_LOGFILEID_INVALID)
                return (0);
        else
                id = fnp->id;
        if (!have_lock)
                MUTEX_LOCK(dbenv, lp->mtx_filelist);

        fnp->id = DB_LOGFILEID_INVALID;

        /* Remove the FNAME from the list of open files. */
        SH_TAILQ_REMOVE(&lp->fq, fnp, q, __fname);

        /*
         * Remove this id from the dbentry table and push it onto the
         * free list.
         */
        if ((ret = __dbreg_rem_dbentry(dblp, id)) == 0) {
                /*
                 * If we are not in recovery but the file was opened
                 * for a recovery operation, then this process aborted
                 * a transaction for another process and the id may
                 * still be in use, so don't reuse this id.
                 */
                if (!F_ISSET(dbp, DB_AM_RECOVER) || IS_RECOVERING(dbenv))
                        ret = __dbreg_push_id(dbenv, dbp, id);
        }

        if (!have_lock)
                MUTEX_UNLOCK(dbenv, lp->mtx_filelist);
        return (ret);
}

/*
 * __dbreg_close_id --
 *      Take a dbreg id away from a dbp that we're closing, and log
 * the unregistry.
 *
 * PUBLIC: int __dbreg_close_id __P((DB *, DB_TXN *, u_int32_t));
 */
int
__dbreg_close_id(dbp, txn, op)
        DB *dbp;
        DB_TXN *txn;
        u_int32_t op;
{
        DBT fid_dbt, r_name, *dbtp;
        DB_ENV *dbenv;
        DB_LOG *dblp;
        DB_LSN r_unused;
        FNAME *fnp;
        LOG *lp;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        /* If we lack an ID, this is a null-op. */
        if (fnp == NULL || fnp->id == DB_LOGFILEID_INVALID)
                return (0);

        MUTEX_LOCK(dbenv, lp->mtx_filelist);

        if (fnp->name_off == INVALID_ROFF)
                dbtp = NULL;
        else {
                memset(&r_name, 0, sizeof(r_name));
                r_name.data = R_ADDR(&dblp->reginfo, fnp->name_off);
                r_name.size =
                    (u_int32_t)strlen((char *)r_name.data) + 1;
                dbtp = &r_name;
        }
        memset(&fid_dbt, 0, sizeof(fid_dbt));
        fid_dbt.data = fnp->ufid;
        fid_dbt.size = DB_FILE_ID_LEN;
        if ((ret = __dbreg_register_log(dbenv, txn, &r_unused,
            F_ISSET(dbp, DB_AM_NOT_DURABLE) ? DB_LOG_NOT_DURABLE : 0,
            op, dbtp, &fid_dbt, fnp->id,
            fnp->s_type, fnp->meta_pgno, TXN_INVALID)) != 0) {
                /*
                 * We are trying to close, but the log write failed.
                 * Unfortunately, close needs to plow forward, because
                 * the application can't do anything with the handle.
                 * Make the entry in the shared memory region so that
                 * when we close the environment, we know that this
                 * happened.  Also, make sure we remove this from the
                 * per-process table, so that we don't try to close it
                 * later.
                 */
                F_SET(fnp, DB_FNAME_NOTLOGGED);
                (void)__dbreg_rem_dbentry(dblp, fnp->id);
                goto err;
        }

        ret = __dbreg_revoke_id(dbp, 1, DB_LOGFILEID_INVALID);

err:    MUTEX_UNLOCK(dbenv, lp->mtx_filelist);
        return (ret);
}

/*
 * __dbreg_push_id and __dbreg_pop_id --
 *      Dbreg ids from closed files are kept on a stack in shared memory
 * for recycling.  (We want to reuse them as much as possible because each
 * process keeps open files in an array by ID.)  Push them to the stack and
 * pop them from it, managing memory as appropriate.
 *
 * The stack is protected by the mtx_filelist, and both functions assume it
 * is already locked.
 */
static int
__dbreg_push_id(dbenv, dbp, id)
        DB_ENV *dbenv;
        DB *dbp;
        int32_t id;
{
        DB_LOG *dblp;
        DB_REP *db_rep;
        LOG *lp;
        REGINFO *infop;
        int32_t *stack, *newstack;
        int ret;

        dblp = dbenv->lg_handle;
        infop = &dblp->reginfo;
        lp = infop->primary;
        db_rep = dbenv->rep_handle;

        /*
         * If our fid generation in replication has changed, this fid should
         * not be pushed back onto the stack.
         */
        if (REP_ON(dbenv) && db_rep->region != NULL &&
           ((REP *)db_rep->region)->gen != dbp->fid_gen)
                return (0);
        /* Check if we have room on the stack. */
        if (lp->free_fid_stack == INVALID_ROFF ||
            lp->free_fids_alloced <= lp->free_fids + 1) {
                LOG_SYSTEM_LOCK(dbenv);
                if ((ret = __db_shalloc(infop,
                    (lp->free_fids_alloced + 20) * sizeof(u_int32_t), 0,
                    &newstack)) != 0) {
                        LOG_SYSTEM_UNLOCK(dbenv);
                        return (ret);
                }

                if (lp->free_fid_stack != INVALID_ROFF) {
                        stack = R_ADDR(infop, lp->free_fid_stack);
                        memcpy(newstack, stack,
                            lp->free_fids_alloced * sizeof(u_int32_t));
                        __db_shalloc_free(infop, stack);
                }
                lp->free_fid_stack = R_OFFSET(infop, newstack);
                lp->free_fids_alloced += 20;
                LOG_SYSTEM_UNLOCK(dbenv);
        }

        stack = R_ADDR(infop, lp->free_fid_stack);
        stack[lp->free_fids++] = id;
        return (0);
}

static int
__dbreg_pop_id(dbenv, id)
        DB_ENV *dbenv;
        int32_t *id;
{
        DB_LOG *dblp;
        LOG *lp;
        int32_t *stack;

        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;

        /* Do we have anything to pop? */
        if (lp->free_fid_stack != INVALID_ROFF && lp->free_fids > 0) {
                stack = R_ADDR(&dblp->reginfo, lp->free_fid_stack);
                *id = stack[--lp->free_fids];
        } else
                *id = DB_LOGFILEID_INVALID;

        return (0);
}

/*
 * __dbreg_pluck_id --
 *      Remove a particular dbreg id from the stack of free ids.  This is
 * used when we open a file, as in recovery, with a specific ID that might
 * be on the stack.
 *
 * Returns success whether or not the particular id was found, and like
 * push and pop, assumes that the mtx_filelist is locked.
 */
static int
__dbreg_pluck_id(dbenv, id)
        DB_ENV *dbenv;
        int32_t id;
{
        DB_LOG *dblp;
        LOG *lp;
        int32_t *stack;
        u_int i;

        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;

        /* Do we have anything to look at? */
        if (lp->free_fid_stack != INVALID_ROFF) {
                stack = R_ADDR(&dblp->reginfo, lp->free_fid_stack);
                for (i = 0; i < lp->free_fids; i++)
                        if (id == stack[i]) {
                                /*
                                 * Found it.  Overwrite it with the top
                                 * id (which may harmlessly be itself),
                                 * and shorten the stack by one.
                                 */
                                stack[i] = stack[lp->free_fids - 1];
                                lp->free_fids--;
                                return (0);
                        }
        }

        return (0);
}

/*
 * __dbreg_log_id --
 *      Used for in-memory named files.  They are created in mpool and
 * are given id's early in the open process so that we can read and
 * create pages in the mpool for the files.  However, at the time that
 * the mpf is created, the file may not be fully created and/or its
 * meta-data may not be fully known, so we can't do a full dbregister.
 * This is a routine exported that will log a complete dbregister
 * record that will allow for both recovery and replication.
 *
 * PUBLIC: int __dbreg_log_id __P((DB *, DB_TXN *, int32_t, int));
 */
int
__dbreg_log_id(dbp, txn, id, needlock)
        DB *dbp;
        DB_TXN *txn;
        int32_t id;
        int needlock;
{
        DBT fid_dbt, r_name;
        DB_ENV *dbenv;
        DB_LOG *dblp;
        DB_LSN unused;
        FNAME *fnp;
        LOG *lp;
        u_int32_t op;
        int ret;

        dbenv = dbp->dbenv;
        dblp = dbenv->lg_handle;
        lp = dblp->reginfo.primary;
        fnp = dbp->log_filename;

        /* Verify that the fnp has been initialized. */
        if (fnp->s_type == DB_UNKNOWN) {
                memcpy(fnp->ufid, dbp->fileid, DB_FILE_ID_LEN);
                fnp->s_type = dbp->type;
        }

        /*
         * Log the registry.  We should only request a new ID in situations
         * where logging is reasonable.
         */
        memset(&fid_dbt, 0, sizeof(fid_dbt));
        memset(&r_name, 0, sizeof(r_name));

        if (needlock)
                MUTEX_LOCK(dbenv, lp->mtx_filelist);

        if (fnp->name_off != INVALID_ROFF) {
                r_name.data = R_ADDR(&dblp->reginfo, fnp->name_off);
                r_name.size = (u_int32_t)strlen((char *)r_name.data) + 1;
        }

        fid_dbt.data = dbp->fileid;
        fid_dbt.size = DB_FILE_ID_LEN;

        op = !F_ISSET(dbp, DB_AM_OPEN_CALLED) ? DBREG_PREOPEN :
            (F_ISSET(dbp, DB_AM_INMEM) ? DBREG_REOPEN : DBREG_OPEN);
        ret = __dbreg_register_log(dbenv, txn, &unused,
            F_ISSET(dbp, DB_AM_NOT_DURABLE) ? DB_LOG_NOT_DURABLE : 0,
            op, r_name.size == 0 ? NULL : &r_name, &fid_dbt, id,
            fnp->s_type, fnp->meta_pgno, fnp->create_txnid);

        if (needlock)
                MUTEX_UNLOCK(dbenv, lp->mtx_filelist);

        return (ret);
}

---