mp_bh.c

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	DB_MPOOL_HASH *hp;
	BH *bhp;
{
	DB_LSN lsn;
	MPOOLFILE *mfp;
	size_t nw;
	int callpgin, ret;

	mfp = dbmfp == NULL ? NULL : dbmfp->mfp;
	callpgin = ret = 0;

	/*
	 * We should never be called with a clean or trash buffer.
	 * The sync code does call us with already locked buffers.
	 */
	DB_ASSERT(F_ISSET(bhp, BH_DIRTY));
	DB_ASSERT(!F_ISSET(bhp, BH_TRASH));

	/*
	 * If we have not already traded the hash bucket lock for the buffer
	 * lock, do so now.
	 */
	if (!F_ISSET(bhp, BH_LOCKED)) {
		F_SET(bhp, BH_LOCKED);
		MUTEX_LOCK(dbenv, &bhp->mutex);
		MUTEX_UNLOCK(dbenv, &hp->hash_mutex);
	}

	/*
	 * It's possible that the underlying file doesn't exist, either
	 * because of an outright removal or because it was a temporary
	 * file that's been closed.
	 *
	 * !!!
	 * Once we pass this point, we know that dbmfp and mfp aren't NULL,
	 * and that we have a valid file reference.
	 */
	if (mfp == NULL || mfp->deadfile)
		goto file_dead;

	/*
	 * If the page is in a file for which we have LSN information, we have
	 * to ensure the appropriate log records are on disk.
	 */
	if (LOGGING_ON(dbenv) && mfp->lsn_off != -1 &&
	    !IS_CLIENT_PGRECOVER(dbenv)) {
		memcpy(&lsn, bhp->buf + mfp->lsn_off, sizeof(DB_LSN));
		if ((ret = __log_flush(dbenv, &lsn)) != 0)
			goto err;
	}

#ifdef DIAGNOSTIC
	/*
	 * Verify write-ahead logging semantics.
	 *
	 * !!!
	 * Two special cases.  There is a single field on the meta-data page,
	 * the last-page-number-in-the-file field, for which we do not log
	 * changes.  If the page was originally created in a database that
	 * didn't have logging turned on, we can see a page marked dirty but
	 * for which no corresponding log record has been written.  However,
	 * the only way that a page can be created for which there isn't a
	 * previous log record and valid LSN is when the page was created
	 * without logging turned on, and so we check for that special-case
	 * LSN value.
	 *
	 * Second, when a client is reading database pages from a master
	 * during an internal backup, we may get pages modified after
	 * the current end-of-log.
	 */
	if (LOGGING_ON(dbenv) && !IS_NOT_LOGGED_LSN(LSN(bhp->buf)) &&
	    !IS_CLIENT_PGRECOVER(dbenv)) {
		/*
		 * There is a potential race here.  If we are in the midst of
		 * switching log files, it's possible we could test against the
		 * old file and the new offset in the log region's LSN.  If we
		 * fail the first test, acquire the log mutex and check again.
		 */
		DB_LOG *dblp;
		DB_MUTEX *mtx;
		LOG *lp;

		dblp = dbenv->lg_handle;
		lp = dblp->reginfo.primary;
		if (!lp->db_log_inmemory &&
		    log_compare(&lp->s_lsn, &LSN(bhp->buf)) <= 0) {
			mtx = R_ADDR(&dblp->reginfo, lp->flush_mutex_off);
			MUTEX_LOCK(dbenv, mtx);
			DB_ASSERT(log_compare(&lp->s_lsn, &LSN(bhp->buf)) > 0);
			MUTEX_UNLOCK(dbenv, mtx);
		}
	}
#endif

	/*
	 * Call any pgout function.  We set the callpgin flag so that we flag
	 * that the contents of the buffer will need to be passed through pgin
	 * before they are reused.
	 */
	if (mfp->ftype != 0 && !F_ISSET(bhp, BH_CALLPGIN)) {
		callpgin = 1;
		if ((ret = __memp_pg(dbmfp, bhp, 0)) != 0)
			goto err;
	}

	/* Write the page. */
	if ((ret = __os_io(dbenv, DB_IO_WRITE, dbmfp->fhp,
	    bhp->pgno, mfp->stat.st_pagesize, bhp->buf, &nw)) != 0) {
		__db_err(dbenv, "%s: write failed for page %lu",
		    __memp_fn(dbmfp), (u_long)bhp->pgno);
		goto err;
	}
	++mfp->stat.st_page_out;

err:
file_dead:
	/*
	 * !!!
	 * Once we pass this point, dbmfp and mfp may be NULL, we may not have
	 * a valid file reference.
	 *
	 * Unlock the buffer and reacquire the hash lock.
	 */
	MUTEX_UNLOCK(dbenv, &bhp->mutex);
	MUTEX_LOCK(dbenv, &hp->hash_mutex);

	/*
	 * If we rewrote the page, it will need processing by the pgin
	 * routine before reuse.
	 */
	if (callpgin)
		F_SET(bhp, BH_CALLPGIN);

	/*
	 * Update the hash bucket statistics, reset the flags.
	 * If we were successful, the page is no longer dirty.
	 */
	if (ret == 0) {
		DB_ASSERT(hp->hash_page_dirty != 0);
		--hp->hash_page_dirty;

		F_CLR(bhp, BH_DIRTY | BH_DIRTY_CREATE);
	}

	/* Regardless, clear any sync wait-for count and remove our lock. */
	bhp->ref_sync = 0;
	F_CLR(bhp, BH_LOCKED);

	return (ret);
}

/*
 * __memp_pg --
 *	Call the pgin/pgout routine.
 *
 * PUBLIC: int __memp_pg __P((DB_MPOOLFILE *, BH *, int));
 */
int
__memp_pg(dbmfp, bhp, is_pgin)
	DB_MPOOLFILE *dbmfp;
	BH *bhp;
	int is_pgin;
{
	DBT dbt, *dbtp;
	DB_ENV *dbenv;
	DB_MPOOL *dbmp;
	DB_MPREG *mpreg;
	MPOOLFILE *mfp;
	int ftype, ret;

	dbenv = dbmfp->dbenv;
	dbmp = dbenv->mp_handle;
	mfp = dbmfp->mfp;

	MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);

	ftype = mfp->ftype;
	for (mpreg = LIST_FIRST(&dbmp->dbregq);
	    mpreg != NULL; mpreg = LIST_NEXT(mpreg, q)) {
		if (ftype != mpreg->ftype)
			continue;
		if (mfp->pgcookie_len == 0)
			dbtp = NULL;
		else {
			dbt.size = (u_int32_t)mfp->pgcookie_len;
			dbt.data = R_ADDR(dbmp->reginfo, mfp->pgcookie_off);
			dbtp = &dbt;
		}
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);

		if (is_pgin) {
			if (mpreg->pgin != NULL &&
			    (ret = mpreg->pgin(dbenv,
			    bhp->pgno, bhp->buf, dbtp)) != 0)
				goto err;
		} else
			if (mpreg->pgout != NULL &&
			    (ret = mpreg->pgout(dbenv,
			    bhp->pgno, bhp->buf, dbtp)) != 0)
				goto err;
		break;
	}

	if (mpreg == NULL)
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);

	return (0);

err:	MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
	__db_err(dbenv, "%s: %s failed for page %lu",
	    __memp_fn(dbmfp), is_pgin ? "pgin" : "pgout", (u_long)bhp->pgno);
	return (ret);
}

/*
 * __memp_bhfree --
 *	Free a bucket header and its referenced data.
 *
 * PUBLIC: void __memp_bhfree
 * PUBLIC:     __P((DB_MPOOL *, DB_MPOOL_HASH *, BH *, u_int32_t));
 */
void
__memp_bhfree(dbmp, hp, bhp, flags)
	DB_MPOOL *dbmp;
	DB_MPOOL_HASH *hp;
	BH *bhp;
	u_int32_t flags;
{
	DB_ENV *dbenv;
	MPOOL *c_mp, *mp;
	MPOOLFILE *mfp;
	u_int32_t n_cache;

	/*
	 * Assumes the hash bucket is locked and the MPOOL is not.
	 */
	dbenv = dbmp->dbenv;
	mp = dbmp->reginfo[0].primary;
	n_cache = NCACHE(mp, bhp->mf_offset, bhp->pgno);

	/*
	 * Delete the buffer header from the hash bucket queue and reset
	 * the hash bucket's priority, if necessary.
	 */
	SH_TAILQ_REMOVE(&hp->hash_bucket, bhp, hq, __bh);
	if (bhp->priority == hp->hash_priority)
		hp->hash_priority =
		    SH_TAILQ_FIRST(&hp->hash_bucket, __bh) == NULL ?
		    0 : SH_TAILQ_FIRST(&hp->hash_bucket, __bh)->priority;

	/*
	 * Discard the hash bucket's mutex, it's no longer needed, and
	 * we don't want to be holding it when acquiring other locks.
	 */
	if (!LF_ISSET(BH_FREE_UNLOCKED))
		MUTEX_UNLOCK(dbenv, &hp->hash_mutex);

	/*
	 * Find the underlying MPOOLFILE and decrement its reference count.
	 * If this is its last reference, remove it.
	 */
	mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);
	MUTEX_LOCK(dbenv, &mfp->mutex);
	if (--mfp->block_cnt == 0 && mfp->mpf_cnt == 0)
		(void)__memp_mf_discard(dbmp, mfp);
	else
		MUTEX_UNLOCK(dbenv, &mfp->mutex);

	R_LOCK(dbenv, &dbmp->reginfo[n_cache]);

	/*
	 * Clear the mutex this buffer recorded; requires the region lock
	 * be held.
	 */
	__db_shlocks_clear(&bhp->mutex, &dbmp->reginfo[n_cache],
	    R_ADDR(&dbmp->reginfo[n_cache], mp->maint_off));

	/*
	 * If we're not reusing the buffer immediately, free the buffer header
	 * and data for real.
	 */
	if (LF_ISSET(BH_FREE_FREEMEM)) {
		__db_shalloc_free(&dbmp->reginfo[n_cache], bhp);
		c_mp = dbmp->reginfo[n_cache].primary;
		c_mp->stat.st_pages--;
	}
	R_UNLOCK(dbenv, &dbmp->reginfo[n_cache]);
}