mp_bh.c

这是linux下运行的mysql软件包,可用于linux 下安装 php + mysql + apach 的网络配置

	 * 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) {
		memcpy(&lsn, bhp->buf + mfp->lsn_off, sizeof(DB_LSN));
		if ((ret = dbenv->log_flush(dbenv, &lsn)) != 0)
			goto err;
	}

#ifdef DIAGNOSTIC
	/*
	 * Verify write-ahead logging semantics.
	 *
	 * !!!
	 * One special case.  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.
	 */
	if (LOGGING_ON(dbenv) && !IS_NOT_LOGGED_LSN(LSN(bhp->buf))) {
		/*
		 * 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;
		LOG *lp;

		dblp = dbenv->lg_handle;
		lp = dblp->reginfo.primary;
		if (!IS_NOT_LOGGED_LSN(LSN(bhp->buf)) &&
		    log_compare(&lp->s_lsn, &LSN(bhp->buf)) <= 0) {
			R_LOCK(dbenv, &dblp->reginfo);
			DB_ASSERT(log_compare(&lp->s_lsn, &LSN(bhp->buf)) > 0);
			R_UNLOCK(dbenv, &dblp->reginfo);
		}
	}
#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) {
		callpgin = 1;
		if ((ret = __memp_pg(dbmfp, bhp, 0)) != 0)
			goto err;
	}

	/* Temporary files may not yet have been created. */
	if (!F_ISSET(dbmfp->fhp, DB_FH_VALID)) {
		MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
		ret = F_ISSET(dbmfp->fhp, DB_FH_VALID) ? 0 :
		    __db_appname(dbenv, DB_APP_TMP, NULL,
		    F_ISSET(dbenv, DB_ENV_DIRECT_DB) ? DB_OSO_DIRECT : 0,
		    dbmfp->fhp, NULL);
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
		if (ret != 0) {
			__db_err(dbenv,
			    "unable to create temporary backing file");
			goto err;
		}
	}

	/* Write the page. */
	db_io.fhp = dbmfp->fhp;
	db_io.mutexp = dbmfp->mutexp;
	db_io.pagesize = db_io.bytes = mfp->stat.st_pagesize;
	db_io.pgno = bhp->pgno;
	db_io.buf = bhp->buf;
	if ((ret = __os_io(dbenv, &db_io, DB_IO_WRITE, &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;

	dbmp = dbmfp->dbmp;
	dbenv = dbmp->dbenv;
	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 = 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 __P((DB_MPOOL *, DB_MPOOL_HASH *, BH *, int));
 */
void
__memp_bhfree(dbmp, hp, bhp, free_mem)
	DB_MPOOL *dbmp;
	DB_MPOOL_HASH *hp;
	BH *bhp;
	int free_mem;
{
	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.
	 */
	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)
		__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],
	    (REGMAINT *)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 (free_mem) {
		__db_shalloc_free(dbmp->reginfo[n_cache].addr, bhp);
		c_mp = dbmp->reginfo[n_cache].primary;
		c_mp->stat.st_pages--;
	}
	R_UNLOCK(dbenv, &dbmp->reginfo[n_cache]);
}

/*
 * __memp_upgrade --
 *	Upgrade a file descriptor from read-only to read-write.
 */
static int
__memp_upgrade(dbmp, dbmfp, mfp)
	DB_MPOOL *dbmp;
	DB_MPOOLFILE *dbmfp;
	MPOOLFILE *mfp;
{
	DB_ENV *dbenv;
	DB_FH *fhp, *tfhp;
	int ret;
	char *rpath;

	dbenv = dbmp->dbenv;
	fhp = NULL;
	rpath = NULL;

	/*
	 * Calculate the real name for this file and try to open it read/write.
	 * We know we have a valid pathname for the file because it's the only
	 * way we could have gotten a file descriptor of any kind.
	 */
	if ((ret = __os_calloc(dbenv, 1, sizeof(DB_FH), &fhp)) != 0)
		goto err;

	if ((ret = __db_appname(dbenv, DB_APP_DATA,
	    R_ADDR(dbmp->reginfo, mfp->path_off), 0, NULL, &rpath)) != 0)
		goto err;

	if (__os_open(dbenv, rpath,
	    F_ISSET(mfp, MP_DIRECT) ? DB_OSO_DIRECT : 0, 0, fhp) != 0) {
		F_SET(dbmfp, MP_UPGRADE_FAIL);
		goto err;
	}

	/*
	 * Swap the descriptors and set the upgrade flag.
	 *
	 * XXX
	 * There is a race here.  If another process schedules a read using the
	 * existing file descriptor and is swapped out before making the system
	 * call, this code could theoretically close the file descriptor out
	 * from under it.  While it's very unlikely, this code should still be
	 * rewritten.
	 */
	tfhp = dbmfp->fhp;
	dbmfp->fhp = fhp;
	fhp = tfhp;

	(void)__os_closehandle(dbenv, fhp);
	F_SET(dbmfp, MP_UPGRADE);

	ret = 0;
	if (0) {
err:		ret = 1;
	}
	if (fhp != NULL)
		__os_free(dbenv, fhp);
	if (rpath != NULL)
		__os_free(dbenv, rpath);

	return (ret);
}