/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996-2001
 *	Sleepycat Software.  All rights reserved.
 */
#include "db_config.h"

#ifndef lint
static const char revid[] = "$Id: mp_bh.c,v 11.46 2001/12/01 21:22:00 bostic Exp $";
#endif /* not lint */

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

#include <string.h>
#include <unistd.h>
#endif

#include "db_int.h"
#include "db_shash.h"
#include "mp.h"
#include "log.h"
#include "db_page.h"

static int __memp_upgrade __P((DB_MPOOL *, DB_MPOOLFILE *, MPOOLFILE *));

/*
 * __memp_bhwrite --
 *	Write the page associated with a given bucket header.
 *
 * PUBLIC: int __memp_bhwrite
 * PUBLIC:     __P((DB_MPOOL *, MPOOLFILE *, BH *, int, int *, int *));
 */
int
__memp_bhwrite(dbmp, mfp, bhp, open_extents, restartp, wrotep)
	DB_MPOOL *dbmp;
	MPOOLFILE *mfp;
	BH *bhp;
	int open_extents, *restartp, *wrotep;
{
	DB_ENV *dbenv;
	DB_MPOOLFILE *dbmfp;
	DB_MPREG *mpreg;
	int incremented, ret;

	dbenv = dbmp->dbenv;

	if (restartp != NULL)
		*restartp = 0;
	if (wrotep != NULL)
		*wrotep = 0;
	incremented = 0;

	/*
	 * If the file has been removed or is a closed temporary file, Jump
	 * right ahead and pretend that we've found the file we want-- the
	 * page-write function knows how to handle the fact that we don't have
	 * (or need!) any real file descriptor information.
	 */
	if (F_ISSET(mfp, MP_DEADFILE)) {
		dbmfp = NULL;
		goto found;
	}

	/*
	 * Walk the process' DB_MPOOLFILE list and find a file descriptor for
	 * the file.  We also check that the descriptor is open for writing.
	 * If we find a descriptor on the file that's not open for writing, we
	 * try and upgrade it to make it writeable.  If that fails, we're done.
	 */
	MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
	for (dbmfp = TAILQ_FIRST(&dbmp->dbmfq);
	    dbmfp != NULL; dbmfp = TAILQ_NEXT(dbmfp, q))
		if (dbmfp->mfp == mfp) {
			if (F_ISSET(dbmfp, MP_READONLY) &&
			    __memp_upgrade(dbmp, dbmfp, mfp)) {
				MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
				return (0);
			}

			/*
			 * Increment the reference count -- see the comment in
			 * memp_fclose().
			 */
			++dbmfp->ref;
			incremented = 1;
			break;
		}
	MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
	if (dbmfp != NULL)
		goto found;

	/*
	 * !!!
	 * Don't try to attach to temporary files.  There are two problems in
	 * trying to do that.  First, if we have different privileges than the
	 * process that "owns" the temporary file, we might create the backing
	 * disk file such that the owning process couldn't read/write its own
	 * buffers, e.g., memp_trickle running as root creating a file owned
	 * as root, mode 600.  Second, if the temporary file has already been
	 * created, we don't have any way of finding out what its real name is,
	 * and, even if we did, it was already unlinked (so that it won't be
	 * left if the process dies horribly).  This decision causes a problem,
	 * however: if the temporary file consumes the entire buffer cache,
	 * and the owner doesn't flush the buffers to disk, we could end up
	 * with resource starvation, and the memp_trickle thread couldn't do
	 * anything about it.  That's a pretty unlikely scenario, though.
	 *
	 * Note that we should never get here when the temporary file
	 * in question has already been closed in another process, in which
	 * case it should be marked MP_DEADFILE.
	 */
	if (F_ISSET(mfp, MP_TEMP)
	    || (F_ISSET(mfp, MP_EXTENT) && !open_extents)) {
		DB_ASSERT(!F_ISSET(mfp, MP_DEADFILE));
		return (0);
	}

	/*
	 * It's not a page from a file we've opened.  If the file requires
	 * input/output processing, see if this process has ever registered
	 * information as to how to write this type of file.  If not, there's
	 * nothing we can do.
	 */
	if (mfp->ftype != 0) {
		MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
		for (mpreg = LIST_FIRST(&dbmp->dbregq);
		    mpreg != NULL; mpreg = LIST_NEXT(mpreg, q))
			if (mpreg->ftype == mfp->ftype)
				break;
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
		if (mpreg == NULL)
			return (0);
	}

	/*
	 * Try and open the file, attaching to the underlying shared area.
	 * Ignore any error, assume it's a permissions problem.
	 *
	 * XXX
	 * There's no negative cache, so we may repeatedly try and open files
	 * that we have previously tried (and failed) to open.
	 */
	if (dbenv->memp_fcreate(dbenv, &dbmfp, 0) != 0)
		return (0);
	if (__memp_fopen_int(dbmfp, mfp,
	    R_ADDR(dbmp->reginfo, mfp->path_off),
	    0, 0, mfp->stat.st_pagesize, 0) != 0) {
		(void)dbmfp->close(dbmfp, 0);
		return (0);
	}
	F_SET(dbmfp, MP_FLUSH);
	if (F_ISSET(mfp, MP_EXTENT))
		dbmp->extents = 1;

found:	ret = __memp_pgwrite(dbmp, dbmfp, bhp, restartp, wrotep);

	if (incremented) {
		MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
		--dbmfp->ref;
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
	}

	return (ret);
}

/*
 * __memp_pgread --
 *	Read a page from a file.
 *
 * PUBLIC: int __memp_pgread __P((DB_MPOOLFILE *, BH *, int));
 */
int
__memp_pgread(dbmfp, bhp, can_create)
	DB_MPOOLFILE *dbmfp;
	BH *bhp;
	int can_create;
{
	DB_IO db_io;
	DB_ENV *dbenv;
	DB_MPOOL *dbmp;
	MPOOLFILE *mfp;
	size_t len, pagesize;
	size_t nr;
	int created, ret;

	dbmp = dbmfp->dbmp;
	dbenv = dbmp->dbenv;
	mfp = dbmfp->mfp;
	pagesize = mfp->stat.st_pagesize;
	created = 0;

	F_SET(bhp, BH_LOCKED | BH_TRASH);
	MUTEX_LOCK(dbenv, &bhp->mutex);
	R_UNLOCK(dbenv, dbmp->reginfo);

	/*
	 * Temporary files may not yet have been created.  We don't create
	 * them now, we create them when the pages have to be flushed.
	 */
	nr = 0;
	if (F_ISSET(dbmfp->fhp, DB_FH_VALID)) {
		db_io.fhp = dbmfp->fhp;
		db_io.mutexp = dbmfp->mutexp;
		db_io.pagesize = db_io.bytes = pagesize;
		db_io.pgno = bhp->pgno;
		db_io.buf = bhp->buf;

		/*
		 * The page may not exist;  if it doesn't, nr may well be 0,
		 * but we expect the underlying OS calls not to return an
		 * error code in this case.
		 */
		if ((ret = __os_io(dbenv, &db_io, DB_IO_READ, &nr)) != 0)
			goto err;
	} else
		ret = 0;

	if (nr < pagesize) {
		if (can_create)
			created = 1;
		else {
			/*
			 * Don't output error messages for short reads.  In
			 * particular, DB recovery processing may request pages
			 * that have never been written to disk or for which
			 * only some part have been written to disk, in which
			 * case we won't find the page.  The caller must know
			 * how to handle the error.
			 */
			ret = DB_PAGE_NOTFOUND;
			goto err;
		}
		/*
		 * Clear any bytes that need to be cleared -- if we did a short
		 * read, we assume that a page was not completely written and
		 * clear even the bytes that we read.  This is so our caller
		 * isn't surprised (for example, if the first sector only of a
		 * DB page was written, the LSN will indicate that the page was
		 * updated, but the page contents will be wrong).  Support for
		 * page checksums might make this unnecessary in the future --
		 * I would prefer not to discard data potentially written by
		 * the application, under any circumstances.
		 *
		 * If we're running in diagnostic mode, corrupt any bytes on
		 * the page that are unknown quantities for the caller.
		 */
		len = mfp->clear_len == 0 ? pagesize : mfp->clear_len;
		memset(bhp->buf, 0, len);
#if defined(DIAGNOSTIC) || defined(UMRW)
		if (len < pagesize)
			memset(bhp->buf + len, CLEAR_BYTE, pagesize - len);
#endif
	}

	/* Call any pgin function. */
	ret = mfp->ftype == 0 ? 0 : __memp_pg(dbmfp, bhp, 1);

	/* Unlock the buffer and reacquire the region lock. */
err:	MUTEX_UNLOCK(dbenv, &bhp->mutex);
	R_LOCK(dbenv, dbmp->reginfo);

	/*
	 * If no errors occurred, the data is now valid, clear the BH_TRASH
	 * flag; regardless, clear the lock bit and let other threads proceed.
	 */
	F_CLR(bhp, BH_LOCKED);
	if (ret == 0) {
		F_CLR(bhp, BH_TRASH);

		/* Update the statistics. */
		if (created)
			++mfp->stat.st_page_create;
		else
			++mfp->stat.st_page_in;
	}

	return (ret);
}

/*
 * __memp_pgwrite --
 *	Write a page to a file.
 *
 * PUBLIC: int __memp_pgwrite
 * PUBLIC:     __P((DB_MPOOL *, DB_MPOOLFILE *, BH *, int *, int *));
 */
int
__memp_pgwrite(dbmp, dbmfp, bhp, restartp, wrotep)
	DB_MPOOL *dbmp;
	DB_MPOOLFILE *dbmfp;
	BH *bhp;
	int *restartp, *wrotep;
{
	DB_ENV *dbenv;
	DB_IO db_io;
	DB_LSN lsn;
	MPOOL *c_mp, *mp;
	MPOOLFILE *mfp;
	size_t nw;
	int callpgin, dosync, ret, syncfail;
	const char *fail;

	dbenv = dbmp->dbenv;
	mp = dbmp->reginfo[0].primary;
	mfp = dbmfp == NULL ? NULL : dbmfp->mfp;

	if (restartp != NULL)
		*restartp = 0;
	if (wrotep != NULL)
		*wrotep = 0;
	callpgin = 0;

	/* We should never be called with a clean or a locked buffer. */
	DB_ASSERT(F_ISSET(bhp, BH_DIRTY));
	DB_ASSERT(!F_ISSET(bhp, BH_LOCKED));

	/*
	 * Lock the buffer, set the I/O in progress flag, and discard the
	 * region lock.
	 */
	MUTEX_LOCK(dbenv, &bhp->mutex);
	F_SET(bhp, BH_LOCKED);
	R_UNLOCK(dbenv, dbmp->reginfo);

	/* Tell the caller that the region lock was discarded. */
	if (restartp != NULL)
		*restartp = 1;

	/*
	 * 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 || F_ISSET(mfp, MP_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 the page is
	 * being written as part of a sync operation, the flush has been done
	 * already, unless it was modified by the application *after* the sync
	 * was scheduled.
	 */
	if (LOGGING_ON(dbenv) && mfp->lsn_off != -1 &&
	    (!F_ISSET(bhp, BH_SYNC) || F_ISSET(bhp, BH_SYNC_LOGFLSH))) {
		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.  So, if the page was original 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 (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)
		ret = 0;
	else {
		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);
		if (!F_ISSET(dbmfp->fhp, DB_FH_VALID) &&
		    ((ret = __db_appname(dbenv, DB_APP_TMP, NULL, NULL,
		    DB_OSO_CREATE | DB_OSO_EXCL | DB_OSO_TEMP,
		    dbmfp->fhp, NULL)) != 0 ||
		    !F_ISSET(dbmfp->fhp, DB_FH_VALID))) {
			MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
			__db_err(dbenv,
			    "unable to create temporary backing file");
			goto err;
		}
		MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
	}

	/* 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) {
		fail = "write";
		goto syserr;
	}
	if (nw != mfp->stat.st_pagesize) {
		ret = EIO;
		fail = "write";
		goto syserr;
	}

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 region lock.
	 */
	MUTEX_UNLOCK(dbenv, &bhp->mutex);
	R_LOCK(dbenv, dbmp->reginfo);

	/*
	 * Clean up the flags based on a successful write.
	 *
	 * If we rewrote the page, it will need processing by the pgin
	 * routine before reuse.
	 */
	if (callpgin)
		F_SET(bhp, BH_CALLPGIN);
	F_CLR(bhp, BH_DIRTY | BH_DIRTY_CREATE | BH_LOCKED);

	/*
	 * If we write a buffer for which a checkpoint is waiting, update
	 * the count of pending buffers (both in the mpool as a whole and
	 * for this file).  If the count for this file goes to zero, set a
	 * flag so we flush the writes.
	 */
	dosync = 0;
	if (F_ISSET(bhp, BH_SYNC)) {
		F_CLR(bhp, BH_SYNC | BH_SYNC_LOGFLSH);

		--mp->lsn_cnt;
		if (mfp != NULL)
			dosync = --mfp->lsn_cnt == 0 ? 1 : 0;
	}

	/* Update the page clean/dirty statistics. */
	c_mp = BH_TO_CACHE(dbmp, bhp);
	++c_mp->stat.st_page_clean;
	DB_ASSERT(c_mp->stat.st_page_dirty != 0);
	--c_mp->stat.st_page_dirty;

	/* Update I/O statistics. */
	if (mfp != NULL)
		++mfp->stat.st_page_out;

	/*
	 * Do the sync after everything else has been updated, so any incoming
	 * checkpoint doesn't see inconsistent information.
	 *
	 * XXX:
	 * Don't lock the region around the sync, fsync(2) has no atomicity
	 * issues.
	 *
	 * XXX:
	 * We ignore errors from the sync -- it makes no sense to return an
	 * error to the calling process, so set a flag causing the checkpoint
	 * to be retried later.  There is a possibility, of course, that a
	 * subsequent checkpoint was started and that we're going to force it
	 * to fail.  That should be unlikely, and fixing it would be difficult.
	 */
	if (dosync) {
		R_UNLOCK(dbenv, dbmp->reginfo);
		syncfail = __os_fsync(dbenv, dbmfp->fhp) != 0;
		R_LOCK(dbenv, dbmp->reginfo);
		if (syncfail)
			F_SET(mp, MP_LSN_RETRY);
	}

	if (wrotep != NULL)
		*wrotep = 1;

	return (0);

syserr:	__db_err(dbenv, "%s: %s failed for page %lu",
	    __memp_fn(dbmfp), fail, (u_long)bhp->pgno);

err:	/* Unlock the buffer and reacquire the region lock. */
	MUTEX_UNLOCK(dbenv, &bhp->mutex);
	R_LOCK(dbenv, dbmp->reginfo);

	/*
	 * Clean up the flags based on a failure.
	 *
	 * The page remains dirty but we remove our lock.  If we rewrote the
	 * page, it will need processing by the pgin routine before reuse.
	 */
	if (callpgin)
		F_SET(bhp, BH_CALLPGIN);
	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_MPOOL *dbmp;
	DB_MPREG *mpreg;
	MPOOLFILE *mfp;
	int ftype, ret;

	dbmp = dbmfp->dbmp;
	mfp = dbmfp->mfp;

	MUTEX_THREAD_LOCK(dbmp->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(dbmp->dbenv, dbmp->mutexp);

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

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

	return (0);

err:	MUTEX_THREAD_UNLOCK(dbmp->dbenv, dbmp->mutexp);
	__db_err(dbmp->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 *, BH *, int));
 */
void
__memp_bhfree(dbmp, bhp, free_mem)
	DB_MPOOL *dbmp;
	BH *bhp;
	int free_mem;
{
	DB_HASHTAB *dbht;
	MPOOL *c_mp, *mp;
	MPOOLFILE *mfp;
	int n_bucket, n_cache;

	mp = dbmp->reginfo[0].primary;
	c_mp = BH_TO_CACHE(dbmp, bhp);
	n_cache = NCACHE(mp, bhp->pgno);
	n_bucket = NBUCKET(c_mp, bhp->mf_offset, bhp->pgno);
	dbht = R_ADDR(&dbmp->reginfo[n_cache], c_mp->htab);

	/* Delete the buffer header from the hash bucket queue. */
	SH_TAILQ_REMOVE(&dbht[n_bucket], bhp, hq, __bh);

	/* Delete the buffer header from the LRU queue. */
	SH_TAILQ_REMOVE(&c_mp->bhq, bhp, q, __bh);

	/* Clear the mutex this buffer recorded */
	__db_shlocks_clear(&bhp->mutex, &dbmp->reginfo[n_cache],
	    (REGMAINT *)R_ADDR(&dbmp->reginfo[n_cache], mp->maint_off));
	/*
	 * 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);
	if (--mfp->block_cnt == 0 && mfp->mpf_cnt == 0)
		__memp_mf_discard(dbmp, mfp);

	DB_ASSERT(c_mp->stat.st_page_clean != 0);
	--c_mp->stat.st_page_clean;

	/*
	 * If we're not reusing it immediately, free the buffer header
	 * and data for real.
	 */
	if (free_mem)
		__db_shalloc_free(dbmp->reginfo[n_cache].addr, bhp);
}

/*
 * __memp_upgrade --
 *	Upgrade a file descriptor from readonly to readwrite.
 */
static int
__memp_upgrade(dbmp, dbmfp, mfp)
	DB_MPOOL *dbmp;
	DB_MPOOLFILE *dbmfp;
	MPOOLFILE *mfp;
{
	DB_FH fh;
	int ret;
	char *rpath;

	/*
	 * !!!
	 * We expect the handle to already be locked.
	 */

	/* Check to see if we've already upgraded. */
	if (F_ISSET(dbmfp, MP_UPGRADE))
		return (0);

	/* Check to see if we've already failed. */
	if (F_ISSET(dbmfp, MP_UPGRADE_FAIL))
		return (1);

	/*
	 * 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 = __db_appname(dbmp->dbenv, DB_APP_DATA,
	    NULL, R_ADDR(dbmp->reginfo, mfp->path_off), 0, NULL, &rpath)) != 0)
		return (ret);
	if (__os_open(dbmp->dbenv, rpath, 0, 0, &fh) != 0) {
		F_SET(dbmfp, MP_UPGRADE_FAIL);
		ret = 1;
	} else {
		/* Swap the descriptors and set the upgrade flag. */
		(void)__os_closehandle(dbmfp->fhp);
		*dbmfp->fhp = fh;
		F_SET(dbmfp, MP_UPGRADE);
		ret = 0;
	}
	__os_freestr(dbmp->dbenv, rpath);
	return (ret);
}
