1 files changed, 359 insertions, 0 deletions
diff --git a/db2/mp/mp_fget.c b/db2/mp/mp_fget.c
new file mode 100644
index 0000000000..418802a3b9
--- /dev/null
+++ b/db2/mp/mp_fget.c
@@ -0,0 +1,359 @@
+/*-
+ * See the file LICENSE for redistribution information.
+ *
+ * Copyright (c) 1996, 1997
+ *	Sleepycat Software.  All rights reserved.
+ */
+#include "config.h"
+
+#ifndef lint
+static const char sccsid[] = "@(#)mp_fget.c	10.22 (Sleepycat) 8/19/97";
+#endif /* not lint */
+
+#ifndef NO_SYSTEM_INCLUDES
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#endif
+
+#include "db_int.h"
+#include "shqueue.h"
+#include "db_shash.h"
+#include "mp.h"
+#include "common_ext.h"
+
+int __sleep_on_every_page_get;		/* XXX: thread debugging option. */
+
+/*
+ * memp_fget --
+ *	Get a page from the file.
+ */
+int
+memp_fget(dbmfp, pgnoaddr, flags, addrp)
+	DB_MPOOLFILE *dbmfp;
+	db_pgno_t *pgnoaddr;
+	u_long flags;
+	void *addrp;
+{
+	BH *bhp, *tbhp;
+	DB_MPOOL *dbmp;
+	MPOOL *mp;
+	MPOOLFILE *mfp;
+	db_pgno_t lastpgno;
+	size_t bucket, mf_offset;
+	off_t size;
+	u_long cnt;
+	int b_incr, b_inserted, readonly_alloc, ret;
+	void *addr;
+
+	dbmp = dbmfp->dbmp;
+
+	/*
+	 * Validate arguments.
+	 *
+	 * !!!
+	 * Don't test for DB_MPOOL_CREATE and DB_MPOOL_NEW flags for readonly
+	 * files here, and create non-existent pages in readonly files if the
+	 * flags are set, later.  The reason is that the hash access method
+	 * wants to get empty pages that don't really exist in readonly files.
+	 * The only alternative is for hash to write the last "bucket" all the
+	 * time, which we don't want to do because one of our big goals in life
+	 * is to keep database files small.  It's sleazy as hell, but we catch
+	 * any attempt to actually write the file in memp_fput().
+	 */
+#define	OKFLAGS	(DB_MPOOL_CREATE | DB_MPOOL_LAST | DB_MPOOL_NEW)
+	if (flags != 0) {
+		if ((ret =
+		    __db_fchk(dbmp->dbenv, "memp_fget", flags, OKFLAGS)) != 0)
+			return (ret);
+
+		switch (flags) {
+		case DB_MPOOL_CREATE:
+		case DB_MPOOL_LAST:
+		case DB_MPOOL_NEW:
+		case 0:
+			break;
+		default:
+			return (__db_ferr(dbmp->dbenv, "memp_fget", 1));
+		}
+	}
+
+#ifdef DEBUG
+	/*
+	 * XXX
+	 * We want to switch threads as often as possible.  Sleep every time
+	 * we get a new page to make it more likely.
+	 */
+	if (__sleep_on_every_page_get && (dbmp->dbenv == NULL ||
+	    dbmp->dbenv->db_yield == NULL || dbmp->dbenv->db_yield() != 0))
+		__db_sleep(0, 1);
+#endif
+
+	mp = dbmp->mp;
+	mfp = dbmfp->mfp;
+	mf_offset = OFFSET(dbmp, mfp);
+	addr = NULL;
+	bhp = NULL;
+	b_incr = b_inserted = readonly_alloc = ret = 0;
+
+	LOCKREGION(dbmp);
+
+	/*
+	 * If mmap'ing the file, just return a pointer.  However, if another
+	 * process has opened the file for writing since we mmap'd it, start
+	 * playing the game by their rules, i.e. everything goes through the
+	 * cache.  All pages previously returned should be safe, as long as
+	 * a locking protocol was observed.
+	 *
+	 * XXX
+	 * We don't discard the map because we don't know when all of the
+	 * pages will have been discarded from the process' address space.
+	 * It would be possible to do so by reference counting the open
+	 * pages from the mmap, but it's unclear to me that it's worth it.
+	 */
+	if (dbmfp->addr != NULL && dbmfp->mfp->can_mmap) {
+		lastpgno = dbmfp->len == 0 ?
+		    0 : (dbmfp->len - 1) / mfp->stat.st_pagesize;
+		if (LF_ISSET(DB_MPOOL_LAST))
+			*pgnoaddr = lastpgno;
+		else {
+			/*
+			 * !!!
+			 * Allocate a page that can never really exist.  See
+			 * the comment above about non-existent pages and the
+			 * hash access method.
+			 */
+			if (LF_ISSET(DB_MPOOL_CREATE | DB_MPOOL_NEW))
+				readonly_alloc = 1;
+			else if (*pgnoaddr > lastpgno) {
+				__db_err(dbmp->dbenv,
+				    "%s: page %lu doesn't exist",
+				    dbmfp->path, (u_long)*pgnoaddr);
+				ret = EINVAL;
+				goto err;
+			}
+		}
+		if (!readonly_alloc) {
+			addr = ADDR(dbmfp, *pgnoaddr * mfp->stat.st_pagesize);
+
+			++mp->stat.st_map;
+			++mfp->stat.st_map;
+
+			goto mapret;
+		}
+	}
+
+	/*
+	 * If requesting the last page or a new page, find the last page.  The
+	 * tricky thing is that the user may have created a page already that's
+	 * after any page that exists in the file.
+	 */
+	if (LF_ISSET(DB_MPOOL_LAST | DB_MPOOL_NEW)) {
+		/*
+		 * Temporary files may not yet have been created.
+		 *
+		 * Don't lock -- there are no atomicity issues for stat(2).
+		 */
+		if (dbmfp->fd == -1)
+			size = 0;
+		else if ((ret = __db_stat(dbmp->dbenv,
+		    dbmfp->path, dbmfp->fd, &size, NULL)) != 0)
+			goto err;
+
+		*pgnoaddr = size == 0 ? 0 : (size - 1) / mfp->stat.st_pagesize;
+
+		/*
+		 * Walk the list of BH's, looking for later pages.  Save the
+		 * pointer if a later page is found so that we don't have to
+		 * search the list twice.
+		 *
+		 * If requesting a new page, return the page one after the last
+		 * page -- which we'll have to create.
+		 */
+		for (tbhp = SH_TAILQ_FIRST(&mp->bhq, __bh);
+		    tbhp != NULL; tbhp = SH_TAILQ_NEXT(tbhp, q, __bh))
+			if (tbhp->pgno >= *pgnoaddr &&
+			    tbhp->mf_offset == mf_offset) {
+				bhp = tbhp;
+				*pgnoaddr = bhp->pgno;
+			}
+		if (LF_ISSET(DB_MPOOL_NEW))
+			++*pgnoaddr;
+	}
+
+	/* If we already found the right buffer, return it. */
+	if (LF_ISSET(DB_MPOOL_LAST) && bhp != NULL) {
+		addr = bhp->buf;
+		goto found;
+	}
+
+	/* If we haven't checked the BH list yet, do the search. */
+	if (!LF_ISSET(DB_MPOOL_LAST | DB_MPOOL_NEW)) {
+		++mp->stat.st_hash_searches;
+		bucket = BUCKET(mp, mf_offset, *pgnoaddr);
+		for (cnt = 0,
+		    bhp = SH_TAILQ_FIRST(&dbmp->htab[bucket], __bh);
+		    bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, mq, __bh)) {
+			++cnt;
+			if (bhp->pgno == *pgnoaddr &&
+			    bhp->mf_offset == mf_offset) {
+				addr = bhp->buf;
+				if (cnt > mp->stat.st_hash_longest)
+					mp->stat.st_hash_longest = cnt;
+				mp->stat.st_hash_examined += cnt;
+				goto found;
+			}
+		}
+		if (cnt > mp->stat.st_hash_longest)
+			mp->stat.st_hash_longest = cnt;
+		mp->stat.st_hash_examined += cnt;
+	}
+
+	/*
+	 * Allocate a new buffer header and data space, and mark the contents
+	 * as useless.
+	 */
+	if ((ret = __memp_ralloc(dbmp, sizeof(BH) -
+	    sizeof(u_int8_t) + mfp->stat.st_pagesize, NULL, &bhp)) != 0)
+		goto err;
+	addr = bhp->buf;
+#ifdef DEBUG
+	if ((ALIGNTYPE)addr & (sizeof(size_t) - 1)) {
+		__db_err(dbmp->dbenv,
+		    "Internal error: BH data NOT size_t aligned.");
+		abort();
+	}
+#endif
+	memset(bhp, 0, sizeof(BH));
+	LOCKINIT(dbmp, &bhp->mutex);
+
+	/*
+	 * Prepend the bucket header to the head of the appropriate MPOOL
+	 * bucket hash list.  Append the bucket header to the tail of the
+	 * MPOOL LRU chain.
+	 *
+	 * We have to do this before we read in the page so we can discard
+	 * our region lock without screwing up the world.
+	 */
+	bucket = BUCKET(mp, mf_offset, *pgnoaddr);
+	SH_TAILQ_INSERT_HEAD(&dbmp->htab[bucket], bhp, mq, __bh);
+	SH_TAILQ_INSERT_TAIL(&mp->bhq, bhp, q);
+	b_inserted = 1;
+
+	/* Set the page number, and associated MPOOLFILE. */
+	bhp->mf_offset = mf_offset;
+	bhp->pgno = *pgnoaddr;
+
+	/*
+	 * If we know we created the page, zero it out and continue.
+	 *
+	 * !!!
+	 * Note: DB_MPOOL_NEW deliberately doesn't call the pgin function.
+	 * If DB_MPOOL_CREATE is used, then the application's pgin function
+	 * has to be able to handle pages of 0's -- if it uses DB_MPOOL_NEW,
+	 * it can detect all of its page creates, and not bother.
+	 *
+	 * Otherwise, read the page into memory, optionally creating it if
+	 * DB_MPOOL_CREATE is set.
+	 *
+	 * Increment the reference count for created buffers, but importantly,
+	 * increment the reference count for buffers we're about to read so
+	 * that the buffer can't move.
+	 */
+	++bhp->ref;
+	b_incr = 1;
+
+	if (LF_ISSET(DB_MPOOL_NEW))
+		memset(addr, 0, mfp->stat.st_pagesize);
+	else {
+		/*
+		 * It's possible for the read function to fail, which means
+		 * that we fail as well.
+		 */
+reread:		if ((ret = __memp_pgread(dbmfp,
+		    bhp, LF_ISSET(DB_MPOOL_CREATE | DB_MPOOL_NEW))) != 0)
+			goto err;
+
+		/*
+		 * !!!
+		 * The __memp_pgread call discarded and reacquired the region
+		 * lock.  Because the buffer reference count was incremented
+		 * before the region lock was discarded the buffer didn't move.
+		 */
+		++mp->stat.st_cache_miss;
+		++mfp->stat.st_cache_miss;
+	}
+
+	if (0) {
+found:		/* Increment the reference count. */
+		if (bhp->ref == UINT16_T_MAX) {
+			__db_err(dbmp->dbenv,
+			    "%s: too many references to page %lu",
+			    dbmfp->path, bhp->pgno);
+			ret = EAGAIN;
+			goto err;
+		}
+		++bhp->ref;
+		b_incr = 1;
+
+		/*
+	 	 * Any found buffer might be trouble.
+		 *
+		 * BH_LOCKED --
+		 * I/O in progress, wait for it to finish.  Because the buffer
+		 * reference count was incremented before the region lock was
+		 * discarded we know the buffer didn't move.
+		 */
+		if (F_ISSET(bhp, BH_LOCKED)) {
+			UNLOCKREGION(dbmp);
+			LOCKBUFFER(dbmp, bhp);
+			/* Waiting for I/O to finish... */
+			UNLOCKBUFFER(dbmp, bhp);
+			LOCKREGION(dbmp);
+		}
+
+		/*
+		 * BH_TRASH --
+		 * The buffer is garbage.
+		 */
+		if (F_ISSET(bhp, BH_TRASH))
+			goto reread;
+
+		/*
+		 * BH_CALLPGIN --
+		 * The buffer was written, and the contents need to be
+		 * converted again.
+		 */
+		if (F_ISSET(bhp, BH_CALLPGIN)) {
+			if ((ret = __memp_pg(dbmfp, bhp, 1)) != 0)
+				goto err;
+			F_CLR(bhp, BH_CALLPGIN);
+		}
+
+		++mp->stat.st_cache_hit;
+		++mfp->stat.st_cache_hit;
+	}
+
+mapret:	LOCKHANDLE(dbmp, &dbmfp->mutex);
+	++dbmfp->pinref;
+	UNLOCKHANDLE(dbmp, &dbmfp->mutex);
+
+	if (0) {
+err:		/*
+		 * If no other process is already waiting on a created buffer,
+		 * go ahead and discard it, it's not useful.
+		 */
+		if (b_incr)
+			--bhp->ref;
+		if (b_inserted && bhp->ref == 0)
+			__memp_bhfree(dbmp, mfp, bhp, 1);
+	}
+
+	UNLOCKREGION(dbmp);
+
+	*(void **)addrp = addr;
+	return (ret);
+}