tdb2: allow multiple opens of the same file.

Finally, we enable sharing of the struct tdb_file.  We add a reference count
so we can free the struct tdb_file when the last tdb is closed.

ccan/tdb2/doc/design.lyx

@@ -853,7 +853,13 @@ Status
 \end_layout
 
 \begin_layout Standard
+
+\change_deleted 0 1300360823
 Incomplete.
+\change_inserted 0 1300360824
+Complete.
+\change_unchanged
+
 \end_layout
 
 \begin_layout Subsection

ccan/tdb2/lock.c

@@ -30,14 +30,11 @@
 #include <ccan/build_assert/build_assert.h>
 
 /* If we were threaded, we could wait for unlock, but we're not, so fail. */
-static bool owner_conflict(struct tdb_context *tdb, struct tdb_lock *lock)
+static enum TDB_ERROR owner_conflict(struct tdb_context *tdb, const char *call)
 {
-	if (lock->owner != tdb) {
-		tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
-			   "Lock already owned by another opener");
-		return true;
-	}
-	return false;
+	return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
+			  "%s: lock owned by another tdb in this process.",
+			  call);
 }
 
 static int fcntl_lock(struct tdb_context *tdb,
@@ -226,6 +223,10 @@ enum TDB_ERROR tdb_allrecord_upgrade(struct tdb_context *tdb)
 				  " already upgraded?");
 	}
 
+	if (tdb->file->allrecord_lock.owner != tdb) {
+		return owner_conflict(tdb, "tdb_allrecord_upgrade");
+	}
+
 	while (count--) {
 		struct timeval tv;
 		if (tdb_brlock(tdb, F_WRLCK,
@@ -306,8 +307,9 @@ static enum TDB_ERROR tdb_nest_lock(struct tdb_context *tdb,
 
 	new_lck = find_nestlock(tdb, offset, NULL);
 	if (new_lck) {
-		if (owner_conflict(tdb, new_lck))
-			return -1;
+		if (new_lck->owner != tdb) {
+			return owner_conflict(tdb, "tdb_nest_lock");
+		}
 
 		if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
 			return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
@@ -470,14 +472,17 @@ enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 	enum TDB_ERROR ecode;
 	tdb_bool_err berr;
 
-	if (tdb->file->allrecord_lock.count
-	    && (ltype == F_RDLCK
-		|| tdb->file->allrecord_lock.ltype == F_WRLCK)) {
-		tdb->file->allrecord_lock.count++;
-		return TDB_SUCCESS;
-	}
-
 	if (tdb->file->allrecord_lock.count) {
+		if (tdb->file->allrecord_lock.owner != tdb) {
+			return owner_conflict(tdb, "tdb_allrecord_lock");
+		}
+
+		if (ltype == F_RDLCK
+		    || tdb->file->allrecord_lock.ltype == F_WRLCK) {
+			tdb->file->allrecord_lock.count++;
+			return TDB_SUCCESS;
+		}
+
 		/* a global lock of a different type exists */
 		return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 				  "tdb_allrecord_lock: already have %s lock",
@@ -658,12 +663,14 @@ enum TDB_ERROR tdb_lock_hashes(struct tdb_context *tdb,
 		+ (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 
 	/* a allrecord lock allows us to avoid per chain locks */
-	if (tdb->file->allrecord_lock.count &&
-	    (ltype == tdb->file->allrecord_lock.ltype || ltype == F_RDLCK)) {
-		return TDB_SUCCESS;
-	}
-
 	if (tdb->file->allrecord_lock.count) {
+		if (tdb->file->allrecord_lock.owner != tdb)
+			return owner_conflict(tdb, "tdb_lock_hashes");
+		if (ltype == tdb->file->allrecord_lock.ltype
+		    || ltype == F_RDLCK) {
+			return TDB_SUCCESS;
+		}
+
 		return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 				  "tdb_lock_hashes:"
 				  " already have %s allrecordlock",

ccan/tdb2/open.c

@@ -1,4 +1,5 @@
 #include "private.h"
+#include <assert.h>
 
 /* all lock info, to detect double-opens (fcntl file don't nest!) */
 static struct tdb_file *files = NULL;
@@ -9,6 +10,7 @@ static struct tdb_file *find_file(dev_t device, ino_t ino)
 
 	for (i = files; i; i = i->next) {
 		if (i->device == device && i->inode == ino) {
+			i->refcnt++;
 			break;
 		}
 	}
@@ -174,6 +176,7 @@ static enum TDB_ERROR tdb_new_file(struct tdb_context *tdb)
 	tdb->file->num_lockrecs = 0;
 	tdb->file->lockrecs = NULL;
 	tdb->file->allrecord_lock.count = 0;
+	tdb->file->refcnt = 1;
 	return TDB_SUCCESS;
 }
 
@@ -291,7 +294,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 				   "tdb_open: could not open file %s: %s",
 				   name, strerror(errno));
-			goto fail;
+			goto fail_errno;
 		}
 
 		/* on exec, don't inherit the fd */
@@ -303,7 +306,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 				   "tdb_open: could not stat open %s: %s",
 				   name, strerror(errno));
-			goto fail;
+			goto fail_errno;
 		}
 
 		ecode = tdb_new_file(tdb);
@@ -316,13 +319,6 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 		tdb->file->inode = st.st_ino;
 		tdb->file->map_ptr = NULL;
 		tdb->file->map_size = sizeof(struct tdb_header);
-	} else {
-		/* FIXME */
-		ecode = tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
-				   "tdb_open: %s (%d,%d) is already open in"
-				   " this process",
-				   name, (int)st.st_dev, (int)st.st_ino);
- 		goto fail;
  	}
 
 	/* ensure there is only one process initialising at once */
@@ -332,7 +328,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	}
 
 	/* If they used O_TRUNC, read will return 0. */
-	rlen = read(tdb->file->fd, &hdr, sizeof(hdr));
+	rlen = pread(tdb->file->fd, &hdr, sizeof(hdr), 0);
 	if (rlen == 0 && (open_flags & O_CREAT)) {
 		ecode = tdb_new_database(tdb, seed, &hdr);
 		if (ecode != TDB_SUCCESS) {
@@ -416,51 +412,54 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 		goto fail;
 	}
 
-	/* Add to linked list. */
-	files = tdb->file;
+	/* Add to linked list if we're new. */
+	if (tdb->file->refcnt == 1)
+		files = tdb->file;
 	return tdb;
 
  fail:
 	/* Map ecode to some logical errno. */
-	if (!saved_errno) {
-		switch (ecode) {
-		case TDB_ERR_CORRUPT:
-		case TDB_ERR_IO:
-			saved_errno = EIO;
-			break;
-		case TDB_ERR_LOCK:
-			saved_errno = EWOULDBLOCK;
-			break;
-		case TDB_ERR_OOM:
-			saved_errno = ENOMEM;
-			break;
-		case TDB_ERR_EINVAL:
-			saved_errno = EINVAL;
-			break;
-		default:
-			saved_errno = EINVAL;
-			break;
-		}
+	switch (ecode) {
+	case TDB_ERR_CORRUPT:
+	case TDB_ERR_IO:
+		saved_errno = EIO;
+		break;
+	case TDB_ERR_LOCK:
+		saved_errno = EWOULDBLOCK;
+		break;
+	case TDB_ERR_OOM:
+		saved_errno = ENOMEM;
+		break;
+	case TDB_ERR_EINVAL:
+		saved_errno = EINVAL;
+		break;
+	default:
+		saved_errno = EINVAL;
+		break;
 	}
 
+fail_errno:
 #ifdef TDB_TRACE
 	close(tdb->tracefd);
 #endif
 	free((char *)tdb->name);
 	if (tdb->file) {
 		tdb_unlock_all(tdb);
-		if (tdb->file->map_ptr) {
-			if (tdb->flags & TDB_INTERNAL) {
-				free(tdb->file->map_ptr);
-			} else
-				tdb_munmap(tdb->file);
+		if (--tdb->file->refcnt == 0) {
+			assert(tdb->file->num_lockrecs == 0);
+			if (tdb->file->map_ptr) {
+				if (tdb->flags & TDB_INTERNAL) {
+					free(tdb->file->map_ptr);
+				} else
+					tdb_munmap(tdb->file);
+			}
+			if (close(tdb->file->fd) != 0)
+				tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
+					   "tdb_open: failed to close tdb fd"
+					   " on error: %s", strerror(errno));
+			free(tdb->file->lockrecs);
+			free(tdb->file);
 		}
-		if (close(tdb->file->fd) != 0)
-			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
-				   "tdb_open: failed to close tdb fd"
-				   " on error: %s", strerror(errno));
-		free(tdb->file->lockrecs);
-		free(tdb->file);
 	}
 
 	free(tdb);
@@ -487,17 +486,21 @@ int tdb_close(struct tdb_context *tdb)
 	free((char *)tdb->name);
 	if (tdb->file) {
 		struct tdb_file **i;
-		ret = close(tdb->file->fd);
 
-		/* Remove from files list */
-		for (i = &files; *i; i = &(*i)->next) {
-			if (*i == tdb->file) {
-				*i = tdb->file->next;
-				break;
+		tdb_unlock_all(tdb);
+		if (--tdb->file->refcnt == 0) {
+			ret = close(tdb->file->fd);
+
+			/* Remove from files list */
+			for (i = &files; *i; i = &(*i)->next) {
+				if (*i == tdb->file) {
+					*i = tdb->file->next;
+					break;
+				}
 			}
+			free(tdb->file->lockrecs);
+			free(tdb->file);
 		}
-		free(tdb->file->lockrecs);
-		free(tdb->file);
 	}
 
 #ifdef TDB_TRACE

ccan/tdb2/private.h

@@ -320,6 +320,9 @@ struct tdb_file {
 	/* Single list of all TDBs, to detect multiple opens. */
 	struct tdb_file *next;
 
+	/* How many are sharing us? */
+	unsigned int refcnt;
+
 	/* Mmap (if any), or malloc (for TDB_INTERNAL). */
 	void *map_ptr;
 

ccan/tdb2/test/failtest_helper.h

@@ -4,9 +4,9 @@
 #include <stdbool.h>
 
 /* FIXME: Check these! */
-#define INITIAL_TDB_MALLOC	"open.c", 195, FAILTEST_MALLOC
-#define URANDOM_OPEN		"open.c", 42, FAILTEST_OPEN
-#define URANDOM_READ		"open.c", 22, FAILTEST_READ
+#define INITIAL_TDB_MALLOC	"open.c", 198, FAILTEST_MALLOC
+#define URANDOM_OPEN		"open.c", 44, FAILTEST_OPEN
+#define URANDOM_READ		"open.c", 24, FAILTEST_READ
 
 bool exit_check_log(struct failtest_call *history, unsigned num);
 bool failmatch(const struct failtest_call *call,

ccan/tdb2/test/run-open-multiple-times.c

@@ -0,0 +1,87 @@
+#include <ccan/tdb2/tdb.c>
+#include <ccan/tdb2/open.c>
+#include <ccan/tdb2/free.c>
+#include <ccan/tdb2/lock.c>
+#include <ccan/tdb2/io.c>
+#include <ccan/tdb2/hash.c>
+#include <ccan/tdb2/check.c>
+#include <ccan/tdb2/transaction.c>
+#include <ccan/tap/tap.h>
+#include "logging.h"
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct tdb_context *tdb, *tdb2;
+	struct tdb_data key = { (unsigned char *)&i, sizeof(i) };
+	struct tdb_data data = { (unsigned char *)&i, sizeof(i) };
+	struct tdb_data d = { NULL, 0 }; /* Bogus GCC warning */
+	int flags[] = { TDB_DEFAULT, TDB_NOMMAP,
+			TDB_CONVERT, TDB_NOMMAP|TDB_CONVERT };
+
+	plan_tests(sizeof(flags) / sizeof(flags[0]) * 28);
+	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
+		tdb = tdb_open("run-open-multiple-times.tdb", flags[i],
+			       O_RDWR|O_CREAT|O_TRUNC, 0600, &tap_log_attr);
+		ok1(tdb);
+		if (!tdb)
+			continue;
+		tdb2 = tdb_open("run-open-multiple-times.tdb", flags[i],
+				O_RDWR|O_CREAT, 0600, &tap_log_attr);
+		ok1(tdb_check(tdb, NULL, NULL) == 0);
+		ok1(tdb_check(tdb2, NULL, NULL) == 0);
+
+		/* Store in one, fetch in the other. */
+		ok1(tdb_store(tdb, key, data, TDB_REPLACE) == 0);
+		ok1(tdb_fetch(tdb2, key, &d) == TDB_SUCCESS);
+		ok1(d.dptr && d.dsize == data.dsize
+		    && memcmp(d.dptr, data.dptr, d.dsize) == 0);
+		free(d.dptr);
+
+		/* Vice versa, with delete. */
+		ok1(tdb_delete(tdb2, key) == 0);
+		ok1(tdb_fetch(tdb, key, &d) == TDB_ERR_NOEXIST);
+
+		/* OK, now close first one, check second still good. */
+		ok1(tdb_close(tdb) == 0);
+
+		ok1(tdb_store(tdb2, key, data, TDB_REPLACE) == 0);
+		ok1(tdb_fetch(tdb2, key, &d) == TDB_SUCCESS);
+		ok1(d.dptr && d.dsize == data.dsize
+		    && memcmp(d.dptr, data.dptr, d.dsize) == 0);
+		free(d.dptr);
+
+		/* Reopen */
+		tdb = tdb_open("run-open-multiple-times.tdb", flags[i],
+			       O_RDWR|O_CREAT, 0600, &tap_log_attr);
+		ok1(tdb);
+
+		ok1(tdb_transaction_start(tdb2) == 0);
+
+		/* Anything in the other one should fail. */
+		ok1(tdb_fetch(tdb, key, &d) == TDB_ERR_LOCK);
+		ok1(tap_log_messages == 1);
+		ok1(tdb_store(tdb, key, data, TDB_REPLACE) == TDB_ERR_LOCK);
+		ok1(tap_log_messages == 2);
+		ok1(tdb_transaction_start(tdb) == TDB_ERR_LOCK);
+		ok1(tap_log_messages == 3);
+		ok1(tdb_chainlock(tdb, key) == TDB_ERR_LOCK);
+		ok1(tap_log_messages == 4);
+
+		/* Transaciton should work as normal. */
+		ok1(tdb_store(tdb2, key, data, TDB_REPLACE) == TDB_SUCCESS);
+
+		/* Now... try closing with locks held. */
+		ok1(tdb_close(tdb2) == 0);
+
+		ok1(tdb_fetch(tdb, key, &d) == TDB_SUCCESS);
+		ok1(d.dptr && d.dsize == data.dsize
+		    && memcmp(d.dptr, data.dptr, d.dsize) == 0);
+		free(d.dptr);
+		ok1(tdb_close(tdb) == 0);
+		ok1(tap_log_messages == 4);
+		tap_log_messages = 0;
+	}
+
+	return exit_status();
+}