tdb2: add TDB_RDONLY flag, allow setting/unsetting it.

You can only unset it if the TDB was originally opened O_RDWR.

Also, cleaned up error handling in tdb_allrecord_lock() so we only get
one log message on a r/o database.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Imported from CCAN commit b87e14495d5b07e1b247218a72329f10ecb3da7f)

lib/tdb2/io.c

@@ -200,7 +200,7 @@ enum TDB_ERROR zero_out(struct tdb_context *tdb, tdb_off_t off, tdb_len_t len)
 	void *p = tdb->methods->direct(tdb, off, len, true);
 	enum TDB_ERROR ecode = TDB_SUCCESS;
 
-	assert(!tdb->read_only);
+	assert(!(tdb->flags & TDB_RDONLY));
 	if (TDB_PTR_IS_ERR(p)) {
 		return TDB_PTR_ERR(p);
 	}
@@ -248,7 +248,7 @@ static enum TDB_ERROR tdb_write(struct tdb_context *tdb, tdb_off_t off,
 {
 	enum TDB_ERROR ecode;
 
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
 				  "Write to read-only database");
 	}
@@ -337,7 +337,7 @@ enum TDB_ERROR tdb_read_convert(struct tdb_context *tdb, tdb_off_t off,
 enum TDB_ERROR tdb_write_off(struct tdb_context *tdb,
 			     tdb_off_t off, tdb_off_t val)
 {
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
 				  "Write to read-only database");
 	}
@@ -416,7 +416,7 @@ static enum TDB_ERROR tdb_expand_file(struct tdb_context *tdb,
 	char buf[8192];
 	enum TDB_ERROR ecode;
 
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
 				  "Expand on read-only database");
 	}
@@ -488,7 +488,7 @@ void *tdb_access_write(struct tdb_context *tdb,
 {
 	void *ret = NULL;
 
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
 			   "Write to read-only database");
 		return TDB_ERR_PTR(TDB_ERR_RDONLY);

lib/tdb2/lock.c

@@ -194,7 +194,7 @@ static enum TDB_ERROR tdb_brlock(struct tdb_context *tdb,
 		return TDB_SUCCESS;
 	}
 
-	if (rw_type == F_WRLCK && tdb->read_only) {
+	if (rw_type == F_WRLCK && (tdb->flags & TDB_RDONLY)) {
 		return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
 				  "Write lock attempted on read-only database");
 	}
@@ -508,8 +508,9 @@ static enum TDB_ERROR tdb_lock_gradual(struct tdb_context *tdb,
 	}
 
 	/* First we try non-blocking. */
-	if (tdb_brlock(tdb, ltype, off, len, nb_flags) == TDB_SUCCESS) {
+	ecode = tdb_brlock(tdb, ltype, off, len, nb_flags);
-		return TDB_SUCCESS;
+	if (ecode != TDB_ERR_LOCK) {
+		return ecode;
 	}
 
 	/* Try locking first half, then second. */

lib/tdb2/open.c

@@ -402,7 +402,8 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	}
 
 	if (tdb_flags & ~(TDB_INTERNAL | TDB_NOLOCK | TDB_NOMMAP | TDB_CONVERT
-			  | TDB_NOSYNC | TDB_SEQNUM | TDB_ALLOW_NESTING)) {
+			  | TDB_NOSYNC | TDB_SEQNUM | TDB_ALLOW_NESTING
+			  | TDB_RDONLY)) {
 		ecode = tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
 				   "tdb_open: unknown flags %u", tdb_flags);
 		goto fail;
@@ -416,10 +417,16 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	}
 
 	if ((open_flags & O_ACCMODE) == O_RDONLY) {
-		tdb->read_only = true;
 		openlock = F_RDLCK;
+		tdb->flags |= TDB_RDONLY;
 	} else {
-		tdb->read_only = false;
+		if (tdb_flags & TDB_RDONLY) {
+			ecode = tdb_logerr(tdb, TDB_ERR_EINVAL,
+					   TDB_LOG_USE_ERROR,
+					   "tdb_open: can't use TDB_RDONLY"
+					   " without O_RDONLY");
+			goto fail;
+		}
 		openlock = F_WRLCK;
 	}
 

lib/tdb2/private.h

@@ -343,9 +343,6 @@ struct tdb_context {
 	/* Are we accessing directly? (debugging check). */
 	int direct_access;
 
-	/* Operating read-only? (Opened O_RDONLY, or in traverse_read) */
-	bool read_only;
-
 	/* Open flags passed to tdb_open. */
 	int open_flags;
 

lib/tdb2/tdb.c

@@ -326,6 +326,29 @@ unsigned int tdb_get_flags(struct tdb_context *tdb)
 	return tdb->flags;
 }
 
+static bool readonly_changable(struct tdb_context *tdb, const char *caller)
+{
+	if (tdb->transaction) {
+		tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
+					     TDB_LOG_USE_ERROR,
+					     "%s: can't change"
+					     " TDB_RDONLY inside transaction",
+					     caller);
+		return false;
+	}
+
+	if (tdb->file->allrecord_lock.count != 0
+	    || tdb->file->num_lockrecs != 0) {
+		tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
+					     TDB_LOG_USE_ERROR,
+					     "%s: can't change"
+					     " TDB_RDONLY holding locks",
+					     caller);
+		return false;
+	}
+	return true;
+}
+
 void tdb_add_flag(struct tdb_context *tdb, unsigned flag)
 {
 	if (tdb->flags & TDB_INTERNAL) {
@@ -351,6 +374,10 @@ void tdb_add_flag(struct tdb_context *tdb, unsigned flag)
 	case TDB_ALLOW_NESTING:
 		tdb->flags |= TDB_ALLOW_NESTING;
 		break;
+	case TDB_RDONLY:
+		if (readonly_changable(tdb, "tdb_add_flag"))
+			tdb->flags |= TDB_RDONLY;
+		break;
 	default:
 		tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
 					     TDB_LOG_USE_ERROR,
@@ -384,6 +411,18 @@ void tdb_remove_flag(struct tdb_context *tdb, unsigned flag)
 	case TDB_ALLOW_NESTING:
 		tdb->flags &= ~TDB_ALLOW_NESTING;
 		break;
+	case TDB_RDONLY:
+		if ((tdb->open_flags & O_ACCMODE) == O_RDONLY) {
+			tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
+						     TDB_LOG_USE_ERROR,
+						     "tdb_remove_flag: can't"
+						     " remove TDB_RDONLY on tdb"
+						     " opened with O_RDONLY");
+			break;
+		}
+		if (readonly_changable(tdb, "tdb_remove_flag"))
+			tdb->flags &= ~TDB_RDONLY;
+		break;
 	default:
 		tdb->last_error = tdb_logerr(tdb, TDB_ERR_EINVAL,
 					     TDB_LOG_USE_ERROR,

lib/tdb2/tdb2.h

@@ -87,6 +87,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 #define TDB_NOSYNC   64 /* don't use synchronous transactions */
 #define TDB_SEQNUM   128 /* maintain a sequence number */
 #define TDB_ALLOW_NESTING   256 /* fake nested transactions */
+#define TDB_RDONLY   512 /* implied by O_RDONLY */
 
 /**
  * tdb_close - close and free a tdb.

lib/tdb2/test/run-92-get-set-readonly.c

@@ -0,0 +1,109 @@
+#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/tdb2/traverse.c>
+#include <ccan/tap/tap.h>
+#include "logging.h"
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct tdb_context *tdb;
+	struct tdb_data key = tdb_mkdata("key", 3);
+	struct tdb_data data = tdb_mkdata("data", 4);
+	int flags[] = { TDB_DEFAULT, TDB_NOMMAP,
+			TDB_CONVERT, TDB_NOMMAP|TDB_CONVERT };
+
+	plan_tests(sizeof(flags) / sizeof(flags[0]) * 48);
+
+	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
+		/* RW -> R0 */
+		tdb = tdb_open("run-92-get-set-readonly.tdb", flags[i],
+			       O_RDWR|O_CREAT|O_TRUNC, 0600, &tap_log_attr);
+		ok1(tdb);
+		ok1(!(tdb_get_flags(tdb) & TDB_RDONLY));
+
+		ok1(tdb_store(tdb, key, data, TDB_INSERT) == TDB_SUCCESS);
+
+		tdb_add_flag(tdb, TDB_RDONLY);
+		ok1(tdb_get_flags(tdb) & TDB_RDONLY);
+
+		/* Can't store, append, delete. */
+		ok1(tdb_store(tdb, key, data, TDB_MODIFY) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 1);
+		ok1(tdb_append(tdb, key, data) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 2);
+		ok1(tdb_delete(tdb, key) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 3);
+
+		/* Can't start a transaction, or any write lock. */
+		ok1(tdb_transaction_start(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 4);
+		ok1(tdb_chainlock(tdb, key) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 5);
+		ok1(tdb_lockall(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 6);
+		ok1(tdb_wipe_all(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 7);
+
+		/* Back to RW. */
+		tdb_remove_flag(tdb, TDB_RDONLY);
+		ok1(!(tdb_get_flags(tdb) & TDB_RDONLY));
+
+		ok1(tdb_store(tdb, key, data, TDB_MODIFY) == TDB_SUCCESS);
+		ok1(tdb_append(tdb, key, data) == TDB_SUCCESS);
+		ok1(tdb_delete(tdb, key) == TDB_SUCCESS);
+
+		ok1(tdb_transaction_start(tdb) == TDB_SUCCESS);
+		ok1(tdb_store(tdb, key, data, TDB_INSERT) == TDB_SUCCESS);
+		ok1(tdb_transaction_commit(tdb) == TDB_SUCCESS);
+
+		ok1(tdb_chainlock(tdb, key) == TDB_SUCCESS);
+		tdb_chainunlock(tdb, key);
+		ok1(tdb_lockall(tdb) == TDB_SUCCESS);
+		tdb_unlockall(tdb);
+		ok1(tdb_wipe_all(tdb) == TDB_SUCCESS);
+		ok1(tap_log_messages == 7);
+
+		tdb_close(tdb);
+
+		/* R0 -> RW */
+		tdb = tdb_open("run-92-get-set-readonly.tdb", flags[i],
+			       O_RDONLY, 0600, &tap_log_attr);
+		ok1(tdb);
+		ok1(tdb_get_flags(tdb) & TDB_RDONLY);
+
+		/* Can't store, append, delete. */
+		ok1(tdb_store(tdb, key, data, TDB_INSERT) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 8);
+		ok1(tdb_append(tdb, key, data) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 9);
+		ok1(tdb_delete(tdb, key) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 10);
+
+		/* Can't start a transaction, or any write lock. */
+		ok1(tdb_transaction_start(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 11);
+		ok1(tdb_chainlock(tdb, key) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 12);
+		ok1(tdb_lockall(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 13);
+		ok1(tdb_wipe_all(tdb) == TDB_ERR_RDONLY);
+		ok1(tap_log_messages == 14);
+
+		/* Can't remove TDB_RDONLY since we opened with O_RDONLY */
+		tdb_remove_flag(tdb, TDB_RDONLY);
+		ok1(tap_log_messages == 15);
+		ok1(tdb_get_flags(tdb) & TDB_RDONLY);
+		tdb_close(tdb);
+
+		ok1(tap_log_messages == 15);
+		tap_log_messages = 0;
+	}
+	return exit_status();
+}

lib/tdb2/transaction.c

@@ -532,7 +532,7 @@ enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb)
 						    " internal tdb");
 	}
 
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		return tdb->last_error = tdb_logerr(tdb, TDB_ERR_RDONLY,
 						    TDB_LOG_USE_ERROR,
 						    "tdb_transaction_start:"
@@ -1196,7 +1196,7 @@ enum TDB_ERROR tdb_transaction_recover(struct tdb_context *tdb)
 		return TDB_SUCCESS;
 	}
 
-	if (tdb->read_only) {
+	if (tdb->flags & TDB_RDONLY) {
 		return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 				  "tdb_transaction_recover:"
 				  " attempt to recover read only database");