tdb2: fix remapping inside tdb_traverse_read

Because we (temporarily!) marked the tdb read_only=true, any remap would
mmap PROT_READ, and the next store would SEGV.

Pulled in more test infrastructure from tdb.

ccan/tdb2/io.c

@@ -48,8 +48,7 @@ void tdb_mmap(struct tdb_context *tdb)
 	if (tdb->flags & TDB_NOMMAP)
 		return;
 
-	tdb->map_ptr = mmap(NULL, tdb->map_size, 
-			    PROT_READ|(tdb->read_only? 0:PROT_WRITE), 
+	tdb->map_ptr = mmap(NULL, tdb->map_size, tdb->mmap_flags,
 			    MAP_SHARED, tdb->fd, 0);
 
 	/*

ccan/tdb2/private.h

@@ -282,9 +282,12 @@ struct tdb_context {
 	/* How much space has been mapped (<= current file size) */
 	tdb_len_t map_size;
 
-	/* Opened read-only? */
+	/* Operating read-only? (Opened O_RDONLY, or in traverse_read) */
 	bool read_only;
 
+	/* mmap read only? */
+	int mmap_flags;
+
 	/* Error code for last tdb error. */
 	enum TDB_ERROR ecode; 
 

ccan/tdb2/tdb.c

@@ -234,8 +234,11 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 		tdb->read_only = true;
 		/* read only databases don't do locking */
 		tdb->flags |= TDB_NOLOCK;
-	} else
+		tdb->mmap_flags = PROT_READ;
+	} else {
 		tdb->read_only = false;
+		tdb->mmap_flags = PROT_READ | PROT_WRITE;
+	}
 
 	/* internal databases don't need any of the rest. */
 	if (tdb->flags & TDB_INTERNAL) {

ccan/tdb2/test/external-agent.c

@@ -0,0 +1,194 @@
+#include "external-agent.h"
+#include "logging.h"
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <err.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <string.h>
+#include <errno.h>
+#include <ccan/tdb2/private.h>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+#include <stdarg.h>
+
+static struct tdb_context *tdb;
+
+#if 1 /* FIXME */
+static unsigned int locking_would_block = 0;
+static bool nonblocking_locks = false;
+#endif
+
+static enum agent_return do_operation(enum operation op, const char *name)
+{
+	TDB_DATA k;
+	enum agent_return ret;
+	TDB_DATA data;
+
+	if (op != OPEN && !tdb) {
+		diag("external: No tdb open!");
+		return OTHER_FAILURE;
+	}
+
+	k.dptr = (void *)name;
+	k.dsize = strlen(name);
+
+	locking_would_block = 0;
+	switch (op) {
+	case OPEN:
+		if (tdb) {
+			diag("Already have tdb %s open", tdb->name);
+			return OTHER_FAILURE;
+		}
+		tdb = tdb_open(name, TDB_DEFAULT, O_RDWR, 0, &tap_log_attr);
+		if (!tdb) {
+			if (!locking_would_block)
+				diag("Opening tdb gave %s", strerror(errno));
+			ret = OTHER_FAILURE;
+		} else
+			ret = SUCCESS;
+		break;
+	case FETCH:
+		data = tdb_fetch(tdb, k);
+		if (data.dptr == NULL) {
+			if (tdb_error(tdb) == TDB_ERR_NOEXIST)
+				ret = FAILED;
+			else
+				ret = OTHER_FAILURE;
+		} else if (data.dsize != k.dsize
+			   || memcmp(data.dptr, k.dptr, k.dsize) != 0) {
+			ret = OTHER_FAILURE;
+		} else {
+			ret = SUCCESS;
+		}
+		free(data.dptr);
+		break;
+	case STORE:
+		ret = tdb_store(tdb, k, k, 0) == 0 ? SUCCESS : OTHER_FAILURE;
+		break;
+#if 0 /* FIXME */
+	case TRANSACTION_START:
+		ret = tdb_transaction_start(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
+		break;
+	case TRANSACTION_COMMIT:
+		ret = tdb_transaction_commit(tdb)==0 ? SUCCESS : OTHER_FAILURE;
+		break;
+	case NEEDS_RECOVERY:
+		ret = tdb_needs_recovery(tdb) ? SUCCESS : FAILED;
+		break;
+#endif
+	case CHECK:
+		ret = tdb_check(tdb, NULL, NULL) == 0 ? SUCCESS : OTHER_FAILURE;
+		break;
+	case CLOSE:
+		ret = tdb_close(tdb) == 0 ? SUCCESS : OTHER_FAILURE;
+		tdb = NULL;
+		break;
+	default:
+		ret = OTHER_FAILURE;
+	}
+
+	if (locking_would_block)
+		ret = WOULD_HAVE_BLOCKED;
+
+	return ret;
+}
+
+struct agent {
+	int cmdfd, responsefd;
+};
+
+/* Do this before doing any tdb stuff.  Return handle, or NULL. */
+struct agent *prepare_external_agent(void)
+{
+	int pid, ret;
+	int command[2], response[2];
+	char name[1+PATH_MAX];
+
+	if (pipe(command) != 0 || pipe(response) != 0)
+		return NULL;
+
+	pid = fork();
+	if (pid < 0)
+		return NULL;
+
+	if (pid != 0) {
+		struct agent *agent = malloc(sizeof(*agent));
+
+		close(command[0]);
+		close(response[1]);
+		agent->cmdfd = command[1];
+		agent->responsefd = response[0];
+		return agent;
+	}
+
+	close(command[1]);
+	close(response[0]);
+
+	/* We want to fail, not block. */
+	nonblocking_locks = true;
+	log_prefix = "external: ";
+	while ((ret = read(command[0], name, sizeof(name))) > 0) {
+		enum agent_return result;
+
+		result = do_operation(name[0], name+1);
+		if (write(response[1], &result, sizeof(result))
+		    != sizeof(result))
+			err(1, "Writing response");
+	}
+	exit(0);
+}
+
+/* Ask the external agent to try to do an operation. */
+enum agent_return external_agent_operation(struct agent *agent,
+					   enum operation op,
+					   const char *name)
+{
+	enum agent_return res;
+	unsigned int len;
+	char *string;
+
+	if (!name)
+		name = "";
+	len = 1 + strlen(name) + 1;
+	string = malloc(len);
+
+	string[0] = op;
+	strcpy(string+1, name);
+
+	if (write(agent->cmdfd, string, len) != len
+	    || read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
+		res = AGENT_DIED;
+
+	free(string);
+	return res;
+}
+
+const char *agent_return_name(enum agent_return ret)
+{
+	return ret == SUCCESS ? "SUCCESS"
+		: ret == WOULD_HAVE_BLOCKED ? "WOULD_HAVE_BLOCKED"
+		: ret == AGENT_DIED ? "AGENT_DIED"
+		: ret == FAILED ? "FAILED"
+		: ret == OTHER_FAILURE ? "OTHER_FAILURE"
+		: "**INVALID**";
+}
+
+const char *operation_name(enum operation op)
+{
+	switch (op) {
+	case OPEN: return "OPEN";
+	case FETCH: return "FETCH";
+	case STORE: return "STORE";
+	case CHECK: return "CHECK";
+#if 0
+	case TRANSACTION_START: return "TRANSACTION_START";
+	case TRANSACTION_COMMIT: return "TRANSACTION_COMMIT";
+	case NEEDS_RECOVERY: return "NEEDS_RECOVERY";
+#endif
+	case CLOSE: return "CLOSE";
+	}
+	return "**INVALID**";
+}

ccan/tdb2/test/external-agent.h

@@ -0,0 +1,42 @@
+#ifndef TDB2_TEST_EXTERNAL_AGENT_H
+#define TDB2_TEST_EXTERNAL_AGENT_H
+
+/* For locking tests, we need a different process to try things at
+ * various times. */
+enum operation {
+	OPEN,
+	FETCH,
+	STORE,
+#if 0
+	TRANSACTION_START,
+	TRANSACTION_COMMIT,
+	NEEDS_RECOVERY,
+#endif
+	CHECK,
+	CLOSE,
+};
+
+/* Do this before doing any tdb stuff.  Return handle, or -1. */
+struct agent *prepare_external_agent(void);
+
+enum agent_return {
+	SUCCESS,
+	WOULD_HAVE_BLOCKED,
+	AGENT_DIED,
+	FAILED, /* For fetch, or NEEDS_RECOVERY */
+	OTHER_FAILURE,
+};
+
+/* Ask the external agent to try to do an operation. 
+ * name == tdb name for OPEN/OPEN_WITH_CLEAR_IF_FIRST,
+ * record name for FETCH/STORE (store stores name as data too)
+ */
+enum agent_return external_agent_operation(struct agent *handle,
+					   enum operation op,
+					   const char *name);
+
+/* Mapping enum -> string. */
+const char *agent_return_name(enum agent_return ret);
+const char *operation_name(enum operation op);
+
+#endif /* TDB2_TEST_EXTERNAL_AGENT_H */

ccan/tdb2/test/logging.c

@@ -6,6 +6,8 @@
 #include "logging.h"
 
 unsigned tap_log_messages;
+const char *log_prefix = "";
+bool suppress_logging;
 
 union tdb_attribute tap_log_attr = {
 	.log = { .base = { .attr = TDB_ATTRIBUTE_LOG },
@@ -19,10 +21,16 @@ void tap_log_fn(struct tdb_context *tdb,
 	va_list ap;
 	char *p;
 
+	if (suppress_logging)
+		return;
+
 	va_start(ap, fmt);
 	if (vasprintf(&p, fmt, ap) == -1)
 		abort();
-	diag("tdb log level %u: %s", level, p);
+	/* Strip trailing \n: diag adds it. */
+	if (p[strlen(p)-1] == '\n')
+		p[strlen(p)-1] = '\0';
+	diag("tdb log level %u: %s%s", level, log_prefix, p);
 	free(p);
 	if (level != TDB_DEBUG_TRACE)
 		tap_log_messages++;

ccan/tdb2/test/logging.h

@@ -4,8 +4,9 @@
 #include <stdbool.h>
 #include <string.h>
 
+extern bool suppress_logging;
+extern const char *log_prefix;
 extern unsigned tap_log_messages;
-
 extern union tdb_attribute tap_log_attr;
 
 void tap_log_fn(struct tdb_context *tdb,

ccan/tdb2/test/run-001-encode.c

@@ -3,6 +3,7 @@
 #include <ccan/tdb2/lock.c>
 #include <ccan/tdb2/hash.c>
 #include <ccan/tdb2/io.c>
+#include <ccan/tdb2/check.c>
 #include <ccan/tap/tap.h>
 #include "logging.h"
 

ccan/tdb2/test/run-001-fls.c

@@ -3,6 +3,7 @@
 #include <ccan/tdb2/lock.c>
 #include <ccan/tdb2/io.c>
 #include <ccan/tdb2/hash.c>
+#include <ccan/tdb2/check.c>
 #include <ccan/tap/tap.h>
 
 static unsigned int dumb_fls(uint64_t num)

ccan/tdb2/test/run-remap-in-read_traverse.c

@@ -0,0 +1,61 @@
+/* We had a bug where we marked the tdb read-only for a tdb_traverse_read.
+ * If we then expanded the tdb, we would remap read-only, and later SEGV. */
+#include <ccan/tdb2/tdb.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/traverse.c>
+#include <ccan/tap/tap.h>
+#include "external-agent.h"
+#include "logging.h"
+
+static bool file_larger(int fd, tdb_len_t size)
+{
+	struct stat st;
+
+	fstat(fd, &st);
+	return st.st_size != size;
+}
+
+static unsigned add_records_to_grow(struct agent *agent, int fd, tdb_len_t size)
+{
+	unsigned int i;
+
+	for (i = 0; !file_larger(fd, size); i++) {
+		char data[20];
+		sprintf(data, "%i", i);
+		if (external_agent_operation(agent, STORE, data) != SUCCESS)
+			return 0;
+	}
+	diag("Added %u records to grow file", i);
+	return i;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct agent *agent;
+	struct tdb_context *tdb;
+	struct tdb_data d = { (unsigned char *)"hello", 5 };
+	const char filename[] = "run-remap-in-read_traverse.tdb";
+
+	plan_tests(4);
+
+	agent = prepare_external_agent();
+
+	tdb = tdb_open(filename, TDB_DEFAULT,
+		       O_RDWR|O_CREAT|O_TRUNC, 0600, &tap_log_attr);
+
+	ok1(external_agent_operation(agent, OPEN, filename) == SUCCESS);
+	i = add_records_to_grow(agent, tdb->fd, tdb->map_size);
+
+	/* Do a read traverse. */
+	ok1(tdb_traverse_read(tdb, NULL, NULL) == i);
+
+	/* Now store something! */
+	ok1(tdb_store(tdb, d, d, TDB_INSERT) == 0);
+	ok1(tap_log_messages == 0);
+	return exit_status();
+}