log: don't create a log file in a current directory

We can set a directory for log and image files.
crtools sets it as a current directory and then creates all files in it.
It works before we don't decide to change a mount name space.

I suggest to open a log dir and create files for help openat.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -311,6 +311,8 @@ static int restore_one_alive_task(int pid, CoreEntry *core)
 	if (prepare_sigactions(pid))
 		return -1;
 
+	log_closedir();
+
 	return prepare_and_sigreturn(pid, core);
 }
 

include/crtools.h

@@ -99,6 +99,7 @@ extern struct cr_options opts;
 
 enum {
 	LOG_FD_OFF = 1,
+	LOG_DIR_FD_OFF,
 	IMG_FD_OFF,
 	SELF_EXE_FD_OFF,
 	PROC_FD_OFF,

include/log.h

@@ -4,6 +4,7 @@
 extern int log_init(const char *output);
 extern void log_fini(void);
 extern int log_init_by_pid(void);
+extern void log_closedir(void);
 
 extern int log_get_fd(void);
 

log.c

@@ -22,6 +22,7 @@
 
 static unsigned int current_loglevel = DEFAULT_LOGLEVEL;
 static int current_logfd = DEFAULT_LOGFD;
+static int logdir = -1;
 
 static char buffer[PAGE_SIZE];
 static char buf_off = 0;
@@ -33,7 +34,27 @@ int log_get_fd(void)
 
 int log_init(const char *output)
 {
-	int new_logfd, sfd;
+	int new_logfd, sfd, dfd;
+
+	dfd = get_service_fd(LOG_DIR_FD_OFF);
+	if (dfd < 0) {
+		pr_msg("Can't obtain logfd");
+		goto err;
+	}
+
+	if (logdir < 0) {
+		int tmp;
+		tmp = open(".", O_RDONLY);
+		if (tmp == -1) {
+			pr_perror("Can't open a current directory");
+			return -1;
+		}
+
+		if (reopen_fd_as(dfd, tmp) < 0)
+			return -1;
+
+		logdir = dfd;
+	}
 
 	sfd = get_service_fd(LOG_FD_OFF);
 	if (sfd < 0) {
@@ -42,7 +63,8 @@ int log_init(const char *output)
 	}
 
 	if (output) {
-		new_logfd = open(output, O_CREAT | O_TRUNC | O_WRONLY | O_APPEND, 0600);
+		new_logfd = openat(logdir, output,
+					O_CREAT | O_TRUNC | O_WRONLY | O_APPEND, 0600);
 		if (new_logfd < 0) {
 			pr_perror("Can't create log file %s", output);
 			return -1;
@@ -95,6 +117,11 @@ void log_fini(void)
 	current_logfd = DEFAULT_LOGFD;
 }
 
+void log_closedir(void)
+{
+	close_safe(&logdir);
+}
+
 void log_set_loglevel(unsigned int level)
 {
 	if (!level)