util: Extend reopen_fd_as_safe

Our loggin engine prints file:line only at invoke point,
so it's unable to see where exactly reopen_fd_as_safe is
failed.

With this patch the output is more human readable

 | Error (util.c:96): fd 7 already in use (called at files.c:359)

Ideally we need full backtrace here, but it's different task.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/util.h

@@ -164,9 +164,9 @@ extern void pr_vma(unsigned int loglevel, const struct vma_area *vma_area);
 extern int move_img_fd(int *img_fd, int want_fd);
 extern int close_safe(int *fd);
 
-extern int reopen_fd_as_safe(int new_fd, int old_fd, bool allow_reuse_fd);
-#define reopen_fd_as(new_fd, old_fd)		reopen_fd_as_safe(new_fd, old_fd, false)
-#define reopen_fd_as_nocheck(new_fd, old_fd)	reopen_fd_as_safe(new_fd, old_fd, true)
+extern int reopen_fd_as_safe(char *file, int line, int new_fd, int old_fd, bool allow_reuse_fd);
+#define reopen_fd_as(new_fd, old_fd)		reopen_fd_as_safe(__FILE__, __LINE__, new_fd, old_fd, false)
+#define reopen_fd_as_nocheck(new_fd, old_fd)	reopen_fd_as_safe(__FILE__, __LINE__, new_fd, old_fd, true)
 
 int open_pid_proc(pid_t pid);
 int close_pid_proc(void);

util.c

@@ -77,7 +77,7 @@ int close_safe(int *fd)
 	return ret;
 }
 
-int reopen_fd_as_safe(int new_fd, int old_fd, bool allow_reuse_fd)
+int reopen_fd_as_safe(char *file, int line, int new_fd, int old_fd, bool allow_reuse_fd)
 {
 	int tmp;
 
@@ -89,9 +89,11 @@ int reopen_fd_as_safe(int new_fd, int old_fd, bool allow_reuse_fd)
 					/*
 					 * Standard descriptors.
 					 */
-					pr_warn("fd %d already in use\n", new_fd);
+					pr_warn("fd %d already in use (called at %s:%d)\n",
+						new_fd, file, line);
 				} else {
-					pr_err("fd %d already in use\n", new_fd);
+					pr_err("fd %d already in use (called at %s:%d)\n",
+						new_fd, file, line);
 					return -1;
 				}
 			}
@@ -99,7 +101,8 @@ int reopen_fd_as_safe(int new_fd, int old_fd, bool allow_reuse_fd)
 
 		tmp = dup2(old_fd, new_fd);
 		if (tmp < 0) {
-			pr_perror("Dup %d -> %d failed", old_fd, new_fd);
+			pr_perror("Dup %d -> %d failed (called at %s:%d)",
+				  old_fd, new_fd, file, line);
 			return tmp;
 		}