util: Introduce buffer size for carrying /proc/self/fd/N path

There's ... a number of places where we want to do something
with /proc/self/fd/%d path. Each time we guess buffer size
that is enough for this. Make standard constant for this and
save some space on stack and drop args for some functions.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -222,13 +222,13 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st)
 
 	if (S_ISREG(st->st_mode)) {
 		int fd, ret;
-		char lpath[32];
+		char lpath[PSFDS];
 
 		/*
 		 * Reopen file locally since it may have no read
 		 * permissions when drained
 		 */
-		snprintf(lpath, sizeof(lpath), "/proc/self/fd/%d", _fd);
+		sprintf(lpath, "/proc/self/fd/%d", _fd);
 		fd = open(lpath, O_RDONLY);
 		if (fd < 0) {
 			pr_perror("Can't open ghost original file");

files.c

@@ -940,7 +940,7 @@ out:
 
 static int fchroot(int fd)
 {
-	char fd_path[32];
+	char fd_path[PSFDS];
 
 	/*
 	 * There's no such thing in syscalls. We can emulate

fsnotify.c

@@ -189,8 +189,7 @@ static void decode_handle(fh_t *handle, FhEntry *img)
 
 static char *get_mark_path(const char *who, struct file_remap *remap,
 			   FhEntry *f_handle, unsigned long i_ino,
-			   unsigned int s_dev, char *buf, size_t size,
-			   int *target)
+			   unsigned int s_dev, char *buf, int *target)
 {
 	char *path = NULL;
 	int mntfd = -1;
@@ -225,7 +224,7 @@ static char *get_mark_path(const char *who, struct file_remap *remap,
 	 * points to, i.e. -- just what we want.
 	 */
 
-	snprintf(buf, size, "/proc/self/fd/%d", *target);
+	sprintf(buf, "/proc/self/fd/%d", *target);
 	path = buf;
 
 	if (log_get_loglevel() >= LOG_DEBUG) {
@@ -246,11 +245,10 @@ static int restore_one_inotify(int inotify_fd, struct fsnotify_mark_info *info)
 {
 	InotifyWdEntry *iwe = info->iwe;
 	int ret = -1, target = -1;
-	char buf[32], *path;
+	char buf[PSFDS], *path;
 
 	path = get_mark_path("inotify", info->remap, iwe->f_handle,
-			     iwe->i_ino, iwe->s_dev, buf, sizeof(buf),
-			     &target);
+			     iwe->i_ino, iwe->s_dev, buf, &target);
 	if (!path)
 		goto err;
 
@@ -291,7 +289,7 @@ static int restore_one_fanotify(int fd, struct fsnotify_mark_info *mark)
 	FanotifyMarkEntry *fme = mark->fme;
 	unsigned int flags = FAN_MARK_ADD;
 	int ret = -1, target = -1;
-	char buf[32], *path = NULL;
+	char buf[PSFDS], *path = NULL;
 
 	if (fme->type == MARK_TYPE__MOUNT) {
 		struct mount_info *m;
@@ -307,7 +305,7 @@ static int restore_one_fanotify(int fd, struct fsnotify_mark_info *mark)
 	} else if (fme->type == MARK_TYPE__INODE) {
 		path = get_mark_path("fanotify", mark->remap,
 				     fme->ie->f_handle, fme->ie->i_ino,
-				     fme->s_dev, buf, sizeof(buf), &target);
+				     fme->s_dev, buf, &target);
 		if (!path)
 			goto err;
 	} else {

include/util.h

@@ -270,6 +270,12 @@ static inline bool dir_dots(struct dirent *de)
 	return !strcmp(de->d_name, ".") || !strcmp(de->d_name, "..");
 }
 
+/*
+ * Size of buffer to carry the worst case or /proc/self/fd/N
+ * path. Since fd is an integer, we can easily estimate one :)
+ */
+#define PSFDS	(sizeof("/proc/self/fd/2147483647"))
+
 extern int read_fd_link(int lfd, char *buf, size_t size);
 
 #define USEC_PER_SEC	1000000L

mount.c

@@ -471,7 +471,7 @@ out:
 static int tmpfs_dump(struct mount_info *pm)
 {
 	int ret = -1;
-	char tmpfs_path[PATH_MAX];
+	char tmpfs_path[PSFDS];
 	int fd, fd_img = -1;
 	DIR *fdir = NULL;
 
@@ -489,8 +489,7 @@ static int tmpfs_dump(struct mount_info *pm)
 	if (fd_img < 0)
 		goto out;
 
-	snprintf(tmpfs_path, sizeof(tmpfs_path),
-				       "/proc/self/fd/%d", fd);
+	sprintf(tmpfs_path, "/proc/self/fd/%d", fd);
 
 	ret = cr_system(-1, fd_img, -1, "tar", (char *[])
 			{ "tar", "--create",

pipes.c

@@ -250,9 +250,9 @@ err:
 static int reopen_pipe(int fd, int flags)
 {
 	int ret;
-	char path[32];
+	char path[PSFDS];
 
-	snprintf(path, sizeof(path), "/proc/self/fd/%d", fd);
+	sprintf(path, "/proc/self/fd/%d", fd);
 	ret = open(path, flags);
 	if (ret < 0)
 		pr_perror("Unable to reopen the pipe %s", path);