[PATCH] losetup: Create loop device if it does not exist

[Joerg Vehlow]

From: Joerg Vehlow <joerg.vehlow at aox-tech.de>

util-linux's losetup creates a loop device, if it is missing.
This is missing in busybox's implementation.

Testcase:
losetup /dev/loop1000 <somepath>
If /dev/loop1000 does not exist busybox give an error but
util-linux's losetup just creates the file

Signed-off-by: Joerg Vehlow <joerg.vehlow at aox-tech.de>
---
 util-linux/losetup.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/util-linux/losetup.c b/util-linux/losetup.c
index cc6c2b1d5..790c41cab 100644
--- a/util-linux/losetup.c
+++ b/util-linux/losetup.c
@@ -147,10 +147,25 @@ int losetup_main(int argc UNUSED_PARAM, char **argv)
 			d = *argv++;
 
 		if (argv[0]) {
+			struct stat statbuf;
+			int n;
 			unsigned flags = (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0;
+
 			if (opt & OPT_P) {
 				flags |= BB_LO_FLAGS_PARTSCAN;
 			}
+
+			// If the loop device does not exist, create it
+			if (stat(d, &statbuf) != 0 && errno == ENOENT) {
+				if (sscanf(d, LOOP_FORMAT, &n) != 1) {
+					errno = 0;
+					bb_perror_msg_and_die("Loop device %s does not exist and does not start with " LOOP_NAME, d);
+				}
+				if (mknod(d, S_IFBLK|0644, makedev(7, n)) != 0) {
+					bb_simple_perror_msg_and_die(d);
+				}
+			}
+
 			if (set_loop(&d, argv[0], offset, flags) < 0)
 				bb_simple_perror_msg_and_die(argv[0]);
 			return EXIT_SUCCESS;
-- 
2.20.1