losetup: Add partition scanning option

Add -P option from util-linux losetup to scan for partitions.

function                                             old     new   delta
losetup_main                                         449     482     +33
packed_usage                                       33264   33292     +28
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 61/0)               Total: 61 bytes

Signed-off-by: Jack O'Sullivan <jackos1998@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 18 insertions, 10 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 33766e989..3a870bf80 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1471,6 +1471,7 @@ extern int set_loop(char **devname, const char *file, unsigned long long offset,
 /* These constants match linux/loop.h (without BB_ prefix): */
 #define BB_LO_FLAGS_READ_ONLY 1
 #define BB_LO_FLAGS_AUTOCLEAR 4
+#define BB_LO_FLAGS_PARTSCAN  8
 
 /* Returns malloced str */
 char *bb_ask_noecho(int fd, int timeout, const char *prompt) FAST_FUNC;
diff --git a/util-linux/losetup.c b/util-linux/losetup.c
index 2248f2cba..b52d693ec 100644
--- a/util-linux/losetup.c
+++ b/util-linux/losetup.c
@@ -20,13 +20,14 @@
 //kbuild:lib-$(CONFIG_LOSETUP) += losetup.o
 
 //usage:#define losetup_trivial_usage
-//usage:       "[-r] [-o OFS] {-f|LOOPDEV} FILE: associate loop devices\n"
+//usage:       "[-rP] [-o OFS] {-f|LOOPDEV} FILE: associate loop devices\n"
 //usage:       "        losetup -c LOOPDEV: reread file size\n"
 //usage:       "        losetup -d LOOPDEV: disassociate\n"
 //usage:       "        losetup -a: show status\n"
 //usage:       "        losetup -f: show next free loop device"
 //usage:#define losetup_full_usage "\n\n"
 //usage:       "        -o OFS  Start OFS bytes into FILE"
+//usage:     "\n        -P      Scan for partitions"
 //usage:     "\n        -r      Read-only"
 //usage:     "\n        -f      Show/use next free loop device"
 //usage:
@@ -35,8 +36,9 @@
 //usage:       "(if any), or disassociate it (with -d). The display shows the offset\n"
 //usage:       "and filename of the file the loop device is currently bound to.\n\n"
 //usage:       "Two arguments (losetup /dev/loop1 file.img) create a new association,\n"
-//usage:       "with an optional offset (-o 12345). Encryption is not yet supported.\n"
-//usage:       "losetup -f will show the first loop free loop device\n\n"
+//usage:       "with optional partition scanning (creates /dev/loop1p1, /dev/loop1p2\n"
+//usage:       "etc. with -P) and with an optional offset (-o 12345). Encryption is\n"
+//usage:       "not yet supported. losetup -f will show the first free loop device\n\n"
 
 #include "libbb.h"
 
@@ -53,13 +55,14 @@ int losetup_main(int argc UNUSED_PARAM, char **argv)
         enum {
                 OPT_c = (1 << 0),
                 OPT_d = (1 << 1),
-                OPT_o = (1 << 2),
-                OPT_f = (1 << 3),
-                OPT_a = (1 << 4),
-                OPT_r = (1 << 5),
+                OPT_P = (1 << 2),
+                OPT_o = (1 << 3),
+                OPT_f = (1 << 4),
+                OPT_a = (1 << 5),
+                OPT_r = (1 << 6),
         };
 
-        opt = getopt32(argv, "^" "cdo:far" "\0" "?2:d--ofar:a--ofr", &opt_o);
+        opt = getopt32(argv, "^" "cdPo:far" "\0" "?2:d--Pofar:a--Pofr", &opt_o);
         argv += optind;
 
         /* LOOPDEV */
@@ -127,7 +130,7 @@ int losetup_main(int argc UNUSED_PARAM, char **argv)
                 }
         }
 
-        /* [-r] [-o OFS] {-f|LOOPDEV} FILE */
+        /* [-rP] [-o OFS] {-f|LOOPDEV} FILE */
         if (argv[0] && ((opt & OPT_f) || argv[1])) {
                 unsigned long long offset = 0;
                 char *d = dev;
@@ -138,7 +141,11 @@ int losetup_main(int argc UNUSED_PARAM, char **argv)
                         d = *argv++;
 
                 if (argv[0]) {
-                        if (set_loop(&d, argv[0], offset, (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0) < 0)
+                        unsigned flags = (opt & OPT_r) ? BB_LO_FLAGS_READ_ONLY : 0;
+                        if (opt & OPT_P) {
+                                flags |= BB_LO_FLAGS_PARTSCAN;
+                        }
+                        if (set_loop(&d, argv[0], offset, flags) < 0)
                                 bb_simple_perror_msg_and_die(argv[0]);
                         return EXIT_SUCCESS;
                 }