[PATCH] losetup: Add partition scanning option

[Denys Vlasenko]

Applied, thanks

On Tue, May 28, 2019 at 4:28 PM Jack O'Sullivan <jackos1998 at gmail.com> wrote:
>
> Add -P option from util-linux losetup to scan for partitions (for
> kernels 3.2 and up).
>
> Signed-off-by: Jack O'Sullivan <jackos1998 at gmail.com>
> ---
>  include/libbb.h      |  1 +
>  util-linux/losetup.c | 27 +++++++++++++++++----------
>  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..b5fc47664 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:       "[-r] [-P] [-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      Automatically 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 */
> +       /* [-r] [-P] [-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 (get_linux_version_code() > KERNEL_VERSION(3,2,0) && 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;
>                 }
> --
> 2.21.0
>
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