This is a trivial patch to add a -f option to losetup. losetup -f shows the
first free loop device. After the patch executable size is not changed in
two of three arch that I've tested:
AMD64: unchanged
i386: unchanged
i386: +4060bytes (different version of gcc)
The code is incorrect if 1) there are less than 10 loop devices and 2) they
are all busy (but I don't know loop devices enough to correct...).
I use a custom version of ubuntu initrd using busybox 1.6.1 for nearly all
executables (resulting in a 700kb smaller initrd.gz). losetup -f is
used during
the boot, so that it'd be better if it got included in busybox.
Untested suggestion to shave a couple of bytes from losetup.c:
char dev[sizeof(LOOP_NAME"0")] = LOOP_NAME"0";
char c;
for (c = '0'; c <= '9'; ++c) {
char *s;
dev[sizeof(LOOP_NAME"0")-2] = c;
s = query_loop(dev);
can be modified into:
char dev[sizeof(LOOP_NAME"0")] = LOOP_NAME"0";
for (; dev[sizeof(dev)-2] <= '9'; ++dev[sizeof(dev)-2]) {
char *s;
s = query_loop(dev);
(stylewise I prefer char dev[] = LOOP_NAME"0"; but I don't know whether
all compilers would accept it and produce correct code).
Cheers,
Loïc
diff -c -r busybox-1.6.1/include/usage.h busybox-1.6.1.loic/include/usage.h
*** busybox-1.6.1/include/usage.h Sat Jun 30 17:06:45 2007
--- busybox-1.6.1.loic/include/usage.h Thu Sep 20 22:41:43 2007
***************
*** 1845,1863 ****
" -f Output data as the log grows"
#define losetup_trivial_usage \
! "[-o OFFSET] [-d] LOOPDEVICE [FILE]]"
#define losetup_full_usage \
"(Dis)associate LOOPDEVICE with FILE, or display current associations" \
"\n\nOptions:\n" \
" -d Disassociate LOOPDEVICE\n" \
! " -o OFFSET Start OFFSET bytes into FILE"
#define losetup_notes_usage \
"No arguments will display all current associations.\n" \
"One argument (losetup /dev/loop1) will display the current association\n" \
"(if any), or disassociate it (with -d). The display shows the offset\n" \
"and filename of the file the loop device is currently bound to.\n\n" \
"Two arguments (losetup /dev/loop1 file.img) create a new association,\n" \
! "with an optional offset (-o 12345). Encryption is not yet supported.\n\n"
#define ls_trivial_usage \
"[-1Aa" USE_FEATURE_LS_TIMESTAMPS("c") "Cd" \
--- 1845,1865 ----
" -f Output data as the log grows"
#define losetup_trivial_usage \
! "{[-o OFFSET] [-d] LOOPDEVICE [FILE] | -f }"
#define losetup_full_usage \
"(Dis)associate LOOPDEVICE with FILE, or display current associations" \
"\n\nOptions:\n" \
" -d Disassociate LOOPDEVICE\n" \
! " -o OFFSET Start OFFSET bytes into FILE\n" \
! " -f Show first free loop device"
#define losetup_notes_usage \
"No arguments will display all current associations.\n" \
"One argument (losetup /dev/loop1) will display the current association\n" \
"(if any), or disassociate it (with -d). The display shows the offset\n" \
"and filename of the file the loop device is currently bound to.\n\n" \
"Two arguments (losetup /dev/loop1 file.img) create a new association,\n" \
! "with an optional offset (-o 12345). Encryption is not yet supported.\n" \
! "losetup -f will show the first loop free loop device\n\n"
#define ls_trivial_usage \
"[-1Aa" USE_FEATURE_LS_TIMESTAMPS("c") "Cd" \
diff -c -r busybox-1.6.1/util-linux/losetup.c busybox-1.6.1.loic/util-linux/losetup.c
*** busybox-1.6.1/util-linux/losetup.c Sat Jun 30 17:06:48 2007
--- busybox-1.6.1.loic/util-linux/losetup.c Thu Sep 20 22:43:22 2007
***************
*** 18,28 ****
char *opt_o;
unsigned long long offset = 0;
! opt = getopt32(argc, argv, "do:", &opt_o);
argc -= optind;
argv += optind;
! if (opt == 0x3) // -d + -o (illegal)
bb_show_usage();
if (opt == 0x1) { // -d
--- 18,28 ----
char *opt_o;
unsigned long long offset = 0;
! opt = getopt32(argc, argv, "do:f", &opt_o);
argc -= optind;
argv += optind;
! if (opt == 0x3 || opt == 0x5 || opt == 0x6) // two options (illegal)
bb_show_usage();
if (opt == 0x1) { // -d
***************
*** 37,43 ****
if (opt == 0x2) // -o
offset = xatoull(opt_o);
! /* -o or no option */
if (argc == 2) {
if (set_loop(&argv[0], argv[1], offset) < 0)
--- 37,46 ----
if (opt == 0x2) // -o
offset = xatoull(opt_o);
! if (opt == 0x4 && argc) // -f does not take any argument
! bb_show_usage();
!
! /* -o, -f or no option */
if (argc == 2) {
if (set_loop(&argv[0], argv[1], offset) < 0)
***************
*** 56,66 ****
char *s;
dev[sizeof(LOOP_NAME"0")-2] = c;
s = query_loop(dev);
! if (s) {
printf("%s: %s\n", dev, s);
if (ENABLE_FEATURE_CLEAN_UP)
free(s);
}
}
}
return EXIT_SUCCESS;
--- 59,74 ----
char *s;
dev[sizeof(LOOP_NAME"0")-2] = c;
s = query_loop(dev);
! if (s && opt != 0x4) {
printf("%s: %s\n", dev, s);
if (ENABLE_FEATURE_CLEAN_UP)
free(s);
}
+ else if (!s && opt == 0x4)
+ {
+ printf("%s\n", dev);
+ return EXIT_SUCCESS;
+ }
}
}
return EXIT_SUCCESS;
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