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- /* losetup.c - Loopback setup
- *
- * Copyright 2012 Rob Landley <rob@landley.net>
- *
- * No standard. (Sigh.)
- USE_LOSETUP(NEWTOY(losetup, ">2S(sizelimit)#s(show)ro#j:fdcaD[!afj]", TOYFLAG_SBIN))
- config LOSETUP
- bool "losetup"
- default y
- help
- usage: losetup [-cdrs] [-o OFFSET] [-S SIZE] {-d DEVICE...|-j FILE|-af|{DEVICE FILE}}
- Associate a loopback device with a file, or show current file (if any)
- associated with a loop device.
- Instead of a device:
- -a Iterate through all loopback devices
- -f Find first unused loop device (may create one)
- -j FILE Iterate through all loopback devices associated with FILE
- existing:
- -c Check capacity (file size changed)
- -d DEV Detach loopback device
- -D Detach all loopback devices
- new:
- -s Show device name (alias --show)
- -o OFF Start association at offset OFF into FILE
- -r Read only
- -S SIZE Limit SIZE of loopback association (alias --sizelimit)
- */
- #define FOR_losetup
- #include "toys.h"
- #include <linux/loop.h>
- GLOBALS(
- char *j;
- long o, S;
- int openflags;
- dev_t jdev;
- ino_t jino;
- char *dir;
- )
- // -f: *device is NULL
- // Perform requested operation on one device. Returns 1 if handled, 0 if error
- static int loopback_setup(char *device, char *file)
- {
- struct loop_info64 *loop = (void *)(toybuf+32);
- int lfd = -1, ffd = -1;
- int racy = !device;
- // Open file (ffd) and loop device (lfd)
- if (file) ffd = xopen(file, TT.openflags);
- if (!device) {
- int i, cfd = open("/dev/loop-control", O_RDWR);
- // We assume /dev is devtmpfs so device creation has no lag. Otherwise
- // just preallocate loop devices and stay within them.
- // mount -o loop depends on found device being at the start of toybuf.
- if (cfd != -1) {
- if (0 <= (i = ioctl(cfd, LOOP_CTL_GET_FREE))) {
- sprintf(device = toybuf, "%s/loop%d", TT.dir, i);
- }
- close(cfd);
- }
- }
- if (device) lfd = open(device, TT.openflags);
- // Stat the loop device to see if there's a current association.
- memset(loop, 0, sizeof(struct loop_info64));
- if (-1 == lfd || ioctl(lfd, LOOP_GET_STATUS64, loop)) {
- if (errno == ENXIO && (FLAG(a) || FLAG(j))) goto done;
- // ENXIO expected if we're just trying to print the first unused device.
- if (errno == ENXIO && FLAG(f) && !file) {
- puts(device);
- goto done;
- }
- if (errno != ENXIO || !file) {
- perror_msg_raw(device ? device : "-f");
- goto done;
- }
- }
- // Skip -j filtered devices
- if (TT.j && (loop->lo_device != TT.jdev || loop->lo_inode != TT.jino))
- goto done;
- // Check size of file or delete existing association
- if (FLAG(c) || FLAG(d)) {
- // The constant is LOOP_SET_CAPACITY
- if (ioctl(lfd, FLAG(c) ? 0x4C07 : LOOP_CLR_FD, 0)) {
- perror_msg_raw(device);
- goto done;
- }
- // Associate file with this device?
- } else if (file) {
- char *f_path = xabspath(file, ABS_PATH);
- if (!f_path) perror_exit("%s", file); // already opened but if deleted since
- if (ioctl(lfd, LOOP_SET_FD, ffd)) {
- free(f_path);
- if (racy && errno == EBUSY) return 1;
- perror_exit("%s=%s", device, file);
- }
- xstrncpy((char *)loop->lo_file_name, f_path, LO_NAME_SIZE);
- free(f_path);
- loop->lo_offset = TT.o;
- loop->lo_sizelimit = TT.S;
- if (ioctl(lfd, LOOP_SET_STATUS64, loop)) perror_exit("%s=%s", device, file);
- if (FLAG(s)) puts(device);
- }
- else {
- xprintf("%s: [%lld]:%llu (%s)", device, (long long)loop->lo_device,
- (long long)loop->lo_inode, loop->lo_file_name);
- if (loop->lo_offset) xprintf(", offset %llu",
- (unsigned long long)loop->lo_offset);
- if (loop->lo_sizelimit) xprintf(", sizelimit %llu",
- (unsigned long long)loop->lo_sizelimit);
- xputc('\n');
- }
- done:
- xclose(ffd);
- xclose(lfd);
- return 0;
- }
- // Perform an action on all currently existing loop devices
- static int dash_a(struct dirtree *node)
- {
- char *s = node->name;
- // Initial /dev node needs to recurse down one level, then only loop[0-9]*
- if (!node->parent) return DIRTREE_RECURSE;
- if (strncmp(s, "loop", 4) || !isdigit(s[4])) return 0;
- s = dirtree_path(node, 0);
- loopback_setup(s, 0);
- free(s);
- return 0;
- }
- void losetup_main(void)
- {
- char **s;
- TT.dir = CFG_TOYBOX_ON_ANDROID ? "/dev/block" : "/dev";
- TT.openflags = FLAG(r) ? O_RDONLY : O_RDWR;
- if (TT.j) {
- struct stat st;
- xstat(TT.j, &st);
- TT.jdev = st.st_dev;
- TT.jino = st.st_ino;
- }
- // With just device, display current association
- // -a, -f substitute for device
- // -j substitute for device
- // new association: S size o offset rs - need a file
- // existing association: cd
- // -f(dc FILE)
- if (FLAG(D)) toys.optflags |= FLAG_a | FLAG_d;
- if (FLAG(f)) {
- if (toys.optc > 1) perror_exit("max 1 arg");
- while (loopback_setup(NULL, *toys.optargs));
- } else if (FLAG(a) || FLAG(j)) {
- if (toys.optc) error_exit("bad args");
- dirtree_read(TT.dir, dash_a);
- // Do we need one DEVICE argument?
- } else {
- char *file = (FLAG(c) || FLAG(d)) ? NULL : toys.optargs[1];
- if (!toys.optc || (file && toys.optc != 2))
- help_exit("needs %d arg%s", 1+!!file, file ? "s" : "");
- for (s = toys.optargs; *s; s++) {
- loopback_setup(*s, file);
- if (file) break;
- }
- }
- }
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