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Maintain our own set of loop devices

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topjohnwu
2018-07-07 01:32:58 +08:00
parent 23c2e22910
commit 1283167595
3 changed files with 32 additions and 11 deletions
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41
native/jni/utils/img.c
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@@ -9,6 +9,7 @@
#include <sys/mount.h>
#include <sys/sendfile.h>
#include <sys/statvfs.h>
#include <sys/sysmacros.h>
#include <linux/loop.h>
#include "magisk.h"
@@ -26,23 +27,41 @@ struct fs_info {
};
static char *loopsetup(const char *img) {
char device[20];
char device[32];
struct loop_info64 info;
int i, lfd, ffd;
int lfd = -1, ffd;
memset(&info, 0, sizeof(info));
// First get an empty loop device
for (i = 0; i <= 7; ++i) {
sprintf(device, "/dev/block/loop%d", i);
lfd = xopen(device, O_RDWR);
if (ioctl(lfd, LOOP_GET_STATUS64, &info) == -1)
break;
close(lfd);
if (access(BLOCKDIR, F_OK) == 0) {
for (int i = 8; i < 100; ++i) {
sprintf(device, BLOCKDIR "/loop%02d", i);
if (access(device, F_OK) != 0)
mknod(device, S_IFBLK | 0600, makedev(7, i * 8));
lfd = open(device, O_RDWR);
if (lfd < 0) /* Kernel does not support this */
break;
if (ioctl(lfd, LOOP_GET_STATUS64, &info) == -1)
break;
close(lfd);
lfd = -1;
}
}
if (i == 8) return NULL;
// Fallback to existing loop in dev, but in reverse order
if (lfd < 0) {
for (int i = 7; i >= 0; --i) {
sprintf(device, "/dev/block/loop%d", i);
lfd = xopen(device, O_RDWR);
if (ioctl(lfd, LOOP_GET_STATUS64, &info) == -1)
break;
close(lfd);
lfd = -1;
}
}
if (lfd < 0)
return NULL;
ffd = xopen(img, O_RDWR);
if (ioctl(lfd, LOOP_SET_FD, ffd) == -1)
return NULL;
strcpy((char *) info.lo_file_name, img);
strncpy((char *) info.lo_file_name, img, sizeof(info.lo_file_name));
ioctl(lfd, LOOP_SET_STATUS64, &info);
close(lfd);
close(ffd);