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dissect: when we invoke dissection on a loop device with partscan help the user

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This adds some simply detection logic for cases where dissection is
invoked on an externally created loop device, and partitions have been
detected on it, but partition scanning so far was off. If this is
detected we now print a brief message indicating what the issue is,
instead of failing with a useless EINVAL message the kernel passed to
us.
This commit is contained in:
Lennart Poettering 2017-10-04 17:40:46 +02:00
parent eb38edce88
commit 759aaedc5c
3 changed files with 30 additions and 9 deletions
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4
src/dissect/dissect.c
View file

@ -216,6 +216,10 @@ int main(int argc, char *argv[]) {
log_error_errno(r, "No suitable root partition found in image %s.", arg_image);
goto finish;
}
if (r == -EPROTONOSUPPORT) {
log_error_errno(r, "Device %s is loopback block device with partition scanning turned off, please turn it on.", arg_image);
goto finish;
}
if (r < 0) {
log_error_errno(r, "Failed to dissect image: %m");
goto finish;

4
src/nspawn/nspawn.c
View file

@ -3883,6 +3883,10 @@ int main(int argc, char *argv[]) {
log_error_errno(r, "--image= is not supported, compiled without blkid support.");
goto finish;
}
if (r == -EPROTONOSUPPORT) {
log_error_errno(r, "Device is loopback block device with partition scanning turned off, please turn it on.");
goto finish;
}
if (r < 0) {
log_error_errno(r, "Failed to dissect image: %m");
goto finish;

31
src/shared/dissect-image.c
View file

@ -266,18 +266,34 @@ int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectI
return -EIO;
}
if (n < z + 1) {
unsigned j;
unsigned j = 0;
/* The kernel has probed fewer partitions than blkid? Maybe the kernel prober is still running
* or it got EBUSY because udev already opened the device. Let's reprobe the device, which is a
* synchronous call that waits until probing is complete. */
for (j = 0; j < 20; j++) {
for (;;) {
if (j++ > 20)
return -EBUSY;
r = ioctl(fd, BLKRRPART, 0);
if (r < 0)
if (ioctl(fd, BLKRRPART, 0) < 0) {
r = -errno;
if (r >= 0 || r != -EBUSY)
if (r == -EINVAL) {
struct loop_info64 info;
/* If we are running on a loop device that has partition scanning off,
* return an explicit recognizable error about this, so that callers
* can generate a proper message explaining the situation. */
if (ioctl(fd, LOOP_GET_STATUS64, &info) >= 0 && (info.lo_flags & LO_FLAGS_PARTSCAN) == 0) {
log_debug("Device is loop device and partition scanning is off!");
return -EPROTONOSUPPORT;
}
}
if (r != -EBUSY)
return r;
} else
break;
/* If something else has the device open, such as an udev rule, the ioctl will return
@ -286,11 +302,8 @@ int dissect_image(int fd, const void *root_hash, size_t root_hash_size, DissectI
*
* This is really something they should fix in the kernel! */
usleep(50 * USEC_PER_MSEC);
(void) usleep(50 * USEC_PER_MSEC);
}
if (r < 0)
return r;
}
e = udev_enumerate_unref(e);