Re: [libvirt] [PATCH v2] util: Set backing file name for LOOP_GET_STATUS64 queries.

From: Julio Faracco <jcfaracco(a)gmail.com&gt; This is an issue for LXC loop devices when you are trying to get loop devices info using `ioctl`. Modern apps uses `/sys/dev/block` to grab information about devices, but if you use the method mention you won't be able to retrive the associated file with that loop device. See example below from cryptsetup sources: static char *_ioctl_backing_file(const char *loop) { struct loop_info64 lo64 = {0}; int loop_fd; loop_fd = open(loop, O_RDONLY); if (loop_fd < 0) return NULL; if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) { close(loop_fd); return NULL; } lo64.lo_file_name[LO_NAME_SIZE-2] = '*'; lo64.lo_file_name[LO_NAME_SIZE-1] = 0; close(loop_fd); return strdup((char*)lo64.lo_file_name); } It will return an empty string because lo_file_name was not set. Function `virFileLoopDeviceOpenSearch()` is using `ioctl` to query data, but it is not checking `lo_file_name` field. v1: I accidentally committed two wrong lines.

Signed-off-by: Julio Faracco <jcfaracco(a)gmail.com&gt; ---

src/util/virfile.c | 8 ++++++++ 1 file changed, 8 insertions(+)