From: Nirbheek Chauhan <nirbheek.chau...@collabora.co.uk> The LOOP_GET_STATUS ioctl truncates filenames to 64 characters. We should get the backing file for a given loop device from /sys/. This is how losetup does it as well.
Signed-off-by: Gene Czarcinski <g...@czarc.net> --- utils.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/utils.c b/utils.c index 51b78d5..7953ef9 100644 --- a/utils.c +++ b/utils.c @@ -20,6 +20,7 @@ #define __USE_XOPEN2K #include <stdio.h> #include <stdlib.h> +#include <string.h> #ifndef __CHECKER__ #include <sys/ioctl.h> #include <sys/mount.h> @@ -653,21 +654,22 @@ int is_loop_device (const char* device) { * the associated file (e.g. /images/my_btrfs.img) */ int resolve_loop_device(const char* loop_dev, char* loop_file, int max_len) { - int loop_fd; - int ret_ioctl; - struct loop_info loopinfo; + int ret; + FILE *f; + char fmt[20]; + char p[PATH_MAX]; + char real_loop_dev[PATH_MAX]; - if ((loop_fd = open(loop_dev, O_RDONLY)) < 0) + if (!realpath(loop_dev, real_loop_dev)) + return -errno; + snprintf(p, PATH_MAX, "/sys/block/%s/loop/backing_file", strrchr(real_loop_dev, '/')); + if (!(f = fopen(p, "r"))) return -errno; - ret_ioctl = ioctl(loop_fd, LOOP_GET_STATUS, &loopinfo); - close(loop_fd); - - if (ret_ioctl == 0) { - strncpy(loop_file, loopinfo.lo_name, max_len); - if (max_len > 0) - loop_file[max_len-1] = 0; - } else + snprintf(fmt, 20, "%%%i[^\n]", max_len-1); + ret = fscanf(f, fmt, loop_file); + fclose(f); + if (ret == EOF) return -errno; return 0; -- 1.8.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html