| Message ID | 1358715858-4469-3-git-send-email-gene@czarc.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jan 20, 2013 at 04:04:07PM -0500, Gene Czarcinski wrote: > From: Nirbheek Chauhan <nirbheek.chauhan@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 <gene@czarc.net> I'd expect Nirbheek's signed off here as well and I've noticed Tested-By: Hector Oron <hector.oron@collabora.co.uk> (https://patchwork.kernel.org/patch/1629581/) Are you guys ok with adding them? david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, Jan 20, 2013 at 04:04:07PM -0500, Gene Czarcinski wrote: > From: Nirbheek Chauhan <nirbheek.chauhan@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. For the record, there was another patch fixing a loop device issue https://patchwork.kernel.org/patch/1861831/ from Michael (CCed), that switched from LOOP_GET_STATUS to LOOP_GET_STATUS64, but afaics both types of the ioctl return at most 64 characters, so parsing /sys appears to be the way to go. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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;