On Wed, Jul 25, 2012 at 5:09 AM, cwillu <cwillu@xxxxxxxxxx> wrote: > On Tue, Jul 24, 2012 at 6:39 PM, Marios Titas <redneb8888@xxxxxxxxx> wrote: >> When I create a btrfs volume of size strictly less than 256 MiB then if I do >> mount /dev/sdb1 /mnt/test >> the kernel tries unsuccessfully to do the mount with many other file systems >> before successfully trying with btrfs. For volumes of size larger than >> or equal to >> 256 MiB it just mounts the volume without doing that. Why is this discrepancy? > > If I understand correctly, the kernel does not implement any fs > detection; this is performed by the mount utility, which indeed may > try a bunch of different filesystems until it finds one that works. > > From man mount: > If no -t option is given, or if the auto type is specified, > mount will try to guess the desired type. Mount uses the blkid > or volume_id library for guessing the filesystem type; if that > does not turn up anything that looks familiar, mount will try to > read the file /etc/filesystems, or, if that does not exist, > /proc/filesystems. All of the filesystem types listed there > will be tried, except for those that are labeled "nodev" (e.g., > devpts, proc and nfs). If /etc/filesystems ends in a line with > a single * only, mount will read /proc/filesystems afterwards. Thanks, that was helpful. It was a blkid bug. It was fixed [1] in util-linux 2.21. [1] https://git.kernel.org/?p=utils/util-linux/util-linux.git;a=commit;h=04f7020 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
