[OpenWrt-Devel] fstools: block command doesn't recognize supported filesystem types because of libblkid-tiny

[Sandy McArthur Jr]

While attempting to pivot overlay using the f2fs filesystem in a 4mib
internal flash storage device on usb flash storage with the final CC
15.05 release I ran into the hurdle that the block command doesn't
understand the magic bytes for an f2fs filesystem.

Chasing the sources as best as I can I found that the block command
from the block-mount package of the fstools package uses libblkid-tiny
which seems to be a subset of the util-linux libblkid sources.

In my limited understanding of the block command it seem the block
command's detection abilities is the only hurdle I'm aware of from
using /etc/config/fstab to mount newly supported filesystems because
the block command thinks undetected devices are not present.
Alternatively a flag to bypass detection and force a mount attempt
could be helpful.

Visually comparing the output of `opkg list kmod-fs-*` and
libblkid-tiny sources it appears the file systems below could benefit
from an updated libblkid-tiny.
* exfat
* f2fs
* isofs iso9660
* minix
* reiserfs
* udf
* xfs

For reference here is the output of `block info`:
# block info
/dev/mtdblock2: UUID="91bc218a-e0578c7b-bd42f6bb-11ad1a81"
VERSION="4.0" TYPE="squashfs"
/dev/mtdblock3: TYPE="jffs2"
/dev/sda2: UUID="8dcb63a3-3d8b-4ed4-9e96-e9399afcec9e" LABEL="usbswap"
VERSION="2" TYPE="swap"

and the output of `blkid` on the same device:
# blkid
/dev/mtdblock2: TYPE="squashfs"
/dev/sda1: LABEL="ovrlay" UUID="77341453-b152-403a-b757-8c22c1d7204a"
TYPE="f2fs" PARTUUID="eb6410a6-01"
/dev/sda2: LABEL="usbswap" UUID="8dcb63a3-3d8b-4ed4-9e96-e9399afcec9e"
TYPE="swap" PARTUUID="eb6410a6-02"
/dev/sda3: PARTUUID="eb6410a6-03"


Links:

libblkid-tiny: http://nbd.name/gitweb.cgi?p=fstools.git;a=tree;f=libblkid-tiny;hb=HEAD

util-linux libblkid:
https://git.kernel.org/cgit/utils/util-linux/util-linux.git/tree/libblkid/src/superblocks


-- 
Sandy McArthur, Jr.

"No nation could preserve its freedom in the midst of continual warfare."
- Letters and Other Writings of James Madison (1865), Vol. IV, p. 491
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