[PATCH v2] ubifs: respect MS_SILENT mount flag

[Daniel]

On 05/27/2014 04:56 PM, Artem Bityutskiy wrote:
> On Tue, 2014-05-27 at 16:11 +0200, Daniel Golle wrote:
>> When attempting to mount a non-ubifs formatted volume, lots of error
>> messages (including a stack dump) are thrown to the kernel log even if
>> the MS_SILENT mount flag is set.
>> Fix this by introducing an additional parameter in ubifs_read_node and
>> use it to pass down the MS_SILENT flag in ubifs_read_sb_node.
>>
>> Signed-off-by: Daniel Golle <daniel at makrotopia.org>
> 
> Thanks. How did you test this patch?

You can test this by trying to mount a non-empty volume which does not contain a
UBIFS superblock (but e.g. squashfs or a U-Boot environment) with
mount -t ubifs -o silent /dev/ubiX_Y /mnt
This should fail without creating any klog lines.

The reason that I want this is that I'm working on integration of UBI support in
OpenWrt, including auto-mounting the "rootfs" volume by default (if it exists)
in case the rootfs and/or rootfstype parameters are not passed-down by the
bootloader, see
https://gitorious.org/openwrt-oxnas/openwrt-oxnas/commit/e1306d7b9bee8a39a33147d93cb399a4621bf3aa

The idea is to have the same level of features and comfort also on devices where
UBI is being used, for MTD devices OpenWrt does something similar
https://dev.openwrt.org/browser/trunk/target/linux/generic/patches-3.14/480-mtd-set-rootfs-to-be-root-dev.patch

However, this is probably distribution-specific hackery, but independently of
that, UBIFS should still respect the MS_SILENT flag just like all other
filesystems do.