Re: [PATCH 1/1] udev-cache: take a read-only rootfs into consideration

[Saul Wold <sgw@linux.intel.com>]

On 06/27/2013 10:00 PM, Qi.Chen@windriver.com wrote:
> From: Chen Qi <Qi.Chen@windriver.com>
>
> In case of a read-only rootfs, no matter the /etc is read-only or
> it's bind mounted with tmpfs, the udev cache handling should be
> skipped, as the data cannot be persisted between reboots.
>
> Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
> ---
>   meta/recipes-core/udev/udev/init       |    5 +++--
>   meta/recipes-core/udev/udev/udev-cache |    6 ++++++
>   2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/meta/recipes-core/udev/udev/init b/meta/recipes-core/udev/udev/init
> index 9b81700..38ea666 100644
> --- a/meta/recipes-core/udev/udev/init
> +++ b/meta/recipes-core/udev/udev/init
> @@ -18,6 +18,7 @@ export TZ=/etc/localtime
>   [ -x @UDEVD@ ] || exit 1
>   [ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
>   [ -f /etc/udev/udev.conf ] && . /etc/udev/udev.conf
> +[ -f /etc/default/rcS ] && . /etc/default/rcS
>
>   readfile () {
>      filename=$1
> @@ -52,8 +53,8 @@ case "$1" in
>       mount -a -t tmpfs 2>/dev/null
>       mkdir -p /var/volatile/tmp
>
> -    # cache handling
> -    if [ "$DEVCACHE" != "" ]; then
> +    # Cache handling. Skip cache handling in case of a read-only rootfs.
> +    if [ "$ROOTFS_READ_ONLY" = "no" -a "$DEVCACHE" != "" ]; then
>               readfile /proc/version
>               VERSION="$READDATA"
>               readfile /proc/cmdline
Do you think it would be possible in a fix embedded device to have the 
udev cache created and installed in a read-only FS?

Sau!

> diff --git a/meta/recipes-core/udev/udev/udev-cache b/meta/recipes-core/udev/udev/udev-cache
> index 8a84fa9..3e0eff6 100644
> --- a/meta/recipes-core/udev/udev/udev-cache
> +++ b/meta/recipes-core/udev/udev/udev-cache
> @@ -15,8 +15,14 @@ export TZ=/etc/localtime
>   [ -x @UDEVD@ ] || exit 1
>   [ -d /sys/class ] || exit 1
>
> +[ -f /etc/default/rcS ] && . /etc/default/rcS
>   [ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
>
> +if [ "$ROOTFS_READ_ONLY" = "yes" ]; then
> +    [ "$VERBOSE" != "no" ] && echo "read-only rootfs, skip udev-cache"
> +    exit 0
> +fi
> +
>   if [ "$DEVCACHE" != "" -a -e /dev/shm/udev.cache ]; then
>   	echo "Populating dev cache"
>   	(cd /; tar cf "$DEVCACHE" dev)
>