udev-cache: take a read-only rootfs into consideration
In case of a read-only rootfs, we skip the process of generating udev cache, as the data cannot be persisted between reboots. However, it's possbile that the $DEVCACHE (default to /etc/dev.tar) exists in a read-only rootfs, no matter how it's generated or installed. In such situation, we try to use $DEVCACHE if possible. Besides the basic changes in the logic of udev cache handling, this patch also adds code to output more information if the udev cache is not used and VERBOSE enabled. This patch also changes the readfile function to readfiles function so that it could handle more than one file at once. (From OE-Core rev: 4ec1266e7e1aacdb9d3d0fc5cd6307b60df1731e) Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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@ -18,15 +18,17 @@ export TZ=/etc/localtime
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[ -x @UDEVD@ ] || exit 1
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[ -x @UDEVD@ ] || exit 1
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[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
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[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
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[ -f /etc/udev/udev.conf ] && . /etc/udev/udev.conf
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[ -f /etc/udev/udev.conf ] && . /etc/udev/udev.conf
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[ -f /etc/default/rcS ] && . /etc/default/rcS
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readfile () {
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readfiles () {
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filename=$1
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READDATA=""
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READDATA=""
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for filename in $@; do
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if [ -r $filename ]; then
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if [ -r $filename ]; then
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while read line; do
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while read line; do
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READDATA="$READDATA$line"
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READDATA="$READDATA$line"
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done < $filename
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done < $filename
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fi
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fi
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done
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}
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}
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case "$1" in
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case "$1" in
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@ -52,29 +54,37 @@ case "$1" in
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mount -a -t tmpfs 2>/dev/null
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mount -a -t tmpfs 2>/dev/null
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mkdir -p /var/volatile/tmp
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mkdir -p /var/volatile/tmp
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# cache handling
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# Cache handling.
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# A list of files which are used as a criteria to judge whether the udev cache could be reused.
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CMP_FILE_LIST="/proc/version /proc/cmdline /proc/devices /proc/atags"
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if [ "$DEVCACHE" != "" ]; then
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if [ "$DEVCACHE" != "" ]; then
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readfile /proc/version
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VERSION="$READDATA"
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readfile /proc/cmdline
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CMDLINE="$READDATA"
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readfile /proc/devices
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DEVICES="$READDATA"
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readfile /proc/atags
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ATAGS="$READDATA"
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if [ -e $DEVCACHE ]; then
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if [ -e $DEVCACHE ]; then
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readfile /etc/udev/cache.data
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readfiles $CMP_FILE_LIST
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if [ "$READDATA" = "$VERSION$CMDLINE$DEVICES$ATAGS" ]; then
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NEWDATA="$READDATA"
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readfiles /etc/udev/cache.data
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OLDDATA="$READDATA"
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if [ "$OLDDATA" = "$NEWDATA" ]; then
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(cd /; tar xf $DEVCACHE > /dev/null 2>&1)
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(cd /; tar xf $DEVCACHE > /dev/null 2>&1)
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not_first_boot=1
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not_first_boot=1
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[ "$VERBOSE" != "no" ] && echo "udev: using cache file $DEVCACHE"
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[ "$VERBOSE" != "no" ] && echo "udev: using cache file $DEVCACHE"
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[ -e /dev/shm/udev.cache ] && rm -f /dev/shm/udev.cache
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[ -e /dev/shm/udev.cache ] && rm -f /dev/shm/udev.cache
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else
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else
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echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
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# Output detailed reason why the cached /dev is not used
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if [ "$VERBOSE" != "no" ]; then
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echo "udev: udev cache not used"
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echo "udev: we use $CMP_FILE_LIST as criteria to judge whether the cache /dev could be resued"
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echo "udev: olddata: $OLDDATA"
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echo "udev: newdata: $NEWDATA"
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fi
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echo "$NEWDATA" > /dev/shm/udev.cache
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fi
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fi
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else
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else
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echo "$VERSION$CMDLINE$DEVICES$ATAGS" > /dev/shm/udev.cache
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if [ "$ROOTFS_READ_ONLY" != "yes" ]; then
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# If rootfs is not read-only, it's possible that a new udev cache would be generated;
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# otherwise, we do not bother to read files.
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readfiles $CMP_FILE_LIST
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echo "$READDATA" > /dev/shm/udev.cache
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fi
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fi
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fi
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fi
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fi
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@ -15,8 +15,14 @@ export TZ=/etc/localtime
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[ -x @UDEVD@ ] || exit 1
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[ -x @UDEVD@ ] || exit 1
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[ -d /sys/class ] || exit 1
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[ -d /sys/class ] || exit 1
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[ -f /etc/default/rcS ] && . /etc/default/rcS
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[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
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[ -f /etc/default/udev-cache ] && . /etc/default/udev-cache
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if [ "$ROOTFS_READ_ONLY" = "yes" ]; then
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[ "$VERBOSE" != "no" ] && echo "udev-cache: read-only rootfs, skip generating udev-cache"
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exit 0
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fi
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if [ "$DEVCACHE" != "" -a -e /dev/shm/udev.cache ]; then
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if [ "$DEVCACHE" != "" -a -e /dev/shm/udev.cache ]; then
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echo "Populating dev cache"
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echo "Populating dev cache"
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(cd /; tar cf "$DEVCACHE" dev)
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(cd /; tar cf "$DEVCACHE" dev)
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