core-agent-linux/misc/block_add_change
Marek Marczykowski bf059e4050 dom0/udev: allow only one xenstore-write at the time
This apparently causes deadlocks when many xenstore-write (one for each block
device) called at the same time.
2013-01-27 00:02:30 +01:00

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#!/bin/bash
NAME=${DEVNAME#/dev/}
DESC="${ID_MODEL} (${ID_FS_LABEL})"
SIZE=$[ $(cat /sys/$DEVPATH/size) * 512 ]
MODE=w
XS_KEY="qubes-block-devices/$NAME"
xs_remove() {
if [ "$QUBES_EXPOSED" == "1" ]; then
xenstore-rm "$XS_KEY"
fi
echo QUBES_EXPOSED=0
}
# Ignore mounted...
if fgrep -q $DEVNAME /proc/mounts; then
xs_remove
exit 0
fi
# ... and used by device-mapper
if [ -n "`ls -A /sys/$DEVPATH/holders 2> /dev/null`" ]; then
xs_remove
exit 0
fi
# ... and "empty" loop devices
if [ "$MAJOR" -eq 7 -a ! -d /sys/$DEVPATH/loop ]; then
xs_remove
exit 0
fi
# Special case for CD
if [ "$ID_TYPE" = "cd" ]; then
if [ "$ID_CDROM_MEDIA" != "1" ]; then
# Hide empty cdrom drive
xs_remove
exit 0
fi
MODE=r
fi
# Special description for loop devices
if [ -d /sys/$DEVPATH/loop ]; then
DESC=$(cat /sys/$DEVPATH/loop/backing_file)
fi
# Get lock only in dom0 - there are so many block devices so it causes xenstore
# deadlocks sometimes.
if [ -f /etc/qubes-release ]; then
# Skip xenstore-write if cannot obtain lock. This can mean very early system startup
# stage without /run mounted (or populated). Devices will be rediscovered later
# by qubes-core startup script.
exec 9>>/var/run/qubes/block-xenstore.lock || exit 0
flock 9
fi
xenstore-write "$XS_KEY/desc" "$DESC" "$XS_KEY/size" "$SIZE" "$XS_KEY/mode" "$MODE"
echo QUBES_EXPOSED=1
# Make sure that block backend is loaded
/sbin/modprobe xen-blkback 2> /dev/null || /sbin/modprobe blkbk