Mailing List Archive

commit 76a484193dbb6a11b101c1d01a5088f468f93080
Author: Jason Andryuk <jandryuk@gmail.com>
AuthorDate: Thu Apr 25 09:46:56 2024 +0200
Commit: Jan Beulich <jbeulich@suse.com>
CommitDate: Thu Apr 25 09:46:56 2024 +0200

hotplug: Update block-tap

Implement a sharing check like the regular block script.

Checking tapback inside block-tap is too late since it needs to be
running to transition the backend to InitWait before block-tap is run.

tap-ctl check will be removed when the requirement for the blktap kernel
driver is removed. Remove it now as it is of limited use.

find_device() needs to be non-fatal allow a sharing check.

Only write physical-device-path because that is all that tapback needs.
Also write_dev doesn't handled files and would incorrectly store
physical-device as 0:0 which would confuse the minor inside tapback

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
---
tools/hotplug/Linux/block-tap | 169 +++++++++++++++++++++++++++++++++++++++---
1 file changed, 157 insertions(+), 12 deletions(-)

diff --git a/tools/hotplug/Linux/block-tap b/tools/hotplug/Linux/block-tap
index 89247921b9..126e472786 100755
--- a/tools/hotplug/Linux/block-tap
+++ b/tools/hotplug/Linux/block-tap
@@ -18,11 +18,11 @@
#
# Usage:
#
-# Target should be specified using the following syntax:
+# Disks should be specified using the following syntax:
#
-# script=block-tap,vdev=xvda,target=<type>:<file>
+# vdev=xvda,backendtype=tap,format=vhd,target=/srv/target.vhd
#
-# Type is either "aio" (for raw files), or "vhd"
+# format is either "aio" (for raw files), or "vhd"

dir=$(dirname "$0")
. "$dir/block-common.sh"
@@ -37,10 +37,6 @@ check_tools()
if ! command -v tap-ctl > /dev/null 2>&1; then
fatal "Unable to find tap-ctl tool"
fi
- modprobe blktap
- if ! tap-ctl check >& /dev/null ; then
- fatal "Blocktap kernel module not available"
- fi
}

# Sets the following global variables based on the params field passed in as
@@ -81,7 +77,109 @@ find_device()
done

if [ -z "$pid" ] || [ -z "$minor" ]; then
- fatal "cannot find required parameters"
+ return 1
+ fi
+
+ return 0
+}
+
+count_using()
+{
+ local file="$1"
+ local dom
+ local dev
+ local f
+
+ local i=0
+ local base_path="$XENBUS_BASE_PATH/$XENBUS_TYPE"
+ for dom in $(xenstore-list "$base_path")
+ do
+ for dev in $(xenstore-list "$base_path/$dom")
+ do
+ f=$(xenstore_read_default "$base_path/$dom/$dev/params" "")
+ f=$(echo "$f" | cut -d ":" -f 2)
+
+ if [ -n "$f" ] && [ "$file" = $f ] ; then
+ i=$(( i + 1 ))
+ fi
+ done
+ done
+
+ echo "$i"
+}
+
+# tap_shared is used to determine if a shared tap can be closed
+# Since a stubdom and a guest both use the same tap, it can only
+# be freed when there is a single one left.
+tap_shared() {
+ [ $( count_using "$file" ) -gt 1 ]
+}
+
+check_tap_sharing()
+{
+ local file="$1"
+ local mode="$2"
+ local dom
+ local dev
+
+ local base_path="$XENBUS_BASE_PATH/$XENBUS_TYPE"
+ for dom in $(xenstore-list "$base_path") ; do
+ for dev in $(xenstore-list "$base_path/$dom") ; do
+ local f=$(xenstore_read_default "$base_path/$dom/$dev/params" "")
+ f=$(echo "$f" | cut -d ":" -f 2)
+
+ if [ -n "$f" ] && [ "$file" = "$f" ] ; then
+ if [ "$mode" = 'w' ] ; then
+ if ! same_vm $dom ; then
+ echo "guest $f"
+ return
+ fi
+ else
+ local m=$(xenstore_read_default "$base_path/$dom/$dev/mode"
+ "")
+ m=$(canonicalise_mode "$m")
+
+ if [ "$m" = 'w' ] ; then
+ if ! same_vm $dom ; then
+ echo "guest $f"
+ return
+ fi
+ fi
+ fi
+ fi
+ done
+ done
+
+ echo 'ok'
+}
+
+tap_create()
+{
+ if ! minor=$( tap-ctl allocate ) ; then
+ fatal "Could not allocate minor"
+ fi
+
+ # Handle with or without kernel blktap
+ minor=${minor#/run/blktap-control/tapdisk/tapdisk-}
+ minor=${minor#/dev/xen/blktap-2/tapdev}
+
+ # tap-ctl is spawning tapdisk which would hold the _lockfd open.
+ # Ensure it is closed before running tap-ctl spawn, which needs to be
+ # done in a subshell to continue holding the lock in the parent.
+ if ! pid=$( ( eval "exec $_lockfd>&-" ; tap-ctl spawn ) ) ; then
+ tap-ctl free -m "$minor"
+ fatal "Could not spawn tapdisk for $minor"
+ fi
+
+ if ! tap-ctl attach -p "$pid" -m "$minor" ; then
+ tap-ctl free -m "$minor"
+ fatal "Could not attach $pid and $minor"
+ fi
+
+ if ! tap-ctl open -p "$pid" -m "$minor" -a "$target" ; then
+ tap-ctl detach -p "$pid" -m "$minor"
+ tap-ctl free -m "$minor"
+ fatal "Could not open \"$target\""
fi
}

@@ -89,15 +187,54 @@ find_device()
# the device
add()
{
- dev=$(tap-ctl create -a $target)
- write_dev $dev
+ local result
+
+ claim_lock "block"
+
+ if find_device; then
+ result=$( check_tap_sharing "$file" "$mode" )
+ if [ "$result" != "ok" ] ; then
+ do_ebusy "tap $type file $file in use " "$mode" "${result%% *}"
+ fi
+ else
+ tap_create
+ fi
+
+ # Create nbd unix path. find_device/tap_create set pid & minor
+ dev=$( printf "/run/blktap-control/nbd%ld.%d" "$pid" "$minor" )
+
+ xenstore_write "$XENBUS_PATH/pid" "$pid"
+ xenstore_write "$XENBUS_PATH/minor" "$minor"
+ # dev, as a unix socket, would end up with major:minor 0:0 in
+ # physical-device if write_dev were used. tapback would be thrown off by
+ # that incorrect minor, so just skip writing physical-device.
+ xenstore_write "$XENBUS_PATH/physical-device-path" "$dev"
+
+ success
+
+ release_lock "block"
}

# Disconnects the device
remove()
{
- find_device
- do_or_die tap-ctl destroy -p ${pid} -m ${minor} > /dev/null
+ local minor
+ local pid
+
+ claim_lock "block"
+
+ if tap_shared ; then
+ return
+ fi
+
+ minor=$( xenstore_read "$XENBUS_PATH/minor" )
+ pid=$( xenstore_read "$XENBUS_PATH/pid" )
+
+ [ -n "$minor" ] || fatal "minor missing"
+ [ -n "$pid" ] || fatal "pid missing"
+ do_or_die tap-ctl destroy -p "$pid" -m "$minor" > /dev/null
+
+ release_lock "block"
}

command=$1
@@ -110,6 +247,14 @@ parse_target "$target"

check_tools || exit 1

+mode=$( xenstore_read $XENBUS_PATH/mode )
+mode=$( canonicalise_mode $mode )
+
+# needed for same_vm
+FRONTEND_ID=$(xenstore_read "$XENBUS_PATH/frontend-id")
+FRONTEND_UUID=$(xenstore_read_default \
+ "/local/domain/$FRONTEND_ID/vm" 'unknown')
+
case $command in
add)
add
--
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