[pve-devel] [PATCH v2 storage] rbd: alloc image: fix #3970 avoid ambiguous rbd path

[Thomas Lamprecht]

On 11.04.22 11:08, Aaron Lauterer wrote:
> On 4/11/22 09:39, Thomas Lamprecht wrote:
>> The obvious question to me is: why bother with this workaround when we can
>> make udev create the symlink now already?
>>
>> Patching the rules file and/or binary shipped by ceph-common, or shipping our
>> own such script + rule, would seem relatively simple.
>
> The thinking was to implement a stop gap to have more time to consider a
> solution that we can upstream.

If the stop-gap would be trivial and non intrusive (compared to the Correct
Solution™) or if it would be really pressing, sure, but IMO the situation here
isn't exactly /that/ clear cut.

> 
> Fabian might have some more thoughts on it but yeah, right now we could patch
> the udev rules and the ceph-rbdnamer which is called by the rule to create
> the current paths and then additionally the cluster specific ones.
> Unfortunately, it seems like the unwieldy cluster fsid is the only identifier
> we have for the cluster.

The unwieldiness doesn't really matter for us here though, this is just an
internal check.

> 
> Some more (smaller) changes might be necessary, if the implementation we
> manage to upstream will be a bit different. But that should not be much of an
> issue AFAICT.

We can always ship our downstream solution to be whatever we want and sync up
on major release, so not a real problem.

FWIW, with storage getting the following patch the symlinks get created (may need
an trigger for reloading udev (or manually `udevadm control -R`).

We'd only need to check to prioritize /deb/rbd-pve/$fsid/... paths first;
do you have time to give that a go?

diff --git a/Makefile b/Makefile
index 431db16..029b586 100644
--- a/Makefile
+++ b/Makefile
@@ -41,6 +41,7 @@ install: PVE pvesm.1 pvesm.bash-completion pvesm.zsh-completion
        install -d ${DESTDIR}${SBINDIR}
        install -m 0755 pvesm ${DESTDIR}${SBINDIR}
        make -C PVE install
+       make -C udev-rbd install
        install -d ${DESTDIR}/usr/share/man/man1
        install -m 0644 pvesm.1 ${DESTDIR}/usr/share/man/man1/
        gzip -9 -n ${DESTDIR}/usr/share/man/man1/pvesm.1
diff --git a/udev-rbd/50-rbd-pve.rules b/udev-rbd/50-rbd-pve.rules
new file mode 100644
index 0000000..79432df
--- /dev/null
+++ b/udev-rbd/50-rbd-pve.rules
@@ -0,0 +1,2 @@
+KERNEL=="rbd[0-9]*", ENV{DEVTYPE}=="disk", PROGRAM="/usr/libexec/ceph-rbdnamer-pve %k", SYMLINK+="rbd-pve/%c"
+KERNEL=="rbd[0-9]*", ENV{DEVTYPE}=="partition", PROGRAM="/usr/libexec/ceph-rbdnamer-pve %k", SYMLINK+="rbd-pve/%c-part%n"
diff --git a/udev-rbd/Makefile b/udev-rbd/Makefile
new file mode 100644
index 0000000..065933b
--- /dev/null
+++ b/udev-rbd/Makefile
@@ -0,0 +1,21 @@
+PACKAGE=libpve-storage-perl
+
+DESTDIR=
+PREFIX=/usr
+LIBEXECDIR=${PREFIX}/libexec
+LIBDIR=${PREFIX}/lib
+
+all:
+
+.PHONY: install
+install: 50-rbd-pve.rules ceph-rbdnamer-pve
+       install -d ${DESTDIR}${LIBEXECDIR}
+       install -m 0755 ceph-rbdnamer-pve ${DESTDIR}${LIBEXECDIR}
+       install -d ${DESTDIR}${LIBDIR}/udev/rules.d
+       install -m 0644 50-rbd-pve.rules ${DESTDIR}${LIBDIR}/udev/rules.d
+
+.PHONY: clean
+clean:
+
+.PHONY: distclean
+distclean: clean
diff --git a/udev-rbd/ceph-rbdnamer-pve b/udev-rbd/ceph-rbdnamer-pve
new file mode 100755
index 0000000..23dd626
--- /dev/null
+++ b/udev-rbd/ceph-rbdnamer-pve
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+DEV=$1
+NUM=`echo $DEV | sed 's#p.*##g; s#[a-z]##g'`
+POOL=`cat /sys/devices/rbd/$NUM/pool`
+CLUSTER_FSID=`cat /sys/devices/rbd/$NUM/cluster_fsid`
+
+if [ -f /sys/devices/rbd/$NUM/pool_ns ]; then
+    NAMESPACE=`cat /sys/devices/rbd/$NUM/pool_ns`
+else
+    NAMESPACE=""
+fi
+IMAGE=`cat /sys/devices/rbd/$NUM/name`
+SNAP=`cat /sys/devices/rbd/$NUM/current_snap`
+
+echo -n "/$CLUSTER_FSID/$POOL"
+
+if [ -n "$NAMESPACE" ]; then
+    echo -n "/$NAMESPACE"
+fi
+echo -n "/$IMAGE"
+if [ "$SNAP" != "-" ]; then
+    echo -n "@$SNAP"