commit 2ac217d408470dcecb69b83d9cbf7a254747fa5b
Author: Peter Rajnoha <prajnoha@redhat.com>
Date:   Fri May 3 13:20:07 2013 +0200

    udev: fire pvscan --cache properly on CHANGE event for MD devices
    
    Commit 756bcabbfe297688ba240a880bc2b55265ad33f0 restricted the
    situations at which the LVM autoactivation fires - only on ADD
    event for devices other than DM. However, this caused a problem
    for MD devices...
    
    MD devices are activated in a very similar way as DM devices:
    the MD dev is created on first appeareance of MD array member
    (ADD event) and stays *inactive* until the array is complete.
    Just then the MD dev turns to active state and this is reported
    to userspace by CHANGE event.
    
    Unfortunately, we can't differentiate between the CHANGE event
    coming from udev trigger/WATCH rule and CHANGE event coming from
    the transition to active state - MD would need to add similar logic
    we already use to detect this in DM world. For now, we just have
    to enable pvscan --cache on *all* CHANGE events for MD so the
    autoactivation of the LVM volumes on top of MD works.
    
    A downside of this is that a spurious CHANGE event for MD dev
    can cause the LVM volumes on top of it to be automatically activated.
    However, one should not open/change the device underneath until
    the device above in the stack is removed! So this situation should
    only happen if one opens the MD dev for read-write by mistake
    (and hence firing the CHANGE event because of the WATCH udev rule),
    or if calling udev trigger manually for the MD dev.
    
    (No WHATS_NEW here as this fixes the commit mentioned
    above and which has not been released yet.)
---
 udev/69-dm-lvm-metad.rules.in | 1 +
 1 file changed, 1 insertion(+)

diff --git a/udev/69-dm-lvm-metad.rules.in b/udev/69-dm-lvm-metad.rules.in
index 66c58b3..a0e48a1 100644
--- a/udev/69-dm-lvm-metad.rules.in
+++ b/udev/69-dm-lvm-metad.rules.in
@@ -21,6 +21,7 @@ SUBSYSTEM!="block", GOTO="lvm_end"
 ENV{ID_FS_TYPE}!="LVM2_member|LVM1_member", GOTO="lvm_end"
 
 ACTION=="remove", GOTO="lvm_scan"
+ACTION=="change", KERNEL=="md[0-9]*", GOTO="lvm_scan"
 
 # If the PV is not a dm device, scan only after device addition (ADD event)
 KERNEL!="dm-[0-9]*", ACTION!="add", GOTO="lvm_end"