The watch option to udev tells udev to watch our mdadm device file for
close events and on a close it rechecks the device. This means that if,
for example, we use mdadm to --grow the array from a 4 disk to 5 disk
array, when mdadm closes the array, udev will re-read the superblock and
update its internal database with the new information. This can also be
used to cause udev to create new device special files if, for example, a
partitioning program is used to modify the partition table on the actual
md device and that program does not call the syscall to reread the
partition table.
Signed-off-by: Doug Ledford <dledford@redhat.com>
- split the rules for handling components of array to be clearly
separate from rules for handling the arrays themselves.
- add call to "-If" when removing a device
- uncomment the --incremental call when adding a device.
Signed-off-by: NeilBrown <neilb@suse.de>
One should use
/sbin/blkid -o udev -p ...
(from util-linux >> 2.16) instead of
vol_id --export ...
Author: Marco d'Itri <md@linux.it>
Bug-Debian: http://bugs.debian.org/541884
Reviewed-by: martin f. krafft <madduck@debian.org>
Signed-off-by: NeilBrown <neilb@suse.de>
sysfs directories for partitions do not have md/* files, but
should not for that reason be ignored.
Thanks to Michal Soltys for original fix.
Signed-off-by: Michal Soltys <soltys@ziu.info>
Signed-off-by: NeilBrown <neilb@suse.de>
I'm not attaching a patch for this because it's so simple. Long story
short, watching both add and change events in udev rules is bad for md
devices. Specifically, the kernel will generate a change event on
things like array stop, and on things like fdisk close. In the case
of array stop, it can result in the array being assembled again
immediately. In the case of fdisk close, the situation is worse.
Let's say you stop all the md devices on some block device in order to
repartition. You run fdisk, change the partition table, then issue a
write of the table. The write of the table triggers the change event
*before* the kernel updates the partition table in memory for the
block device, causing udev to rerun the incremental rules on the old
partition table and restart all the arrays you just stopped with the
old partition table layout, at which point the kernel is unable to
reread the partition table. So, once you've enable incremental
assembly, it becomes apparent that what we really want is to only
start devices on add, not on add|change.
--
Doug Ledford <dledford@redhat.com>
Doug Ledford
NeilBrown
Marco d'Itri