From: Jeff Mahoney Subject: udev: use device mapper target name for btrfs device ready References: bnc#888215 When udev gets a change event for a block device, it calls the builtin btrfs helper to scan it for a btrfs file system. If the file system was mounted using a device mapper node, mount(8) will have looked up the device mapper table and used the /dev/mapper/ node for mount. If something like partprobe runs, and then causes change events to be handled, the btrfs ready event is handled using /dev/dm-N instead of the device mapper named node. Btrfs caches the last name passed to the scanning ioctl and uses that to report the device name for things like /proc/mounts. So, after running partprobe we go from: /dev/mapper/test-test on /mnt type btrfs (rw,relatime,space_cache) ... to ... /dev/dm-0 on /mnt type btrfs (rw,relatime,space_cache) This doesn't apply only to LVM device, but multipath as well. If the device is a DM device, udev will have already cached the table name from sysfs and we can use that to pass /dev/mapper/ to the builtin so that the correct name is used. Signed-off-by: Jeff Mahoney --- rules/64-btrfs.rules | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/rules/64-btrfs.rules +++ b/rules/64-btrfs.rules @@ -6,7 +6,8 @@ ENV{ID_FS_TYPE}!="btrfs", GOTO="btrfs_en ENV{SYSTEMD_READY}=="0", GOTO="btrfs_end" # let the kernel know about this btrfs filesystem, and check if it is complete -IMPORT{builtin}="btrfs ready $devnode" +ENV{DM_NAME}=="", IMPORT{builtin}="btrfs ready $devnode" +ENV{DM_NAME}=="?*", IMPORT{builtin}="btrfs ready /dev/mapper/$env{DM_NAME}" # mark the device as not ready to be used by the system ENV{ID_BTRFS_READY}=="0", ENV{SYSTEMD_READY}="0"