md: Allow md devices to be created by name.

Using sequential numbers to identify md devices is somewhat artificial.
Using names can be a lot more user-friendly.

Also, creating md devices by opening the device special file is a bit
awkward.

So this patch provides a new option for creating and naming devices.

Writing a name such as "md_home" to
    /sys/modules/md_mod/parameters/new_array
will cause an array with that name to be created.  It will appear in
/sys/block/ /proc/partitions and /proc/mdstat as 'md_home'.
It will have an arbitrary minor number allocated.

md devices that a created by an open are destroyed on the last
close when the device is inactive.
For named md devices, they will not be destroyed until the array
is explicitly stopped, either with the STOP_ARRAY ioctl or by
writing 'clear' to /sys/block/md_XXXX/md/array_state.

The name of the array must start 'md_' to avoid conflict with
other devices.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index e3d17c7f954e..dac4217194b8 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -139,6 +139,7 @@ struct mddev_s
         struct kobject                  kobj;
         int                             hold_active;
 #define UNTIL_IOCTL     1
+#define UNTIL_STOP      2
 
         /* Superblock information */
         int                             major_version,