On Mon, Nov 01, 2004 at 09:33:33PM -0800, Andrew Morton wrote:
md has the misfortune of working in a way that doesn't fit very well
with some aspects of the blkdev layer.
To create an md array, you open /dev/mdX, and use some ioctls to set
up the array. Thus the block device must exist internally as a block
device before any details about it are available.
Similarly, to shut down an array, you open /dev/mdX and use an ioctl
to shut it down. This it will still be open (though only once) after
it has been shut down.
(as I understand it) I can only safely use blk_cleanup_queue on the
queue after (or during) the last close. Thus I cannot use it while
shutting down an array.
However I need to release the md personality as part of shutting down
the array, so I have to disable the unplug function (which is handled
by the personality).
I could change ->unplug_fn to point to something safe, but there is
still a race with the timer going off at just the wrong time.
hm, OK. So perhaps using /dev/mdX as a control channel for creating and
destroying /dev/mdX was unfortunate design. Ho hum.
would it be unfeasible to create a custom (misc) character device, say
/dev/mdadm and use that to control arrays instead of /dev/md0?
Regards,
L.
--
Luca Berra -- bluca@xxxxxxxxxx
Communication Media & Services S.r.l.
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