Hi Mike,
On 05/25/2010 08:46 AM +0900, Mike Snitzer wrote:
> Index: linux-2.6/drivers/md/dm-ioctl.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-ioctl.c
> +++ linux-2.6/drivers/md/dm-ioctl.c
> @@ -1201,6 +1203,15 @@ static int table_load(struct dm_ioctl *p
> goto out;
> }
>
> + /* setup md->queue to reflect md's and table's type (may block) */
> + r = dm_setup_md_queue(md);
> + if (r) {
> + DMWARN("unable to setup device queue for this table.");
> + dm_table_destroy(t);
> + dm_unlock_md_type(md);
> + goto out;
> + }
> +
dm_setup_md_queue() should be put just after dm_set_md_type() of patch#1.
Then, you can make sure that dm_setup_md_queue() is called only once
and dm_setup_md_queue() should be much simpler.
> +/*
> + * Fully initialize a request-based queue (->elevator, ->request_fn, etc).
> + */
> +static int dm_init_request_based_queue(struct mapped_device *md)
> +{
> + struct request_queue *q = NULL;
> +
> + /* Avoid re-initializing the queue if already fully initialized */
> + if (!md->queue->elevator) {
> + /* Fully initialize the queue */
> + q = blk_init_allocated_queue(md->queue, dm_request_fn, NULL);
> + if (!q)
> + return 0;
When blk_init_allocated_queue() fails, the block-layer seems not to
guarantee that the queue is still available.
You should create appropriate block-layer interfaces and/or take proper
recovery action here.
However, if the failure is not realistic, rather than complicating this
patch, you can just put a big comment and WARN_ON() for now, and fix it
in a separate patch-set.
> +static void dm_clear_request_based_queue(struct mapped_device *md)
> +{
> + if (dm_bio_based_md_queue(md))
> + return; /* queue already bio-based */
> +
> + /* Unregister elevator from sysfs and clear ->request_fn */
> + elv_unregister_queue(md->queue);
> + md->queue->request_fn = NULL;
> +}
> +
> +/*
> + * Setup the DM device's queue based on md's type
> + */
> +int dm_setup_md_queue(struct mapped_device *md)
> +{
> + BUG_ON(!mutex_is_locked(&md->type_lock));
> + BUG_ON(dm_unknown_md_type(md));
> +
> + if (dm_request_based_md_type(md)) {
> + if (!dm_init_request_based_queue(md)) {
> + DMWARN("Cannot initialize queue for Request-based dm");
> + return -EINVAL;
> + }
> + } else if (dm_bio_based_md_type(md))
> + dm_clear_request_based_queue(md);
> +
> + return 0;
> +}
These unregister/clear works shouldn't be needed if dm_setup_md_queue()
is called only once as I mentioned above.
Thanks,
Kiyoshi Ueda
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