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SubjectRe: [PATCH 2/2] dm: stay in blk_queue_bypass until queue becomes initialized
On Mon, Oct 29, 2012 at 05:45:15PM +0100, Peter Zijlstra wrote:
> On Mon, 2012-10-29 at 12:38 -0400, Vivek Goyal wrote:
> > Ok, so the question is what's wrong with calling synchronize_rcu() inside
> > a mutex with CONFIG_PREEMPT=y. I don't know. Ccing paul mckenney and
> > peterz.
>
> int blkcg_activate_policy(struct request_queue *q,
>
> {
>
> ...
>
> preloaded = !radix_tree_preload(GFP_KERNEL);
>
> blk_queue_bypass_start(q);
>
>
>
>
> where:
>
> int radix_tree_preload(gfp_t gfp_mask)
> {
> struct radix_tree_preload *rtp;
> struct radix_tree_node *node;
> int ret = -ENOMEM;
>
> preempt_disable();
>
>
> Seems obvious why it explodes..

Oh right. Thanks Peter. So just calling blk_queue_bypass_start() before
radix_tree_preload() should fix it. Junichi, can you please give it
a try.

Thanks
Vivek


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