Commit 3f19cd23 authored Apr 11, 2017 by Jan Kara Committed by Jens Axboe Apr 11, 2017

block: Fix list corruption of blk stats callback list



When CFQ calls wbt_disable_default(), it will call
blk_stat_remove_callback() to stop gathering IO statistics for the
purposes of writeback throttling. Later, when request_queue is
unregistered, wbt_exit() will call blk_stat_remove_callback() again
which will try to delete callback from the list again and possibly cause
list corruption.

Fix the problem by making wbt_disable_default() called wbt_exit() which
is properly guarded against being called multiple times.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent f5c0b091

block/blk-wbt.c

+4 −8

Original line number	Diff line number	Diff line
		@@ -654,18 +654,14 @@ void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on)
		}

		/*
		* Disable wbt, if enabled by default. Only called from CFQ, if we have
		* cgroups enabled
		* Disable wbt, if enabled by default. Only called from CFQ.
		*/
		void wbt_disable_default(struct request_queue *q)
		{
		struct rq_wb *rwb = q->rq_wb;

		if (rwb && rwb->enable_state == WBT_STATE_ON_DEFAULT) {
		blk_stat_remove_callback(q, rwb->cb);
		rwb->win_nsec = rwb->min_lat_nsec = 0;
		wbt_update_limits(rwb);
		}
		if (rwb && rwb->enable_state == WBT_STATE_ON_DEFAULT)
		wbt_exit(q);
		}
		EXPORT_SYMBOL_GPL(wbt_disable_default);