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xen-blkfront: fix a deadlock while handling discard response 

When we get -EOPNOTSUPP response for a discard request, we will clear
the discard flag on the request queue so we won't attempt to send discard
requests to backend again, and this should be protected under rq->queue_lock.
However, when we setup the request queue, we pass blkif_io_lock to
blk_init_queue so rq->queue_lock is blkif_io_lock indeed, and this lock
is already taken when we are in blkif_interrpt, so remove the
spin_lock/spin_unlock when we clear the discard flag or we will end up
with deadlock here

Signed-off-by: Li Dongyang <lidongyang@novell.com>
[v1: Updated description a bit and removed comment from source]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Li Dongyang 2011-09-14 14:02:40 +08:00 committed by Konrad Rzeszutek Wilk
parent ed30bf317c
commit 69ef68cef9
1 changed files with 0 additions and 2 deletions
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2
drivers/block/xen-blkfront.c
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@ -747,9 +747,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
info->gd->disk_name);
error = -EOPNOTSUPP;
info->feature_discard = 0;
spin_lock(rq->queue_lock);
queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
spin_unlock(rq->queue_lock);
}
__blk_end_request_all(req, error);
break;