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Commit 6927d920 authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

xen/blkback: Fix two races in the handling of barrier requests. 



There are two windows of opportunity to cause a race when
processing a barrier request. This patch fixes this.

Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent dda18528

drivers/block/xen-blkback/blkback.c

+5 −5
Original line number Diff line number Diff line
@@ -456,15 +456,15 @@ static void xen_blk_drain_io(struct xen_blkif *blkif) 
{

	atomic_set(&blkif->drain, 1);

	do {

		/* The initial value is one, and one refcnt taken at the

		 * start of the xen_blkif_schedule thread. */

		if (atomic_read(&blkif->refcnt) <= 2)

			break;

		wait_for_completion_interruptible_timeout(

				&blkif->drain_complete, HZ);



		if (!atomic_read(&blkif->drain))

			break;

		/* The initial value is one, and one refcnt taken at the

		 * start of the xen_blkif_schedule thread. */

		if (atomic_read(&blkif->refcnt) <= 2)

			break;

	} while (!kthread_should_stop());

	atomic_set(&blkif->drain, 0);

}
@@ -502,11 +502,11 @@ static void __end_block_io_op(struct pending_req *pending_req, int error) 
		make_response(pending_req->blkif, pending_req->id,

			      pending_req->operation, pending_req->status);

		xen_blkif_put(pending_req->blkif);

		free_req(pending_req);

		if (atomic_read(&pending_req->blkif->refcnt) <= 2) {

			if (atomic_read(&pending_req->blkif->drain))

				complete(&pending_req->blkif->drain_complete);

		}

		free_req(pending_req);

	}

}