Re: [PATCH 02/11] block: Fix race of bdev open with gendisk shutdown

Hello,

On Mon, Mar 06, 2017 at 05:33:55PM +0100, Jan Kara wrote:

+	disk->flags &= ~GENHD_FL_UP;
+	/*
+	 * Make sure __blkdev_open() sees the disk is going away before
+	 * starting to unhash bdev inodes.
+	 */
+	smp_wmb();

But which rmb is this paired with?  Without paring memory barriers
don't do anything.  Given that this isn't a super hot path, I think
it'd be far better to stick to a simpler synchronization mechanism.

Thanks.

-- 
tejun