65d56083b4
In all but one case the spa_namespace_lock is taken before the bdev->bd_mutex lock. But Linux __blkdev_get() function calls fops->open() with the bdev->bd_mutex lock held and we must somehow still safely acquire the spa_namespace_lock. To avoid a potential lock inversion deadlock we preemptively try to take the spa_namespace_lock(). Normally it will not be contended and this is safe because spa_open_common() handles the case where the caller already holds the spa_namespace_lock. When it is contended we risk a lock inversion if we were to block waiting for the lock. Luckily, the __blkdev_get() function allows us to return -ERESTARTSYS which will result in bdev->bd_mutex being dropped, reacquired, and fops->open() being called again. This process can be repeated safely until both locks are acquired. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Jorgen Lundman <lundman@lundman.net> Closes #612 |
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| Makefile.in | ||