Hello, On Mon, Aug 29, 2016 at 11:33:41PM +0200, Vegard Nossum wrote: > On 08/29/2016 09:55 PM, Tejun Heo wrote: > > I think the right thing to do there is doing blkdev_get() / > > blkdev_put() around func() invocation in iterate_bdevs() rather than > > holding bd_mutex across the callback. Can you please verify whether > > that works? > > Didn't work for me, I kept getting use-after-free in __blkdev_get() on > bdev->bd_invalidated after it calls bdev->bd_disk->fops->open(). I tried > a few related things without much luck. I see. It could be that it's doing blkdev_get() on a dying device. > The only thing that worked for me without holding the mutex across the > call was this: ... > + mutex_lock(&bdev->bd_mutex); > + bdev->bd_openers++; > + bdev->bd_holders++; > + mutex_unlock(&bdev->bd_mutex); > + > + func(bdev, arg); > + > + mutex_lock(&bdev->bd_mutex); > + bdev->bd_openers--; > + bdev->bd_holders--; > + mutex_unlock(&bdev->bd_mutex); And this might not be too far fetched. I think what we want is * Bump bd_openers if there are other users already; otherwise, skip. * blkdev_put() after the callback is finished. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
