Re: [PATCH] EVMS core 1/4: evms.c

[Alexander Viro]

On Fri, 4 Oct 2002, Christoph Hellwig wrote:

> I don't think this is_busy check is a good idea.  Anyways
> it should be better something like this (then in block_dev.c):
> 
> int bd_busy(struct block_device *bdev)
> {
> 	int res = 0;
> 	spin_lock(&bdev_lock);
> 	if (bdev->bd_holder)
> 		res = -EBUSY;
> 	spin_unlock(&bdev_lock);
> 	return res;
> }

It's completely useless - any code that actually relies on its value is
racy, since there's nothing to prevent bd_claim() from being called
just as we drop bdev_lock.

The same applies to original version - if you want to protect some area,
use bd_claim() and don't release it until you are out of critical area,
damnit.