Re: MD/DM and barriers (was Re: [patch] ext2/3: documentconditions when reliable operation is possible)

From: Pavel Machek
Date: Tue Sep 01 2009 - 16:29:04 EST

On Thu 2009-08-27 12:54:05, Jeff Garzik wrote:
> On 08/27/2009 09:10 AM, Ric Wheeler wrote:
>> One thing that does need fixing for some MD configurations is to stress
>> again that we need to make sure that barrier operations are properly
>> supported or users will need to disable the write cache on devices with
>> volatile write caches.
> Agreed; chime in on Christoph's linux-vfs thread if people have input.
> I quickly glanced at MD and DM. Currently, upstream, we see a lot of
> if (unlikely(bio_barrier(bio))) {
> bio_endio(bio, -EOPNOTSUPP);
> return 0;
> }
> in DM and MD make_request functions.
> Only md/raid1 supports barriers at present, it seems. None of the other
> MD drivers support barriers.

Not even md/raid0? Ouch :-(.

(cesky, pictures)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at