Re: status of bugzilla #99171 - mdraid broken for O_DIRECT

[Roland <devzero@web.de>]

good evening,

are you really sure fs-fsdevel is the right place to report this?

i just was able to reproduce the mdraid breakage without any filesystem 
involved,  just put lvm on top of mdraid and passed lvm logical volumes 
from that to the debian vm, and then ran "break-raid-odirect /dev/sdb" 
inside vm.

meanwhile,  btrfs issue with O_DIRECT seems to be fixed,  at least from 
my quick tests, reported at 
https://bugzilla.kernel.org/show_bug.cgi?id=99171#c35 . btrfs fix is 
also linked there.

regards
Roland

Am 16.10.25 um 08:02 schrieb Hannes Reinecke:
> On 10/16/25 01:09, Roland wrote:
> [ .. ]>
>> thank you for your feedback.
>>
>> i see, things are complicated and O_DIRECT is a very special beast....
>>
>> meanwhile, i gave bcachefs a try today , because it looks interesting .
>>
>> like zfs, it does not seem to be affected by this problem, at least 
>> from my first tests reported at 
>> https://bugzilla.kernel.org/show_bug.cgi? id=99171#c26 (i hope this 
>> is a valid test for consistency)
>>
>> so we have at least a second "software raid" technology besides zfs, 
>> which does NOT suffer from the "by design" O_DIRECT breakage.
>>
>> that's at least surprising me, as bcachefs is far from production 
>> ready,  and i wonder why it just seems to work at this early stage of 
>> development.
>>
> Hmm. True.
>
> I would suggest bringing up this topic on linux-fsdevel; there is
> always a chance that there is a bug somewhere.
> At least some explanation would be warranted why bcachefs does not
> suffer from this issue.
>
> Cheers,
>
> Hannes