linux-kernel - Re: [RFC PATCH v1 0/7] Block/XFS: Support alternative mirror device retry

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20181128074544.GA20702@infradead.org>
Date:   Tue, 27 Nov 2018 23:45:44 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     Allison Henderson <allison.henderson@...cle.com>,
        linux-block@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        martin.petersen@...cle.com, shirley.ma@...cle.com,
        bob.liu@...cle.com
Subject: Re: [RFC PATCH v1 0/7] Block/XFS: Support alternative mirror device
 retry

On Wed, Nov 28, 2018 at 04:33:03PM +1100, Dave Chinner wrote:
> 	- how does propagation through stacked layers work?

The only way it works is by each layering driving it.  Thus my
recommendation above bilding on your earlier one to use an index
that is filled by the driver at I/O completion time.

E.g.

	bio_init:		bi_leg = -1

	raid1:			submit bio to lower driver
	raid 1 completion:	set bi_leg to 0 or 1

Now if we want to allow stacking we need to save/restore bi_leg
before submitting to the underlying device.  Which is possible,
but quite a bit of work in the drivers.

> 	- is it generic/abstract enough to be able to work with
> 	  RAID5/6 to trigger verification/recovery from the parity
> 	  information in the stripe?

If we get the non -1 bi_leg for paritity raid this is an inidicator
that parity rebuild needs to happen.  For multi-parity setups we could
also use different levels there.