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

From: Alasdair G Kergon
Date: Thu Aug 27 2009 - 14:11:28 EST

On Thu, Aug 27, 2009 at 12:54:05PM -0400, Jeff Garzik wrote:
> DM has some barrier code... but the above code was pasted from DM's
> make_request function, so I am guessing that DM's barrier stuff is
> incomplete and disabled at present.

That code is from the new request-based multipath implementation in 2.6.31
which doesn't yet.

But bio-based dm does support barriers now. (Just missing some patches to
complete the dm-raid1 support that are still under review IIRC.)

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