Re: Question about REQ_FLUSH and bios with data

From: scameron
Date: Fri Aug 09 2013 - 15:11:46 EST

On Fri, Aug 09, 2013 at 02:09:34PM -0500, scameron@xxxxxxxxxxxxxxxxxx wrote:
> So, I'm working on a block driver using the make_request_fn
> interface, and have to handle a bio that comes in with
> (bi_rw & REQ_FLUSH) set AND data to transfer.
> According to Documentation/block/writeback_cache_control.txt:
> The REQ_FLUSH flag can be OR ed into the r/w flags of a
> bio submitted from the filesystem and will make sure the
> volatile cache of the storage device has been flushed
> before the actual I/O operation is started.
> So I've written code that handles that case, along with the
> various error cases I might encounter, I think, which leads
> to my question:
> How do I get such a bio with a data transfer AND the REQ_FLUSH bit
> set to come into the driver? Just wondering how to test this case.
> Thanks,
> (I cc'ed Tejun Heo just because his name is in block/blk-flush.c)
> -- steve

Oops, you'd think I'd know Jens's email address by now.

-- steve

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