Messages in this thread | | | Subject | Re: [PATCH 1/7] Make DISCARD_BARRIER and DISCARD_NOBARRIER writes instead of reads | From | David Woodhouse <> | Date | Thu, 03 Sep 2009 18:52:20 +0100 |
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On Sat, 2009-08-29 at 19:03 -0400, Christoph Hellwig wrote: > > The commands are conceptually writes, and in the case of IDE and SCSI > commands actually are writes. They were only reads because we thought > that would interact better with the elevators. Now the elevators know > about discard requests, that advantage no longer exists.
Can you drop the final sentence of that? It isn't true, and I never said it.
s/. Now.*/, but that isn't necessary, and making them writes makes it easier for the low-level IDE and SCSI code to cope with the fact that the command has to be sent with a payload./
The elevators _still_ don't know about discards, and will still let reads and writes (and discards, which are just a special case of writes) to the same sector all cross each other on the queue unless there's some external factor to prevent it.
-- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation
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