Messages in this thread | | | Date | Thu, 26 Mar 2009 16:46:11 +0100 | From | Jens Axboe <> | Subject | Re: Linux 2.6.29 |
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On Thu, Mar 26 2009, Hugh Dickins wrote: > On Thu, 26 Mar 2009, Jens Axboe wrote: > > On Wed, Mar 25 2009, Hugh Dickins wrote: > > > > > > Tangential question, but am I right in thinking that BIO_RW_BARRIER > > > similarly bars across all partitions, whereas its WRITE_BARRIER and > > > DISCARD_BARRIER users would actually prefer it to apply to just one? > > > > All the barriers refer to just that range which the barrier itself > > references. > > Ah, thank you: then I had a fundamental misunderstanding of them, > and need to go away and work that out some more. > > Though I didn't read it before asking, doesn't the I/O Barriers section > of Documentation/block/biodoc.txt give a very different impression?
I'm sensing a miscommunication here... The ordering constraint is across devices, at least that is how it is implemented. For file system barriers (like BIO_RW_BARRIER), it could be per-partition instead. Doing so would involve some changes at the block layer side, not necessarily trivial. So I think you were asking about ordering, I was answering about the write guarantee :-)
-- Jens Axboe
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