[stgt] stgt basic kernel interface questions

[FUJITA Tomonori]

On Mon, 28 Jun 2010 12:46:53 -0700
Joe Eykholt <jeykholt at cisco.com> wrote:

> I'm struggling to understand a few things.  Is there an
> architecture manual I can look at or a good e-mail thread
> that's discussed the overall design?

Sorry, no doc about the design. Please feel free to ask anything.


> My specific question at this point deals with how the kernel
> knows the status of a WRITE command.
> 
> My guess is that for WRITEs, the user-kernel interactions are:
> 
> 1. TGT_KEVENT_CMD_REQ - kernel presents command to tgtd.
> 2. TGT_UEVENT_CMD_RSP - tgtd gives buffer address to kernel
> 	- send XFER_RDY
> 	- kernel fills in buffer
> 3. TGT_KEVENT_CMD_DONE - kernel indicates write data in buffer
> 	
> .... then, what tells the kernel it's safe to send the response?
> If we do it between 2 and 3, then the data isn't really safe yet.
> Is there another TGT_UEVENT_CMD_RSP?

You mean that the data might not be committed to disk persistently?
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