[stgt] stgt basic kernel interface questions

[FUJITA Tomonori]

On Thu, 08 Jul 2010 22:48:13 -0700
Joe Eykholt <jeykholt at cisco.com> wrote:

> > When scsi_tgt_cmd_done calls scsi_unmap_user_pages (via queue_work),
> > we start to commit dirty pages to disk; __bio_unmap_user set pages
> > dirty. When the dirty bit of all the pages is cleared, the data is
> > committed safely. LLDs could check it, I think. If the write cache of
> > backing store is enabled, we more tricks though.
> 
> Would that work for all backing store alternatives or just the
> default of writing to a file via mmap?

Tgt kernel drivers can support only I/O via mmap. Otherwise, we need
to copy data between user and kernel space.

We could add an explicit message but we should try hard to avoid it. I
really want to investigate this before adding another message.
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