[stgt] stgt basic kernel interface questions

[FUJITA Tomonori]

On Mon, 05 Jul 2010 12:08:48 -0700
Joe Eykholt <jeykholt at cisco.com> wrote:

> Even if tgtd has read the pages and the LLD could tell,
> it wouldn't know they've made it safely to backing store.

I'm not sure what you mean. tgtd doesn't write data to disk.

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.
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