On Thu, Sep 20, 2012 at 04:20:00PM -0700, Tejun Heo wrote:
> Hello,
>
> On Mon, Sep 10, 2012 at 05:22:14PM -0700, Kent Overstreet wrote:
> > static void req_bio_endio(struct request *rq, struct bio *bio,
> > unsigned int nbytes, int error)
> > {
> > + /*
> > + * XXX: bio_endio() does this. only need this because of the weird
> > + * flush seq thing.
> > + */
> > if (error)
> > clear_bit(BIO_UPTODATE, &bio->bi_flags);
> > else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
> > error = -EIO;
>
> Isn't this also necessary to record errors on partial completions?
Ah yeah, you're right. Meant to delete that comment anyways.
> Other than that, I definitely like this. It would be nice to note
> that the custom partial bio advancing in blk_update_request() is
> replaced with multiple calls to req_bio_endio(). I don't think it has
> any meaningful performance implications. It's just nice to future
> readers of the commit.
The number of calls to req_bio_endio() isn't changing...
blk_update_request() called it for partial completions before. It's just
where the bio itself is updated that's getting shuffled around.
Or did you mean that bio_advance() is getting called on every bio
instead of the custom advancing in blk_update_request() before? That is
different, yeah - it's now always looping over the iovec, not just for
partial completions.
Yeah, I will note that in the commit message, in case Jens sees a
performance regression from it :)
> Also, it would be really nice if you can verify this actually works
> with partial blk_update_request(). sector update bug in the previous
> patch scares me a bit. Implementing some debug hacks in the
> completion path might be the easiest way to verify. A subtle bug here
> could be pretty painful.
Any suggestions on how to trigger partial updates?
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