Re: [BUG] raid1: barrier retry does not work correctly with write-behind

[Paul Clements <paul.clements@steeleye.com>]

Paul Clements wrote:

> I think bio_clone gives us that already. I may have missed something but 
> I think we have everything we need:
> 
> When a bio comes into raid1's make_request we bio_clone for each drive 
> and attach those to r1_bio->bios. We also have behind_pages, which 
> contains the pages. I think maybe instead of cloning r1_bio->master_bio, 
> we can just clone r1_bio->bios[i]. Does that make sense?

Never mind, of course that won't work...it's basically the same as using 
the failed bio.

Yes, so we need a copy of the bvec too. Would it be easier, or less 
risky just to create an entire "spare" bio, cloned from the master bio 
during make_request as the other r1_bio->bios[] are, and then use that 
if we need it? Maybe too much overhead, but it should guarantee that 
none of the fields have been monkey-ed with by an underlying disk. May 
be easier than trying to allocate and construct bvecs by hand?

--
Paul