Re: [dm-devel] [PATCH v2 01/26] block: Convert integrity tobvec_alloc_bs(), and a bugfix

[Kent Overstreet]

On Wed, Sep 12, 2012 at 03:39:18PM -0400, Martin K. Petersen wrote:
> >>>>> "Kent" == Kent Overstreet <koverstreet@xxxxxxxxxx> writes:
> 
> Kent,
> 
> Kent> To fix the bug first, I'd have to reorder struct bio_pair and then
> Kent> just delete two lines of code from bio_integrity_split(). But the
> Kent> reordering is unnecessary with the refactoring.
> 
> Well, a bug is a bug and the fix needs to go into stable. So we will
> need a patch that does not depend on your changes.

Alright, good point.

> I don't have a problem with adding a pointer so clones can point to the
> parent's vector. But embedding the vector into the bip was a feature.
> If you check the git log you'll see that originally I did use separate
> vector allocations.

Looks like that was 7878cba9f0037f5599004b03a1260b32d9050360 - If I
follow your commit message your primary goal was to back the bip vecs by
a per bio set mempool?

I didn't break that (excepting the issue Vivek noted) - but it is true
that my patch adds another allocation (when nr_vecs > BIP_INLINE_VECS,
anyways).

I don't know how big of a deal you think that extra allocation is. If
you're against it, this patch isn't really necessary for the immutable
bvecs I'm working on - just need it if we want integrity bvecs to be
shared like regular bvecs will be.

Something else I noticed is bio_integrity_add_page() doesn't merge bvecs
when possible, like the regular bio_add_page(). If changing it to merge
bvecs wouldn't break anything, then probably most integrity bvecs would
be under BIP_INLINE_VECS.

Thoughts?
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