Re: [dm-devel] [PATCH v2 22/26] block: Add bio_alloc_pages()

[Kent Overstreet <koverstreet google com>]

On Thu, Sep 20, 2012 at 05:47:11PM -0700, Tejun Heo wrote:
> On Mon, Sep 10, 2012 at 05:22:33PM -0700, Kent Overstreet wrote:
> > +	bio_for_each_segment_all(bv, bio, i) {
> > +		bv->bv_page = alloc_page(gfp_mask);
> > +		if (!bv->bv_page) {
> > +			while (bv-- != bio->bi_io_vec)
> > +				__free_page(bv->bv_page);
> 
> I don't know.  I feel stupid.  I think it's because the loop variable
> changes between loop condition test and actual body of loop.  How
> about the following?  It is pointing to the member of the same array
> so I think it's not even violating pointer comparison rules.
> 
> 	while (--bv >= bio->bi_io_vec)
> 		__free_page(bv->bv_page);

I can't remember why I did it that way, but I think I like yours better
- I'll change it.