Hello,

On Wed, Aug 08, 2012 at 05:21:54PM -0700, Kent Overstreet wrote:

quoted

What's wrong with good ol' NULL?

If it's NULL, we can't distinguish between bios where that field wasn't
set (i.e. bios that were statically allocated somewhere) from bios that
were allocated by bio_kmalloc().

It's just there to make debugging easier - if bi_cnt goes to 0 on a bio
where it shouldn't we'll catch it at the BUG_ON() in bio_free() instead
of kfreeing a bad pointer.

I fail to see how that improves anything.  slab will complain clearly
if it gets passed in a pointer to static area.  The benefit is
imaginery.  If there's no bioset, it's NULL.  Let's please keep things
usual.

Thanks.

-- 
tejun