On Fri, 10 Mar 2017, Mike Snitzer wrote:
> On Fri, Mar 10 2017 at 7:34am -0500,
> Lars Ellenberg <lars.ellenberg@xxxxxxxxxx> wrote:
>
> > > --- a/block/blk-core.c
> > > +++ b/block/blk-core.c
> > > @@ -1975,7 +1975,14 @@ generic_make_request_checks(struct bio *bio)
> > > */
> > > blk_qc_t generic_make_request(struct bio *bio)
> > > {
> > > - struct bio_list bio_list_on_stack;
> > > + /*
> > > + * bio_list_on_stack[0] contains bios submitted by the current
> > > + * make_request_fn.
> > > + * bio_list_on_stack[1] contains bios that were submitted before
> > > + * the current make_request_fn, but that haven't been processed
> > > + * yet.
> > > + */
> > > + struct bio_list bio_list_on_stack[2];
> > > blk_qc_t ret = BLK_QC_T_NONE;
> >
> > May I suggest that, if you intend to assign something that is not a
> > plain &(struct bio_list), but a &(struct bio_list[2]),
> > you change the task member so it is renamed (current->bio_list vs
> > current->bio_lists, plural, is what I did last year).
> > Or you will break external modules, silently, and horribly (or,
> > rather, they won't notice, but break the kernel).
> > Examples of such modules would be DRBD, ZFS, quite possibly others.
>
> drbd is upstream -- so what is the problem? (if you are having to
> distribute drbd independent of the upstream drbd then why is drbd
> upstream?)
>
> As for ZFS, worrying about ZFS kABI breakage is the last thing we should
> be doing.
It's better to make external modules not compile than to silently
introduce bugs in them. So yes, I would rename that.
Mikulas
> So Nack from me on this defensive make-work for external modules.
>
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