On Sun, Oct 25, 2015 at 04:18:05PM -0700, Hugh Dickins wrote: > On Thu, 15 Oct 2015, Andrea Arcangeli wrote: > > > get_mergeable_page() can only return NULL (in case of errors) or the > > pinned mergeable page. It can't return an error different than > > NULL. This makes it more readable and less confusion in addition to > > optimizing the check. > > > > Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> > > I share your sentiment, prefer to avoid an unnecessary IS_ERR_OR_NULL. > And you may be right that it's unnecessary; but that's far from clear > to me, and you haven't changed the IS_ERR_OR_NULL after follow_page() > in get_mergeable_page() where it originates, so I wonder if you just > got confused on this. > > Even if you have established that there's currently no way that > follow_page(vma, addr, FOLL_GET) could return an -errno on a vma > validated by find_mergeable_vma(), I think we'd still be better off > to allow for some future -errno there; but I'd be happy for you to > keep the change below, but also adjust get_mergeable_page() to > convert an -errno immediately to NULL after follow_page(). > > So, I think this is gently Nacked in its present form, > but a replacement eagerly Acked. The "out:" label is followed by page = NULL, so if follow_page returns an error, get_mergeable_page still cannot return an error. If this wasn't the case, get_mergeable_page would return an uninitialized pointer if find_mergeable_vma would return NULL. I guess the IS_ERR_OR_NULL that I removed, was the direct result of overlooking the location of the "out:". If there was a return after the "out:" the readability would have been improved, but I haven't touched the code around the "out:". That's the way it was before. Now I'll add a return in this same patch after the "out:" before resubmitting without 1/6. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>