Messages in this thread | | | Date | Tue, 6 Aug 2019 00:32:02 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH v2] iommu: revisit iommu_insert_resv_region() implementation |
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A couple nitpicks below:
On Thu, Aug 01, 2019 at 05:59:46PM +0200, Eric Auger wrote: > - * The new element is sorted by address with respect to the other > - * regions of the same type. In case it overlaps with another > - * region of the same type, regions are merged. In case it > - * overlaps with another region of different type, regions are > - * not merged. > + * Elements are sorted by start address and overlapping segments > + * of the same type are merged. > */ > +int iommu_insert_resv_region(struct iommu_resv_region *new, > + struct list_head *regions) > { > + struct iommu_resv_region *iter, *tmp, *nr, *top; > + struct list_head stack; > + bool added = false; > > + INIT_LIST_HEAD(&stack);
Nit: you could just use
LIST_HEAD(&stack);
to declare and initialize the variable in a single line.
> + nr = iommu_alloc_resv_region(new->start, new->length, > + new->prot, new->type); > + if (!nr) > return -ENOMEM; > > + /* First add the new elt based on start address sorting */
/elt/element/ ?
> + list_for_each_entry(iter, regions, list) { > + if (nr->start < iter->start) { > + list_add_tail(&nr->list, &iter->list); > + added = true; > + break; > + } else if (nr->start == iter->start && nr->type <= iter->type) { > + list_add_tail(&nr->list, &iter->list); > + added = true; > + break; > + }
Nit: no need for an else after a a break. But then again both branches look identical, so why don't you just merge them:
if (nr->start < iter->start || (nr->start == iter->start && nr->type <= iter->type)) { list_add_tail(&nr->list, &iter->list); added = true; break;
}
> + if (!added) > + list_add_tail(&nr->list, regions);
Probably down to preference, but I'd just use a goto to jump past the list_add and save the added variable.
> + /* Merge overlapping segments of type nr->type, if any */ > + list_for_each_entry_safe(iter, tmp, regions, list) { > + phys_addr_t top_end, iter_end = iter->start + iter->length - 1; > + bool found = false; > + > + /* no merge needed on elements of different types than @nr */ > + if (iter->type != nr->type) { > + list_move_tail(&iter->list, &stack); > + continue; > + } > + > + /* look for the last stack element of same type as @iter */ > + list_for_each_entry_reverse(top, &stack, list) > + if (top->type == iter->type) { > + found = true; > + break; > + } > + if (!found) {
Same here.
> + list_move_tail(&iter->list, &stack); > + continue; > + } > + > + top_end = top->start + top->length - 1; > + > + if (iter->start > top_end + 1) { > + list_move_tail(&iter->list, &stack); > + } else { > + top->length = max(top_end, iter_end) - top->start + 1; > + list_del(&iter->list); > + kfree(iter); > + }
I wonder if the body of the outer list_for_each_entry_safe loop would be a bit nicer in a helper, but again that is probably just down to personal preference.
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