+void nvdimm_clear_from_poison_list(struct nvdimm_bus *nvdimm_bus,
+ phys_addr_t start, unsigned int len)
+{
+ struct list_head *poison_list = &nvdimm_bus->poison_list;
+ u64 clr_end = start + len - 1;
+ struct nd_poison *pl, *next;
+
+ nvdimm_bus_lock(&nvdimm_bus->dev);
+ WARN_ON_ONCE(list_empty(poison_list));
+
+ /*
+ * [start, clr_end] is the poison interval being cleared.
+ * [pl->start, pl_end] is the poison_list entry we're comparing
+ * the above interval against. The poison list entry may need
+ * to be modified (update either start or length), deleted, or
+ * split into two based on the overlap characteristics
+ */
+
+ list_for_each_entry_safe(pl, next, poison_list, list) {
+ u64 pl_end = pl->start + pl->length - 1;
+
+ /* Skip intervals with no intersection */
+ if (pl_end < start)
+ continue;
+ if (pl->start > clr_end)
+ continue;
+ /* Delete completely overlapped poison entries */
+ if ((pl->start >= start) && (pl_end <= clr_end)) {
+ list_del(&pl->list);
+ kfree(pl);
+ continue;
+ }
+ /* Adjust start point of partially cleared entries */
+ if ((start <= pl->start) && (clr_end > pl->start)) {
+ pl->length -= clr_end - pl->start + 1;
+ pl->start = clr_end + 1;
+ continue;
+ }
+ /* Adjust pl->length for partial clearing at the tail end */
+ if ((pl->start < start) && (pl_end <= clr_end)) {
+ /* pl->start remains the same */
+ pl->length = start - pl->start;
+ continue;
+ }
+ /*
+ * If clearing in the middle of an entry, we split it into
+ * two by modifying the current entry to represent one half of
+ * the split, and adding a new entry for the second half.
+ */
+ if ((pl->start < start) && (pl_end > clr_end)) {
+ u64 new_start = clr_end + 1;
+ u64 new_len = pl_end - new_start + 1;
+
+ /* Add new entry covering the right half */
+ add_poison(nvdimm_bus, new_start, new_len, GFP_NOIO);
+ /* Adjust this entry to cover the left half */
+ pl->length = start - pl->start;
+ continue;
+ }
+ }
+ nvdimm_bus_unlock(&nvdimm_bus->dev);
+}
+EXPORT_SYMBOL_GPL(nvdimm_clear_from_poison_list);
+