+#define AV_FIND BIT(0)
+#define AV_ADD BIT(1)
+#define AV_FIND_OR_ADD (AV_FIND | AV_ADD)
+
+/**
+ * find_or_add_av - internal function to find a volume, add a volume or do
+ * both (find and add if missing).
+ * @ai: attaching information
+ * @vol_id: the requested volume ID
+ * @flags: a combination of the %AV_FIND and %AV_ADD flags describing the
+ * expected operation. If only %AV_ADD is set, -EEXIST is returned
+ * if the volume already exists. If only %AV_FIND is set, NULL is
+ * returned if the volume does not exist. And if both flags are
+ * set, the helper first tries to find an existing volume, and if
+ * it does not exist it creates a new one.
+ * @created: in value used to inform the caller whether it"s a newly created
+ * volume or not.
+ *
+ * This function returns a pointer to a volume description or an ERR_PTR if
+ * the operation failed. It can also return NULL if only %AV_FIND is set and
+ * the volume does not exist.
+ */
+static struct ubi_ainf_volume *find_or_add_av(struct ubi_attach_info *ai,
+ int vol_id, unsigned int flags,
+ bool *created)
+{
+ struct ubi_ainf_volume *av;
+ struct rb_node **p = &ai->volumes.rb_node, *parent = NULL;
+
+ /* Walk the volume RB-tree to look if this volume is already present */
+ while (*p) {
+ parent = *p;
+ av = rb_entry(parent, struct ubi_ainf_volume, rb);
+
+ if (vol_id == av->vol_id) {
+ *created = false;
+
+ if (!(flags & AV_FIND))
+ return ERR_PTR(-EEXIST);
+
+ return av;
+ }
+
+ if (vol_id > av->vol_id)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+
+ if (!(flags & AV_ADD))
+ return NULL;
+
+ /* The volume is absent - add it */
+ av = kzalloc(sizeof(*av), GFP_KERNEL);
+ if (!av)
+ return ERR_PTR(-ENOMEM);
+
+ av->vol_id = vol_id;
+
+ if (vol_id > ai->highest_vol_id)
+ ai->highest_vol_id = vol_id;
+
+ rb_link_node(&av->rb, parent, p);
+ rb_insert_color(&av->rb, &ai->volumes);
+ ai->vols_found += 1;
+ *created = true;
+ dbg_bld("added volume %d", vol_id);
+ return av;
+}
+
+/**
+ * ubi_find_or_add_av - search for a volume in the attaching information and
+ * add one if it does not exist.
+ * @ai: attaching information
+ * @vol_id: the requested volume ID
+ * @created: whether the volume has been created or not
+ *
+ * This function returns a pointer to the new volume description or an
+ * ERR_PTR if the operation failed.
+ */
+static struct ubi_ainf_volume *ubi_find_or_add_av(struct ubi_attach_info *ai,
+ int vol_id, bool *created)
+{
+ return find_or_add_av(ai, vol_id, AV_FIND_OR_ADD, created);
+}
+
+/**
+ * ubi_alloc_aeb - allocate an aeb element
+ * @ai: attaching information
+ * @pnum: physical eraseblock number
+ * @ec: erase counter of the physical eraseblock
+ *
+ * Allocate an aeb object and initialize the pnum and ec information.
+ * vol_id and lnum are set to UBI_UNKNOWN, and the other fields are
+ * initialized to zero.
+ * Note that the element is not added in any list or RB tree.
+ */
+struct ubi_ainf_peb *ubi_alloc_aeb(struct ubi_attach_info *ai, int pnum,
+ int ec)
+{
+ struct ubi_ainf_peb *aeb;
+
+ aeb = kmem_cache_zalloc(ai->aeb_slab_cache, GFP_KERNEL);
+ if (!aeb)
+ return NULL;
+
+ aeb->pnum = pnum;
+ aeb->ec = ec;
+ aeb->vol_id = UBI_UNKNOWN;
+ aeb->lnum = UBI_UNKNOWN;
+
+ return aeb;
+}
+
+/**
+ * ubi_free_aeb - free an aeb element
+ * @ai: attaching information
+ * @aeb: the element to free
+ *
+ * Free an aeb object. The caller must have removed the element from any list
+ * or RB tree.
+ */
+void ubi_free_aeb(struct ubi_attach_info *ai, struct ubi_ainf_peb *aeb)
+{
+ kmem_cache_free(ai->aeb_slab_cache, aeb);
+}