LU-8998 llapi: add LLAPI_LAYOUT_COMP_USE_PREV

[fs/lustre-release.git] / lustre / utils / liblustreapi_layout.c

diff --git a/lustre/utils/liblustreapi_layout.c b/lustre/utils/liblustreapi_layout.c
index af54943..15627ea 100644 (file)
--- a/lustre/utils/liblustreapi_layout.c
+++ b/lustre/utils/liblustreapi_layout.c
@@ -1820,13 +1820,15 @@ int llapi_layout_comp_use_id(struct llapi_layout *layout, uint32_t comp_id)
  * \param[in] pos      the position to be moved, it can be:
  *                     LLAPI_LAYOUT_COMP_USE_FIRST: use first component
  *                     LLAPI_LAYOUT_COMP_USE_LAST: use last component
- *                     LLAPI_LAYOUT_COMP_USE_NEXT: use next component
+ *                     LLAPI_LAYOUT_COMP_USE_NEXT: use component after current
+ *                     LLAPI_LAYOUT_COMP_USE_PREV: use component before current
  *
  * \retval     =0 : moved successfully
- * \retval     =1 : at last component with NEXT
+ * \retval     =1 : at last component with NEXT, at first component with PREV
  * \retval     <0 if error occurs
  */
-int llapi_layout_comp_use(struct llapi_layout *layout, uint32_t pos)
+int llapi_layout_comp_use(struct llapi_layout *layout,
+                         enum llapi_layout_comp_use pos)
 {
        struct llapi_layout_comp *comp, *head, *tail;
 
@@ -1839,21 +1841,32 @@ int llapi_layout_comp_use(struct llapi_layout *layout, uint32_t pos)
                return -1;
        }
 
-       head = list_entry(layout->llot_comp_list.next, typeof(*head),
-                         llc_list);
-       tail = list_entry(layout->llot_comp_list.prev, typeof(*tail),
-                         llc_list);
-
-       if (pos == LLAPI_LAYOUT_COMP_USE_NEXT) {
-               if (comp == tail)
+       head = list_entry(layout->llot_comp_list.next, typeof(*head), llc_list);
+       tail = list_entry(layout->llot_comp_list.prev, typeof(*tail), llc_list);
+       switch (pos) {
+       case LLAPI_LAYOUT_COMP_USE_FIRST:
+               layout->llot_cur_comp = head;
+               break;
+       case LLAPI_LAYOUT_COMP_USE_NEXT:
+               if (comp == tail) {
+                       errno = ENOENT;
                        return 1;
+               }
                layout->llot_cur_comp = list_entry(comp->llc_list.next,
                                                   typeof(*comp), llc_list);
-       } else if (pos == LLAPI_LAYOUT_COMP_USE_FIRST) {
-               layout->llot_cur_comp = head;
-       } else if (pos == LLAPI_LAYOUT_COMP_USE_LAST) {
+               break;
+       case LLAPI_LAYOUT_COMP_USE_LAST:
                layout->llot_cur_comp = tail;
-       } else {
+               break;
+       case LLAPI_LAYOUT_COMP_USE_PREV:
+               if (comp == head) {
+                       errno = ENOENT;
+                       return 1;
+               }
+               layout->llot_cur_comp = list_entry(comp->llc_list.prev,
+                                                  typeof(*comp), llc_list);
+               break;
+       default:
                errno = EINVAL;
                return -1;
        }