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-rw-r--r--fs/xfs/xfs_trans_ail.c67
1 files changed, 29 insertions, 38 deletions
diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 43233e92f0f6..c15aa29fa169 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -299,7 +299,7 @@ xfs_trans_ail_cursor_last(
* Splice the log item list into the AIL at the given LSN. We splice to the
* tail of the given LSN to maintain insert order for push traversals. The
* cursor is optional, allowing repeated updates to the same LSN to avoid
- * repeated traversals.
+ * repeated traversals. This should not be called with an empty list.
*/
static void
xfs_ail_splice(
@@ -308,50 +308,39 @@ xfs_ail_splice(
struct list_head *list,
xfs_lsn_t lsn)
{
- struct xfs_log_item *lip = cur ? cur->item : NULL;
- struct xfs_log_item *next_lip;
+ struct xfs_log_item *lip;
+
+ ASSERT(!list_empty(list));
/*
- * Get a new cursor if we don't have a placeholder or the existing one
- * has been invalidated.
+ * Use the cursor to determine the insertion point if one is
+ * provided. If not, or if the one we got is not valid,
+ * find the place in the AIL where the items belong.
*/
- if (!lip || (__psint_t)lip & 1) {
+ lip = cur ? cur->item : NULL;
+ if (!lip || (__psint_t) lip & 1)
lip = __xfs_trans_ail_cursor_last(ailp, lsn);
- if (!lip) {
- /* The list is empty, so just splice and return. */
- if (cur)
- cur->item = NULL;
- list_splice(list, &ailp->xa_ail);
- return;
- }
- }
+ /*
+ * If a cursor is provided, we know we're processing the AIL
+ * in lsn order, and future items to be spliced in will
+ * follow the last one being inserted now. Update the
+ * cursor to point to that last item, now while we have a
+ * reliable pointer to it.
+ */
+ if (cur)
+ cur->item = list_entry(list->prev, struct xfs_log_item, li_ail);
/*
- * Our cursor points to the item we want to insert _after_, so we have
- * to update the cursor to point to the end of the list we are splicing
- * in so that it points to the correct location for the next splice.
- * i.e. before the splice
- *
- * lsn -> lsn -> lsn + x -> lsn + x ...
- * ^
- * | cursor points here
- *
- * After the splice we have:
- *
- * lsn -> lsn -> lsn -> lsn -> .... -> lsn -> lsn + x -> lsn + x ...
- * ^ ^
- * | cursor points here | needs to move here
- *
- * So we set the cursor to the last item in the list to be spliced
- * before we execute the splice, resulting in the cursor pointing to
- * the correct item after the splice occurs.
+ * Finally perform the splice. Unless the AIL was empty,
+ * lip points to the item in the AIL _after_ which the new
+ * items should go. If lip is null the AIL was empty, so
+ * the new items go at the head of the AIL.
*/
- if (cur) {
- next_lip = list_entry(list->prev, struct xfs_log_item, li_ail);
- cur->item = next_lip;
- }
- list_splice(list, &lip->li_ail);
+ if (lip)
+ list_splice(list, &lip->li_ail);
+ else
+ list_splice(list, &ailp->xa_ail);
}
/*
@@ -682,6 +671,7 @@ xfs_trans_ail_update_bulk(
int i;
LIST_HEAD(tmp);
+ ASSERT(nr_items > 0); /* Not required, but true. */
mlip = xfs_ail_min(ailp);
for (i = 0; i < nr_items; i++) {
@@ -701,7 +691,8 @@ xfs_trans_ail_update_bulk(
list_add(&lip->li_ail, &tmp);
}
- xfs_ail_splice(ailp, cur, &tmp, lsn);
+ if (!list_empty(&tmp))
+ xfs_ail_splice(ailp, cur, &tmp, lsn);
if (!mlip_changed) {
spin_unlock(&ailp->xa_lock);