1 files changed, 36 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index c9618080317e..b6308f6740ec 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -274,6 +274,42 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
 #if defined(CONFIG_NFS_V4_1)
 
 /*
+ * nfs4_free_slot - free a slot and efficiently update slot table.
+ *
+ * freeing a slot is trivially done by clearing its respective bit
+ * in the bitmap.
+ * If the freed slotid equals highest_used_slotid we want to update it
+ * so that the server would be able to size down the slot table if needed,
+ * otherwise we know that the highest_used_slotid is still in use.
+ * When updating highest_used_slotid there may be "holes" in the bitmap
+ * so we need to scan down from highest_used_slotid to 0 looking for the now
+ * highest slotid in use.
+ * If none found, highest_used_slotid is set to -1.
+ */
+static void
+nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
+{
+        int slotid = free_slotid;
+
+        spin_lock(&tbl->slot_tbl_lock);
+        /* clear used bit in bitmap */
+        __clear_bit(slotid, tbl->used_slots);
+
+        /* update highest_used_slotid when it is freed */
+        if (slotid == tbl->highest_used_slotid) {
+                slotid = find_last_bit(tbl->used_slots, tbl->max_slots);
+                if (slotid >= 0 && slotid < tbl->max_slots)
+                        tbl->highest_used_slotid = slotid;
+                else
+                        tbl->highest_used_slotid = -1;
+        }
+        rpc_wake_up_next(&tbl->slot_tbl_waitq);
+        spin_unlock(&tbl->slot_tbl_lock);
+        dprintk("%s: free_slotid %u highest_used_slotid %d\n", __func__,
+                free_slotid, tbl->highest_used_slotid);
+}
+
+/*
  * nfs4_find_slot - efficiently look for a free slot
  *
  * nfs4_find_slot looks for an unset bit in the used_slots bitmap.