1 files changed, 33 insertions, 0 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 90aed76e593b..a0946a0d116e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -273,6 +273,39 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
 
 #if defined(CONFIG_NFS_V4_1)
 
+/*
+ * nfs4_find_slot - efficiently look for a free slot
+ *
+ * nfs4_find_slot looks for an unset bit in the used_slots bitmap.
+ * If found, we mark the slot as used, update the highest_used_slotid,
+ * and respectively set up the sequence operation args.
+ * The slot number is returned if found, or NFS4_MAX_SLOT_TABLE otherwise.
+ */
+static u8
+nfs4_find_slot(struct nfs4_slot_table *tbl, struct rpc_task *task)
+{
+        int slotid;
+        u8 ret_id = NFS4_MAX_SLOT_TABLE;
+        BUILD_BUG_ON((u8)NFS4_MAX_SLOT_TABLE != (int)NFS4_MAX_SLOT_TABLE);
+
+        spin_lock(&tbl->slot_tbl_lock);
+        dprintk("--> %s used_slots=%04lx highest_used=%d max_slots=%d\n",
+                __func__, tbl->used_slots[0], tbl->highest_used_slotid,
+                tbl->max_slots);
+        slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slots);
+        if (slotid >= tbl->max_slots)
+                goto out;
+        __set_bit(slotid, tbl->used_slots);
+        if (slotid > tbl->highest_used_slotid)
+                tbl->highest_used_slotid = slotid;
+        ret_id = slotid;
+out:
+        dprintk("<-- %s used_slots=%04lx highest_used=%d slotid=%d \n",
+                __func__, tbl->used_slots[0], tbl->highest_used_slotid, ret_id);
+        spin_unlock(&tbl->slot_tbl_lock);
+        return ret_id;
+}
+
 static int nfs41_setup_sequence(struct nfs4_session *session,
                                 struct nfs4_sequence_args *args,
                                 struct nfs4_sequence_res *res,