ocfs2: Add "preferred slot" mount option

ocfs2 will attempt to assign the node the slot# provided in the mount
option. Failure to assign the preferred slot is not an error. This small
feature can be useful for automated testing.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/ocfs2/slot_map.c b/fs/ocfs2/slot_map.c
index d8b79067dc14..af4882b62cfa 100644
--- a/fs/ocfs2/slot_map.c
+++ b/fs/ocfs2/slot_map.c
@@ -121,17 +121,25 @@ static s16 __ocfs2_node_num_to_slot(struct ocfs2_slot_info *si,
         return ret;
 }
 
-static s16 __ocfs2_find_empty_slot(struct ocfs2_slot_info *si)
+static s16 __ocfs2_find_empty_slot(struct ocfs2_slot_info *si, s16 preferred)
 {
         int i;
         s16 ret = OCFS2_INVALID_SLOT;
 
+        if (preferred >= 0 && preferred < si->si_num_slots) {
+                if (OCFS2_INVALID_SLOT == si->si_global_node_nums[preferred]) {
+                        ret = preferred;
+                        goto out;
+                }
+        }
+
         for(i = 0; i < si->si_num_slots; i++) {
                 if (OCFS2_INVALID_SLOT == si->si_global_node_nums[i]) {
                         ret = (s16) i;
                         break;
                 }
         }
+out:
         return ret;
 }
 
@@ -248,7 +256,7 @@ int ocfs2_find_slot(struct ocfs2_super *osb)
         if (slot == OCFS2_INVALID_SLOT) {
                 /* if no slot yet, then just take 1st available
                  * one. */
-                slot = __ocfs2_find_empty_slot(si);
+                slot = __ocfs2_find_empty_slot(si, osb->preferred_slot);
                 if (slot == OCFS2_INVALID_SLOT) {
                         spin_unlock(&si->si_lock);
                         mlog(ML_ERROR, "no free slots available!\n");