3 files changed, 12 insertions, 4 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 6702bd86581..18ae43f4255 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -196,8 +196,8 @@ typedef struct xfs_perag_busy {
 #define XFS_PAGB_NUM_SLOTS      128
 #endif
 
-typedef struct xfs_perag
-{
+typedef struct xfs_perag {
+        atomic_t        pag_ref;        /* perag reference count */
         char            pagf_init;      /* this agf's entry is initialized */
         char            pagi_init;      /* this agi's entry is initialized */
         char            pagf_metadata;  /* the agf is preferred to be metadata */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index c04dd83cb57..f241fec2607 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -215,6 +215,7 @@ xfs_free_perag(
         for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
                 spin_lock(&mp->m_perag_lock);
                 pag = radix_tree_delete(&mp->m_perag_tree, agno);
+                ASSERT(atomic_read(&pag->pag_ref) == 0);
                 spin_unlock(&mp->m_perag_lock);
                 ASSERT(pag);
                 kmem_free(pag->pagb_list);
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index cfa7a5d22e7..16b22120b98 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -384,7 +384,7 @@ xfs_daddr_to_agbno(struct xfs_mount *mp, xfs_daddr_t d)
 }
 
 /*
- * perag get/put wrappers for eventual ref counting
+ * perag get/put wrappers for ref counting
  */
 static inline struct xfs_perag *
 xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
@@ -393,6 +393,12 @@ xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
 
         spin_lock(&mp->m_perag_lock);
         pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+        if (pag) {
+                ASSERT(atomic_read(&pag->pag_ref) >= 0);
+                /* catch leaks in the positive direction during testing */
+                ASSERT(atomic_read(&pag->pag_ref) < 1000);
+                atomic_inc(&pag->pag_ref);
+        }
         spin_unlock(&mp->m_perag_lock);
         return pag;
 }
@@ -400,7 +406,8 @@ xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
 static inline void
 xfs_perag_put(struct xfs_perag *pag)
 {
-        /* nothing to see here, move along */
+        ASSERT(atomic_read(&pag->pag_ref) > 0);
+        atomic_dec(&pag->pag_ref);
 }
 
 /*