diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
index bb0c700..46e25c68 100644
--- a/fs/xfs/libxfs/xfs_ag.c
+++ b/fs/xfs/libxfs/xfs_ag.c
@@ -95,6 +95,68 @@ xfs_perag_put(
 }
 
 /*
+ * Active references for perag structures. This is for short term access to the
+ * per ag structures for walking trees or accessing state. If an AG is being
+ * shrunk or is offline, then this will fail to find that AG and return NULL
+ * instead.
+ */
+struct xfs_perag *
+xfs_perag_grab(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		agno)
+{
+	struct xfs_perag	*pag;
+
+	rcu_read_lock();
+	pag = radix_tree_lookup(&mp->m_perag_tree, agno);
+	if (pag) {
+		trace_xfs_perag_grab(mp, pag->pag_agno,
+				atomic_read(&pag->pag_active_ref), _RET_IP_);
+		if (!atomic_inc_not_zero(&pag->pag_active_ref))
+			pag = NULL;
+	}
+	rcu_read_unlock();
+	return pag;
+}
+
+/*
+ * search from @first to find the next perag with the given tag set.
+ */
+struct xfs_perag *
+xfs_perag_grab_tag(
+	struct xfs_mount	*mp,
+	xfs_agnumber_t		first,
+	int			tag)
+{
+	struct xfs_perag	*pag;
+	int			found;
+
+	rcu_read_lock();
+	found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
+					(void **)&pag, first, 1, tag);
+	if (found <= 0) {
+		rcu_read_unlock();
+		return NULL;
+	}
+	trace_xfs_perag_grab_tag(mp, pag->pag_agno,
+			atomic_read(&pag->pag_active_ref), _RET_IP_);
+	if (!atomic_inc_not_zero(&pag->pag_active_ref))
+		pag = NULL;
+	rcu_read_unlock();
+	return pag;
+}
+
+void
+xfs_perag_rele(
+	struct xfs_perag	*pag)
+{
+	trace_xfs_perag_rele(pag->pag_mount, pag->pag_agno,
+			atomic_read(&pag->pag_active_ref), _RET_IP_);
+	if (atomic_dec_and_test(&pag->pag_active_ref))
+		wake_up(&pag->pag_active_wq);
+}
+
+/*
  * xfs_initialize_perag_data
  *
  * Read in each per-ag structure so we can count up the number of
@@ -196,6 +258,10 @@ xfs_free_perag(
 		cancel_delayed_work_sync(&pag->pag_blockgc_work);
 		xfs_buf_hash_destroy(pag);
 
+		/* drop the mount's active reference */
+		xfs_perag_rele(pag);
+		XFS_IS_CORRUPT(pag->pag_mount,
+				atomic_read(&pag->pag_active_ref) != 0);
 		call_rcu(&pag->rcu_head, __xfs_free_perag);
 	}
 }
@@ -314,6 +380,7 @@ xfs_initialize_perag(
 		INIT_DELAYED_WORK(&pag->pag_blockgc_work, xfs_blockgc_worker);
 		INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
 		init_waitqueue_head(&pag->pagb_wait);
+		init_waitqueue_head(&pag->pag_active_wq);
 		pag->pagb_count = 0;
 		pag->pagb_tree = RB_ROOT;
 #endif /* __KERNEL__ */
@@ -322,6 +389,9 @@ xfs_initialize_perag(
 		if (error)
 			goto out_remove_pag;
 
+		/* Active ref owned by mount indicates AG is online. */
+		atomic_set(&pag->pag_active_ref, 1);
+
 		/* first new pag is fully initialized */
 		if (first_initialised == NULLAGNUMBER)
 			first_initialised = index;
diff --git a/fs/xfs/libxfs/xfs_ag.h b/fs/xfs/libxfs/xfs_ag.h
index 191b22b..aeb21c8d 100644
--- a/fs/xfs/libxfs/xfs_ag.h
+++ b/fs/xfs/libxfs/xfs_ag.h
@@ -32,7 +32,9 @@ struct xfs_ag_resv {
 struct xfs_perag {
 	struct xfs_mount *pag_mount;	/* owner filesystem */
 	xfs_agnumber_t	pag_agno;	/* AG this structure belongs to */
-	atomic_t	pag_ref;	/* perag reference count */
+	atomic_t	pag_ref;	/* passive reference count */
+	atomic_t	pag_active_ref;	/* active reference count */
+	wait_queue_head_t pag_active_wq;/* woken active_ref falls to zero */
 	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 */
@@ -111,11 +113,18 @@ int xfs_initialize_perag(struct xfs_mount *mp, xfs_agnumber_t agcount,
 int xfs_initialize_perag_data(struct xfs_mount *mp, xfs_agnumber_t agno);
 void xfs_free_perag(struct xfs_mount *mp);
 
+/* Passive AG references */
 struct xfs_perag *xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno);
 struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *mp, xfs_agnumber_t agno,
 		unsigned int tag);
 void xfs_perag_put(struct xfs_perag *pag);
 
+/* Active AG references */
+struct xfs_perag *xfs_perag_grab(struct xfs_mount *, xfs_agnumber_t);
+struct xfs_perag *xfs_perag_grab_tag(struct xfs_mount *, xfs_agnumber_t,
+				   int tag);
+void xfs_perag_rele(struct xfs_perag *pag);
+
 /*
  * Per-ag geometry infomation and validation
  */
@@ -193,14 +202,18 @@ xfs_perag_next(
 	struct xfs_mount	*mp = pag->pag_mount;
 
 	*agno = pag->pag_agno + 1;
-	xfs_perag_put(pag);
-	if (*agno > end_agno)
-		return NULL;
-	return xfs_perag_get(mp, *agno);
+	xfs_perag_rele(pag);
+	while (*agno <= end_agno) {
+		pag = xfs_perag_grab(mp, *agno);
+		if (pag)
+			return pag;
+		(*agno)++;
+	}
+	return NULL;
 }
 
 #define for_each_perag_range(mp, agno, end_agno, pag) \
-	for ((pag) = xfs_perag_get((mp), (agno)); \
+	for ((pag) = xfs_perag_grab((mp), (agno)); \
 		(pag) != NULL; \
 		(pag) = xfs_perag_next((pag), &(agno), (end_agno)))
 
@@ -213,11 +226,11 @@ xfs_perag_next(
 	for_each_perag_from((mp), (agno), (pag))
 
 #define for_each_perag_tag(mp, agno, pag, tag) \
-	for ((agno) = 0, (pag) = xfs_perag_get_tag((mp), 0, (tag)); \
+	for ((agno) = 0, (pag) = xfs_perag_grab_tag((mp), 0, (tag)); \
 		(pag) != NULL; \
 		(agno) = (pag)->pag_agno + 1, \
-		xfs_perag_put(pag), \
-		(pag) = xfs_perag_get_tag((mp), (agno), (tag)))
+		xfs_perag_rele(pag), \
+		(pag) = xfs_perag_grab_tag((mp), (agno), (tag)))
 
 struct aghdr_init_data {
 	/* per ag data */
diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
index d50d0ea..dbbc703 100644
--- a/fs/xfs/scrub/bmap.c
+++ b/fs/xfs/scrub/bmap.c
@@ -662,7 +662,7 @@ xchk_bmap_check_rmaps(
 		error = xchk_bmap_check_ag_rmaps(sc, whichfork, pag);
 		if (error ||
 		    (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)) {
-			xfs_perag_put(pag);
+			xfs_perag_rele(pag);
 			return error;
 		}
 	}
diff --git a/fs/xfs/scrub/fscounters.c b/fs/xfs/scrub/fscounters.c
index 4777e7b..ef97670 100644
--- a/fs/xfs/scrub/fscounters.c
+++ b/fs/xfs/scrub/fscounters.c
@@ -117,7 +117,7 @@ xchk_fscount_warmup(
 	if (agi_bp)
 		xfs_buf_relse(agi_bp);
 	if (pag)
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	return error;
 }
 
@@ -249,7 +249,7 @@ xchk_fscount_aggregate_agcounts(
 
 	}
 	if (pag)
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	if (error) {
 		xchk_set_incomplete(sc);
 		return error;
diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 88a8850..120d284 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -688,11 +688,11 @@ __xfs_getfsmap_datadev(
 		info->agf_bp = NULL;
 	}
 	if (info->pag) {
-		xfs_perag_put(info->pag);
+		xfs_perag_rele(info->pag);
 		info->pag = NULL;
 	} else if (pag) {
 		/* loop termination case */
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	}
 
 	return error;
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index ddeaccc..0f4a014 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1767,7 +1767,7 @@ xfs_icwalk(
 		if (error) {
 			last_error = error;
 			if (error == -EFSCORRUPTED) {
-				xfs_perag_put(pag);
+				xfs_perag_rele(pag);
 				break;
 			}
 		}
diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
index 7558486..c31857d 100644
--- a/fs/xfs/xfs_iwalk.c
+++ b/fs/xfs/xfs_iwalk.c
@@ -591,7 +591,7 @@ xfs_iwalk(
 	}
 
 	if (iwag.pag)
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	xfs_iwalk_free(&iwag);
 	return error;
 }
@@ -683,7 +683,7 @@ xfs_iwalk_threaded(
 			break;
 	}
 	if (pag)
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	if (polled)
 		xfs_pwork_poll(&pctl);
 	return xfs_pwork_destroy(&pctl);
@@ -776,7 +776,7 @@ xfs_inobt_walk(
 	}
 
 	if (iwag.pag)
-		xfs_perag_put(pag);
+		xfs_perag_rele(pag);
 	xfs_iwalk_free(&iwag);
 	return error;
 }
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 57bf59f..f5dc46c 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -927,7 +927,7 @@ xfs_reflink_recover_cow(
 	for_each_perag(mp, agno, pag) {
 		error = xfs_refcount_recover_cow_leftovers(mp, pag);
 		if (error) {
-			xfs_perag_put(pag);
+			xfs_perag_rele(pag);
 			break;
 		}
 	}
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 2ac98d8..eb5e49d 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -189,6 +189,9 @@ DEFINE_EVENT(xfs_perag_class, name,	\
 DEFINE_PERAG_REF_EVENT(xfs_perag_get);
 DEFINE_PERAG_REF_EVENT(xfs_perag_get_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_put);
+DEFINE_PERAG_REF_EVENT(xfs_perag_grab);
+DEFINE_PERAG_REF_EVENT(xfs_perag_grab_tag);
+DEFINE_PERAG_REF_EVENT(xfs_perag_rele);
 DEFINE_PERAG_REF_EVENT(xfs_perag_set_inode_tag);
 DEFINE_PERAG_REF_EVENT(xfs_perag_clear_inode_tag);