xfs: give xfs_refcount_intent its own perag reference

Give the xfs_refcount_intent a passive reference to the perag structure
data.  This reference will be used to enable scrub intent draining
functionality in subsequent patches.  Any space being modified by a
refcount intent is already allocated, so we need to be able to operate
even if the AG is being shrunk or offlined.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_refcount.c

@@ -1332,26 +1332,22 @@ xfs_refcount_finish_one(
 	xfs_agblock_t			bno;
 	unsigned long			nr_ops = 0;
 	int				shape_changes = 0;
-	struct xfs_perag		*pag;
 
-	pag = xfs_perag_get(mp, XFS_FSB_TO_AGNO(mp, ri->ri_startblock));
 	bno = XFS_FSB_TO_AGBNO(mp, ri->ri_startblock);
 
 	trace_xfs_refcount_deferred(mp, XFS_FSB_TO_AGNO(mp, ri->ri_startblock),
 			ri->ri_type, XFS_FSB_TO_AGBNO(mp, ri->ri_startblock),
 			ri->ri_blockcount);
 
-	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_REFCOUNT_FINISH_ONE)) {
-		error = -EIO;
-		goto out_drop;
-	}
+	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_REFCOUNT_FINISH_ONE))
+		return -EIO;
 
 	/*
 	 * If we haven't gotten a cursor or the cursor AG doesn't match
 	 * the startblock, get one now.
 	 */
 	rcur = *pcur;
-	if (rcur != NULL && rcur->bc_ag.pag != pag) {
+	if (rcur != NULL && rcur->bc_ag.pag != ri->ri_pag) {
 		nr_ops = rcur->bc_ag.refc.nr_ops;
 		shape_changes = rcur->bc_ag.refc.shape_changes;
 		xfs_refcount_finish_one_cleanup(tp, rcur, 0);
@@ -1359,12 +1355,12 @@ xfs_refcount_finish_one(
 		*pcur = NULL;
 	}
 	if (rcur == NULL) {
-		error = xfs_alloc_read_agf(pag, tp, XFS_ALLOC_FLAG_FREEING,
-				&agbp);
+		error = xfs_alloc_read_agf(ri->ri_pag, tp,
+				XFS_ALLOC_FLAG_FREEING, &agbp);
 		if (error)
-			goto out_drop;
+			return error;
 
-		rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, pag);
+		rcur = xfs_refcountbt_init_cursor(mp, tp, agbp, ri->ri_pag);
 		rcur->bc_ag.refc.nr_ops = nr_ops;
 		rcur->bc_ag.refc.shape_changes = shape_changes;
 	}
@@ -1375,7 +1371,7 @@ xfs_refcount_finish_one(
 		error = xfs_refcount_adjust(rcur, &bno, &ri->ri_blockcount,
 				XFS_REFCOUNT_ADJUST_INCREASE);
 		if (error)
-			goto out_drop;
+			return error;
 		if (ri->ri_blockcount > 0)
 			error = xfs_refcount_continue_op(rcur, ri, bno);
 		break;
@@ -1383,31 +1379,29 @@ xfs_refcount_finish_one(
 		error = xfs_refcount_adjust(rcur, &bno, &ri->ri_blockcount,
 				XFS_REFCOUNT_ADJUST_DECREASE);
 		if (error)
-			goto out_drop;
+			return error;
 		if (ri->ri_blockcount > 0)
 			error = xfs_refcount_continue_op(rcur, ri, bno);
 		break;
 	case XFS_REFCOUNT_ALLOC_COW:
 		error = __xfs_refcount_cow_alloc(rcur, bno, ri->ri_blockcount);
 		if (error)
-			goto out_drop;
+			return error;
 		ri->ri_blockcount = 0;
 		break;
 	case XFS_REFCOUNT_FREE_COW:
 		error = __xfs_refcount_cow_free(rcur, bno, ri->ri_blockcount);
 		if (error)
-			goto out_drop;
+			return error;
 		ri->ri_blockcount = 0;
 		break;
 	default:
 		ASSERT(0);
-		error = -EFSCORRUPTED;
+		return -EFSCORRUPTED;
 	}
 	if (!error && ri->ri_blockcount > 0)
-		trace_xfs_refcount_finish_one_leftover(mp, pag->pag_agno,
+		trace_xfs_refcount_finish_one_leftover(mp, ri->ri_pag->pag_agno,
 				ri->ri_type, bno, ri->ri_blockcount);
-out_drop:
-	xfs_perag_put(pag);
 	return error;
 }
 
@@ -1435,6 +1429,7 @@ __xfs_refcount_add(
 	ri->ri_startblock = startblock;
 	ri->ri_blockcount = blockcount;
 
+	xfs_refcount_update_get_group(tp->t_mountp, ri);
 	xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_REFCOUNT, &ri->ri_list);
 }
 

fs/xfs/libxfs/xfs_refcount.h

@@ -50,6 +50,7 @@ enum xfs_refcount_intent_type {
 
 struct xfs_refcount_intent {
 	struct list_head			ri_list;
+	struct xfs_perag			*ri_pag;
 	enum xfs_refcount_intent_type		ri_type;
 	xfs_extlen_t				ri_blockcount;
 	xfs_fsblock_t				ri_startblock;
@@ -67,6 +68,9 @@ xfs_refcount_check_domain(
 	return true;
 }
 
+void xfs_refcount_update_get_group(struct xfs_mount *mp,
+		struct xfs_refcount_intent *ri);
+
 void xfs_refcount_increase_extent(struct xfs_trans *tp,
 		struct xfs_bmbt_irec *irec);
 void xfs_refcount_decrease_extent(struct xfs_trans *tp,

fs/xfs/xfs_refcount_item.c

@@ -20,6 +20,7 @@
 #include "xfs_error.h"
 #include "xfs_log_priv.h"
 #include "xfs_log_recover.h"
+#include "xfs_ag.h"
 
 struct kmem_cache	*xfs_cui_cache;
 struct kmem_cache	*xfs_cud_cache;
@@ -279,14 +280,13 @@ xfs_refcount_update_diff_items(
 	const struct list_head		*a,
 	const struct list_head		*b)
 {
-	struct xfs_mount		*mp = priv;
 	struct xfs_refcount_intent	*ra;
 	struct xfs_refcount_intent	*rb;
 
 	ra = container_of(a, struct xfs_refcount_intent, ri_list);
 	rb = container_of(b, struct xfs_refcount_intent, ri_list);
-	return  XFS_FSB_TO_AGNO(mp, ra->ri_startblock) -
-		XFS_FSB_TO_AGNO(mp, rb->ri_startblock);
+
+	return ra->ri_pag->pag_agno - rb->ri_pag->pag_agno;
 }
 
 /* Set the phys extent flags for this reverse mapping. */
@@ -365,6 +365,26 @@ xfs_refcount_update_create_done(
 	return &xfs_trans_get_cud(tp, CUI_ITEM(intent))->cud_item;
 }
 
+/* Take a passive ref to the AG containing the space we're refcounting. */
+void
+xfs_refcount_update_get_group(
+	struct xfs_mount		*mp,
+	struct xfs_refcount_intent	*ri)
+{
+	xfs_agnumber_t			agno;
+
+	agno = XFS_FSB_TO_AGNO(mp, ri->ri_startblock);
+	ri->ri_pag = xfs_perag_get(mp, agno);
+}
+
+/* Release a passive AG ref after finishing refcounting work. */
+static inline void
+xfs_refcount_update_put_group(
+	struct xfs_refcount_intent	*ri)
+{
+	xfs_perag_put(ri->ri_pag);
+}
+
 /* Process a deferred refcount update. */
 STATIC int
 xfs_refcount_update_finish_item(
@@ -386,6 +406,8 @@ xfs_refcount_update_finish_item(
 		       ri->ri_type == XFS_REFCOUNT_DECREASE);
 		return -EAGAIN;
 	}
+
+	xfs_refcount_update_put_group(ri);
 	kmem_cache_free(xfs_refcount_intent_cache, ri);
 	return error;
 }
@@ -406,6 +428,8 @@ xfs_refcount_update_cancel_item(
 	struct xfs_refcount_intent	*ri;
 
 	ri = container_of(item, struct xfs_refcount_intent, ri_list);
+
+	xfs_refcount_update_put_group(ri);
 	kmem_cache_free(xfs_refcount_intent_cache, ri);
 }
 
@@ -520,9 +544,13 @@ xfs_cui_item_recover(
 
 		fake.ri_startblock = pmap->pe_startblock;
 		fake.ri_blockcount = pmap->pe_len;
-		if (!requeue_only)
+
+		if (!requeue_only) {
+			xfs_refcount_update_get_group(mp, &fake);
 			error = xfs_trans_log_finish_refcount_update(tp, cudp,
 					&fake, &rcur);
+			xfs_refcount_update_put_group(&fake);
+		}
 		if (error == -EFSCORRUPTED)
 			XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
 					&cuip->cui_format,