xfs: insert the pag structures into the xarray later

Cleaning up is much easier if a structure can't be looked up yet, so only
insert the pag once it is fully set up.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Author: Christoph Hellwig

fs/xfs/libxfs/xfs_ag.c

@@ -307,15 +307,6 @@ xfs_perag_alloc(
 	if (!pag)
 		return -ENOMEM;
 
-	pag->pag_agno = index;
-	pag->pag_mount = mp;
-
-	error = xa_insert(&mp->m_perags, index, pag, GFP_KERNEL);
-	if (error) {
-		WARN_ON_ONCE(error == -EBUSY);
-		goto out_free_pag;
-	}
-
 #ifdef __KERNEL__
 	/* Place kernel structure only init below this point. */
 	spin_lock_init(&pag->pag_ici_lock);
@@ -331,10 +322,7 @@ xfs_perag_alloc(
 
 	error = xfs_buf_cache_init(&pag->pag_bcache);
 	if (error)
-		goto out_remove_pag;
-
-	/* Active ref owned by mount indicates AG is online. */
-	atomic_set(&pag->pag_active_ref, 1);
+		goto out_defer_drain_free;
 
 	/*
 	 * Pre-calculated geometry
@@ -344,12 +332,23 @@ xfs_perag_alloc(
 	__xfs_agino_range(mp, pag->block_count, &pag->agino_min,
 			&pag->agino_max);
 
+	pag->pag_agno = index;
+	pag->pag_mount = mp;
+	/* Active ref owned by mount indicates AG is online. */
+	atomic_set(&pag->pag_active_ref, 1);
+
+	error = xa_insert(&mp->m_perags, index, pag, GFP_KERNEL);
+	if (error) {
+		WARN_ON_ONCE(error == -EBUSY);
+		goto out_buf_cache_destroy;
+	}
+
 	return 0;
 
-out_remove_pag:
+out_buf_cache_destroy:
+	xfs_buf_cache_destroy(&pag->pag_bcache);
+out_defer_drain_free:
 	xfs_defer_drain_free(&pag->pag_intents_drain);
-	pag = xa_erase(&mp->m_perags, index);
-out_free_pag:
 	kfree(pag);
 	return error;
 }