xfs: hoist out xfs_resizefs_init_new_ags()

Move out related logic for initializing new added AGs to a new helper
in preparation for shrinking. No logic changes.
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_fsops.c

@@ -20,6 +20,64 @@
 #include "xfs_ag.h"
 #include "xfs_ag_resv.h"
 
+/*
+ * Write new AG headers to disk. Non-transactional, but need to be
+ * written and completed prior to the growfs transaction being logged.
+ * To do this, we use a delayed write buffer list and wait for
+ * submission and IO completion of the list as a whole. This allows the
+ * IO subsystem to merge all the AG headers in a single AG into a single
+ * IO and hide most of the latency of the IO from us.
+ *
+ * This also means that if we get an error whilst building the buffer
+ * list to write, we can cancel the entire list without having written
+ * anything.
+ */
+static int
+xfs_resizefs_init_new_ags(
+	struct xfs_trans	*tp,
+	struct aghdr_init_data	*id,
+	xfs_agnumber_t		oagcount,
+	xfs_agnumber_t		nagcount,
+	xfs_rfsblock_t		delta,
+	bool			*lastag_extended)
+{
+	struct xfs_mount	*mp = tp->t_mountp;
+	xfs_rfsblock_t		nb = mp->m_sb.sb_dblocks + delta;
+	int			error;
+
+	*lastag_extended = false;
+
+	INIT_LIST_HEAD(&id->buffer_list);
+	for (id->agno = nagcount - 1;
+	     id->agno >= oagcount;
+	     id->agno--, delta -= id->agsize) {
+
+		if (id->agno == nagcount - 1)
+			id->agsize = nb - (id->agno *
+					(xfs_rfsblock_t)mp->m_sb.sb_agblocks);
+		else
+			id->agsize = mp->m_sb.sb_agblocks;
+
+		error = xfs_ag_init_headers(mp, id);
+		if (error) {
+			xfs_buf_delwri_cancel(&id->buffer_list);
+			return error;
+		}
+	}
+
+	error = xfs_buf_delwri_submit(&id->buffer_list);
+	if (error)
+		return error;
+
+	xfs_trans_agblocks_delta(tp, id->nfree);
+
+	if (delta) {
+		*lastag_extended = true;
+		error = xfs_ag_extend_space(mp, tp, id, delta);
+	}
+	return error;
+}
+
 /*
  * growfs operations
  */
@@ -34,6 +92,7 @@ xfs_growfs_data_private(
 	xfs_agnumber_t		nagimax = 0;
 	xfs_rfsblock_t		nb, nb_div, nb_mod;
 	xfs_rfsblock_t		delta;
+	bool			lastag_extended;
 	xfs_agnumber_t		oagcount;
 	struct xfs_trans	*tp;
 	struct aghdr_init_data	id = {};
@@ -74,48 +133,11 @@ xfs_growfs_data_private(
 	if (error)
 		return error;
 
-	/*
-	 * Write new AG headers to disk. Non-transactional, but need to be
-	 * written and completed prior to the growfs transaction being logged.
-	 * To do this, we use a delayed write buffer list and wait for
-	 * submission and IO completion of the list as a whole. This allows the
-	 * IO subsystem to merge all the AG headers in a single AG into a single
-	 * IO and hide most of the latency of the IO from us.
-	 *
-	 * This also means that if we get an error whilst building the buffer
-	 * list to write, we can cancel the entire list without having written
-	 * anything.
-	 */
-	INIT_LIST_HEAD(&id.buffer_list);
-	for (id.agno = nagcount - 1;
-	     id.agno >= oagcount;
-	     id.agno--, delta -= id.agsize) {
-
-		if (id.agno == nagcount - 1)
-			id.agsize = nb -
-				(id.agno * (xfs_rfsblock_t)mp->m_sb.sb_agblocks);
-		else
-			id.agsize = mp->m_sb.sb_agblocks;
-
-		error = xfs_ag_init_headers(mp, &id);
-		if (error) {
-			xfs_buf_delwri_cancel(&id.buffer_list);
-			goto out_trans_cancel;
-		}
-	}
-	error = xfs_buf_delwri_submit(&id.buffer_list);
+	error = xfs_resizefs_init_new_ags(tp, &id, oagcount, nagcount,
+					  delta, &lastag_extended);
 	if (error)
 		goto out_trans_cancel;
 
-	xfs_trans_agblocks_delta(tp, id.nfree);
-
-	/* If there are new blocks in the old last AG, extend it. */
-	if (delta) {
-		error = xfs_ag_extend_space(mp, tp, &id, delta);
-		if (error)
-			goto out_trans_cancel;
-	}
-
 	/*
 	 * Update changed superblock fields transactionally. These are not
 	 * seen by the rest of the world until the transaction commit applies
@@ -123,9 +145,8 @@ xfs_growfs_data_private(
 	 */
 	if (nagcount > oagcount)
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_AGCOUNT, nagcount - oagcount);
-	if (nb > mp->m_sb.sb_dblocks)
-		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS,
-				 nb - mp->m_sb.sb_dblocks);
+	if (delta)
+		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS, delta);
 	if (id.nfree)
 		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, id.nfree);
 
@@ -152,7 +173,7 @@ xfs_growfs_data_private(
 	 * If we expanded the last AG, free the per-AG reservation
 	 * so we can reinitialize it with the new size.
 	 */
-	if (delta) {
+	if (lastag_extended) {
 		struct xfs_perag	*pag;
 
 		pag = xfs_perag_get(mp, id.agno);