On Mon, Mar 22, 2021 at 07:28:07AM -0400, Brian Foster wrote:

On Fri, Mar 05, 2021 at 10:57:00AM +0800, Gao Xiang wrote:

quoted

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 <redacted>
Signed-off-by: Gao Xiang <redacted>
---
 fs/xfs/xfs_fsops.c | 107 +++++++++++++++++++++++++++------------------
 1 file changed, 64 insertions(+), 43 deletions(-)

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 9f9ba8bd0213..fc9e799b2ae3 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/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_resetagres)

Nit: I'd just call this lastag_extended or something that otherwise
indicates what this function reports (as opposed to trying to tell the
caller what to do).

ok, if other people don't oppose of it.

quoted

+{
+	struct xfs_mount	*mp = tp->t_mountp;
+	xfs_rfsblock_t		nb = mp->m_sb.sb_dblocks + delta;
+	int			error;
+
+	*lastag_resetagres = 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_resetagres = true;
+		error = xfs_ag_extend_space(mp, tp, id, delta);
+	}
+	return error;
+}
+
 /*
  * growfs operations
  */

...

quoted

@@ -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 > 0)
+		xfs_trans_mod_sb(tp, XFS_TRANS_SB_DBLOCKS, delta);

Hm.. isn't delta still unsigned as of this patch?

Not sure if some difference exists, I could update it as "if (delta)",
therefore it seems [PATCH v8 4/5] won't modify this anymore.

Thanks,
Gao Xiang

Brian

quoted

 	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_resetagres) {
 		struct xfs_perag	*pag;
 
 		pag = xfs_perag_get(mp, id.agno);

-- 
2.27.0