Hi Darrick,

On Fri, Jan 08, 2021 at 01:19:42PM -0800, Darrick J. Wong wrote:

On Sat, Jan 09, 2021 at 03:09:19AM +0800, Gao Xiang wrote:

...

quoted

 	delta = nb;	/* use delta as a temporary here */

Yikes, can this become a separate variable please?

Ok.

quoted

 	nb_mod = do_div(delta, mp->m_sb.sb_agblocks);

@@ -99,10 +102,18 @@ xfs_growfs_data_private(
 	if (nb_mod && nb_mod < XFS_MIN_AG_BLOCKS) {
 		nagcount--;
 		nb = (xfs_rfsblock_t)nagcount * mp->m_sb.sb_agblocks;
-		if (nb < mp->m_sb.sb_dblocks)
+		if (nagcount < 2)
 			return -EINVAL;
 	}
-	delta = nb - mp->m_sb.sb_dblocks;
+
+	if (nb > mp->m_sb.sb_dblocks) {
+		delta = nb - mp->m_sb.sb_dblocks;
+		extend = true;
+	} else {
+		delta = mp->m_sb.sb_dblocks - nb;
+		extend = false;

/me wonders why delta isn't simply int64_t, and then you can do things
like:

if (delta > 0)
	growfs
else if (delta < 0)
	shrinkfs

?

Yeah, delta changed into a signed variable in mycurrent experimental
shrinking entire AG hack as well. Will update this here in advance.

Thanks,
Gao Xiang