xfs: allow inode allocations in post-growfs disk space

commit 9de67c3b upstream.

Today, if we perform an xfs_growfs which adds allocation groups,
mp->m_maxagi is not properly updated when the growfs is complete.

Therefore inodes will continue to be allocated only in the
AGs which existed prior to the growfs, and the new space
won't be utilized.

This is because of this path in xfs_growfs_data_private():

xfs_growfs_data_private
	xfs_initialize_perag(mp, nagcount, &nagimax);
		if (mp->m_flags & XFS_MOUNT_32BITINODES)
			index = xfs_set_inode32(mp);
		else
			index = xfs_set_inode64(mp);

		if (maxagi)
			*maxagi = index;

where xfs_set_inode* iterates over the (old) agcount in
mp->m_sb.sb_agblocks, which has not yet been updated
in the growfs path.  So "index" will be returned based on
the old agcount, not the new one, and new AGs are not available
for inode allocation.

Fix this by explicitly passing the proper AG count (which
xfs_initialize_perag() already has) down another level,
so that xfs_set_inode* can make the proper decision about
acceptable AGs for inode allocation in the potentially
newly-added AGs.

This has been broken since 3.7, when these two
xfs_set_inode* functions were added in commit 2d2194f6.
Prior to that, we looped over "agcount" not sb_agblocks
in these calculations.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/xfs/xfs_mount.c

@@ -250,9 +250,9 @@ xfs_initialize_perag(
 		mp->m_flags &= ~XFS_MOUNT_32BITINODES;
 
 	if (mp->m_flags & XFS_MOUNT_32BITINODES)
-		index = xfs_set_inode32(mp);
+		index = xfs_set_inode32(mp, agcount);
 	else
-		index = xfs_set_inode64(mp);
+		index = xfs_set_inode64(mp, agcount);
 
 	if (maxagi)
 		*maxagi = index;

fs/xfs/xfs_super.c

@@ -597,8 +597,13 @@ xfs_max_file_offset(
 	return (((__uint64_t)pagefactor) << bitshift) - 1;
 }
 
+/*
+ * xfs_set_inode32() and xfs_set_inode64() are passed an agcount
+ * because in the growfs case, mp->m_sb.sb_agcount is not updated
+ * yet to the potentially higher ag count.
+ */
 xfs_agnumber_t
-xfs_set_inode32(struct xfs_mount *mp)
+xfs_set_inode32(struct xfs_mount *mp, xfs_agnumber_t agcount)
 {
 	xfs_agnumber_t	index = 0;
 	xfs_agnumber_t	maxagi = 0;
@@ -620,10 +625,10 @@ xfs_set_inode32(struct xfs_mount *mp)
 		do_div(icount, sbp->sb_agblocks);
 		max_metadata = icount;
 	} else {
-		max_metadata = sbp->sb_agcount;
+		max_metadata = agcount;
 	}
 
-	for (index = 0; index < sbp->sb_agcount; index++) {
+	for (index = 0; index < agcount; index++) {
 		ino = XFS_AGINO_TO_INO(mp, index, agino);
 
 		if (ino > XFS_MAXINUMBER_32) {
@@ -648,11 +653,11 @@ xfs_set_inode32(struct xfs_mount *mp)
 }
 
 xfs_agnumber_t
-xfs_set_inode64(struct xfs_mount *mp)
+xfs_set_inode64(struct xfs_mount *mp, xfs_agnumber_t agcount)
 {
 	xfs_agnumber_t index = 0;
 
-	for (index = 0; index < mp->m_sb.sb_agcount; index++) {
+	for (index = 0; index < agcount; index++) {
 		struct xfs_perag	*pag;
 
 		pag = xfs_perag_get(mp, index);
@@ -1188,6 +1193,7 @@ xfs_fs_remount(
 	char			*options)
 {
 	struct xfs_mount	*mp = XFS_M(sb);
+	xfs_sb_t		*sbp = &mp->m_sb;
 	substring_t		args[MAX_OPT_ARGS];
 	char			*p;
 	int			error;
@@ -1208,10 +1214,10 @@ xfs_fs_remount(
 			mp->m_flags &= ~XFS_MOUNT_BARRIER;
 			break;
 		case Opt_inode64:
-			mp->m_maxagi = xfs_set_inode64(mp);
+			mp->m_maxagi = xfs_set_inode64(mp, sbp->sb_agcount);
 			break;
 		case Opt_inode32:
-			mp->m_maxagi = xfs_set_inode32(mp);
+			mp->m_maxagi = xfs_set_inode32(mp, sbp->sb_agcount);
 			break;
 		default:
 			/*

fs/xfs/xfs_super.h

@@ -76,8 +76,8 @@ extern __uint64_t xfs_max_file_offset(unsigned int);
 
 extern void xfs_flush_inodes(struct xfs_mount *mp);
 extern void xfs_blkdev_issue_flush(struct xfs_buftarg *);
-extern xfs_agnumber_t xfs_set_inode32(struct xfs_mount *);
-extern xfs_agnumber_t xfs_set_inode64(struct xfs_mount *);
+extern xfs_agnumber_t xfs_set_inode32(struct xfs_mount *, xfs_agnumber_t agcount);
+extern xfs_agnumber_t xfs_set_inode64(struct xfs_mount *, xfs_agnumber_t agcount);
 
 extern const struct export_operations xfs_export_operations;
 extern const struct xattr_handler *xfs_xattr_handlers[];