ext4: enable the lazy init thread when remounting read/write

In commit a44be64b ("ext4: don't clear SB_RDONLY when remounting
r/w until quota is re-enabled") we defer clearing tyhe SB_RDONLY flag
in struct super.  However, we didn't defer when we checked sb_rdonly()
to determine the lazy itable init thread should be enabled, with the
next result that the lazy inode table initialization would not be
properly started.  This can cause generic/231 to fail in ext4's
nojournal mode.

Fix this by moving when we decide to start or stop the lazy itable
init thread to after we clear the SB_RDONLY flag when we are
remounting the file system read/write.

Fixes a44be64b ("ext4: don't clear SB_RDONLY when remounting r/w until...")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20230527035729.1001605-1-tytso@mit.eduSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -6588,18 +6588,6 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
 		}
 	}
 
-	/*
-	 * Reinitialize lazy itable initialization thread based on
-	 * current settings
-	 */
-	if (sb_rdonly(sb) || !test_opt(sb, INIT_INODE_TABLE))
-		ext4_unregister_li_request(sb);
-	else {
-		ext4_group_t first_not_zeroed;
-		first_not_zeroed = ext4_has_uninit_itable(sb);
-		ext4_register_li_request(sb, first_not_zeroed);
-	}
-
 	/*
 	 * Handle creation of system zone data early because it can fail.
 	 * Releasing of existing data is done when we are sure remount will
@@ -6637,6 +6625,18 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
 	if (enable_rw)
 		sb->s_flags &= ~SB_RDONLY;
 
+	/*
+	 * Reinitialize lazy itable initialization thread based on
+	 * current settings
+	 */
+	if (sb_rdonly(sb) || !test_opt(sb, INIT_INODE_TABLE))
+		ext4_unregister_li_request(sb);
+	else {
+		ext4_group_t first_not_zeroed;
+		first_not_zeroed = ext4_has_uninit_itable(sb);
+		ext4_register_li_request(sb, first_not_zeroed);
+	}
+
 	if (!ext4_has_feature_mmp(sb) || sb_rdonly(sb))
 		ext4_stop_mmpd(sbi);