Linux: sync mapped data on umount

Signed-off-by: Pavel Snajdr <[email protected]>

module/os/linux/zfs/zfs_vfsops.c

@@ -1546,9 +1546,24 @@ void
 zfs_preumount(struct super_block *sb)
 {
 	zfsvfs_t *zfsvfs = sb->s_fs_info;
+	znode_t *zp;
 
 	/* zfsvfs is NULL when zfs_domount fails during mount */
 	if (zfsvfs) {
+		/*
+		* Since we have to disable zpl_prune_sb when umounting,
+		* because the shrinker gets freed before zpl_kill_sb is
+		* ever called, the umount might be unable to sync open files.
+		*
+		* Let's do it here.
+		*/
+		mutex_enter(&zfsvfs->z_znodes_lock);
+		list_for_each_entry(zp, &zfsvfs->z_all_znodes, z_link_node) {
+			if (zp->z_sa_hdl)
+				filemap_write_and_wait(zp->z_vnode->i_mapping);
+		}
+		mutex_exit(&zfsvfs->z_znodes_lock);
+
 		zfs_unlinked_drain_stop_wait(zfsvfs);
 		zfsctl_destroy(sb->s_fs_info);
 		/*