ubifs: Re-statistic cleaned znode count if commit failed

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6D1Y2
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=b83cff7f4920e4e636041940f8c1dfb1131ebc5b

--------------------------------

Dirty znodes will be written on flash in committing process with
following states:

	      process A			|  znode state
------------------------------------------------------
do_commit				| DIRTY_ZNODE
  ubifs_tnc_start_commit		| DIRTY_ZNODE
   get_znodes_to_commit			| DIRTY_ZNODE | COW_ZNODE
    layout_commit			| DIRTY_ZNODE | COW_ZNODE
     fill_gap                           | 0
  write master				| 0 or OBSOLETE_ZNODE

	      process B			|  znode state
------------------------------------------------------
do_commit				| DIRTY_ZNODE[1]
  ubifs_tnc_start_commit		| DIRTY_ZNODE
   get_znodes_to_commit			| DIRTY_ZNODE | COW_ZNODE
  ubifs_tnc_end_commit			| DIRTY_ZNODE | COW_ZNODE
   write_index                          | 0
  write master				| 0 or OBSOLETE_ZNODE[2] or
					| DIRTY_ZNODE[3]

[1] znode is dirtied without concurrent committing process
[2] znode is copied up (re-dirtied by other process) before cleaned
    up in committing process
[3] znode is re-dirtied after cleaned up in committing process

Currently, the clean znode count is updated in free_obsolete_znodes(),
which is called only in normal path. If do_commit failed, clean znode
count won't be updated, which triggers a failure ubifs assertion[4] in
ubifs_tnc_close():
 ubifs_assert_failed [ubifs]: UBIFS assert failed: freed == n

[4] Commit 380347e9 ("UBIFS: Add an assertion for clean_zn_cnt").

Fix it by re-statisticing cleaned znode count in tnc_destroy_cnext().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216704
Fixes: 1e51764a ("UBIFS: add new flash file system")
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>

fs/ubifs/tnc.c

@@ -3090,6 +3090,21 @@ static void tnc_destroy_cnext(struct ubifs_info *c)
 		cnext = cnext->cnext;
 		if (ubifs_zn_obsolete(znode))
 			kfree(znode);
+		else if (!ubifs_zn_cow(znode)) {
+			/*
+			 * Don't forget to update clean znode count after
+			 * committing failed, because ubifs will check this
+			 * count while closing tnc. Non-obsolete znode could
+			 * be re-dirtied during committing process, so dirty
+			 * flag is untrustable. The flag 'COW_ZNODE' is set
+			 * for each dirty znode before committing, and it is
+			 * cleared as long as the znode become clean, so we
+			 * can statistic clean znode count according to this
+			 * flag.
+			 */
+			atomic_long_inc(&c->clean_zn_cnt);
+			atomic_long_inc(&ubifs_clean_zn_cnt);
+		}
 	} while (cnext && cnext != c->cnext);
 }