[Ocfs2-devel] [PATCH] ocfs2/journal: fix umount hang after flushing journal failure

[Gechangwei]

Hi,

When journal flushing in ocfs2_commit_cache() fails, following umount procedure at stage of shutting journal may be blocked due to non-zero transactions number.

Once jbd2_journal_flush() fails, the journal will be marked as ABORT state inner JBD2. There is no way to come back afterwards.

So there is no chance to set transactions number to zero, thus, shutting journal may be blocked .


ocfs2_commit_thread()

    ocfs2_commit_cache()

        jbd2_journal_flush() -> failure takes journal into ABORT state, thus, transaction number will never set to zero


The back trace is cited blow:

[<ffffffff8109de0c>] kthread_stop+0x4c/0x150
[<ffffffffc056a887>] ocfs2_journal_shutdown+0xa7/0x400 [ocfs2]
[<ffffffffc059fbde>] ocfs2_dismount_volume+0xbe/0x4a0 [ocfs2]
[<ffffffffc059fff7>] ocfs2_put_super+0x37/0xb0 [ocfs2]
[<ffffffff8120534e>] generic_shutdown_super+0x7e/0x110
[<ffffffff81205410>] kill_block_super+0x30/0x80
[<ffffffff81205669>] deactivate_locked_super+0x59/0x90
[<ffffffff812062ee>] deactivate_super+0x4e/0x70
[<ffffffff81222423>] cleanup_mnt+0x43/0x90
[<ffffffff812224c2>] __cleanup_mnt+0x12/0x20
[<ffffffff8109c247>] task_work_run+0xb7/0xf0
[<ffffffff81016f7c>] do_notify_resume+0x8c/0xa0
[<ffffffff817f8384>] int_signal+0x12/0x17
[<ffffffffffffffff>] 0xffffffffffffffff

Through crash debug tool, It can seen that j_num_trans field is set to 2.

struct ocfs2_journal {
  j_state = OCFS2_JOURNAL_IN_SHUTDOWN,
  j_journal = 0xffff8800b4926000,
  j_inode = 0xffff880122aba298,
  j_osb = 0xffff880093caa000,
  j_bh = 0xffff8800a09df888,
  j_num_trans = {
    counter = 0x2
  },
  j_lock = {
    {
      rlock = {
        raw_lock = {
          {


To solve this issue, I propose a patch. Any comments will be welcomed.

Since journal has been marked as ABORT and flushing journal failure will free all corresponding buffer heads, it will be safe to directly set transactions number to zero.


From 98f42f5f52851ed84eb372a3e09a413a30ea2664 Mon Sep 17 00:00:00 2001
From: gechangwei <ge.changwei at h3c.com><mailto:ge.changwei at h3c.com>
Date: Sat, 7 Jan 2017 19:48:13 +0800
Subject: [PATCH] fix umount hang after flushing journal failure

Signed-off-by: gechangwei <ge.changwei at h3c.com><mailto:ge.changwei at h3c.com>
---
 fs/ocfs2/journal.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index a244f14..dab2094 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -326,6 +326,7 @@ static int ocfs2_commit_cache(struct ocfs2_super *osb)
     status = jbd2_journal_flush(journal->j_journal);
     jbd2_journal_unlock_updates(journal->j_journal);
     if (status < 0) {
+        atomic_set(&journal->j_num_trans, 0);
         up_write(&journal->j_trans_barrier);
         mlog_errno(status);
         goto finally;
--
2.5.1.windows.1



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