Re: [Ocfs2-devel] [PATCH v3] ocfs2: call journal flush to mark journal as empty after journal recovery when mount
From: Jiangyiwen
Date: Sun Dec 22 2019 - 20:55:39 EST
On 2019/12/21 15:24, Changwei Ge wrote:
On 12/20/19 8:52 PM, Jiangyiwen wrote:
On 2019/12/20 17:33, Likai wrote:
On 2019/12/20 17:14, piaojun wrote:
On 2019/12/20 9:11, Joseph Qi wrote:
On 19/12/19 22:15, piaojun wrote:
On 2019/12/17 10:01, Kai Li wrote:
If journal is dirty when mount, it will be replayed but jbd2 sb
log tail cannot be updated to mark a new start because
journal->j_flag has already been set with JBD2_ABORT first
in journal_init_common. When a new transaction is committed, it
will be recored in block 1 first(journal->j_tail is set to 1 in
journal_reset).If emergency restart happens again before journal
super block is updated unfortunately, the new recorded trans will
not be replayed in the next mount.
The following steps describe this procedure in detail.
1. mount and touch some files
2. these transactions are committed to journal area but not
checkpointed
3. emergency restart
4. mount again and its journals are replayed
5. journal super block's first s_start is 1, but its s_seq is
not updated
6. touch a new file and its trans is committed but not checkpointed
Hi,
I wonder that in this step, does the function
jbd2_journal_commit_transaction() return?
I understand only jbd2_journal_commit_transaction() return it means
the transaction
is committed completely, and the s_seq can be updated in
jbd2_journal_commit_transaction()->jbd2_update_log_tail(), so I don't
know how
this scenario happened.
If emergency restart happens in before jbd2_journal_commit_transaction()
The trick is that jbd2 kernel thread even doesn't have a chance to to
update tail. Assuming that a timepoint sits between *mount completion*
and the *first iteration* of committing work that jbd2 thread.
Hi Changwei,
So I think if *first iteration* of committing work in jbd2 kernel thread
is not
completed, and then the transaction should not be considered a valid
transaction.
In addition, since we use ordered mode in jbd2, filesystem only ensure
metadata consistency not data consistency. In above scenario, the filesystem
is still normal without any damage.
Thanks,
Yiwen.
-Changwei
return,
I think this transaction shouldn't be a valid transaction.
Can you explain where the specific function is executed?
Thanks,
Yiwen.
7. emergency restart again
8. mount and journal is dirty, but trans committed in 6 will not be
replayed.
This exception happens easily when this lun is used by only one
node. If it
is used by multi-nodes, other node will replay its journal and its
journal super block will be updated after recovery like what
this patch
does.
ocfs2_recover_node->ocfs2_replay_journal.
The following jbd2 journal can be generated by touching a new
file after
journal is replayed, and seq 15 is the first valid commit, but
first seq
is 13 in journal super block.
logdump:
Block 0: Journal Superblock
Seq: 0 Type: 4 (JBD2_SUPERBLOCK_V2)
Blocksize: 4096 Total Blocks: 32768 First Block: 1
First Commit ID: 13 Start Log Blknum: 1
Error: 0
Feature Compat: 0
Feature Incompat: 2 block64
Feature RO compat: 0
Journal UUID: 4ED3822C54294467A4F8E87D2BA4BC36
FS Share Cnt: 1 Dynamic Superblk Blknum: 0
Per Txn Block Limit Journal: 0 Data: 0
Block 1: Journal Commit Block
Seq: 14 Type: 2 (JBD2_COMMIT_BLOCK)
Block 2: Journal Descriptor
Seq: 15 Type: 1 (JBD2_DESCRIPTOR_BLOCK)
No. Blocknum Flags
0. 587 none
UUID: 00000000000000000000000000000000
1. 8257792 JBD2_FLAG_SAME_UUID
2. 619 JBD2_FLAG_SAME_UUID
3. 24772864 JBD2_FLAG_SAME_UUID
4. 8257802 JBD2_FLAG_SAME_UUID
5. 513 JBD2_FLAG_SAME_UUID JBD2_FLAG_LAST_TAG
...
Block 7: Inode
Inode: 8257802 Mode: 0640 Generation: 57157641 (0x3682809)
FS Generation: 2839773110 (0xa9437fb6)
CRC32: 00000000 ECC: 0000
Type: Regular Attr: 0x0 Flags: Valid
Dynamic Features: (0x1) InlineData
User: 0 (root) Group: 0 (root) Size: 7
Links: 1 Clusters: 0
ctime: 0x5de5d870 0x11104c61 -- Tue Dec 3 11:37:20.286280801 2019
atime: 0x5de5d870 0x113181a1 -- Tue Dec 3 11:37:20.288457121 2019
mtime: 0x5de5d870 0x11104c61 -- Tue Dec 3 11:37:20.286280801 2019
dtime: 0x0 -- Thu Jan 1 08:00:00 1970
...
Block 9: Journal Commit Block
Seq: 15 Type: 2 (JBD2_COMMIT_BLOCK)
The following is jouranl recovery log when recovering the upper
jbd2
journal when mount again.
syslog:
[ 2265.648622] ocfs2: File system on device (252,1) was not
unmounted cleanly, recovering it.
[ 2265.649695] fs/jbd2/recovery.c:(do_one_pass, 449): Starting
recovery pass 0
[ 2265.650407] fs/jbd2/recovery.c:(do_one_pass, 449): Starting
recovery pass 1
[ 2265.650409] fs/jbd2/recovery.c:(do_one_pass, 449): Starting
recovery pass 2
[ 2265.650410] fs/jbd2/recovery.c:(jbd2_journal_recover, 278):
JBD2: recovery, exit status 0, recovered transactions 13 to 13
Due to first commit seq 13 recorded in journal super is not
consistent
with the value recorded in block 1(seq is 14), journal recovery
will be
terminated before seq 15 even though it is an unbroken commit,
inode
8257802 is a new file and it will be lost.
Signed-off-by: Kai Li <li.kai4@xxxxxxx>
---
fs/ocfs2/journal.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index 1afe57f425a0..68ba354cf361 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -1066,6 +1066,14 @@ int ocfs2_journal_load(struct
ocfs2_journal *journal, int local, int replayed)
ocfs2_clear_journal_error(osb->sb, journal->j_journal,
osb->slot_num);
+ if (replayed) {
+ jbd2_journal_lock_updates(journal->j_journal);
+ status = jbd2_journal_flush(journal->j_journal);
What if jbd2_journal_flush gets failed? The 's_sequence' and
's_start'
won't be reset, and I wonder if the problem still remains.
Yes, but we don't want this to fail the mount process, instead we
just log
an error and system administrator should know the result.
Thanks for your reply and I have another question about this issue.
IMO
the second trans is not complete as jbd2 sb has not been updated,
so we
do not need to replay it when mount again.
Jun
I don't think so. The problem is that jbd2 sb should be updated to mark
a new start after mount rather than whether trans committed later is
complete or not.
In fact , the trans is complete too as the commit log described.
Thanks
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