Ocfs2 devel - Aug 2014 - [patch 06/10] ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty() in ocfs2_write_end_nolock()

From: yangwenfang <vicky.yangwenfang at huawei.com>
Subject: ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty() in
ocfs2_write_end_nolock()

After we call ocfs2_journal_access_di() in ocfs2_write_begin(),
jbd2_journal_restart() may also be called, in this function transaction
A's t_updates-- and obtains a new transaction B.  If
jbd2_journal_commit_transaction() is happened to commit transaction A,
when t_updates==0, it will continue to complete commit and unfile buffer.

So when jbd2_journal_dirty_metadata(), the handle is pointed a new
transaction B, and the buffer head's journal head is already freed,
jh->b_transaction == NULL, jh->b_next_transaction == NULL, it returns
EINVAL, So it triggers the BUG_ON(status).

thread 1:                             jbd2:
ocfs2_write_begin                     jbd2_journal_commit_transaction
ocfs2_write_begin_nolock
  ocfs2_start_trans
    jbd2__journal_start(t_updates+1,
                       transaction A)
    ocfs2_journal_access_di
    ocfs2_write_cluster_by_desc
      ocfs2_mark_extent_written
        ocfs2_change_extent_flag
          ocfs2_split_extent
            ocfs2_extend_rotate_transaction
              jbd2_journal_restart
              (t_updates-1,transaction B) t_updates==0
                                        __jbd2_journal_refile_buffer

ocfs2_write_end
ocfs2_write_end_nolock
    ocfs2_journal_dirty
        jbd2_journal_dirty_metadata(bug)
   ocfs2_commit_trans

In ext4, I found that: jbd2_journal_get_write_access() called by

ext4_write_end.
ext4_write_begin
    ext4_journal_start
        __ext4_journal_start_sb
            ext4_journal_check_start
            jbd2__journal_start

ext4_write_end
    ext4_mark_inode_dirty
        ext4_reserve_inode_write
            ext4_journal_get_write_access
                jbd2_journal_get_write_access
        ext4_mark_iloc_dirty
            ext4_do_update_inode
                ext4_handle_dirty_metadata
                    jbd2_journal_dirty_metadata


So I think we should put ocfs2_journal_access_di before
  ocfs2_journal_dirty in the ocfs2_write_end.  and it works well after my
  modification.

Signed-off-by: vicky <vicky.yangwenfang at huawei.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 fs/ocfs2/aops.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff -puN
fs/ocfs2/aops.c~ocfs2-call-ocfs2_journal_access_di-before-ocfs2_journal_dirty-in-ocfs2_write_end_nolock
fs/ocfs2/aops.c
---
a/fs/ocfs2/aops.c~ocfs2-call-ocfs2_journal_access_di-before-ocfs2_journal_dirty-in-ocfs2_write_end_nolock
+++ a/fs/ocfs2/aops.c
@@ -1817,16 +1817,6 @@ try_again:
 		if (ret)
 			goto out_commit;
 	}
-	/*
-	 * We don't want this to fail in ocfs2_write_end(), so do it
-	 * here.
-	 */
-	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
-				      OCFS2_JOURNAL_ACCESS_WRITE);
-	if (ret) {
-		mlog_errno(ret);
-		goto out_quota;
-	}
 
 	/*
 	 * Fill our page array first. That way we've grabbed enough so
@@ -1977,7 +1967,7 @@ int ocfs2_write_end_nolock(struct addres
 			   loff_t pos, unsigned len, unsigned copied,
 			   struct page *page, void *fsdata)
 {
-	int i;
+	int i, ret;
 	unsigned from, to, start = pos & (PAGE_CACHE_SIZE - 1);
 	struct inode *inode = mapping->host;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
@@ -2027,6 +2017,14 @@ int ocfs2_write_end_nolock(struct addres
 		}
 	}
 
+	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (ret) {
+		copied = ret;
+		mlog_errno(ret);
+		goto out;
+	}
+
 out_write_size:
 	pos += copied;
 	if (pos > i_size_read(inode)) {
@@ -2041,6 +2039,7 @@ out_write_size:
 	ocfs2_update_inode_fsync_trans(handle, inode, 1);
 	ocfs2_journal_dirty(handle, wc->w_di_bh);
 
+out:
 	ocfs2_commit_trans(osb, handle);
 
 	ocfs2_run_deallocs(osb, &wc->w_dealloc);
_

On Wed, Aug 06, 2014 at 01:32:11PM -0700, Andrew Morton
wrote:
> From: yangwenfang <vicky.yangwenfang at huawei.com>
> Subject: ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty()
in ocfs2_write_end_nolock()
> 
> After we call ocfs2_journal_access_di() in ocfs2_write_begin(),
> jbd2_journal_restart() may also be called, in this function transaction
> A's t_updates-- and obtains a new transaction B.  If
> jbd2_journal_commit_transaction() is happened to commit transaction A,
> when t_updates==0, it will continue to complete commit and unfile buffer.
> 
> So when jbd2_journal_dirty_metadata(), the handle is pointed a new
> transaction B, and the buffer head's journal head is already freed,
> jh->b_transaction == NULL, jh->b_next_transaction == NULL, it returns
> EINVAL, So it triggers the BUG_ON(status).
> 
> thread 1:                             jbd2:
> ocfs2_write_begin                     jbd2_journal_commit_transaction
> ocfs2_write_begin_nolock
>   ocfs2_start_trans
>     jbd2__journal_start(t_updates+1,
>                        transaction A)
>     ocfs2_journal_access_di
>     ocfs2_write_cluster_by_desc
>       ocfs2_mark_extent_written
>         ocfs2_change_extent_flag
>           ocfs2_split_extent
>             ocfs2_extend_rotate_transaction
>               jbd2_journal_restart
>               (t_updates-1,transaction B) t_updates==0
>                                         __jbd2_journal_refile_buffer
> 
> ocfs2_write_end
> ocfs2_write_end_nolock
>     ocfs2_journal_dirty
>         jbd2_journal_dirty_metadata(bug)
>    ocfs2_commit_trans
> 
> In ext4, I found that: jbd2_journal_get_write_access() called by
> 
> ext4_write_end.
> ext4_write_begin
>     ext4_journal_start
>         __ext4_journal_start_sb
>             ext4_journal_check_start
>             jbd2__journal_start
> 
> ext4_write_end
>     ext4_mark_inode_dirty
>         ext4_reserve_inode_write
>             ext4_journal_get_write_access
>                 jbd2_journal_get_write_access
>         ext4_mark_iloc_dirty
>             ext4_do_update_inode
>                 ext4_handle_dirty_metadata
>                     jbd2_journal_dirty_metadata
> 
> 
> So I think we should put ocfs2_journal_access_di before
>   ocfs2_journal_dirty in the ocfs2_write_end.  and it works well after my
>   modification.
Putting the journal_access_di in ocfs2_write_end is the correct thing to do,
thanks. I think we want to keep the journal_access_di in ocfs2_write_begin
though as we may change the disk inode when marking unwritten extents
(see the call to ocfs2_mark_extent_written()). So:

- I would remove the comment above journal_access_di in write_begin but not
  the actual call as we may dirty the inode buffer later.

- Move the call to journal_access_di to the top of ocfs2_write_end_nolock as
  I believe you might be missing some inode buffer updates there too.

Thanks,
	--Mark

--
Mark Fasheh