[Ocfs2-devel] [PATCH V2] ocfs2: call ocfs2_journal_access_di() before ocfs2_journal_dirty() in ocfs2_write_end_nolock()

[yangwenfang]

1.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

2. 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

3.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>
---
 fs/ocfs2/aops.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index d310d12..230e686 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1818,16 +1818,6 @@ 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
@@ -1978,7 +1968,7 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
                           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);
@@ -2028,6 +2018,14 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
                }
        }

+       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)) {
@@ -2042,6 +2040,7 @@ 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);
--
1.8.3.4