jbd2: Avoid possible NULL dereference in jbd2_journal_begin_ordered_truncate()

If we race with commit code setting i_transaction to NULL, we could
possibly dereference it.  Proper locking requires the journal pointer
(to access journal->j_list_lock), which we don't have.  So we have to
change the prototype of the function so that filesystem passes us the
journal pointer.  Also add a more detailed comment about why the
function jbd2_journal_begin_ordered_truncate() does what it does and
how it should be used.

Thanks to Dan Carpenter <[email protected]> for pointing to the
suspitious code.

Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Acked-by: Joel Becker <[email protected]>
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: Dan Carpenter <[email protected]>

0 files changed, 0 insertions, 0 deletions