• Jan Kara's avatar
    jbd: Fix assertion failure in fs/jbd/checkpoint.c · d4beaf4a
    Jan Kara authored
    Before we start committing a transaction, we call
    __journal_clean_checkpoint_list() to cleanup transaction's written-back
    buffers.
    
    If this call happens to remove all of them (and there were already some
    buffers), __journal_remove_checkpoint() will decide to free the transaction
    because it isn't (yet) a committing transaction and soon we fail some
    assertion - the transaction really isn't ready to be freed :).
    
    We change the check in __journal_remove_checkpoint() to free only a
    transaction in T_FINISHED state.  The locking there is subtle though (as
    everywhere in JBD ;().  We use j_list_lock to protect the check and a
    subsequent call to __journal_drop_transaction() and do the same in the end
    of journal_commit_transaction() which is the only place where a transaction
    can get to T_FINISHED state.
    
    Probably I'm too paranoid here and such locking is not really necessary -
    checkpoint lists are processed only from log_do_checkpoint() where a
    transaction must be already committed to be processed or from
    __journal_clean_checkpoint_list() where kjournald itself calls it and thus
    transaction cannot change state either.  Better be safe if something
    changes in future...
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    Cc: <linux-ext4@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    d4beaf4a
checkpoint.c 19.2 KB