On Fri, Sep 14, 2012 at 02:58:04AM -0600, Liu Bo wrote: > In some workloads we have nested joining transaction operations, > eg. > run_delalloc_nocow > btrfs_join_transaction > cow_file_range > btrfs_join_transaction > > it can be a serious bug since each trans handler has only two > block_rsv, orig_rsv and block_rsv, which means we may lose our > first block_rsv after two joining transaction operations: > > 1) btrfs_start_transaction > trans->block_rsv = A > > 2) btrfs_join_transaction > trans->orig_rsv = trans->block_rsv; ---> orig_rsv is now A > trans->block_rsv = B > > 3) btrfs_join_transaction > trans->orig_rsv = trans->block_rsv; ---> orig_rsv is now B > trans->block_rsv = C > ... > I'd like to see the actual stack trace where this happens, because I don't think it can happen. And if it is we need to look at that specific case and adjust it as necessary and not add a bunch of kmallocs just to track the block_rsv, because frankly it's not that big of a deal, it was just put into place in case somebody wasn't expecting a call they made to start another transaction and reset the block_rsv, which I don't actually think happens anywhere. So NAK on this patch, give me more information so I can figure out the right way to deal with this. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
