On Fri, Sep 11 2009, Ed Cashin wrote: > The Documentation/block/barrier.txt information seems geared toward > block device drivers that handle I/O requests from the request_queue, > and not drivers that handle bios directly by providing their own > make_request_fn via blk_queue_make_request. > > So I think the section quoted below does not apply to such a > bio-handling driver. > > * Currently, no matter which ordered mode is used, there can be only > one barrier request in progress. All I/O barriers are held off by > block layer until the previous I/O barrier is complete.
Right, that synchronization does not exist at the bio level. > The implication is that when a bio_barrier(bio) is seen by the > make_request_fn, it should sleep until any in-progress barrier bio has > been completed. Is that correct? Yes, that is correct. -- Jens Axboe -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to [email protected] Please read the FAQ at http://kernelnewbies.org/FAQ
