On Mon, May 02, 2016 at 06:41:51PM +0300, Boaz Harrosh wrote: > > All IO in a dax filesystem used to go through dax_do_io, which cannot > > handle media errors, and thus cannot provide a recovery path that can > > send a write through the driver to clear errors. > > > > Add a new iocb flag for DAX, and set it only for DAX mounts. In the IO > > path for DAX filesystems, use the same direct_IO path for both DAX and > > direct_io iocbs, but use the flags to identify when we are in O_DIRECT > > mode vs non O_DIRECT with DAX, and for O_DIRECT, use the conventional > > direct_IO path instead of DAX. > > > > Really? What are your thinking here? > > What about all the current users of O_DIRECT, you have just made them > 4 times slower and "less concurrent*" then "buffred io" users. Since > direct_IO path will queue an IO request and all. > (And if it is not so slow then why do we need dax_do_io at all? [Rhetorical]) > > I hate it that you overload the semantics of a known and expected > O_DIRECT flag, for special pmem quirks. This is an incompatible > and unrelated overload of the semantics of O_DIRECT. Agreed - makig O_DIRECT less direct than not having it is plain stupid, and I somehow missed this initially. This whole DAX story turns into a major nightmare, and I fear all our hodge podge tweaks to the semantics aren't helping it. It seems like we simply need an explicit O_DAX for the read/write bypass if can't sort out the semantics (error, writer synchronization) just as we need a special flag for MMAP.. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
