On 8/13/2015 10:00 AM, Jeff Moyer wrote: > Boaz Harrosh <boaz@xxxxxxxxxxxxx> writes: > >> On 08/13/2015 12:11 AM, Jeff Moyer wrote: >>> Boaz Harrosh <boaz@xxxxxxxxxxxxx> writes: >>> >>>> On 08/07/2015 11:41 PM, Jeff Moyer wrote: >>>> <> >>>>> >>>>>> We need to cope with the case where the end of a partition isn't on a >>>>>> page boundary though. >>>>> >>>>> Well, that's usually done by falling back to buffered I/O. I gave that >>>>> a try and panicked the box. :) I'll keep looking into it, but probably >>>>> won't have another patch until next week. >>>>> >>>> >>>> lets slow down for a sec, please. >>>> >>>> We have all established that an unaligned partition start is BAD and not supported? >>> >>> No. Unaligned partitions on RAID arrays or 512e devices are bad because >>> they result in suboptimal performance. They are most certainly still >>> supported, though. >>> >> >> What ? >> >> I meant for dax on pmem or brd. I meant that we *do not* support dax access >> on an unaligned partition start. (None dax is perfectly supported) > > Sorry, I thought your statement was broader than that. > >> We did it this way because of the direct_access API that returns a pfn >> with is PAGE_SIZE. We could introduce a pfn+offset but we thought it is >> not worth it, and that dax should be page aligned for code simplicity > > I'd be fine with changing the persistent memory block device to only > support 4k logical, 4k physical block size. That probably makes the > most sense. If that's what we want, the current patch doesn't do that. https://lists.01.org/pipermail/linux-nvdimm/2015-July/001555.html It causes the physical block size to be PAGE_SIZE but the logical block size is still 512. However, the minimum_io_size is now 4096 (same as physical block size, I assume). The optimal_io_size is still 0. What does that mean? Whatever we go with, we should do something because 4.2rc6 is still broken, unable to create a xfs file system on a pmem device, ever since the change to use DAX on block devices with O_DIRECT. -- ljk > > Cheers, > Jeff > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
