Re: [PATCH 0/7] libnvdimm/pfn: Fix section-alignment padding
From: Dan Williams
Date: Wed Feb 20 2019 - 12:11:21 EST
On Tue, Feb 12, 2019 at 1:37 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> Lately Linux has encountered platforms that collide Persistent Memory
> regions between each other, specifically cases where ->start_pad needed
> to be non-zero. This lead to commit ae86cbfef381 "libnvdimm, pfn: Pad
> pfn namespaces relative to other regions". That commit allowed
> namespaces to be mapped with devm_memremap_pages(). However dax
> operations on those configurations currently fail if attempted within the
> ->start_pad range because pmem_device->data_offset was still relative to
> raw resource base not relative to the section aligned resource range
> mapped by devm_memremap_pages().
> Luckily __bdev_dax_supported() caught these failures and simply disabled
> dax. However, to fix this situation a non-backwards compatible change
> needs to be made to the interpretation of the nd_pfn info-block.
> ->start_pad needs to be accounted in ->map.map_offset (formerly
> ->data_offset), and ->map.map_base (formerly ->phys_addr) needs to be
> adjusted to the section aligned resource base used to establish
> ->map.map formerly (formerly ->virt_addr).
> See patch 7 "libnvdimm/pfn: Fix 'start_pad' implementation" for more
> details, and the ndctl patch series "Improve support + testing for
> labels + info-blocks" for the corresponding regression test.
Hello valued reviewers, can I plead for a sanity check of at least
"libnvdimm/pfn: Introduce super-block minimum version requirements"
and "libnvdimm/pfn: Fix 'start_pad' implementation"? In particular
Jeff / Johannes this has end user / distro impact in that users may
lose access to namespaces that are upgraded to v1.3 info-blocks and
then boot an old kernel. I did not see a way around that sharp edge.
> Dan Williams (7):
> libnvdimm/pfn: Account for PAGE_SIZE > info-block-size in nd_pfn_init()
> libnvdimm/pmem: Honor force_raw for legacy pmem regions
> dax: Check the end of the block-device capacity with dax_direct_access()
> libnvdimm/pfn: Introduce super-block minimum version requirements
> libnvdimm/pfn: Remove dax_label_reserve
> libnvdimm/pfn: Introduce 'struct pfn_map_info'
> libnvdimm/pfn: Fix 'start_pad' implementation
> drivers/dax/pmem.c | 9 +-
> drivers/dax/super.c | 39 ++++++--
> drivers/nvdimm/namespace_devs.c | 4 +
> drivers/nvdimm/nd.h | 15 +++
> drivers/nvdimm/pfn.h | 4 +
> drivers/nvdimm/pfn_devs.c | 181 ++++++++++++++++++++++++++++-----------
> drivers/nvdimm/pmem.c | 111 +++++++++++-------------
> drivers/nvdimm/pmem.h | 12 ---
> tools/testing/nvdimm/pmem-dax.c | 15 ++-
> 9 files changed, 244 insertions(+), 146 deletions(-)