Re: [PATCH v2 06/20] drbd: add DAX/PMEM support for metadata access

[Christoph Böhmwalder]

On 10/6/26 17:45, Christoph Böhmwalder wrote:
> When DRBD's metadata device resides on persistent memory (PMEM/NVDIMM),
> accessing it by reading and writing full blocks is unnecessarily
> costly.
> Add a DAX-based metadata path that directly maps the metadata region,
> enabling byte-granular, IRQ-safe access without having to go through
> the block layer.
>
> The PMEM path also introduces a more efficient activity log layout:
> instead of writing journal transactions, the in-memory LRU-cache hash
> table is stored directly in persistent memory and updated in-place.
> Similarly, the resync bitmap is accessed directly from PMEM rather than
> being loaded into and flushed from DRAM.
>
> This is compiled in only when CONFIG_DEV_DAX_PMEM is enabled.
>
> Co-developed-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
> Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
> Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@xxxxxxxxxx>
> ---
>   drivers/block/drbd/Makefile        |   1 +
>   drivers/block/drbd/drbd_dax_pmem.c | 172 +++++++++++++++++++++++++++++
>   drivers/block/drbd/drbd_dax_pmem.h |  43 ++++++++
>   3 files changed, 216 insertions(+)
>   create mode 100644 drivers/block/drbd/drbd_dax_pmem.c
>   create mode 100644 drivers/block/drbd/drbd_dax_pmem.h

Sorry, the CCs for DAX got dropped, adding them now. Original link:
https://lore.kernel.org/linux-block/20261006154607.3936501-7-christoph.boehmwalder@xxxxxxxxxx/