linux-kernel - [PATCH v7 0/5] Add DAX ABI for memmap_on

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Date: Wed, 24 Jan 2024 12:03:45 -0800
From: Vishal Verma <vishal.l.verma@...el.com>
To: Dan Williams <dan.j.williams@...el.com>, 
 Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Oscar Salvador <osalvador@...e.de>
Cc: linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev, 
 linux-cxl@...r.kernel.org, David Hildenbrand <david@...hat.com>, 
 Dave Hansen <dave.hansen@...ux.intel.com>, 
 Huang Ying <ying.huang@...el.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org, 
 Michal Hocko <mhocko@...e.com>, Li Zhijian <lizhijian@...itsu.com>, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH v7 0/5] Add DAX ABI for memmap_on_memory

This series adds sysfs ABI to control memmap_on_memory behavior for DAX
devices.

Patch 1 replaces incorrect device_lock() usage with a local rwsem - this
was identified during review.

Patch 2 is also a preparatory patch that replaces sprintf() for sysfs
operations with sysfs_emit()

Patch 3 adds the missing documentation for the sysfs ABI for DAX regions
and Dax devices.

Patch 4 exports mhp_supports_memmap_on_memory().

Patch 5 adds the new ABI for toggling memmap_on_memory semantics for dax
devices.

---
Changes in v7:
- Rebase to v6.8-rc1
- Remove an unnecessary 'size' variable. (Matthew)
- Replace device lock (ab)use in dax/bus.c with local rwsems (Greg)
- Replace sprintf() usage with sysfs_emit() (Greg)
- Link to v6: https://lore.kernel.org/r/20231214-vv-dax_abi-v6-0-ad900d698438@intel.com

Changes in v6:
- Use sysfs_emit() in memmap_on_memory_show() (Greg)
- Change the ABI documentation date for memmap_on_memory to January 2024
  as that's likely when the 6.8 merge window will fall (Greg)
- Fix dev->driver check (Ying)
- Link to v5: https://lore.kernel.org/r/20231214-vv-dax_abi-v5-0-3f7b006960b4@intel.com

Changes in v5:
- Export and check mhp_supports_memmap_on_memory() in the DAX sysfs ABI
  (David)
- Obtain dax_drv under the device lock (Ying)
- Check dax_drv for NULL before dereferencing it (Ying)
- Clean up some repetition in sysfs-bus-dax documentation entries
  (Jonathan)
- A few additional cleanups enabled by guard(device) (Jonathan)
- Drop the DEFINE_GUARD() part of patch 2, add dependency on Dan's patch
  above so it can be backported / applied separately (Jonathan, Dan)
- Link to v4: https://lore.kernel.org/r/20231212-vv-dax_abi-v4-0-1351758f0c92@intel.com

Changes in v4:
- Hold the device lock when checking if the dax_dev is bound to kmem
  (Ying, Dan)
- Remove dax region checks (and locks) as they were unnecessary.
- Introduce guard(device) for device lock/unlock (Dan)
- Convert the rest of drivers/dax/bus.c to guard(device)
- Link to v3: https://lore.kernel.org/r/20231211-vv-dax_abi-v3-0-acf6cc1bde9f@intel.com

Changes in v3:
- Fix typo in ABI docs (Zhijian Li)
- Add kernel config and module parameter dependencies to the ABI docs
  entry (David Hildenbrand)
- Ensure kmem isn't active when setting the sysfs attribute (Ying
  Huang)
- Simplify returning from memmap_on_memory_store()
- Link to v2: https://lore.kernel.org/r/20231206-vv-dax_abi-v2-0-f4f4f2336d08@intel.com

Changes in v2:
- Fix CC lists, patch 1/2 didn't get sent correctly in v1
- Link to v1: https://lore.kernel.org/r/20231206-vv-dax_abi-v1-0-474eb88e201c@intel.com

Cc: <linux-kernel@...r.kernel.org>
Cc: <nvdimm@...ts.linux.dev>
Cc: <linux-cxl@...r.kernel.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: <linux-mm@...ck.org>
To: Dan Williams <dan.j.williams@...el.com>
To: Vishal Verma <vishal.l.verma@...el.com>
To: Dave Jiang <dave.jiang@...el.com>
To: Andrew Morton <akpm@...ux-foundation.org>
To: Oscar Salvador <osalvador@...e.de>

---
Vishal Verma (5):
      dax/bus.c: replace driver-core lock usage by a local rwsem
      dax/bus.c: replace several sprintf() with sysfs_emit()
      Documentatiion/ABI: Add ABI documentation for sys-bus-dax
      mm/memory_hotplug: export mhp_supports_memmap_on_memory()
      dax: add a sysfs knob to control memmap_on_memory behavior

 include/linux/memory_hotplug.h          |   6 +
 drivers/dax/bus.c                       | 295 +++++++++++++++++++++++---------
 mm/memory_hotplug.c                     |  17 +-
 Documentation/ABI/testing/sysfs-bus-dax | 153 +++++++++++++++++
 4 files changed, 381 insertions(+), 90 deletions(-)
---
base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
change-id: 20231025-vv-dax_abi-17a219c46076

Best regards,
-- 
Vishal Verma <vishal.l.verma@...el.com>