[PATCH v5 0/3] Fix DM DAX handling

[Ross Zwisler]

This series fixes a few issues that I found with DM's handling of DAX
devices.  Here are some of the issues I found:

 * We can create a dm-stripe or dm-linear device which is made up of an
   fsdax PMEM namespace and a raw PMEM namespace but which can hold a
   filesystem mounted with the -o dax mount option.  DAX operations to
   the raw PMEM namespace part lack struct page and can fail in
   interesting/unexpected ways when doing things like fork(), examining
   memory with gdb, etc.

 * We can create a dm-stripe or dm-linear device which is made up of an
   fsdax PMEM namespace and a BRD ramdisk which can hold a filesystem
   mounted with the -o dax mount option.  All I/O to this filesystem
   will fail.

---

Changes since v4:
 * No code changes.
 * Updated the changelogs for patches 1 and 3.
 * Removed the Cc: stable from patch 1.
 * Added a Fixes: tag to patch 2.

Ross Zwisler (3):
  pmem: only set QUEUE_FLAG_DAX for fsdax mode
  dax: bdev_dax_supported() check for QUEUE_FLAG_DAX
  dm: prevent DAX mounts if not supported

 drivers/dax/super.c   | 8 ++++++++
 drivers/md/dm-table.c | 7 ++++---
 drivers/md/dm.c       | 3 +--
 drivers/nvdimm/pmem.c | 3 ++-
 4 files changed, 15 insertions(+), 6 deletions(-)

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2.14.4