This series introduces atomic write support for software RAID 0/1/10.

The main changes are to ensure that we can calculate the stacked device
request_queue limits appropriately for atomic writes. Fundamentally, if
some bottom does not support atomic writes, then atomic writes are not
supported for the top device. Furthermore, the atomic writes limits are
the lowest common supported limits from all bottom devices.

Flag BLK_FEAT_ATOMIC_WRITES_STACKED is introduced to enable atomic writes
for stacked devices selectively. This ensures that we can analyze and test
atomic writes support per individual md/dm personality (prior to
enabling).

Based on bio_split() rework at
https://lore.kernel.org/linux-block/20241031095918.99964-1-john.g.garry@oracle.com/T/#m7bed4a956a439ac4a9fa72f0bc41d1b08ca047c6

Differences to v2:
- Refactor blk_stack_atomic_writes_limits() (Christoph)
- Relocate RAID 1/10 BB check (Kaui)
- Add RB tag from Christoph (Thanks!)
- Set REQ_ATOMIC for RAID 1/10

Differences to RFC:
- Add support for RAID 1/10
- Add sanity checks for atomic write limits
- Use BLK_FEAT_ATOMIC_WRITES_STACKED, rather than BLK_FEAT_ATOMIC_WRITES
- Drop patch issue of truncating atomic writes
 - will send separately

John Garry (5):
  block: Add extra checks in blk_validate_atomic_write_limits()
  block: Support atomic writes limits for stacked devices
  md/raid0: Atomic write support
  md/raid1: Atomic write support
  md/raid10: Atomic write support

 block/blk-settings.c   | 132 +++++++++++++++++++++++++++++++++++++++++
 drivers/md/raid0.c     |   1 +
 drivers/md/raid1.c     |  14 ++++-
 drivers/md/raid10.c    |  14 ++++-
 include/linux/blkdev.h |   4 ++
 5 files changed, 161 insertions(+), 4 deletions(-)

-- 
2.31.1