This patch introduces dm-pcache, a new DM target that places a DAX-
capable persistent-memory device in front of any slower block device and
uses it as a high-throughput, low-latency  cache.

Design highlights
-----------------
- DAX data path – data is copied directly between DRAM and the pmem
  mapping, bypassing the block layer’s overhead.

- Segmented, crash-consistent layout
  - all layout metadata are dual-replicated CRC-protected.
  - atomic kset flushes; key replay on mount guarantees cache integrity
    even after power loss.

- Striped multi-tree index
  - Multi‑tree indexing for high parallelism.
  - overlap-resolution logic ensures non-intersecting cached extents.

- Background services
  - write-back worker flushes dirty keys in order, preserving backing-device
    crash consistency. This is important for checkpoint in cloud storage.
  - garbage collector reclaims clean segments when utilisation exceeds a
    tunable threshold.

- Data integrity – optional CRC32 on cached payload; metadata always protected.

Comparison with existing block-level caches
---------------------------------------------------------------------------------------------------------------------------------
| Feature                          | pcache (this patch)             | bcache                       | dm-writecache             |
|----------------------------------|---------------------------------|------------------------------|---------------------------|
| pmem access method               | DAX                             | bio (block I/O)              | DAX                       |
| Write latency (4 K rand-write)   | ~5 µs                           | ~20 µs                       | ~5 µs                     |
| Concurrency                      | multi subtree index             | global index tree            | single tree + wc_lock     |
| IOPS (4K randwrite, 32 numjobs)  | 2.1 M                           | 352 K                        | 283 K                     |
| Read-cache support               | YES                             | YES                          | NO                        |
| Deployment                       | no re-format of backend         | backend devices must be      | no re-format of backend   |
|                                  |                                 | reformatted                  |                           |
| Write-back ordering              | log-structured;                 | no ordering guarantee        | no ordering guarantee     |
|                                  | preserves app-IO-order          |                              |                           |
| Data integrity checks            | metadata + data CRC(optional)   | metadata CRC only            | none                      |
---------------------------------------------------------------------------------------------------------------------------------

Signed-off-by: Dongsheng Yang <dongsheng.yang@linux.dev>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

dm-vdo docs currently has no explicit title heading but instead there
are multiple section headings as top-level heading. As such, these
sections are rendered as titles and inflates number of entries in the
toctree index.

Promote the first section heading ("dm-vdo") to title heading.

Fixes: 04bf7ac646ab ("dm: add documentation for dm-vdo target")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

found/fixed the following typos

- flushs -> flushes

in `Documentation/admin-guide/device-mapper/delay.rst`

Signed-off-by: Soham Metha <sohammetha01@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Fixed the following typos in device-mapper documentation:
- explicitely -> explicitly
- approriate -> appropriate

Signed-off-by: Shubham Sharma <slopixelz@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

1. convert KB/MB/GB to KiB/MiB/GiB;
2. change the number of sectors for 128MiB from 256000 to 262144 as
256000 sectors is neither 128 MB nor 128 MiB.

Signed-off-by: LongPing Wei <weilongping@oppo.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Calling verity_verify_io in bh for IO of all sizes is not suitable for
embedded devices. From our tests, it can improve the performance of 4K
synchronise random reads.
For example:
./fio --name=rand_read --ioengine=psync --rw=randread --bs=4K \
 --direct=1 --numjobs=8 --runtime=60 --time_based --group_reporting \
 --filename=/dev/block/mapper/xx-verity

But it will degrade the performance of 512K synchronise sequential reads
on our devices.
For example:
./fio --name=read --ioengine=psync --rw=read --bs=512K --direct=1 \
 --numjobs=8 --runtime=60 --time_based --group_reporting \
 --filename=/dev/block/mapper/xx-verity

A parameter array is introduced by this change. And users can modify the
default config by /sys/module/dm_verity/parameters/use_bh_bytes.

The default limits for NONE/RT/BE is set to 8192.
The default limits for IDLE is set to 0.

Call verity_verify_io directly when verity_end_io is not in hardirq.

Signed-off-by: LongPing Wei <weilongping@oppo.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

This patch adds documentation for new option introduced in commit
4441686b24a1 ("dm-crypt: Allow to specify the integrity key size as option").

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

This patch adds documentation for new 'I' mode for dm-integrity
introduced in commit
fb0987682c62 ("dm-integrity: introduce the Inline mode").

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

This patch adds documentation for options introduced in commit
f811b83879fb ("dm-verity: introduce the options restart_on_error and panic_on_error").

Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Pull device mapper updates from Mikulas Patocka:

 - Misc VDO fixes

 - Remove unused declarations dm_get_rq_mapinfo() and dm_zone_map_bio()

 - Dm-delay: Improve kernel documentation

 - Dm-crypt: Allow to specify the integrity key size as an option

 - Dm-bufio: Remove pointless NULL check

 - Small code cleanups: Use ERR_CAST; remove unlikely() around IS_ERR;
   use __assign_bit

 - Dm-integrity: Fix gcc 5 warning; convert comma to semicolon; fix
   smatch warning

 - Dm-integrity: Support recalculation in the 'I' mode

 - Revert "dm: requeue IO if mapping table not yet available"

 - Dm-crypt: Small refactoring to make the code more readable

 - Dm-cache: Remove pointless error check

 - Dm: Fix spelling errors

 - Dm-verity: Restart or panic on an I/O error if restart or panic was
   requested

 - Dm-verity: Fallback to platform keyring also if key in trusted
   keyring is rejected

* tag 'for-6.12/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (26 commits)
  dm verity: fallback to platform keyring also if key in trusted keyring is rejected
  dm-verity: restart or panic on an I/O error
  dm: fix spelling errors
  dm-cache: remove pointless error check
  dm vdo: handle unaligned discards correctly
  dm vdo indexer: Convert comma to semicolon
  dm-crypt: Use common error handling code in crypt_set_keyring_key()
  dm-crypt: Use up_read() together with key_put() only once in crypt_set_keyring_key()
  Revert "dm: requeue IO if mapping table not yet available"
  dm-integrity: check mac_size against HASH_MAX_DIGESTSIZE in sb_mac()
  dm-integrity: support recalculation in the 'I' mode
  dm integrity: Convert comma to semicolon
  dm integrity: fix gcc 5 warning
  dm: Make use of __assign_bit() API
  dm integrity: Remove extra unlikely helper
  dm: Convert to use ERR_CAST()
  dm bufio: Remove NULL check of list_entry()
  dm-crypt: Allow to specify the integrity key size as option
  dm: Remove unused declaration and empty definition "dm_zone_map_bio"
  dm delay: enhance kernel documentation
  ...