kernel/linux.git/drivers/md/Kconfig, branch v6.19.11

dm-verity: use SHA-256 library for SHA-256

2025-10-20T13:47:27+00:00

When the hash algorithm is SHA-256 and the verity version is not 0, use the SHA-256 library instead of crypto_shash. This is a prerequisite for making dm-verity interleave the computation of SHA-256 hashes for increased performance. That optimization is available in the SHA-256 library but not in crypto_shash. Even without interleaved hashing, switching to the library also slightly improves performance by itself because it avoids the overhead of crypto_shash, including indirect calls and other API overhead. (Benchmark on x86_64, AMD Zen 5: hashing 4K blocks gets 2.1% faster.) SHA-256 is by far the most common hash algorithm used with dm-verity. It makes sense to optimize for the common case and fall back to the generic crypto layer for uncommon cases, as suggested by Linus: https://lore.kernel.org/r/CAHk-=wgp-fOSsZsYrbyzqCAfEvrt5jQs1jL-97Wc4seMNTUyng@mail.gmail.com Signed-off-by: Eric Biggers Signed-off-by: Mikulas Patocka

dm-crypt: Use MD5 library instead of crypto_shash

2025-10-20T12:51:35+00:00

The lmk IV mode, which dm-crypt supports for Loop-AES compatibility, involves an MD5 computation. Update its implementation to use the MD5 library API instead of crypto_shash. This has many benefits, such as: - Simpler code. Notably, much of the error-handling code is no longer needed, since the library functions can't fail. - Reduced stack usage. crypt_iv_lmk_one() now allocates only 112 bytes on the stack instead of 520 bytes. - The library functions are strongly typed, preventing bugs like https://lore.kernel.org/r/f1625ddc-e82e-4b77-80c2-dc8e45b54848@gmail.com - Slightly improved performance, as the library provides direct access to the MD5 code without unnecessary overhead such as indirect calls. To preserve the existing behavior of lmk support being disabled when the kernel is booted with "fips=1", make crypt_iv_lmk_ctr() check fips_enabled itself. Previously it relied on crypto_alloc_shash("md5") failing. (I don't know for sure that lmk *actually* needs to be disallowed in FIPS mode; this just preserves the existing behavior.) Signed-off-by: Eric Biggers Signed-off-by: Mikulas Patocka Acked-by: Ard Biesheuvel

Merge tag 'for-6.18/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

2025-10-04T01:48:02+00:00

Pull device mapper updates from Mikulas Patocka: - a new dm-pcache target for read/write caching on persistent memory - fix typos in docs - misc small refactoring - mark dm-error with DM_TARGET_PASSES_INTEGRITY - dm-request-based: fix NULL pointer dereference and quiesce_depth out of sync - dm-linear: optimize REQ_PREFLUSH - dm-vdo: return error on corrupted metadata - dm-integrity: support asynchronous hash interface * tag 'for-6.18/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (27 commits) dm raid: use proper md_ro_state enumerators dm-integrity: prefer synchronous hash interface dm-integrity: enable asynchronous hash interface dm-integrity: rename internal_hash dm-integrity: add the "offset" argument dm-integrity: allocate the recalculate buffer with kmalloc dm-integrity: introduce integrity_kmap and integrity_kunmap dm-integrity: replace bvec_kmap_local with kmap_local_page dm-integrity: use internal variable for digestsize dm vdo: return error on corrupted metadata in start_restoring_volume functions dm vdo: Update code to use mem_is_zero dm: optimize REQ_PREFLUSH with data when using the linear target dm-pcache: use int type to store negative error codes dm: fix "writen"->"written" dm-pcache: cleanup: fix coding style report by checkpatch.pl dm-pcache: remove ctrl_lock for pcache_cache_segment dm: fix NULL pointer dereference in __dm_suspend() dm: fix queue start/stop imbalance under suspend/load/resume races dm-pcache: add persistent cache target in device-mapper dm error: mark as DM_TARGET_PASSES_INTEGRITY ...

md/md-llbitmap: introduce new lockless bitmap

2025-09-06T09:27:51+00:00

Redundant data is used to enhance data fault tolerance, and the storage method for redundant data vary depending on the RAID levels. And it's important to maintain the consistency of redundant data. Bitmap is used to record which data blocks have been synchronized and which ones need to be resynchronized or recovered. Each bit in the bitmap represents a segment of data in the array. When a bit is set, it indicates that the multiple redundant copies of that data segment may not be consistent. Data synchronization can be performed based on the bitmap after power failure or readding a disk. If there is no bitmap, a full disk synchronization is required. Due to known performance issues with md-bitmap and the unreasonable implementations: - self-managed IO submitting like filemap_write_page(); - global spin_lock I have decided not to continue optimizing based on the current bitmap implementation, this new bitmap is invented without locking from IO fast path and can be used with fast disks. For designs and details, see the comments in drivers/md-llbitmap.c. Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-12-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Li Nan

md/md-bitmap: introduce CONFIG_MD_BITMAP

2025-09-06T09:12:22+00:00

Now that all implementations are internal, it's sensible to add a config option for md-bitmap, and it's a good way for isolation. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-16-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

dm-pcache: add persistent cache target in device-mapper

2025-08-25T13:25:29+00:00

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 Signed-off-by: Mikulas Patocka

Merge tag 'crc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux

2025-04-08T19:09:28+00:00

Pull CRC cleanups from Eric Biggers: "Finish cleaning up the CRC kconfig options by removing the remaining unnecessary prompts and an unnecessary 'default y', removing CONFIG_LIBCRC32C, and documenting all the CRC library options" * tag 'crc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux: lib/crc: remove CONFIG_LIBCRC32C lib/crc: document all the CRC library kconfig options lib/crc: remove unnecessary prompt for CONFIG_CRC_ITU_T lib/crc: remove unnecessary prompt for CONFIG_CRC_T10DIF lib/crc: remove unnecessary prompt for CONFIG_CRC16 lib/crc: remove unnecessary prompt for CONFIG_CRC_CCITT lib/crc: remove unnecessary prompt for CONFIG_CRC32 and drop 'default y'

lib/crc: remove CONFIG_LIBCRC32C

2025-04-04T18:31:42+00:00

Now that LIBCRC32C does nothing besides select CRC32, make every option that selects LIBCRC32C instead select CRC32 directly. Then remove LIBCRC32C. Reviewed-by: Christoph Hellwig Reviewed-by: "Martin K. Petersen" Acked-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20250401221600.24878-8-ebiggers@kernel.org Signed-off-by: Eric Biggers

dm-crypt: switch to using the crc32 library

2025-02-03T13:10:10+00:00

Now that the crc32() library function takes advantage of architecture-specific optimizations, it is unnecessary to go through the crypto API. Just use crc32(). This is much simpler, and it improves performance due to eliminating the crypto API overhead. (However, this only affects the TCW IV mode of dm-crypt, which is a compatibility mode that is rarely used compared to other dm-crypt modes.) Signed-off-by: Eric Biggers Signed-off-by: Mikulas Patocka

md: reintroduce md-linear

2025-01-13T15:36:29+00:00

THe md-linear is removed by commit 849d18e27be9 ("md: Remove deprecated CONFIG_MD_LINEAR") because it has been marked as deprecated for a long time. However, md-linear is used widely for underlying disks with different size, sadly we didn't know this until now, and it's true useful to create partitions and assemble multiple raid and then append one to the other. People have to use dm-linear in this case now, however, they will prefer to minimize the number of involved modules. Fixes: 849d18e27be9 ("md: Remove deprecated CONFIG_MD_LINEAR") Cc: stable@vger.kernel.org Signed-off-by: Yu Kuai Acked-by: Coly Li Acked-by: Mike Snitzer Link: https://lore.kernel.org/r/20250102112841.1227111-1-yukuai1@huaweicloud.com Signed-off-by: Song Liu