kernel/linux.git/drivers/md/dm-pcache/cache_key.c, branch linux-7.1.y

Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses

2026-02-22T16:26:33+00:00

Conversion performed via this Coccinelle script: // SPDX-License-Identifier: GPL-2.0-only // Options: --include-headers-for-types --all-includes --include-headers --keep-comments virtual patch @gfp depends on patch && !(file in "tools") && !(file in "samples")@ identifier ALLOC = {kmalloc_obj,kmalloc_objs,kmalloc_flex, kzalloc_obj,kzalloc_objs,kzalloc_flex, kvmalloc_obj,kvmalloc_objs,kvmalloc_flex, kvzalloc_obj,kvzalloc_objs,kvzalloc_flex}; @@ ALLOC(... - , GFP_KERNEL ) $ make coccicheck MODE=patch COCCI=gfp.cocci Build and boot tested x86_64 with Fedora 42's GCC and Clang: Linux version 6.19.0+ (user@host) (gcc (GCC) 15.2.1 20260123 (Red Hat 15.2.1-7), GNU ld version 2.44-12.fc42) #1 SMP PREEMPT_DYNAMIC 1970-01-01 Linux version 6.19.0+ (user@host) (clang version 20.1.8 (Fedora 20.1.8-4.fc42), LLD 20.1.8) #1 SMP PREEMPT_DYNAMIC 1970-01-01 Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

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