kernel/linux.git/drivers/md/bcache/writeback.c, branch v6.19.11

bcache: WQ_PERCPU added to alloc_workqueue users

2025-11-13T16:18:06+00:00

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they’re needed and reducing noise when CPUs are isolated. This patch continues the effort to refactor worqueue APIs, which has begun with the change introducing new workqueues and a new alloc_workqueue flag: commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq") commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag") This change adds a new WQ_PERCPU flag to explicitly request alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND must now use WQ_PERCPU. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Signed-off-by: Coly Li Signed-off-by: Jens Axboe

bcache: drop discard sysfs interface

2025-11-13T16:18:06+00:00

Since discard code is removed, now the sysfs interface to enable discard is useless. This patch removes the corresponding sysfs entry, and remove bool variable 'discard' from struct cache as well. Signed-off-by: Coly Li Signed-off-by: Jens Axboe

block: remove the bi_inline_vecs variable sized array from struct bio

2025-09-09T13:31:59+00:00

Bios are embedded into other structures, and at least spare is unhappy about embedding structures with variable sized arrays. There's no real need to the array anyway, we can replace it with a helper pointing to the memory just behind the bio, and with the previous cleanups there is very few site doing anything special with it. Signed-off-by: Christoph Hellwig Reviewed-by: John Garry Signed-off-by: Jens Axboe

block: add a bio_init_inline helper

2025-09-09T13:31:59+00:00

Just a simpler wrapper around bio_init for callers that want to initialize a bio with inline bvecs. Signed-off-by: Christoph Hellwig Reviewed-by: John Garry Reviewed-by: Yu Kuai Signed-off-by: Jens Axboe

Revert "bcache: remove heap-related macros and switch to generic min_heap"

2025-06-20T03:48:03+00:00

This reverts commit 866898efbb25bb44fd42848318e46db9e785973a. The generic bottom-up min_heap implementation causes performance regression in invalidate_buckets_lru(), a hot path in bcache. Before the cache is fully populated, new_bucket_prio() often returns zero, leading to many equal comparisons. In such cases, bottom-up sift_down performs up to 2 * log2(n) comparisons, while the original top-down approach completes with just O() comparisons, resulting in a measurable performance gap. The performance degradation is further worsened by the non-inlined min_heap API functions introduced in commit 92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap API functions"), adding function call overhead to this critical path. As reported by Robert, bcache now suffers from latency spikes, with P100 (max) latency increasing from 600 ms to 2.4 seconds every 5 minutes. These regressions degrade bcache's effectiveness as a low-latency cache layer and lead to frequent timeouts and application stalls in production environments. This revert aims to restore bcache's original low-latency behavior. Link: https://lore.kernel.org/lkml/CAJhEC05+0S69z+3+FB2Cd0hD+pCRyWTKLEOsc8BOmH73p1m+KQ@mail.gmail.com Link: https://lkml.kernel.org/r/20250614202353.1632957-3-visitorckw@gmail.com Fixes: 866898efbb25 ("bcache: remove heap-related macros and switch to generic min_heap") Fixes: 92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap API functions") Signed-off-by: Kuan-Wei Chiu Reported-by: Robert Pang Closes: https://lore.kernel.org/linux-bcache/CAJhEC06F_AtrPgw2-7CvCqZgeStgCtitbD-ryuPpXQA-JG5XXw@mail.gmail.com Acked-by: Coly Li Cc: Ching-Chun (Jim) Huang Cc: Kent Overstreet Cc: Signed-off-by: Andrew Morton

block: Delete bio_set_prio()

2024-12-23T15:17:23+00:00

Since commit 43b62ce3ff0a ("block: move bio io prio to a new field"), macro bio_set_prio() does nothing but set bio->bi_ioprio. All other places just set bio->bi_ioprio directly, so replace bio_set_prio() remaining callsites with setting bio->bi_ioprio directly and delete that macro. Signed-off-by: John Garry Acked-by: Jack Wang Reviewed-by: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20241202111957.2311683-3-john.g.garry@oracle.com Signed-off-by: Jens Axboe

bcache: remove heap-related macros and switch to generic min_heap

2024-06-25T05:25:00+00:00

Drop the heap-related macros from bcache and replacing them with the generic min_heap implementation from include/linux. By doing so, code readability is improved by using functions instead of macros. Moreover, the min_heap implementation in include/linux adopts a bottom-up variation compared to the textbook version currently used in bcache. This bottom-up variation allows for approximately 50% reduction in the number of comparison operations during heap siftdown, without changing the number of swaps, thus making it more efficient. Link: https://lkml.kernel.org/ioyfizrzq7w7mjrqcadtzsfgpuntowtjdw5pgn4qhvsdp4mqqg@nrlek5vmisbu Link: https://lkml.kernel.org/r/20240524152958.919343-16-visitorckw@gmail.com Signed-off-by: Kuan-Wei Chiu Reviewed-by: Ian Rogers Acked-by: Coly Li Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Bagas Sanjaya Cc: Brian Foster Cc: Ching-Chun (Jim) Huang Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kent Overstreet Cc: Mark Rutland Cc: Matthew Sakai Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Randy Dunlap Signed-off-by: Andrew Morton

bcache: fix variable length array abuse in btree_iter

2024-05-09T01:15:01+00:00

btree_iter is used in two ways: either allocated on the stack with a fixed size MAX_BSETS, or from a mempool with a dynamic size based on the specific cache set. Previously, the struct had a fixed-length array of size MAX_BSETS which was indexed out-of-bounds for the dynamically-sized iterators, which causes UBSAN to complain. This patch uses the same approach as in bcachefs's sort_iter and splits the iterator into a btree_iter with a flexible array member and a btree_iter_stack which embeds a btree_iter as well as a fixed-length data array. Cc: stable@vger.kernel.org Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039368 Signed-off-by: Matthew Mirvish Signed-off-by: Coly Li Link: https://lore.kernel.org/r/20240509011117.2697-3-colyli@suse.de Signed-off-by: Jens Axboe

Merge tag 'bcachefs-2023-11-29' of https://evilpiepirate.org/git/bcachefs

2023-12-01T21:02:16+00:00

Pull more bcachefs bugfixes from Kent Overstreet: - bcache & bcachefs were broken with CFI enabled; patch for closures to fix type punning - mark erasure coding as extra-experimental; there are incompatible disk space accounting changes coming for erasure coding, and I'm still seeing checksum errors in some tests - several fixes for durability-related issues (durability is a device specific setting where we can tell bcachefs that data on a given device should be counted as replicated x times) - a fix for a rare livelock when a btree node merge then updates a parent node that is almost full - fix a race in the device removal path, where dropping a pointer in a btree node to a device would be clobbered by an in flight btree write updating the btree node key on completion - fix one SRCU lock hold time warning in the btree gc code - ther's still a bunch more of these to fix - fix a rare race where we'd start copygc before initializing the "are we rw" percpu refcount; copygc would think we were already ro and die immediately * tag 'bcachefs-2023-11-29' of https://evilpiepirate.org/git/bcachefs: (23 commits) bcachefs: Extra kthread_should_stop() calls for copygc bcachefs: Convert gc_alloc_start() to for_each_btree_key2() bcachefs: Fix race between btree writes and metadata drop bcachefs: move journal seq assertion bcachefs: -EROFS doesn't count as move_extent_start_fail bcachefs: trace_move_extent_start_fail() now includes errcode bcachefs: Fix split_race livelock bcachefs: Fix bucket data type for stripe buckets bcachefs: Add missing validation for jset_entry_data_usage bcachefs: Fix zstd compress workspace size bcachefs: bpos is misaligned on big endian bcachefs: Fix ec + durability calculation bcachefs: Data update path won't accidentaly grow replicas bcachefs: deallocate_extra_replicas() bcachefs: Proper refcounting for journal_keys bcachefs: preserve device path as device name bcachefs: Fix an endianness conversion bcachefs: Start gc, copygc, rebalance threads after initing writes ref bcachefs: Don't stop copygc thread on device resize bcachefs: Make sure bch2_move_ratelimit() also waits for move_ops ...

closures: CLOSURE_CALLBACK() to fix type punning

2023-11-24T05:29:58+00:00

Control flow integrity is now checking that type signatures match on indirect function calls. That breaks closures, which embed a work_struct in a closure in such a way that a closure_fn may also be used as a workqueue fn by the underlying closure code. So we have to change closure fns to take a work_struct as their argument - but that results in a loss of clarity, as closure fns have different semantics from normal workqueue functions (they run owning a ref on the closure, which must be released with continue_at() or closure_return()). Thus, this patc introduces CLOSURE_CALLBACK() and closure_type() macros as suggested by Kees, to smooth things over a bit. Suggested-by: Kees Cook Cc: Coly Li Signed-off-by: Kent Overstreet