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Fri, 27 Mar 2026 04:48:08 -0700 (PDT) From: Chengkaitao To: axboe@kernel.dk, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, morbo@google.com, justinstitt@google.com Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, rust-for-linux@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev, Kaitao Cheng Subject: [RFC 1/2] block: Introduce the UFQ I/O scheduler Date: Fri, 27 Mar 2026 19:47:40 +0800 Message-ID: <20260327114741.91500-2-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260327114741.91500-1-pilgrimtao@gmail.com> References: <20260327114741.91500-1-pilgrimtao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Kaitao Cheng Introduce IOSCHED_UFQ, a blk-mq elevator ("ufq: User-programmable Flexible Queueing") whose policy is supplied by an eBPF program via struct_ops (insert, dispatch, merge, finish, etc.). When no eBPF program is attached, the UFQ I/O scheduler uses a simple, per-ctx queueing policy (similar to none). After an eBPF program is attached, the user-defined scheduling policy replaces UFQ=E2=80=99s built-in queueing policy, while per-ctx queues remain available as a fallback mechanism. Signed-off-by: Kaitao Cheng --- block/Kconfig.iosched | 8 + block/Makefile | 1 + block/blk-merge.c | 49 +++- block/blk-mq-sched.h | 4 + block/blk-mq.c | 8 +- block/blk-mq.h | 2 +- block/blk.h | 2 + block/ufq-bpfops.c | 213 +++++++++++++++++ block/ufq-iosched.c | 526 ++++++++++++++++++++++++++++++++++++++++++ block/ufq-iosched.h | 38 +++ block/ufq-kfunc.c | 91 ++++++++ 11 files changed, 934 insertions(+), 8 deletions(-) create mode 100644 block/ufq-bpfops.c create mode 100644 block/ufq-iosched.c create mode 100644 block/ufq-iosched.h create mode 100644 block/ufq-kfunc.c diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched index 27f11320b8d1..56afc425cc52 100644 --- a/block/Kconfig.iosched +++ b/block/Kconfig.iosched @@ -44,4 +44,12 @@ config BFQ_CGROUP_DEBUG Enable some debugging help. Currently it exports additional stat files in a cgroup which can be useful for debugging. =20 +config IOSCHED_UFQ + tristate "UFQ I/O scheduler" + default y + help + The UFQ I/O scheduler is a programmable I/O scheduler. When + enabled, an out-of-kernel I/O scheduler based on eBPF can be + designed to interact with it, leveraging its customizable + hooks to redefine I/O scheduling policies. endmenu diff --git a/block/Makefile b/block/Makefile index c65f4da93702..9bb9144079aa 100644 --- a/block/Makefile +++ b/block/Makefile @@ -24,6 +24,7 @@ obj-$(CONFIG_MQ_IOSCHED_DEADLINE) +=3D mq-deadline.o obj-$(CONFIG_MQ_IOSCHED_KYBER) +=3D kyber-iosched.o bfq-y :=3D bfq-iosched.o bfq-wf2q.o bfq-cgroup.o obj-$(CONFIG_IOSCHED_BFQ) +=3D bfq.o +obj-$(CONFIG_IOSCHED_UFQ) +=3D ufq-iosched.o ufq-bpfops.o ufq-kfunc.o =20 obj-$(CONFIG_BLK_DEV_INTEGRITY) +=3D bio-integrity.o blk-integrity.o t10-p= i.o \ bio-integrity-auto.o diff --git a/block/blk-merge.c b/block/blk-merge.c index fcf09325b22e..8bdc459ae631 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -774,8 +774,8 @@ u8 bio_seg_gap(struct request_queue *q, struct bio *pre= v, struct bio *next, * For non-mq, this has to be called with the request spinlock acquired. * For mq with scheduling, the appropriate queue wide lock should be held. */ -static struct request *attempt_merge(struct request_queue *q, - struct request *req, struct request *next) +static struct request *attempt_merge(struct request_queue *q, struct reque= st *req, + struct request *next, bool nohash) { if (!rq_mergeable(req) || !rq_mergeable(next)) return NULL; @@ -842,7 +842,7 @@ static struct request *attempt_merge(struct request_que= ue *q, =20 req->__data_len +=3D blk_rq_bytes(next); =20 - if (!blk_discard_mergable(req)) + if (!nohash && !blk_discard_mergable(req)) elv_merge_requests(q, req, next); =20 blk_crypto_rq_put_keyslot(next); @@ -868,7 +868,7 @@ static struct request *attempt_back_merge(struct reques= t_queue *q, struct request *next =3D elv_latter_request(q, rq); =20 if (next) - return attempt_merge(q, rq, next); + return attempt_merge(q, rq, next, false); =20 return NULL; } @@ -879,11 +879,17 @@ static struct request *attempt_front_merge(struct req= uest_queue *q, struct request *prev =3D elv_former_request(q, rq); =20 if (prev) - return attempt_merge(q, prev, rq); + return attempt_merge(q, prev, rq, false); =20 return NULL; } =20 +struct request *bpf_attempt_merge(struct request_queue *q, struct request = *rq, + struct request *next) +{ + return attempt_merge(q, rq, next, true); +} + /* * Try to merge 'next' into 'rq'. Return true if the merge happened, false * otherwise. The caller is responsible for freeing 'next' if the merge @@ -892,7 +898,7 @@ static struct request *attempt_front_merge(struct reque= st_queue *q, bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, struct request *next) { - return attempt_merge(q, rq, next); + return attempt_merge(q, rq, next, false); } =20 bool blk_rq_merge_ok(struct request *rq, struct bio *bio) @@ -1169,3 +1175,34 @@ bool blk_mq_sched_try_merge(struct request_queue *q,= struct bio *bio, } } EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); + +bool blk_mq_sched_merge_fn(struct request_queue *q, struct bio *bio, + unsigned int nr_segs, struct request **merged_request, + struct request *rq, enum elv_merge type, void (*fn) + (struct request_queue *, struct request *, enum elv_merge)) +{ + switch (type) { + case ELEVATOR_BACK_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (bio_attempt_back_merge(rq, bio, nr_segs) !=3D BIO_MERGE_OK) + return false; + *merged_request =3D attempt_back_merge(q, rq); + if (!*merged_request) + fn(q, rq, ELEVATOR_BACK_MERGE); + return true; + case ELEVATOR_FRONT_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (bio_attempt_front_merge(rq, bio, nr_segs) !=3D BIO_MERGE_OK) + return false; + *merged_request =3D attempt_front_merge(q, rq); + if (!*merged_request) + fn(q, rq, ELEVATOR_FRONT_MERGE); + return true; + case ELEVATOR_DISCARD_MERGE: + return bio_attempt_discard_merge(q, rq, bio) =3D=3D BIO_MERGE_OK; + default: + return false; + } +} diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h index 5678e15bd33c..e5f7187044c4 100644 --- a/block/blk-mq-sched.h +++ b/block/blk-mq-sched.h @@ -7,6 +7,10 @@ =20 #define MAX_SCHED_RQ (16 * BLKDEV_DEFAULT_RQ) =20 +bool blk_mq_sched_merge_fn(struct request_queue *q, struct bio *bio, + unsigned int nr_segs, struct request **merged_request, + struct request *rq, enum elv_merge type, void (*fn) + (struct request_queue *, struct request *, enum elv_merge)); bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs, struct request **merged_request); bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, diff --git a/block/blk-mq.c b/block/blk-mq.c index 3da2215b2912..b8282f9a534b 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -796,7 +796,7 @@ static void blk_mq_finish_request(struct request *rq) } } =20 -static void __blk_mq_free_request(struct request *rq) +void __blk_mq_free_request(struct request *rq) { struct request_queue *q =3D rq->q; struct blk_mq_ctx *ctx =3D rq->mq_ctx; @@ -1844,6 +1844,12 @@ static bool dispatch_rq_from_ctx(struct sbitmap *sb,= unsigned int bitnr, if (list_empty(&ctx->rq_lists[type])) sbitmap_clear_bit(sb, bitnr); } + + if (dispatch_data->rq) { + dispatch_data->rq->rq_flags |=3D RQF_STARTED; + if (hctx->queue->last_merge =3D=3D dispatch_data->rq) + hctx->queue->last_merge =3D NULL; + } spin_unlock(&ctx->lock); =20 return !dispatch_data->rq; diff --git a/block/blk-mq.h b/block/blk-mq.h index aa15d31aaae9..3f85cae7bf57 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -56,7 +56,7 @@ void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, s= truct list_head *list); struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *start); void blk_mq_put_rq_ref(struct request *rq); - +void __blk_mq_free_request(struct request *rq); /* * Internal helpers for allocating/freeing the request map */ diff --git a/block/blk.h b/block/blk.h index f6053e9dd2aa..2da3958ec27b 100644 --- a/block/blk.h +++ b/block/blk.h @@ -449,6 +449,8 @@ static inline unsigned get_max_segment_size(const struc= t queue_limits *lim, =20 int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs); +struct request *bpf_attempt_merge(struct request_queue *q, struct request = *rq, + struct request *next); bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, struct request *next); unsigned int blk_recalc_rq_segments(struct request *rq); diff --git a/block/ufq-bpfops.c b/block/ufq-bpfops.c new file mode 100644 index 000000000000..c293ed834829 --- /dev/null +++ b/block/ufq-bpfops.c @@ -0,0 +1,213 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2026 KylinSoft Corporation. + * Copyright (c) 2026 Kaitao Cheng + */ +#include +#include +#include +#include +#include +#include +#include +#include "ufq-iosched.h" + +struct ufq_iosched_ops ufq_ops; + +static const struct bpf_func_proto * +bpf_ufq_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *pr= og) +{ + return bpf_base_func_proto(func_id, prog); +} + +static bool bpf_ufq_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (type !=3D BPF_READ) + return false; + if (off < 0 || off >=3D sizeof(__u64) * MAX_BPF_FUNC_ARGS) + return false; + if (off % size !=3D 0) + return false; + + /* + * merge_req's third argument is int *type. btf_ctx_access() treats + * pointers that are not "pointer to struct" as scalars (no reg_type), + * so loading the pointer from ctx leaves a SCALAR and *type stores + * fail verification. Model it as a read/write buffer of merge_type. + */ + if (off =3D=3D 16 && size =3D=3D sizeof(__u64) && + prog->aux->attach_func_name && + !strcmp(prog->aux->attach_func_name, "merge_req")) { + if (!btf_ctx_access(off, size, type, prog, info)) + return false; + info->reg_type =3D PTR_TO_BUF; + return true; + } + + return btf_ctx_access(off, size, type, prog, info); +} + +static const struct bpf_verifier_ops bpf_ufq_verifier_ops =3D { + .get_func_proto =3D bpf_ufq_get_func_proto, + .is_valid_access =3D bpf_ufq_is_valid_access, +}; + +static int bpf_ufq_init_member(const struct btf_type *t, + const struct btf_member *member, + void *kdata, const void *udata) +{ + const struct ufq_iosched_ops *uops =3D udata; + struct ufq_iosched_ops *ops =3D kdata; + u32 moff =3D __btf_member_bit_offset(t, member) / 8; + int ret; + + switch (moff) { + case offsetof(struct ufq_iosched_ops, name): + ret =3D bpf_obj_name_cpy(ops->name, uops->name, + sizeof(ops->name)); + if (ret < 0) + return ret; + if (ret =3D=3D 0) + return -EINVAL; + return 1; + /* other var adding .... */ + } + + return 0; +} + +static int bpf_ufq_check_member(const struct btf_type *t, + const struct btf_member *member, + const struct bpf_prog *prog) +{ + return 0; +} + +static int bpf_ufq_enable(struct ufq_iosched_ops *ops) +{ + ufq_ops =3D *ops; + return 0; +} + +static void bpf_ufq_disable(struct ufq_iosched_ops *ops) +{ + memset(&ufq_ops, 0, sizeof(ufq_ops)); +} + +static int bpf_ufq_reg(void *kdata, struct bpf_link *link) +{ + return bpf_ufq_enable(kdata); +} + +static void bpf_ufq_unreg(void *kdata, struct bpf_link *link) +{ + bpf_ufq_disable(kdata); +} + +static int bpf_ufq_init(struct btf *btf) +{ + return 0; +} + +static int bpf_ufq_update(void *kdata, void *old_kdata, struct bpf_link *l= ink) +{ + /* + * UFQ does not support live-updating an already-attached BPF scheduler: + * partial failure during callback setup (e.g. init_sched) would be hard + * to reason about, and update can race with unregister/teardown. + */ + return -EOPNOTSUPP; +} + +static int bpf_ufq_validate(void *kdata) +{ + return 0; +} + +static int init_sched_stub(struct request_queue *q) +{ + return -EPERM; +} + +static int exit_sched_stub(struct request_queue *q) +{ + return -EPERM; +} + +static int insert_req_stub(struct request_queue *q, struct request *rq, + blk_insert_t flags) +{ + return 0; +} + +static struct request *dispatch_req_stub(struct request_queue *q) +{ + return NULL; +} + +static bool has_req_stub(struct request_queue *q, int rqs_count) +{ + return rqs_count > 0; +} + +static void finish_req_stub(struct request *rq) +{ +} + +static struct request *former_req_stub(struct request_queue *q, struct req= uest *rq) +{ + return NULL; +} + +static struct request *next_req_stub(struct request_queue *q, struct reque= st *rq) +{ + return NULL; +} + +static struct request *merge_req_stub(struct request_queue *q, struct requ= est *rq, + int *type) +{ + *type =3D ELEVATOR_NO_MERGE; + return NULL; +} + +static void req_merged_stub(struct request_queue *q, struct request *rq, + int type) +{ +} + +static struct ufq_iosched_ops __bpf_ops_ufq_ops =3D { + .init_sched =3D init_sched_stub, + .exit_sched =3D exit_sched_stub, + .insert_req =3D insert_req_stub, + .dispatch_req =3D dispatch_req_stub, + .has_req =3D has_req_stub, + .former_req =3D former_req_stub, + .next_req =3D next_req_stub, + .merge_req =3D merge_req_stub, + .req_merged =3D req_merged_stub, + .finish_req =3D finish_req_stub, +}; + +static struct bpf_struct_ops bpf_iosched_ufq_ops =3D { + .verifier_ops =3D &bpf_ufq_verifier_ops, + .reg =3D bpf_ufq_reg, + .unreg =3D bpf_ufq_unreg, + .check_member =3D bpf_ufq_check_member, + .init_member =3D bpf_ufq_init_member, + .init =3D bpf_ufq_init, + .update =3D bpf_ufq_update, + .validate =3D bpf_ufq_validate, + .name =3D "ufq_iosched_ops", + .owner =3D THIS_MODULE, + .cfi_stubs =3D &__bpf_ops_ufq_ops +}; + +int bpf_ufq_ops_init(void) +{ + return register_bpf_struct_ops(&bpf_iosched_ufq_ops, ufq_iosched_ops); +} + diff --git a/block/ufq-iosched.c b/block/ufq-iosched.c new file mode 100644 index 000000000000..8c10e0d74b0e --- /dev/null +++ b/block/ufq-iosched.c @@ -0,0 +1,526 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2026 KylinSoft Corporation. + * Copyright (c) 2026 Kaitao Cheng + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "elevator.h" +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-sched.h" +#include "blk-mq-debugfs.h" +#include "ufq-iosched.h" + +/* For testing and debugging */ +struct ufq_ops_stats { + atomic_t dispatch_ok_count; + atomic64_t dispatch_ok_sectors; + atomic_t dispatch_null_count; + atomic_t insert_ok_count; + atomic64_t insert_ok_sectors; + atomic_t insert_err_count; + atomic_t merge_ok_count; + atomic64_t merge_ok_sectors; + atomic_t finish_ok_count; + atomic64_t finish_ok_sectors; +}; + +struct ufq_data { + struct request_queue *q; + u32 async_depth; + atomic_t rqs_count; + struct ufq_ops_stats ops_stats; +}; + +enum ufq_priv_state { + UFQ_PRIV_NOT_IN_SCHED =3D 0, + UFQ_PRIV_IN_BPF =3D 1, + UFQ_PRIV_IN_UFQ =3D 2, + UFQ_PRIV_IN_SCHED =3D 3, +}; + +static void ufq_request_merged(struct request_queue *q, struct request *re= q, + enum elv_merge type) +{ + if (ufq_ops.req_merged) + ufq_ops.req_merged(q, req, (int)type); +} + +static struct request *ufq_dispatch_request(struct blk_mq_hw_ctx *hctx) +{ + struct ufq_data *ufq =3D hctx->queue->elevator->elevator_data; + struct blk_mq_ctx *ctx; + struct request *rq =3D NULL; + unsigned short idx; + + if (ufq_ops.dispatch_req) { + rq =3D ufq_ops.dispatch_req(hctx->queue); + if (!rq) { + atomic_inc(&ufq->ops_stats.dispatch_null_count); + return NULL; + } + atomic_inc(&ufq->ops_stats.dispatch_ok_count); + atomic64_add(blk_rq_sectors(rq), &ufq->ops_stats.dispatch_ok_sectors); + + ctx =3D rq->mq_ctx; + spin_lock(&ctx->lock); + list_del_init(&rq->queuelist); + rq->rq_flags |=3D RQF_STARTED; + if (hctx->queue->last_merge =3D=3D rq) + hctx->queue->last_merge =3D NULL; + if (list_empty(&ctx->rq_lists[rq->mq_hctx->type])) + sbitmap_clear_bit(&rq->mq_hctx->ctx_map, + ctx->index_hw[rq->mq_hctx->type]); + spin_unlock(&ctx->lock); + rq->elv.priv[0] =3D (void *)((uintptr_t)rq->elv.priv[0] + & ~UFQ_PRIV_IN_UFQ); + } else { + ctx =3D READ_ONCE(hctx->dispatch_from); + rq =3D blk_mq_dequeue_from_ctx(hctx, ctx); + if (rq) { + idx =3D rq->mq_ctx->index_hw[hctx->type]; + if (++idx =3D=3D hctx->nr_ctx) + idx =3D 0; + WRITE_ONCE(hctx->dispatch_from, hctx->ctxs[idx]); + } + } + + if (rq) + atomic_dec(&ufq->rqs_count); + return rq; +} + +/* + * Called by __blk_mq_alloc_request(). The shallow_depth value set by this + * function is used by __blk_mq_get_tag(). + */ +static void ufq_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) +{ + struct ufq_data *ufq =3D data->q->elevator->elevator_data; + + /* Do not throttle synchronous reads. */ + if (op_is_sync(opf) && !op_is_write(opf)) + return; + + /* + * Throttle asynchronous requests and writes such that these requests + * do not block the allocation of synchronous requests. + */ + data->shallow_depth =3D ufq->async_depth; +} + +static void ufq_depth_updated(struct request_queue *q) +{ + struct ufq_data *ufq =3D q->elevator->elevator_data; + + ufq->async_depth =3D q->nr_requests; + q->async_depth =3D q->nr_requests; + blk_mq_set_min_shallow_depth(q, 1); +} + +static int ufq_init_sched(struct request_queue *q, struct elevator_queue *= eq) +{ + struct ufq_data *ufq; + + ufq =3D kzalloc_node(sizeof(*ufq), GFP_KERNEL, q->node); + if (!ufq) + return -ENOMEM; + + eq->elevator_data =3D ufq; + ufq->q =3D q; + + blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q); + q->elevator =3D eq; + + q->async_depth =3D q->nr_requests; + ufq->async_depth =3D q->nr_requests; + + if (ufq_ops.init_sched) + ufq_ops.init_sched(q); + + ufq_depth_updated(q); + return 0; +} + +static void ufq_exit_sched(struct elevator_queue *e) +{ + struct ufq_data *ufq =3D e->elevator_data; + + if (ufq_ops.exit_sched) + ufq_ops.exit_sched(ufq->q); + + WARN_ON_ONCE(atomic_read(&ufq->rqs_count)); + + kfree(ufq); +} + +static void ufq_merged_request(struct request_queue *q, struct request *rq, + enum elv_merge type) +{ + struct elevator_queue *e =3D q->elevator; + + if (e->type->ops.request_merged) + e->type->ops.request_merged(q, rq, type); + + q->last_merge =3D rq; +} + +static bool ufq_sched_try_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs, struct request **merged_request) +{ + enum elv_merge type =3D ELEVATOR_NO_MERGE; + struct request *rq =3D NULL, *last; + bool ret; + + + /* + * Levels of merges: + * nomerges: No merges at all attempted + * noxmerges: Only simple one-hit cache try + * merges: All merge tries attempted + */ + if (blk_queue_nomerges(q) || !bio_mergeable(bio)) + return false; + + last =3D q->last_merge; + if (last) { + spin_lock(&last->mq_ctx->lock); + if (last =3D=3D q->last_merge && elv_bio_merge_ok(last, bio)) { + type =3D blk_try_merge(last, bio); + if (type !=3D ELEVATOR_NO_MERGE) { + rq =3D last; + goto merge; + } + } + spin_unlock(&last->mq_ctx->lock); + } + + if (blk_queue_noxmerges(q)) + return false; + + if (ufq_ops.find_req_from_sector) { + rq =3D ufq_ops.find_req_from_sector(q, bio->bi_iter.bi_sector, + bio_end_sector(bio)); + if (rq && elv_bio_merge_ok(rq, bio)) + type =3D blk_try_merge(rq, bio); + else + return false; + } + + if (!rq || type =3D=3D ELEVATOR_NO_MERGE) + return false; + + spin_lock(&rq->mq_ctx->lock); +merge: + ret =3D blk_mq_sched_merge_fn(q, bio, nr_segs, merged_request, rq, + type, ufq_merged_request); + spin_unlock(&rq->mq_ctx->lock); + + return ret; +} + +/* + * Attempt to merge a bio into an existing request. This function is called + * before @bio is associated with a request. + */ +static bool ufq_bio_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs) +{ + struct ufq_data *ufq =3D q->elevator->elevator_data; + struct request *free =3D NULL; + bool ret; + + ret =3D ufq_sched_try_merge(q, bio, nr_segs, &free); + + if (free) { + blk_mq_free_request(free); + atomic_dec(&ufq->rqs_count); + } + + return ret; +} + +static enum elv_merge ufq_try_insert_merge(struct request_queue *q, + struct request **new) +{ + struct request *target =3D NULL, *free =3D NULL, *last, *rq =3D *new; + struct ufq_data *ufq =3D q->elevator->elevator_data; + enum elv_merge type =3D ELEVATOR_NO_MERGE; + int merge_type =3D ELEVATOR_NO_MERGE; + + if (!rq_mergeable(rq)) + return ELEVATOR_NO_MERGE; + + if (blk_queue_nomerges(q)) + return ELEVATOR_NO_MERGE; + + last =3D q->last_merge; + if (last) { + spin_lock(&last->mq_ctx->lock); + if (last =3D=3D q->last_merge && bpf_attempt_merge(q, last, rq)) { + spin_unlock(&last->mq_ctx->lock); + type =3D ELEVATOR_BACK_MERGE; + free =3D rq; + *new =3D NULL; + goto end; + } + spin_unlock(&last->mq_ctx->lock); + } + + if (blk_queue_noxmerges(q)) + return ELEVATOR_NO_MERGE; + + if (ufq_ops.merge_req) { + target =3D ufq_ops.merge_req(q, rq, &merge_type); + type =3D (enum elv_merge)merge_type; + } + + if (type =3D=3D ELEVATOR_NO_MERGE || !target) { + return ELEVATOR_NO_MERGE; + } else if (type =3D=3D ELEVATOR_FRONT_MERGE) { + spin_lock(&target->mq_ctx->lock); + free =3D bpf_attempt_merge(q, rq, target); + if (!free) { + spin_unlock(&target->mq_ctx->lock); + pr_err("ufq-iosched: front merge failed\n"); + return ELEVATOR_NO_MERGE; + } + rq->elv.priv[0] =3D (void *)((uintptr_t)rq->elv.priv[0] + | UFQ_PRIV_IN_UFQ); + list_replace_init(&target->queuelist, &rq->queuelist); + rq->fifo_time =3D target->fifo_time; + q->last_merge =3D rq; + } else if (type =3D=3D ELEVATOR_BACK_MERGE) { + spin_lock(&target->mq_ctx->lock); + free =3D bpf_attempt_merge(q, target, rq); + if (!free) { + spin_unlock(&target->mq_ctx->lock); + pr_err("ufq-iosched: back merge failed\n"); + return ELEVATOR_NO_MERGE; + } + *new =3D target; + q->last_merge =3D target; + } + + spin_unlock(&target->mq_ctx->lock); +end: + atomic_inc(&ufq->ops_stats.merge_ok_count); + atomic64_add(blk_rq_sectors(free), &ufq->ops_stats.merge_ok_sectors); + blk_mq_free_request(free); + return type; +} + +static void ufq_insert_requests(struct blk_mq_hw_ctx *hctx, + struct list_head *list, + blk_insert_t flags) +{ + struct request_queue *q =3D hctx->queue; + struct ufq_data *ufq =3D q->elevator->elevator_data; + struct blk_mq_ctx *ctx; + enum elv_merge type; + int bit, ret =3D 0; + + while (!list_empty(list)) { + struct request *rq; + + rq =3D list_first_entry(list, struct request, queuelist); + list_del_init(&rq->queuelist); + + type =3D ufq_try_insert_merge(q, &rq); + if (type =3D=3D ELEVATOR_NO_MERGE) { + rq->fifo_time =3D jiffies; + ctx =3D rq->mq_ctx; + rq->elv.priv[0] =3D (void *)((uintptr_t)rq->elv.priv[0] + | UFQ_PRIV_IN_UFQ); + spin_lock(&ctx->lock); + if (flags & BLK_MQ_INSERT_AT_HEAD) + list_add(&rq->queuelist, &ctx->rq_lists[hctx->type]); + else + list_add_tail(&rq->queuelist, + &ctx->rq_lists[hctx->type]); + + bit =3D ctx->index_hw[hctx->type]; + if (!sbitmap_test_bit(&hctx->ctx_map, bit)) + sbitmap_set_bit(&hctx->ctx_map, bit); + q->last_merge =3D rq; + spin_unlock(&ctx->lock); + atomic_inc(&ufq->rqs_count); + } + + if (rq && ufq_ops.insert_req) { + rq->elv.priv[0] =3D (void *)((uintptr_t)rq->elv.priv[0] + | UFQ_PRIV_IN_BPF); + ret =3D ufq_ops.insert_req(q, rq, flags); + if (ret) { + atomic_inc(&ufq->ops_stats.insert_err_count); + pr_err("ufq-iosched: bpf insert_req error (%d)\n", ret); + } else { + atomic_inc(&ufq->ops_stats.insert_ok_count); + atomic64_add(blk_rq_sectors(rq), &ufq->ops_stats.insert_ok_sectors); + } + } + } +} + +static void ufq_prepare_request(struct request *rq) +{ + rq->elv.priv[0] =3D (void *)(uintptr_t)UFQ_PRIV_NOT_IN_SCHED; +} + +static void ufq_finish_request(struct request *rq) +{ + struct ufq_data *ufq =3D rq->q->elevator->elevator_data; + + /* + * The block layer core may call ufq_finish_request() without having + * called ufq_insert_requests(). Skip requests that bypassed I/O + * scheduling. + */ + if (!((uintptr_t)rq->elv.priv[0] & UFQ_PRIV_IN_BPF)) + return; + + if (ufq_ops.finish_req) + ufq_ops.finish_req(rq); + + atomic_inc(&ufq->ops_stats.finish_ok_count); + atomic64_add(blk_rq_stats_sectors(rq), &ufq->ops_stats.finish_ok_sectors); +} + +static struct request *ufq_find_next_request(struct request_queue *q, stru= ct request *rq) +{ + if (ufq_ops.next_req) + return ufq_ops.next_req(q, rq); + + return NULL; +} + +static struct request *ufq_find_former_request(struct request_queue *q, st= ruct request *rq) +{ + if (ufq_ops.former_req) + return ufq_ops.former_req(q, rq); + + return NULL; +} + +static bool ufq_has_work(struct blk_mq_hw_ctx *hctx) +{ + struct ufq_data *ufq =3D hctx->queue->elevator->elevator_data; + int rqs_count =3D atomic_read(&ufq->rqs_count); + + WARN_ON_ONCE(rqs_count < 0); + if (ufq_ops.has_req) + return ufq_ops.has_req(hctx->queue, rqs_count); + + return rqs_count > 0; +} + +#ifdef CONFIG_BLK_DEBUG_FS +static int ufq_ops_stats_show(void *data, struct seq_file *m) +{ + struct request_queue *q =3D data; + struct ufq_data *ufq =3D q->elevator->elevator_data; + struct ufq_ops_stats *s =3D &ufq->ops_stats; + + /* for debug */ + seq_printf(m, "dispatch_ok_count %d\n", + atomic_read(&s->dispatch_ok_count)); + seq_printf(m, "dispatch_ok_sectors %lld\n", + (long long)atomic64_read(&s->dispatch_ok_sectors)); + seq_printf(m, "dispatch_null_count %d\n", + atomic_read(&s->dispatch_null_count)); + seq_printf(m, "insert_ok_count %d\n", + atomic_read(&s->insert_ok_count)); + seq_printf(m, "insert_ok_sectors %lld\n", + (long long)atomic64_read(&s->insert_ok_sectors)); + seq_printf(m, "insert_err_count %d\n", + atomic_read(&s->insert_err_count)); + seq_printf(m, "merge_ok_count %d\n", + atomic_read(&s->merge_ok_count)); + seq_printf(m, "merge_ok_sectors %lld\n", + (long long)atomic64_read(&s->merge_ok_sectors)); + seq_printf(m, "finish_ok_count %d\n", + atomic_read(&s->finish_ok_count)); + seq_printf(m, "finish_ok_sectors %lld\n", + (long long)atomic64_read(&s->finish_ok_sectors)); + return 0; +} + +static const struct blk_mq_debugfs_attr ufq_iosched_debugfs_attrs[] =3D { + {"ops_stats", 0400, ufq_ops_stats_show}, + {}, +}; +#endif + +static struct elevator_type ufq_iosched_mq =3D { + .ops =3D { + .depth_updated =3D ufq_depth_updated, + .limit_depth =3D ufq_limit_depth, + .insert_requests =3D ufq_insert_requests, + .dispatch_request =3D ufq_dispatch_request, + .prepare_request =3D ufq_prepare_request, + .finish_request =3D ufq_finish_request, + .next_request =3D ufq_find_next_request, + .former_request =3D ufq_find_former_request, + .bio_merge =3D ufq_bio_merge, + .request_merged =3D ufq_request_merged, + .has_work =3D ufq_has_work, + .init_sched =3D ufq_init_sched, + .exit_sched =3D ufq_exit_sched, + }, + +#ifdef CONFIG_BLK_DEBUG_FS + .queue_debugfs_attrs =3D ufq_iosched_debugfs_attrs, +#endif + .elevator_name =3D "ufq", + .elevator_alias =3D "ufq_iosched", + .elevator_owner =3D THIS_MODULE, +}; +MODULE_ALIAS("ufq-iosched"); + +static int __init ufq_init(void) +{ + int ret; + + ret =3D elv_register(&ufq_iosched_mq); + if (ret) + return ret; + + ret =3D bpf_ufq_kfunc_init(); + if (ret) { + pr_err("ufq-iosched: Failed to register kfunc sets (%d)\n", ret); + elv_unregister(&ufq_iosched_mq); + return ret; + } + + ret =3D bpf_ufq_ops_init(); + if (ret) { + pr_err("ufq-iosched: Failed to register struct_ops (%d)\n", ret); + elv_unregister(&ufq_iosched_mq); + return ret; + } + + return 0; +} + +static void __exit ufq_exit(void) +{ + elv_unregister(&ufq_iosched_mq); +} + +module_init(ufq_init); +module_exit(ufq_exit); + +MODULE_AUTHOR("Kaitao Cheng "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("User-programmable Flexible Queueing"); diff --git a/block/ufq-iosched.h b/block/ufq-iosched.h new file mode 100644 index 000000000000..c717362eab31 --- /dev/null +++ b/block/ufq-iosched.h @@ -0,0 +1,38 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (c) 2026 KylinSoft Corporation. + * Copyright (c) 2026 Kaitao Cheng + */ +#ifndef _BLOCK_UFQ_IOSCHED_H +#define _BLOCK_UFQ_IOSCHED_H + +#include "elevator.h" +#include "blk-mq.h" + +#ifndef BPF_IOSCHED_NAME_MAX +#define BPF_IOSCHED_NAME_MAX 16 +#endif + +struct ufq_iosched_ops { + int (*init_sched)(struct request_queue *q); + int (*insert_req)(struct request_queue *q, struct request *rq, + blk_insert_t flags); + int (*exit_sched)(struct request_queue *q); + bool (*has_req)(struct request_queue *q, int rqs_count); + void (*req_merged)(struct request_queue *q, struct request *rq, int type); + void (*finish_req)(struct request *rq); + struct request *(*merge_req)(struct request_queue *q, struct request *rq, + int *type); + struct request *(*find_req_from_sector)(struct request_queue *q, + sector_t start, sector_t end); + struct request *(*former_req)(struct request_queue *q, struct request *rq= ); + struct request *(*next_req)(struct request_queue *q, struct request *rq); + struct request *(*dispatch_req)(struct request_queue *q); + char name[BPF_IOSCHED_NAME_MAX]; +}; +extern struct ufq_iosched_ops ufq_ops; + +int bpf_ufq_ops_init(void); +int bpf_ufq_kfunc_init(void); + +#endif /* _BLOCK_UFQ_IOSCHED_H */ diff --git a/block/ufq-kfunc.c b/block/ufq-kfunc.c new file mode 100644 index 000000000000..35acc98fd979 --- /dev/null +++ b/block/ufq-kfunc.c @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2026 KylinSoft Corporation. + * Copyright (c) 2026 Kaitao Cheng + */ +#include +#include +#include +#include +#include +#include +#include +#include "blk.h" +#include "ufq-iosched.h" + +__bpf_kfunc_start_defs(); + +__bpf_kfunc struct request *bpf_request_from_id(struct request_queue *q, + sector_t offset) +{ + return elv_rqhash_find(q, offset); +} + +__bpf_kfunc struct request *bpf_request_acquire(struct request *rq) +{ + if (req_ref_inc_not_zero(rq)) + return rq; + return NULL; +} + +__bpf_kfunc bool bpf_request_put(struct request *rq) +{ + if (req_ref_put_and_test(rq)) + return false; + + return true; +} + +__bpf_kfunc void bpf_request_release(struct request *rq) +{ + if (req_ref_put_and_test(rq)) + __blk_mq_free_request(rq); +} + +__bpf_kfunc_end_defs(); + +#if defined(CONFIG_X86_KERNEL_IBT) +static const void * const __used __section(".discard.ibt_endbr_noseal") +__ibt_noseal_bpf_request_release =3D (void *)bpf_request_release; +#endif + +BTF_KFUNCS_START(ufq_kfunc_set_ops) +BTF_ID_FLAGS(func, bpf_request_from_id, KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_request_acquire, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_request_put) +BTF_ID_FLAGS(func, bpf_request_release, KF_RELEASE) +BTF_KFUNCS_END(ufq_kfunc_set_ops) + +static const struct btf_kfunc_id_set bpf_ufq_kfunc_set =3D { + .owner =3D THIS_MODULE, + .set =3D &ufq_kfunc_set_ops, +}; + +BTF_ID_LIST(bpf_ufq_dtor_kfunc_ids) +BTF_ID(struct, request) +BTF_ID(func, bpf_request_release) + +int bpf_ufq_kfunc_init(void) +{ + int ret; + const struct btf_id_dtor_kfunc bpf_ufq_dtor_kfunc[] =3D { + { + .btf_id =3D bpf_ufq_dtor_kfunc_ids[0], + .kfunc_btf_id =3D bpf_ufq_dtor_kfunc_ids[1] + }, + }; + + ret =3D register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_ufq_kfun= c_set); + if (ret) + return ret; + ret =3D register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_ufq_kfunc_s= et); + if (ret) + return ret; + ret =3D register_btf_id_dtor_kfuncs(bpf_ufq_dtor_kfunc, + ARRAY_SIZE(bpf_ufq_dtor_kfunc), + THIS_MODULE); + if (ret) + return ret; + + return 0; +} --=20 2.43.0