From 4fe2c963154c31227bec2f2d690e01f9cab383ea Mon Sep 17 00:00:00 2001 From: Jackie Liu Date: Mon, 9 Sep 2019 20:50:40 +0800 Subject: [PATCH] io_uring: add support for link with drain To support the link with drain, we need to do two parts. There is an sqes: 0 1 2 3 4 5 6 +-----+-----+-----+-----+-----+-----+-----+ | N | L | L | L+D | N | N | N | +-----+-----+-----+-----+-----+-----+-----+ First, we need to ensure that the io before the link is completed, there is a easy way is set drain flag to the link list's head, so all subsequent io will be inserted into the defer_list. +-----+ (0) | N | +-----+ | (2) (3) (4) +-----+ +-----+ +-----+ +-----+ (1) | L+D | --> | L | --> | L+D | --> | N | +-----+ +-----+ +-----+ +-----+ | +-----+ (5) | N | +-----+ | +-----+ (6) | N | +-----+ Second, ensure that the following IO will not be completed first, an easy way is to create a mirror of drain io and insert it into defer_list, in this way, as long as drain io is not processed, the following io in the defer_list will not be actively process. +-----+ (0) | N | +-----+ | (2) (3) (4) +-----+ +-----+ +-----+ +-----+ (1) | L+D | --> | L | --> | L+D | --> | N | +-----+ +-----+ +-----+ +-----+ | +-----+ ('3) | D | <== This is a shadow of (3) +-----+ | +-----+ (5) | N | +-----+ | +-----+ (6) | N | +-----+ Signed-off-by: Jackie Liu Signed-off-by: Jens Axboe --- fs/io_uring.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 97 insertions(+), 17 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index cf6d807fa414..eff29d705a26 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -312,6 +312,7 @@ struct io_kiocb { #define REQ_F_LINK 64 /* linked sqes */ #define REQ_F_LINK_DONE 128 /* linked sqes done */ #define REQ_F_FAIL_LINK 256 /* fail rest of links */ +#define REQ_F_SHADOW_DRAIN 512 /* link-drain shadow req */ u64 user_data; u32 result; u32 sequence; @@ -343,6 +344,7 @@ struct io_submit_state { }; static void io_sq_wq_submit_work(struct work_struct *work); +static void __io_free_req(struct io_kiocb *req); static struct kmem_cache *req_cachep; @@ -448,6 +450,11 @@ static void io_commit_cqring(struct io_ring_ctx *ctx) __io_commit_cqring(ctx); while ((req = io_get_deferred_req(ctx)) != NULL) { + if (req->flags & REQ_F_SHADOW_DRAIN) { + /* Just for drain, free it. */ + __io_free_req(req); + continue; + } req->flags |= REQ_F_IO_DRAINED; queue_work(ctx->sqo_wq, &req->work); } @@ -2015,10 +2022,14 @@ static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s, flags = READ_ONCE(s->sqe->flags); fd = READ_ONCE(s->sqe->fd); - if (flags & IOSQE_IO_DRAIN) { + if (flags & IOSQE_IO_DRAIN) req->flags |= REQ_F_IO_DRAIN; - req->sequence = s->sequence; - } + /* + * All io need record the previous position, if LINK vs DARIN, + * it can be used to mark the position of the first IO in the + * link list. + */ + req->sequence = s->sequence; if (!io_op_needs_file(s->sqe)) return 0; @@ -2040,20 +2051,11 @@ static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s, return 0; } -static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, +static int __io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, struct sqe_submit *s) { int ret; - ret = io_req_defer(ctx, req, s->sqe); - if (ret) { - if (ret != -EIOCBQUEUED) { - io_free_req(req); - io_cqring_add_event(ctx, s->sqe->user_data, ret); - } - return 0; - } - ret = __io_submit_sqe(ctx, req, s, true); if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) { struct io_uring_sqe *sqe_copy; @@ -2096,6 +2098,64 @@ static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, return ret; } +static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req, + struct sqe_submit *s) +{ + int ret; + + ret = io_req_defer(ctx, req, s->sqe); + if (ret) { + if (ret != -EIOCBQUEUED) { + io_free_req(req); + io_cqring_add_event(ctx, s->sqe->user_data, ret); + } + return 0; + } + + return __io_queue_sqe(ctx, req, s); +} + +static int io_queue_link_head(struct io_ring_ctx *ctx, struct io_kiocb *req, + struct sqe_submit *s, struct io_kiocb *shadow) +{ + int ret; + int need_submit = false; + + if (!shadow) + return io_queue_sqe(ctx, req, s); + + /* + * Mark the first IO in link list as DRAIN, let all the following + * IOs enter the defer list. all IO needs to be completed before link + * list. + */ + req->flags |= REQ_F_IO_DRAIN; + ret = io_req_defer(ctx, req, s->sqe); + if (ret) { + if (ret != -EIOCBQUEUED) { + io_free_req(req); + io_cqring_add_event(ctx, s->sqe->user_data, ret); + return 0; + } + } else { + /* + * If ret == 0 means that all IOs in front of link io are + * running done. let's queue link head. + */ + need_submit = true; + } + + /* Insert shadow req to defer_list, blocking next IOs */ + spin_lock_irq(&ctx->completion_lock); + list_add_tail(&shadow->list, &ctx->defer_list); + spin_unlock_irq(&ctx->completion_lock); + + if (need_submit) + return __io_queue_sqe(ctx, req, s); + + return 0; +} + #define SQE_VALID_FLAGS (IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK) static void io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s, @@ -2241,6 +2301,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes, { struct io_submit_state state, *statep = NULL; struct io_kiocb *link = NULL; + struct io_kiocb *shadow_req = NULL; bool prev_was_link = false; int i, submitted = 0; @@ -2255,11 +2316,20 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes, * that's the end of the chain. Submit the previous link. */ if (!prev_was_link && link) { - io_queue_sqe(ctx, link, &link->submit); + io_queue_link_head(ctx, link, &link->submit, shadow_req); link = NULL; } prev_was_link = (sqes[i].sqe->flags & IOSQE_IO_LINK) != 0; + if (link && (sqes[i].sqe->flags & IOSQE_IO_DRAIN)) { + if (!shadow_req) { + shadow_req = io_get_req(ctx, NULL); + shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN); + refcount_dec(&shadow_req->refs); + } + shadow_req->sequence = sqes[i].sequence; + } + if (unlikely(mm_fault)) { io_cqring_add_event(ctx, sqes[i].sqe->user_data, -EFAULT); @@ -2273,7 +2343,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes, } if (link) - io_queue_sqe(ctx, link, &link->submit); + io_queue_link_head(ctx, link, &link->submit, shadow_req); if (statep) io_submit_state_end(&state); @@ -2409,6 +2479,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) { struct io_submit_state state, *statep = NULL; struct io_kiocb *link = NULL; + struct io_kiocb *shadow_req = NULL; bool prev_was_link = false; int i, submit = 0; @@ -2428,11 +2499,20 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) * that's the end of the chain. Submit the previous link. */ if (!prev_was_link && link) { - io_queue_sqe(ctx, link, &link->submit); + io_queue_link_head(ctx, link, &link->submit, shadow_req); link = NULL; } prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0; + if (link && (s.sqe->flags & IOSQE_IO_DRAIN)) { + if (!shadow_req) { + shadow_req = io_get_req(ctx, NULL); + shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN); + refcount_dec(&shadow_req->refs); + } + shadow_req->sequence = s.sequence; + } + s.has_user = true; s.needs_lock = false; s.needs_fixed_file = false; @@ -2442,7 +2522,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit) io_commit_sqring(ctx); if (link) - io_queue_sqe(ctx, link, &link->submit); + io_queue_link_head(ctx, link, &link->submit, shadow_req); if (statep) io_submit_state_end(statep); -- 2.11.0