From b63534c41e20b474483b4ddf47efc858c17352e0 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 4 Jun 2020 11:28:00 -0600 Subject: [PATCH] io_uring: re-issue block requests that failed because of resources Mark the plug with nowait == true, which will cause requests to avoid blocking on request allocation. If they do, we catch them and reissue them from a task_work based handler. Normally we can catch -EAGAIN directly, but the hard case is for split requests. As an example, the application issues a 512KB request. The block core will split this into 128KB if that's the max size for the device. The first request issues just fine, but we run into -EAGAIN for some latter splits for the same request. As the bio is split, we don't get to see the -EAGAIN until one of the actual reads complete, and hence we cannot handle it inline as part of submission. This does potentially cause re-reads of parts of the range, as the whole request is reissued. There's currently no better way to handle this. Signed-off-by: Jens Axboe --- fs/io_uring.c | 148 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 124 insertions(+), 24 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index c5ee6d1a92d3..f3dbf83fabf3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -900,6 +900,13 @@ static int io_file_get(struct io_submit_state *state, struct io_kiocb *req, static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe); +static ssize_t io_import_iovec(int rw, struct io_kiocb *req, + struct iovec **iovec, struct iov_iter *iter, + bool needs_lock); +static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size, + struct iovec *iovec, struct iovec *fast_iov, + struct iov_iter *iter); + static struct kmem_cache *req_cachep; static const struct file_operations io_uring_fops; @@ -1978,12 +1985,115 @@ static void io_complete_rw_common(struct kiocb *kiocb, long res) __io_cqring_add_event(req, res, cflags); } +static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx) +{ + struct mm_struct *mm = current->mm; + + if (mm) { + kthread_unuse_mm(mm); + mmput(mm); + } +} + +static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx, + struct io_kiocb *req) +{ + if (io_op_defs[req->opcode].needs_mm && !current->mm) { + if (unlikely(!mmget_not_zero(ctx->sqo_mm))) + return -EFAULT; + kthread_use_mm(ctx->sqo_mm); + } + + return 0; +} + +#ifdef CONFIG_BLOCK +static bool io_resubmit_prep(struct io_kiocb *req, int error) +{ + struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs; + ssize_t ret = -ECANCELED; + struct iov_iter iter; + int rw; + + if (error) { + ret = error; + goto end_req; + } + + switch (req->opcode) { + case IORING_OP_READV: + case IORING_OP_READ_FIXED: + case IORING_OP_READ: + rw = READ; + break; + case IORING_OP_WRITEV: + case IORING_OP_WRITE_FIXED: + case IORING_OP_WRITE: + rw = WRITE; + break; + default: + printk_once(KERN_WARNING "io_uring: bad opcode in resubmit %d\n", + req->opcode); + goto end_req; + } + + ret = io_import_iovec(rw, req, &iovec, &iter, false); + if (ret < 0) + goto end_req; + ret = io_setup_async_rw(req, ret, iovec, inline_vecs, &iter); + if (!ret) + return true; + kfree(iovec); +end_req: + io_cqring_add_event(req, ret); + req_set_fail_links(req); + io_put_req(req); + return false; +} + +static void io_rw_resubmit(struct callback_head *cb) +{ + struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work); + struct io_ring_ctx *ctx = req->ctx; + int err; + + __set_current_state(TASK_RUNNING); + + err = io_sq_thread_acquire_mm(ctx, req); + + if (io_resubmit_prep(req, err)) { + refcount_inc(&req->refs); + io_queue_async_work(req); + } +} +#endif + +static bool io_rw_reissue(struct io_kiocb *req, long res) +{ +#ifdef CONFIG_BLOCK + struct task_struct *tsk; + int ret; + + if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker()) + return false; + + tsk = req->task; + init_task_work(&req->task_work, io_rw_resubmit); + ret = task_work_add(tsk, &req->task_work, true); + if (!ret) + return true; +#endif + return false; +} + static void io_complete_rw(struct kiocb *kiocb, long res, long res2) { struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb); - io_complete_rw_common(kiocb, res); - io_put_req(req); + if (!io_rw_reissue(req, res)) { + io_complete_rw_common(kiocb, res); + io_put_req(req); + } } static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2) @@ -2169,6 +2279,9 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, if (kiocb->ki_flags & IOCB_NOWAIT) req->flags |= REQ_F_NOWAIT; + if (kiocb->ki_flags & IOCB_DIRECT) + io_get_req_task(req); + if (force_nonblock) kiocb->ki_flags |= IOCB_NOWAIT; @@ -2668,6 +2781,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) iov_count = iov_iter_count(&iter); ret = rw_verify_area(READ, req->file, &kiocb->ki_pos, iov_count); if (!ret) { + unsigned long nr_segs = iter.nr_segs; ssize_t ret2 = 0; if (req->file->f_op->read_iter) @@ -2679,6 +2793,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock) if (!force_nonblock || (ret2 != -EAGAIN && ret2 != -EIO)) { kiocb_done(kiocb, ret2); } else { + iter.count = iov_count; + iter.nr_segs = nr_segs; copy_iov: ret = io_setup_async_rw(req, io_size, iovec, inline_vecs, &iter); @@ -2765,6 +2881,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock) iov_count = iov_iter_count(&iter); ret = rw_verify_area(WRITE, req->file, &kiocb->ki_pos, iov_count); if (!ret) { + unsigned long nr_segs = iter.nr_segs; ssize_t ret2; /* @@ -2802,6 +2919,8 @@ static int io_write(struct io_kiocb *req, bool force_nonblock) if (!force_nonblock || ret2 != -EAGAIN) { kiocb_done(kiocb, ret2); } else { + iter.count = iov_count; + iter.nr_segs = nr_segs; copy_iov: ret = io_setup_async_rw(req, io_size, iovec, inline_vecs, &iter); @@ -4282,28 +4401,6 @@ static void io_async_queue_proc(struct file *file, struct wait_queue_head *head, __io_queue_proc(&pt->req->apoll->poll, pt, head); } -static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx) -{ - struct mm_struct *mm = current->mm; - - if (mm) { - kthread_unuse_mm(mm); - mmput(mm); - } -} - -static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx, - struct io_kiocb *req) -{ - if (io_op_defs[req->opcode].needs_mm && !current->mm) { - if (unlikely(!mmget_not_zero(ctx->sqo_mm))) - return -EFAULT; - kthread_use_mm(ctx->sqo_mm); - } - - return 0; -} - static void io_async_task_func(struct callback_head *cb) { struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work); @@ -5814,6 +5911,9 @@ static void io_submit_state_start(struct io_submit_state *state, unsigned int max_ios) { blk_start_plug(&state->plug); +#ifdef CONFIG_BLOCK + state->plug.nowait = true; +#endif state->free_reqs = 0; state->file = NULL; state->ios_left = max_ios; -- 2.20.1