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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 <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
parent
4503b7676a
commit
b63534c41e
148
fs/io_uring.c
148
fs/io_uring.c
@ -900,6 +900,13 @@ static int io_file_get(struct io_submit_state *state, struct io_kiocb *req,
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static void __io_queue_sqe(struct io_kiocb *req,
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const struct io_uring_sqe *sqe);
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static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
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struct iovec **iovec, struct iov_iter *iter,
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bool needs_lock);
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static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
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struct iovec *iovec, struct iovec *fast_iov,
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struct iov_iter *iter);
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static struct kmem_cache *req_cachep;
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static const struct file_operations io_uring_fops;
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@ -1978,12 +1985,115 @@ static void io_complete_rw_common(struct kiocb *kiocb, long res)
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__io_cqring_add_event(req, res, cflags);
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}
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static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
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{
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struct mm_struct *mm = current->mm;
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if (mm) {
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kthread_unuse_mm(mm);
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mmput(mm);
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}
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}
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static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx,
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struct io_kiocb *req)
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{
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if (io_op_defs[req->opcode].needs_mm && !current->mm) {
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if (unlikely(!mmget_not_zero(ctx->sqo_mm)))
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return -EFAULT;
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kthread_use_mm(ctx->sqo_mm);
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}
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return 0;
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}
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#ifdef CONFIG_BLOCK
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static bool io_resubmit_prep(struct io_kiocb *req, int error)
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{
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struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
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ssize_t ret = -ECANCELED;
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struct iov_iter iter;
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int rw;
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if (error) {
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ret = error;
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goto end_req;
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}
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switch (req->opcode) {
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case IORING_OP_READV:
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case IORING_OP_READ_FIXED:
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case IORING_OP_READ:
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rw = READ;
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break;
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case IORING_OP_WRITEV:
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case IORING_OP_WRITE_FIXED:
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case IORING_OP_WRITE:
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rw = WRITE;
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break;
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default:
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printk_once(KERN_WARNING "io_uring: bad opcode in resubmit %d\n",
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req->opcode);
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goto end_req;
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}
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ret = io_import_iovec(rw, req, &iovec, &iter, false);
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if (ret < 0)
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goto end_req;
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ret = io_setup_async_rw(req, ret, iovec, inline_vecs, &iter);
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if (!ret)
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return true;
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kfree(iovec);
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end_req:
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io_cqring_add_event(req, ret);
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req_set_fail_links(req);
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io_put_req(req);
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return false;
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}
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static void io_rw_resubmit(struct callback_head *cb)
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{
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struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
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struct io_ring_ctx *ctx = req->ctx;
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int err;
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__set_current_state(TASK_RUNNING);
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err = io_sq_thread_acquire_mm(ctx, req);
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if (io_resubmit_prep(req, err)) {
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refcount_inc(&req->refs);
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io_queue_async_work(req);
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}
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}
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#endif
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static bool io_rw_reissue(struct io_kiocb *req, long res)
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{
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#ifdef CONFIG_BLOCK
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struct task_struct *tsk;
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int ret;
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if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
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return false;
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tsk = req->task;
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init_task_work(&req->task_work, io_rw_resubmit);
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ret = task_work_add(tsk, &req->task_work, true);
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if (!ret)
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return true;
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#endif
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return false;
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}
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static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
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{
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struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
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io_complete_rw_common(kiocb, res);
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io_put_req(req);
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if (!io_rw_reissue(req, res)) {
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io_complete_rw_common(kiocb, res);
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io_put_req(req);
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}
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}
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static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
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@ -2169,6 +2279,9 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
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if (kiocb->ki_flags & IOCB_NOWAIT)
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req->flags |= REQ_F_NOWAIT;
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if (kiocb->ki_flags & IOCB_DIRECT)
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io_get_req_task(req);
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if (force_nonblock)
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kiocb->ki_flags |= IOCB_NOWAIT;
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@ -2668,6 +2781,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
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iov_count = iov_iter_count(&iter);
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ret = rw_verify_area(READ, req->file, &kiocb->ki_pos, iov_count);
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if (!ret) {
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unsigned long nr_segs = iter.nr_segs;
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ssize_t ret2 = 0;
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if (req->file->f_op->read_iter)
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@ -2679,6 +2793,8 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
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if (!force_nonblock || (ret2 != -EAGAIN && ret2 != -EIO)) {
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kiocb_done(kiocb, ret2);
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} else {
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iter.count = iov_count;
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iter.nr_segs = nr_segs;
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copy_iov:
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ret = io_setup_async_rw(req, io_size, iovec,
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inline_vecs, &iter);
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@ -2765,6 +2881,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock)
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iov_count = iov_iter_count(&iter);
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ret = rw_verify_area(WRITE, req->file, &kiocb->ki_pos, iov_count);
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if (!ret) {
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unsigned long nr_segs = iter.nr_segs;
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ssize_t ret2;
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/*
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@ -2802,6 +2919,8 @@ static int io_write(struct io_kiocb *req, bool force_nonblock)
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if (!force_nonblock || ret2 != -EAGAIN) {
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kiocb_done(kiocb, ret2);
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} else {
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iter.count = iov_count;
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iter.nr_segs = nr_segs;
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copy_iov:
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ret = io_setup_async_rw(req, io_size, iovec,
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inline_vecs, &iter);
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@ -4282,28 +4401,6 @@ static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
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__io_queue_proc(&pt->req->apoll->poll, pt, head);
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}
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static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
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{
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struct mm_struct *mm = current->mm;
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if (mm) {
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kthread_unuse_mm(mm);
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mmput(mm);
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}
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}
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static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx,
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struct io_kiocb *req)
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{
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if (io_op_defs[req->opcode].needs_mm && !current->mm) {
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if (unlikely(!mmget_not_zero(ctx->sqo_mm)))
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return -EFAULT;
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kthread_use_mm(ctx->sqo_mm);
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}
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return 0;
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}
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static void io_async_task_func(struct callback_head *cb)
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{
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struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
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@ -5814,6 +5911,9 @@ static void io_submit_state_start(struct io_submit_state *state,
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unsigned int max_ios)
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{
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blk_start_plug(&state->plug);
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#ifdef CONFIG_BLOCK
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state->plug.nowait = true;
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#endif
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state->free_reqs = 0;
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state->file = NULL;
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state->ios_left = max_ios;
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