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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright 2023 Red Hat4 */5 6#include "completion.h"7 8#include <linux/kernel.h>9 10#include "logger.h"11#include "permassert.h"12 13#include "status-codes.h"14#include "types.h"15#include "vio.h"16#include "vdo.h"17 18/**19 * DOC: vdo completions.20 *21 * Most of vdo's data structures are lock free, each either belonging to a single "zone," or22 * divided into a number of zones whose accesses to the structure do not overlap. During normal23 * operation, at most one thread will be operating in any given zone. Each zone has a24 * vdo_work_queue which holds vdo_completions that are to be run in that zone. A completion may25 * only be enqueued on one queue or operating in a single zone at a time.26 *27 * At each step of a multi-threaded operation, the completion performing the operation is given a28 * callback, error handler, and thread id for the next step. A completion is "run" when it is29 * operating on the correct thread (as specified by its callback_thread_id). If the value of its30 * "result" field is an error (i.e. not VDO_SUCCESS), the function in its "error_handler" will be31 * invoked. If the error_handler is NULL, or there is no error, the function set as its "callback"32 * will be invoked. Generally, a completion will not be run directly, but rather will be33 * "launched." In this case, it will check whether it is operating on the correct thread. If it is,34 * it will run immediately. Otherwise, it will be enqueue on the vdo_work_queue associated with the35 * completion's "callback_thread_id". When it is dequeued, it will be on the correct thread, and36 * will get run. In some cases, the completion should get queued instead of running immediately,37 * even if it is being launched from the correct thread. This is usually in cases where there is a38 * long chain of callbacks, all on the same thread, which could overflow the stack. In such cases,39 * the completion's "requeue" field should be set to true. Doing so will skip the current thread40 * check and simply enqueue the completion.41 *42 * A completion may be "finished," in which case its "complete" field will be set to true before it43 * is next run. It is a bug to attempt to set the result or re-finish a finished completion.44 * Because a completion's fields are not safe to examine from any thread other than the one on45 * which the completion is currently operating, this field is used only to aid in detecting46 * programming errors. It can not be used for cross-thread checking on the status of an operation.47 * A completion must be "reset" before it can be reused after it has been finished. Resetting will48 * also clear any error from the result field.49 **/50 51void vdo_initialize_completion(struct vdo_completion *completion,52 struct vdo *vdo,53 enum vdo_completion_type type)54{55 memset(completion, 0, sizeof(*completion));56 completion->vdo = vdo;57 completion->type = type;58 vdo_reset_completion(completion);59}60 61static inline void assert_incomplete(struct vdo_completion *completion)62{63 VDO_ASSERT_LOG_ONLY(!completion->complete, "completion is not complete");64}65 66/**67 * vdo_set_completion_result() - Set the result of a completion.68 *69 * Older errors will not be masked.70 */71void vdo_set_completion_result(struct vdo_completion *completion, int result)72{73 assert_incomplete(completion);74 if (completion->result == VDO_SUCCESS)75 completion->result = result;76}77 78/**79 * vdo_launch_completion_with_priority() - Run or enqueue a completion.80 * @priority: The priority at which to enqueue the completion.81 *82 * If called on the correct thread (i.e. the one specified in the completion's callback_thread_id83 * field) and not marked for requeue, the completion will be run immediately. Otherwise, the84 * completion will be enqueued on the specified thread.85 */86void vdo_launch_completion_with_priority(struct vdo_completion *completion,87 enum vdo_completion_priority priority)88{89 thread_id_t callback_thread = completion->callback_thread_id;90 91 if (completion->requeue || (callback_thread != vdo_get_callback_thread_id())) {92 vdo_enqueue_completion(completion, priority);93 return;94 }95 96 vdo_run_completion(completion);97}98 99/** vdo_finish_completion() - Mark a completion as complete and then launch it. */100void vdo_finish_completion(struct vdo_completion *completion)101{102 assert_incomplete(completion);103 completion->complete = true;104 if (completion->callback != NULL)105 vdo_launch_completion(completion);106}107 108void vdo_enqueue_completion(struct vdo_completion *completion,109 enum vdo_completion_priority priority)110{111 struct vdo *vdo = completion->vdo;112 thread_id_t thread_id = completion->callback_thread_id;113 114 if (VDO_ASSERT(thread_id < vdo->thread_config.thread_count,115 "thread_id %u (completion type %d) is less than thread count %u",116 thread_id, completion->type,117 vdo->thread_config.thread_count) != VDO_SUCCESS)118 BUG();119 120 completion->requeue = false;121 completion->priority = priority;122 completion->my_queue = NULL;123 vdo_enqueue_work_queue(vdo->threads[thread_id].queue, completion);124}125 126/**127 * vdo_requeue_completion_if_needed() - Requeue a completion if not called on the specified thread.128 *129 * Return: True if the completion was requeued; callers may not access the completion in this case.130 */131bool vdo_requeue_completion_if_needed(struct vdo_completion *completion,132 thread_id_t callback_thread_id)133{134 if (vdo_get_callback_thread_id() == callback_thread_id)135 return false;136 137 completion->callback_thread_id = callback_thread_id;138 vdo_enqueue_completion(completion, VDO_WORK_Q_DEFAULT_PRIORITY);139 return true;140}141