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author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-03-13 19:57:23 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-03-13 19:57:23 +0300 |
commit | 61387b8dcf1dc0f30cf690956a48768a3fce1810 (patch) | |
tree | 78f176823ac74dc82f26462ce347735cf73b79f0 /drivers/md/dm-vdo/completion.c | |
parent | c0499a081285dcacacd10b0cb20ccba777411b88 (diff) | |
parent | cb824724dccb3195d22cad96e7b65fe13621d0a6 (diff) | |
download | linux-61387b8dcf1dc0f30cf690956a48768a3fce1810.tar.xz |
Merge tag 'for-6.9/dm-vdo' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper VDO target from Mike Snitzer:
"Introduce the DM vdo target which provides block-level deduplication,
compression, and thin provisioning. Please see:
Documentation/admin-guide/device-mapper/vdo.rst
Documentation/admin-guide/device-mapper/vdo-design.rst
The DM vdo target handles its concurrency by pinning an IO, and
subsequent stages of handling that IO, to a particular VDO thread.
This aspect of VDO is "unique" but its overall implementation is very
tightly coupled to its mostly lockless threading model. As such, VDO
is not easily changed to use more traditional finer-grained locking
and Linux workqueues. Please see the "Zones and Threading" section of
vdo-design.rst
The DM vdo target has been used in production for many years but has
seen significant changes over the past ~6 years to prepare it for
upstream inclusion. The codebase is still large but it is isolated to
drivers/md/dm-vdo/ and has been made considerably more approachable
and maintainable.
Matt Sakai has been added to the MAINTAINERS file to reflect that he
will send VDO changes upstream through the DM subsystem maintainers"
* tag 'for-6.9/dm-vdo' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (142 commits)
dm vdo: document minimum metadata size requirements
dm vdo: remove meaningless version number constant
dm vdo: remove vdo_perform_once
dm vdo block-map: Remove stray semicolon
dm vdo string-utils: change from uds_ to vdo_ namespace
dm vdo logger: change from uds_ to vdo_ namespace
dm vdo funnel-queue: change from uds_ to vdo_ namespace
dm vdo indexer: fix use after free
dm vdo logger: remove log level to string conversion code
dm vdo: document log_level parameter
dm vdo: add 'log_level' module parameter
dm vdo: remove all sysfs interfaces
dm vdo target: eliminate inappropriate uses of UDS_SUCCESS
dm vdo indexer: update ASSERT and ASSERT_LOG_ONLY usage
dm vdo encodings: update some stale comments
dm vdo permassert: audit all of ASSERT to test for VDO_SUCCESS
dm-vdo funnel-workqueue: return VDO_SUCCESS from make_simple_work_queue
dm vdo thread-utils: return VDO_SUCCESS on vdo_create_thread success
dm vdo int-map: return VDO_SUCCESS on success
dm vdo: check for VDO_SUCCESS return value from memory-alloc functions
...
Diffstat (limited to 'drivers/md/dm-vdo/completion.c')
-rw-r--r-- | drivers/md/dm-vdo/completion.c | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/drivers/md/dm-vdo/completion.c b/drivers/md/dm-vdo/completion.c new file mode 100644 index 000000000000..5ad85334632d --- /dev/null +++ b/drivers/md/dm-vdo/completion.c @@ -0,0 +1,140 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright 2023 Red Hat + */ + +#include "completion.h" + +#include <linux/kernel.h> + +#include "logger.h" +#include "permassert.h" + +#include "status-codes.h" +#include "types.h" +#include "vio.h" +#include "vdo.h" + +/** + * DOC: vdo completions. + * + * Most of vdo's data structures are lock free, each either belonging to a single "zone," or + * divided into a number of zones whose accesses to the structure do not overlap. During normal + * operation, at most one thread will be operating in any given zone. Each zone has a + * vdo_work_queue which holds vdo_completions that are to be run in that zone. A completion may + * only be enqueued on one queue or operating in a single zone at a time. + * + * At each step of a multi-threaded operation, the completion performing the operation is given a + * callback, error handler, and thread id for the next step. A completion is "run" when it is + * operating on the correct thread (as specified by its callback_thread_id). If the value of its + * "result" field is an error (i.e. not VDO_SUCCESS), the function in its "error_handler" will be + * invoked. If the error_handler is NULL, or there is no error, the function set as its "callback" + * will be invoked. Generally, a completion will not be run directly, but rather will be + * "launched." In this case, it will check whether it is operating on the correct thread. If it is, + * it will run immediately. Otherwise, it will be enqueue on the vdo_work_queue associated with the + * completion's "callback_thread_id". When it is dequeued, it will be on the correct thread, and + * will get run. In some cases, the completion should get queued instead of running immediately, + * even if it is being launched from the correct thread. This is usually in cases where there is a + * long chain of callbacks, all on the same thread, which could overflow the stack. In such cases, + * the completion's "requeue" field should be set to true. Doing so will skip the current thread + * check and simply enqueue the completion. + * + * A completion may be "finished," in which case its "complete" field will be set to true before it + * is next run. It is a bug to attempt to set the result or re-finish a finished completion. + * Because a completion's fields are not safe to examine from any thread other than the one on + * which the completion is currently operating, this field is used only to aid in detecting + * programming errors. It can not be used for cross-thread checking on the status of an operation. + * A completion must be "reset" before it can be reused after it has been finished. Resetting will + * also clear any error from the result field. + **/ + +void vdo_initialize_completion(struct vdo_completion *completion, + struct vdo *vdo, + enum vdo_completion_type type) +{ + memset(completion, 0, sizeof(*completion)); + completion->vdo = vdo; + completion->type = type; + vdo_reset_completion(completion); +} + +static inline void assert_incomplete(struct vdo_completion *completion) +{ + VDO_ASSERT_LOG_ONLY(!completion->complete, "completion is not complete"); +} + +/** + * vdo_set_completion_result() - Set the result of a completion. + * + * Older errors will not be masked. + */ +void vdo_set_completion_result(struct vdo_completion *completion, int result) +{ + assert_incomplete(completion); + if (completion->result == VDO_SUCCESS) + completion->result = result; +} + +/** + * vdo_launch_completion_with_priority() - Run or enqueue a completion. + * @priority: The priority at which to enqueue the completion. + * + * If called on the correct thread (i.e. the one specified in the completion's callback_thread_id + * field) and not marked for requeue, the completion will be run immediately. Otherwise, the + * completion will be enqueued on the specified thread. + */ +void vdo_launch_completion_with_priority(struct vdo_completion *completion, + enum vdo_completion_priority priority) +{ + thread_id_t callback_thread = completion->callback_thread_id; + + if (completion->requeue || (callback_thread != vdo_get_callback_thread_id())) { + vdo_enqueue_completion(completion, priority); + return; + } + + vdo_run_completion(completion); +} + +/** vdo_finish_completion() - Mark a completion as complete and then launch it. */ +void vdo_finish_completion(struct vdo_completion *completion) +{ + assert_incomplete(completion); + completion->complete = true; + if (completion->callback != NULL) + vdo_launch_completion(completion); +} + +void vdo_enqueue_completion(struct vdo_completion *completion, + enum vdo_completion_priority priority) +{ + struct vdo *vdo = completion->vdo; + thread_id_t thread_id = completion->callback_thread_id; + + if (VDO_ASSERT(thread_id < vdo->thread_config.thread_count, + "thread_id %u (completion type %d) is less than thread count %u", + thread_id, completion->type, + vdo->thread_config.thread_count) != VDO_SUCCESS) + BUG(); + + completion->requeue = false; + completion->priority = priority; + completion->my_queue = NULL; + vdo_enqueue_work_queue(vdo->threads[thread_id].queue, completion); +} + +/** + * vdo_requeue_completion_if_needed() - Requeue a completion if not called on the specified thread. + * + * Return: True if the completion was requeued; callers may not access the completion in this case. + */ +bool vdo_requeue_completion_if_needed(struct vdo_completion *completion, + thread_id_t callback_thread_id) +{ + if (vdo_get_callback_thread_id() == callback_thread_id) + return false; + + completion->callback_thread_id = callback_thread_id; + vdo_enqueue_completion(completion, VDO_WORK_Q_DEFAULT_PRIORITY); + return true; +} |