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io_uring/io-wq: return 2-step work swap scheme

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Saving one lock/unlock for io-wq is not super important, but adds some
ugliness in the code. More important, atomic decs not turning it to zero
for some archs won't give the right ordering/barriers so the
io_steal_work() may pretty easily get subtly and completely broken.

Return back 2-step io-wq work exchange and clean it up.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-02-04 13:52:08 +00:00 committed by Jens Axboe
parent ea64ec02b3
commit 5280f7e530
3 changed files with 12 additions and 34 deletions
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16
fs/io-wq.c
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@ -555,23 +555,21 @@ static void io_worker_handle_work(struct io_worker *worker)
/* handle a whole dependent link */
do {
struct io_wq_work *old_work, *next_hashed, *linked;
struct io_wq_work *next_hashed, *linked;
unsigned int hash = io_get_work_hash(work);
next_hashed = wq_next_work(work);
io_impersonate_work(worker, work);
wq->do_work(work);
io_assign_current_work(worker, NULL);
old_work = work;
linked = wq->do_work(work);
linked = wq->free_work(work);
work = next_hashed;
if (!work && linked && !io_wq_is_hashed(linked)) {
work = linked;
linked = NULL;
}
io_assign_current_work(worker, work);
wq->free_work(old_work);
if (linked)
io_wqe_enqueue(wqe, linked);
@ -850,11 +848,9 @@ static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
struct io_wq *wq = wqe->wq;
do {
struct io_wq_work *old_work = work;
work->flags |= IO_WQ_WORK_CANCEL;
work = wq->do_work(work);
wq->free_work(old_work);
wq->do_work(work);
work = wq->free_work(work);
} while (work);
}

4
fs/io-wq.h
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@ -106,8 +106,8 @@ static inline struct io_wq_work *wq_next_work(struct io_wq_work *work)
return container_of(work->list.next, struct io_wq_work, list);
}
typedef void (free_work_fn)(struct io_wq_work *);
typedef struct io_wq_work *(io_wq_work_fn)(struct io_wq_work *);
typedef struct io_wq_work *(free_work_fn)(struct io_wq_work *);
typedef void (io_wq_work_fn)(struct io_wq_work *);
struct io_wq_data {
struct user_struct *user;

26
fs/io_uring.c
View File

@ -2379,22 +2379,6 @@ static inline void io_put_req_deferred(struct io_kiocb *req, int refs)
io_free_req_deferred(req);
}
static struct io_wq_work *io_steal_work(struct io_kiocb *req)
{
struct io_kiocb *nxt;
/*
* A ref is owned by io-wq in which context we're. So, if that's the
* last one, it's safe to steal next work. False negatives are Ok,
* it just will be re-punted async in io_put_work()
*/
if (refcount_read(&req->refs) != 1)
return NULL;
nxt = io_req_find_next(req);
return nxt ? &nxt->work : NULL;
}
static void io_double_put_req(struct io_kiocb *req)
{
/* drop both submit and complete references */
@ -6343,7 +6327,7 @@ static int io_issue_sqe(struct io_kiocb *req, bool force_nonblock,
return 0;
}
static struct io_wq_work *io_wq_submit_work(struct io_wq_work *work)
static void io_wq_submit_work(struct io_wq_work *work)
{
struct io_kiocb *req = container_of(work, struct io_kiocb, work);
struct io_kiocb *timeout;
@ -6394,8 +6378,6 @@ static struct io_wq_work *io_wq_submit_work(struct io_wq_work *work)
if (lock_ctx)
mutex_unlock(&lock_ctx->uring_lock);
}
return io_steal_work(req);
}
static inline struct file *io_file_from_index(struct io_ring_ctx *ctx,
@ -8067,12 +8049,12 @@ static int io_sqe_files_update(struct io_ring_ctx *ctx, void __user *arg,
return __io_sqe_files_update(ctx, &up, nr_args);
}
static void io_free_work(struct io_wq_work *work)
static struct io_wq_work *io_free_work(struct io_wq_work *work)
{
struct io_kiocb *req = container_of(work, struct io_kiocb, work);
/* Consider that io_steal_work() relies on this ref */
io_put_req(req);
req = io_put_req_find_next(req);
return req ? &req->work : NULL;
}
static int io_init_wq_offload(struct io_ring_ctx *ctx,