From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Pavel Begunkov asml.silence@gmail.com
commit 5280f7e530f71ba85baf90169393196976ad0e52 upstream
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io-wq.c | 16 ++++++---------- fs/io-wq.h | 4 ++-- fs/io_uring.c | 26 ++++---------------------- 3 files changed, 12 insertions(+), 34 deletions(-)
--- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -555,23 +555,21 @@ get_next:
/* 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_w 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); }
--- a/fs/io-wq.h +++ b/fs/io-wq.h @@ -106,8 +106,8 @@ static inline struct io_wq_work *wq_next 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; --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2365,22 +2365,6 @@ static inline void io_put_req_deferred(s 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 */ @@ -6378,7 +6362,7 @@ static int io_issue_sqe(struct io_kiocb 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; @@ -6429,8 +6413,6 @@ static struct io_wq_work *io_wq_submit_w 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, @@ -8062,12 +8044,12 @@ static int io_sqe_files_update(struct io 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,