From 4dd2824d6d5914949b5fe589538bc2622d84c5dd Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Mon, 15 Jun 2020 10:33:13 +0300 Subject: io_uring: lazy get task There will be multiple places where req->task is used, so refcount-pin it lazily with introduced *io_{get,put}_req_task(). We need to always have valid ->task for cancellation reasons, but don't care about pinning it in some cases. That's why it sets req->task in io_req_init() and implements get/put laziness with a flag. This also removes using @current from polling io_arm_poll_handler(), etc., but doesn't change observable behaviour. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe --- fs/io_uring.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) (limited to 'fs') diff --git a/fs/io_uring.c b/fs/io_uring.c index b6bcd5a7f4bc..5f946eb8b740 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -541,6 +541,7 @@ enum { REQ_F_NO_FILE_TABLE_BIT, REQ_F_QUEUE_TIMEOUT_BIT, REQ_F_WORK_INITIALIZED_BIT, + REQ_F_TASK_PINNED_BIT, /* not a real bit, just to check we're not overflowing the space */ __REQ_F_LAST_BIT, @@ -598,6 +599,8 @@ enum { REQ_F_QUEUE_TIMEOUT = BIT(REQ_F_QUEUE_TIMEOUT_BIT), /* io_wq_work is initialized */ REQ_F_WORK_INITIALIZED = BIT(REQ_F_WORK_INITIALIZED_BIT), + /* req->task is refcounted */ + REQ_F_TASK_PINNED = BIT(REQ_F_TASK_PINNED_BIT), }; struct async_poll { @@ -910,6 +913,21 @@ struct sock *io_uring_get_socket(struct file *file) } EXPORT_SYMBOL(io_uring_get_socket); +static void io_get_req_task(struct io_kiocb *req) +{ + if (req->flags & REQ_F_TASK_PINNED) + return; + get_task_struct(req->task); + req->flags |= REQ_F_TASK_PINNED; +} + +/* not idempotent -- it doesn't clear REQ_F_TASK_PINNED */ +static void __io_put_req_task(struct io_kiocb *req) +{ + if (req->flags & REQ_F_TASK_PINNED) + put_task_struct(req->task); +} + static void io_file_put_work(struct work_struct *work); /* @@ -1399,9 +1417,7 @@ static void __io_req_aux_free(struct io_kiocb *req) kfree(req->io); if (req->file) io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE)); - if (req->task) - put_task_struct(req->task); - + __io_put_req_task(req); io_req_work_drop_env(req); } @@ -4367,8 +4383,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req) memcpy(&apoll->work, &req->work, sizeof(req->work)); had_io = req->io != NULL; - get_task_struct(current); - req->task = current; + io_get_req_task(req); req->apoll = apoll; INIT_HLIST_NODE(&req->hash_node); @@ -4556,8 +4571,7 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe events = READ_ONCE(sqe->poll_events); poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP; - get_task_struct(current); - req->task = current; + io_get_req_task(req); return 0; } @@ -5818,7 +5832,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, req->flags = 0; /* one is dropped after submission, the other at completion */ refcount_set(&req->refs, 2); - req->task = NULL; + req->task = current; req->result = 0; if (unlikely(req->opcode >= IORING_OP_LAST)) -- cgit v1.2.3