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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 <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-06-15 10:33:13 +03:00 committed by Jens Axboe
parent 67c4d9e693
commit 4dd2824d6d
1 changed files with 22 additions and 8 deletions
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30
fs/io_uring.c
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@ -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))