[PATCH 5.9 06/74] io_uring: unconditionally grab req->task

Greg Kroah-Hartman
2020-10-31T11:44:02Z

From: Jens Axboe <axboe@kernel.dk>

commit e3bc8e9dad7f2f83cc807111d4472164c9210153 upstream.

Sometimes we assign a weak reference to it, sometimes we grab a
reference to it. Clean this up and make it unconditional, and drop the
flag related to tracking this state.

Reviewed-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_uring.c | 47 +++++++++--------------------------------------
1 file changed, 9 insertions(+), 38 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -553,7 +553,6 @@ enum {
REQ_F_BUFFER_SELECTED_BIT,
REQ_F_NO_FILE_TABLE_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,
@@ -599,8 +598,6 @@ enum {
REQ_F_NO_FILE_TABLE = BIT(REQ_F_NO_FILE_TABLE_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 {
@@ -942,14 +939,6 @@ struct sock *io_uring_get_socket(struct
}
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;
-}
-
static inline void io_clean_op(struct io_kiocb *req)
{
if (req->flags & (REQ_F_NEED_CLEANUP | REQ_F_BUFFER_SELECTED |
@@ -957,13 +946,6 @@ static inline void io_clean_op(struct io
__io_clean_op(req);
}

-/* 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_sq_thread_drop_mm(void)
{
struct mm_struct *mm = current->mm;
@@ -1589,7 +1571,8 @@ static void __io_free_req_finish(struct
{
struct io_ring_ctx *ctx = req->ctx;

- __io_put_req_task(req);
+ put_task_struct(req->task);
+
if (likely(!io_is_fallback_req(req)))
kmem_cache_free(req_cachep, req);
else
@@ -1916,16 +1899,13 @@ static void io_req_free_batch(struct req
if (req->flags & REQ_F_LINK_HEAD)
io_queue_next(req);

- if (req->flags & REQ_F_TASK_PINNED) {
- if (req->task != rb->task) {
- if (rb->task)
- put_task_struct_many(rb->task, rb->task_refs);
- rb->task = req->task;
- rb->task_refs = 0;
- }
- rb->task_refs++;
- req->flags &= ~REQ_F_TASK_PINNED;
+ if (req->task != rb->task) {
+ if (rb->task)
+ put_task_struct_many(rb->task, rb->task_refs);
+ rb->task = req->task;
+ rb->task_refs = 0;
}
+ rb->task_refs++;

WARN_ON_ONCE(io_dismantle_req(req));
rb->reqs[rb->to_free++] = req;
@@ -2550,9 +2530,6 @@ static int io_prep_rw(struct io_kiocb *r
if (kiocb->ki_flags & IOCB_NOWAIT)
req->flags |= REQ_F_NOWAIT;

- if (kiocb->ki_flags & IOCB_DIRECT)
- io_get_req_task(req);
-
if (force_nonblock)
kiocb->ki_flags |= IOCB_NOWAIT;

@@ -2564,7 +2541,6 @@ static int io_prep_rw(struct io_kiocb *r
kiocb->ki_flags |= IOCB_HIPRI;
kiocb->ki_complete = io_complete_rw_iopoll;
req->iopoll_completed = 0;
- io_get_req_task(req);
} else {
if (kiocb->ki_flags & IOCB_HIPRI)
return -EINVAL;
@@ -3132,8 +3108,6 @@ static bool io_rw_should_retry(struct io
kiocb->ki_flags |= IOCB_WAITQ;
kiocb->ki_flags &= ~IOCB_NOWAIT;
kiocb->ki_waitq = wait;
-
- io_get_req_task(req);
return true;
}

@@ -4965,7 +4939,6 @@ static bool io_arm_poll_handler(struct i
apoll->double_poll = NULL;

req->flags |= REQ_F_POLLED;
- io_get_req_task(req);
req->apoll = apoll;
INIT_HLIST_NODE(&req->hash_node);

@@ -5148,8 +5121,6 @@ static int io_poll_add_prep(struct io_ki
#endif
poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP |
(events & EPOLLEXCLUSIVE);
-
- io_get_req_task(req);
return 0;
}

@@ -6336,7 +6307,6 @@ static int io_submit_sqe(struct io_kiocb
return ret;
}
trace_io_uring_link(ctx, req, head);
- io_get_req_task(req);
list_add_tail(&req->link_list, &head->link_list);

/* last request of a link, enqueue the link */
@@ -6461,6 +6431,7 @@ static int io_init_req(struct io_ring_ct
/* one is dropped after submission, the other at completion */
refcount_set(&req->refs, 2);
req->task = current;
+ get_task_struct(req->task);
req->result = 0;

if (unlikely(req->opcode >= IORING_OP_LAST))