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io_uring/io-wq: make io_wq_work flags atomic
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The work flags can be set/accessed from different tasks, both the
originator of the request, and the io-wq workers. While modifications
aren't concurrent, it still makes KMSAN unhappy. There's no real
downside to just making the flag reading/manipulation use proper
atomics here.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Jens Axboe authored and Jens Axboe committed Jun 16, 2024
1 parent f2a9329 commit 3474d1b
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Showing 4 changed files with 18 additions and 17 deletions.
2 changes: 1 addition & 1 deletion include/linux/io_uring_types.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ struct io_wq_work_list {

struct io_wq_work {
struct io_wq_work_node list;
unsigned flags;
atomic_t flags;
/* place it here instead of io_kiocb as it fills padding and saves 4B */
int cancel_seq;
};
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19 changes: 10 additions & 9 deletions io_uring/io-wq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,7 @@ static inline struct io_wq_acct *io_get_acct(struct io_wq *wq, bool bound)
static inline struct io_wq_acct *io_work_get_acct(struct io_wq *wq,
struct io_wq_work *work)
{
return io_get_acct(wq, !(work->flags & IO_WQ_WORK_UNBOUND));
return io_get_acct(wq, !(atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND));
}

static inline struct io_wq_acct *io_wq_get_acct(struct io_worker *worker)
Expand Down Expand Up @@ -451,7 +451,7 @@ static void __io_worker_idle(struct io_wq *wq, struct io_worker *worker)

static inline unsigned int io_get_work_hash(struct io_wq_work *work)
{
return work->flags >> IO_WQ_HASH_SHIFT;
return atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT;
}

static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash)
Expand Down Expand Up @@ -592,8 +592,9 @@ static void io_worker_handle_work(struct io_wq_acct *acct,

next_hashed = wq_next_work(work);

if (unlikely(do_kill) && (work->flags & IO_WQ_WORK_UNBOUND))
work->flags |= IO_WQ_WORK_CANCEL;
if (do_kill &&
(atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND))
atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
wq->do_work(work);
io_assign_current_work(worker, NULL);

Expand Down Expand Up @@ -891,7 +892,7 @@ static bool io_wq_worker_wake(struct io_worker *worker, void *data)
static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)
{
do {
work->flags |= IO_WQ_WORK_CANCEL;
atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
wq->do_work(work);
work = wq->free_work(work);
} while (work);
Expand Down Expand Up @@ -926,7 +927,7 @@ static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
{
struct io_wq_acct *acct = io_work_get_acct(wq, work);
unsigned long work_flags = work->flags;
unsigned int work_flags = atomic_read(&work->flags);
struct io_cb_cancel_data match = {
.fn = io_wq_work_match_item,
.data = work,
Expand All @@ -939,7 +940,7 @@ void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
* been marked as one that should not get executed, cancel it here.
*/
if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
(work->flags & IO_WQ_WORK_CANCEL)) {
(work_flags & IO_WQ_WORK_CANCEL)) {
io_run_cancel(work, wq);
return;
}
Expand Down Expand Up @@ -982,15 +983,15 @@ void io_wq_hash_work(struct io_wq_work *work, void *val)
unsigned int bit;

bit = hash_ptr(val, IO_WQ_HASH_ORDER);
work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
atomic_or(IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT), &work->flags);
}

static bool __io_wq_worker_cancel(struct io_worker *worker,
struct io_cb_cancel_data *match,
struct io_wq_work *work)
{
if (work && match->fn(work, match->data)) {
work->flags |= IO_WQ_WORK_CANCEL;
atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
__set_notify_signal(worker->task);
return true;
}
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2 changes: 1 addition & 1 deletion io_uring/io-wq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@ bool io_wq_worker_stopped(void);

static inline bool io_wq_is_hashed(struct io_wq_work *work)
{
return work->flags & IO_WQ_WORK_HASHED;
return atomic_read(&work->flags) & IO_WQ_WORK_HASHED;
}

typedef bool (work_cancel_fn)(struct io_wq_work *, void *);
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12 changes: 6 additions & 6 deletions io_uring/io_uring.c
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Original file line number Diff line number Diff line change
Expand Up @@ -462,9 +462,9 @@ static void io_prep_async_work(struct io_kiocb *req)
}

req->work.list.next = NULL;
req->work.flags = 0;
atomic_set(&req->work.flags, 0);
if (req->flags & REQ_F_FORCE_ASYNC)
req->work.flags |= IO_WQ_WORK_CONCURRENT;
atomic_or(IO_WQ_WORK_CONCURRENT, &req->work.flags);

if (req->file && !(req->flags & REQ_F_FIXED_FILE))
req->flags |= io_file_get_flags(req->file);
Expand All @@ -480,7 +480,7 @@ static void io_prep_async_work(struct io_kiocb *req)
io_wq_hash_work(&req->work, file_inode(req->file));
} else if (!req->file || !S_ISBLK(file_inode(req->file)->i_mode)) {
if (def->unbound_nonreg_file)
req->work.flags |= IO_WQ_WORK_UNBOUND;
atomic_or(IO_WQ_WORK_UNBOUND, &req->work.flags);
}
}

Expand Down Expand Up @@ -520,7 +520,7 @@ static void io_queue_iowq(struct io_kiocb *req)
* worker for it).
*/
if (WARN_ON_ONCE(!same_thread_group(req->task, current)))
req->work.flags |= IO_WQ_WORK_CANCEL;
atomic_or(IO_WQ_WORK_CANCEL, &req->work.flags);

trace_io_uring_queue_async_work(req, io_wq_is_hashed(&req->work));
io_wq_enqueue(tctx->io_wq, &req->work);
Expand Down Expand Up @@ -1736,14 +1736,14 @@ void io_wq_submit_work(struct io_wq_work *work)
io_arm_ltimeout(req);

/* either cancelled or io-wq is dying, so don't touch tctx->iowq */
if (work->flags & IO_WQ_WORK_CANCEL) {
if (atomic_read(&work->flags) & IO_WQ_WORK_CANCEL) {
fail:
io_req_task_queue_fail(req, err);
return;
}
if (!io_assign_file(req, def, issue_flags)) {
err = -EBADF;
work->flags |= IO_WQ_WORK_CANCEL;
atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
goto fail;
}

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