io_uring: support for IO polling
Add support for a polled io_uring instance. When a read or write is submitted to a polled io_uring, the application must poll for completions on the CQ ring through io_uring_enter(2). Polled IO may not generate IRQ completions, hence they need to be actively found by the application itself. To use polling, io_uring_setup() must be used with the IORING_SETUP_IOPOLL flag being set. It is illegal to mix and match polled and non-polled IO on an io_uring. Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
Родитель
c992fe2925
Коммит
def596e955
275
fs/io_uring.c
275
fs/io_uring.c
|
|
@ -124,6 +124,14 @@ struct io_ring_ctx {
|
|||
|
||||
struct {
|
||||
spinlock_t completion_lock;
|
||||
bool poll_multi_file;
|
||||
/*
|
||||
* ->poll_list is protected by the ctx->uring_lock for
|
||||
* io_uring instances that don't use IORING_SETUP_SQPOLL.
|
||||
* For SQPOLL, only the single threaded io_sq_thread() will
|
||||
* manipulate the list, hence no extra locking is needed there.
|
||||
*/
|
||||
struct list_head poll_list;
|
||||
} ____cacheline_aligned_in_smp;
|
||||
|
||||
#if defined(CONFIG_UNIX)
|
||||
|
|
@ -135,6 +143,7 @@ struct sqe_submit {
|
|||
const struct io_uring_sqe *sqe;
|
||||
unsigned short index;
|
||||
bool has_user;
|
||||
bool needs_lock;
|
||||
};
|
||||
|
||||
struct io_kiocb {
|
||||
|
|
@ -146,12 +155,15 @@ struct io_kiocb {
|
|||
struct list_head list;
|
||||
unsigned int flags;
|
||||
#define REQ_F_FORCE_NONBLOCK 1 /* inline submission attempt */
|
||||
#define REQ_F_IOPOLL_COMPLETED 2 /* polled IO has completed */
|
||||
u64 user_data;
|
||||
u64 error;
|
||||
|
||||
struct work_struct work;
|
||||
};
|
||||
|
||||
#define IO_PLUG_THRESHOLD 2
|
||||
#define IO_IOPOLL_BATCH 8
|
||||
|
||||
static struct kmem_cache *req_cachep;
|
||||
|
||||
|
|
@ -196,6 +208,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
|
|||
mutex_init(&ctx->uring_lock);
|
||||
init_waitqueue_head(&ctx->wait);
|
||||
spin_lock_init(&ctx->completion_lock);
|
||||
INIT_LIST_HEAD(&ctx->poll_list);
|
||||
return ctx;
|
||||
}
|
||||
|
||||
|
|
@ -297,12 +310,153 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx)
|
|||
return NULL;
|
||||
}
|
||||
|
||||
static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr)
|
||||
{
|
||||
if (*nr) {
|
||||
kmem_cache_free_bulk(req_cachep, *nr, reqs);
|
||||
io_ring_drop_ctx_refs(ctx, *nr);
|
||||
*nr = 0;
|
||||
}
|
||||
}
|
||||
|
||||
static void io_free_req(struct io_kiocb *req)
|
||||
{
|
||||
io_ring_drop_ctx_refs(req->ctx, 1);
|
||||
kmem_cache_free(req_cachep, req);
|
||||
}
|
||||
|
||||
/*
|
||||
* Find and free completed poll iocbs
|
||||
*/
|
||||
static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
|
||||
struct list_head *done)
|
||||
{
|
||||
void *reqs[IO_IOPOLL_BATCH];
|
||||
struct io_kiocb *req;
|
||||
int to_free = 0;
|
||||
|
||||
while (!list_empty(done)) {
|
||||
req = list_first_entry(done, struct io_kiocb, list);
|
||||
list_del(&req->list);
|
||||
|
||||
io_cqring_fill_event(ctx, req->user_data, req->error, 0);
|
||||
|
||||
reqs[to_free++] = req;
|
||||
(*nr_events)++;
|
||||
|
||||
fput(req->rw.ki_filp);
|
||||
if (to_free == ARRAY_SIZE(reqs))
|
||||
io_free_req_many(ctx, reqs, &to_free);
|
||||
}
|
||||
io_commit_cqring(ctx);
|
||||
|
||||
io_free_req_many(ctx, reqs, &to_free);
|
||||
}
|
||||
|
||||
static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
|
||||
long min)
|
||||
{
|
||||
struct io_kiocb *req, *tmp;
|
||||
LIST_HEAD(done);
|
||||
bool spin;
|
||||
int ret;
|
||||
|
||||
/*
|
||||
* Only spin for completions if we don't have multiple devices hanging
|
||||
* off our complete list, and we're under the requested amount.
|
||||
*/
|
||||
spin = !ctx->poll_multi_file && *nr_events < min;
|
||||
|
||||
ret = 0;
|
||||
list_for_each_entry_safe(req, tmp, &ctx->poll_list, list) {
|
||||
struct kiocb *kiocb = &req->rw;
|
||||
|
||||
/*
|
||||
* Move completed entries to our local list. If we find a
|
||||
* request that requires polling, break out and complete
|
||||
* the done list first, if we have entries there.
|
||||
*/
|
||||
if (req->flags & REQ_F_IOPOLL_COMPLETED) {
|
||||
list_move_tail(&req->list, &done);
|
||||
continue;
|
||||
}
|
||||
if (!list_empty(&done))
|
||||
break;
|
||||
|
||||
ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
|
||||
if (ret < 0)
|
||||
break;
|
||||
|
||||
if (ret && spin)
|
||||
spin = false;
|
||||
ret = 0;
|
||||
}
|
||||
|
||||
if (!list_empty(&done))
|
||||
io_iopoll_complete(ctx, nr_events, &done);
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
/*
|
||||
* Poll for a mininum of 'min' events. Note that if min == 0 we consider that a
|
||||
* non-spinning poll check - we'll still enter the driver poll loop, but only
|
||||
* as a non-spinning completion check.
|
||||
*/
|
||||
static int io_iopoll_getevents(struct io_ring_ctx *ctx, unsigned int *nr_events,
|
||||
long min)
|
||||
{
|
||||
while (!list_empty(&ctx->poll_list)) {
|
||||
int ret;
|
||||
|
||||
ret = io_do_iopoll(ctx, nr_events, min);
|
||||
if (ret < 0)
|
||||
return ret;
|
||||
if (!min || *nr_events >= min)
|
||||
return 0;
|
||||
}
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* We can't just wait for polled events to come to us, we have to actively
|
||||
* find and complete them.
|
||||
*/
|
||||
static void io_iopoll_reap_events(struct io_ring_ctx *ctx)
|
||||
{
|
||||
if (!(ctx->flags & IORING_SETUP_IOPOLL))
|
||||
return;
|
||||
|
||||
mutex_lock(&ctx->uring_lock);
|
||||
while (!list_empty(&ctx->poll_list)) {
|
||||
unsigned int nr_events = 0;
|
||||
|
||||
io_iopoll_getevents(ctx, &nr_events, 1);
|
||||
}
|
||||
mutex_unlock(&ctx->uring_lock);
|
||||
}
|
||||
|
||||
static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
|
||||
long min)
|
||||
{
|
||||
int ret = 0;
|
||||
|
||||
do {
|
||||
int tmin = 0;
|
||||
|
||||
if (*nr_events < min)
|
||||
tmin = min - *nr_events;
|
||||
|
||||
ret = io_iopoll_getevents(ctx, nr_events, tmin);
|
||||
if (ret <= 0)
|
||||
break;
|
||||
ret = 0;
|
||||
} while (min && !*nr_events && !need_resched());
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
static void kiocb_end_write(struct kiocb *kiocb)
|
||||
{
|
||||
if (kiocb->ki_flags & IOCB_WRITE) {
|
||||
|
|
@ -329,6 +483,53 @@ static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
|
|||
io_free_req(req);
|
||||
}
|
||||
|
||||
static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
|
||||
{
|
||||
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
|
||||
|
||||
kiocb_end_write(kiocb);
|
||||
|
||||
req->error = res;
|
||||
if (res != -EAGAIN)
|
||||
req->flags |= REQ_F_IOPOLL_COMPLETED;
|
||||
}
|
||||
|
||||
/*
|
||||
* After the iocb has been issued, it's safe to be found on the poll list.
|
||||
* Adding the kiocb to the list AFTER submission ensures that we don't
|
||||
* find it from a io_iopoll_getevents() thread before the issuer is done
|
||||
* accessing the kiocb cookie.
|
||||
*/
|
||||
static void io_iopoll_req_issued(struct io_kiocb *req)
|
||||
{
|
||||
struct io_ring_ctx *ctx = req->ctx;
|
||||
|
||||
/*
|
||||
* Track whether we have multiple files in our lists. This will impact
|
||||
* how we do polling eventually, not spinning if we're on potentially
|
||||
* different devices.
|
||||
*/
|
||||
if (list_empty(&ctx->poll_list)) {
|
||||
ctx->poll_multi_file = false;
|
||||
} else if (!ctx->poll_multi_file) {
|
||||
struct io_kiocb *list_req;
|
||||
|
||||
list_req = list_first_entry(&ctx->poll_list, struct io_kiocb,
|
||||
list);
|
||||
if (list_req->rw.ki_filp != req->rw.ki_filp)
|
||||
ctx->poll_multi_file = true;
|
||||
}
|
||||
|
||||
/*
|
||||
* For fast devices, IO may have already completed. If it has, add
|
||||
* it to the front so we find it first.
|
||||
*/
|
||||
if (req->flags & REQ_F_IOPOLL_COMPLETED)
|
||||
list_add(&req->list, &ctx->poll_list);
|
||||
else
|
||||
list_add_tail(&req->list, &ctx->poll_list);
|
||||
}
|
||||
|
||||
/*
|
||||
* If we tracked the file through the SCM inflight mechanism, we could support
|
||||
* any file. For now, just ensure that anything potentially problematic is done
|
||||
|
|
@ -349,6 +550,7 @@ static bool io_file_supports_async(struct file *file)
|
|||
static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
|
||||
bool force_nonblock)
|
||||
{
|
||||
struct io_ring_ctx *ctx = req->ctx;
|
||||
struct kiocb *kiocb = &req->rw;
|
||||
unsigned ioprio;
|
||||
int fd, ret;
|
||||
|
|
@ -384,12 +586,22 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
|
|||
kiocb->ki_flags |= IOCB_NOWAIT;
|
||||
req->flags |= REQ_F_FORCE_NONBLOCK;
|
||||
}
|
||||
if (kiocb->ki_flags & IOCB_HIPRI) {
|
||||
ret = -EINVAL;
|
||||
goto out_fput;
|
||||
}
|
||||
if (ctx->flags & IORING_SETUP_IOPOLL) {
|
||||
ret = -EOPNOTSUPP;
|
||||
if (!(kiocb->ki_flags & IOCB_DIRECT) ||
|
||||
!kiocb->ki_filp->f_op->iopoll)
|
||||
goto out_fput;
|
||||
|
||||
kiocb->ki_complete = io_complete_rw;
|
||||
req->error = 0;
|
||||
kiocb->ki_flags |= IOCB_HIPRI;
|
||||
kiocb->ki_complete = io_complete_rw_iopoll;
|
||||
} else {
|
||||
if (kiocb->ki_flags & IOCB_HIPRI) {
|
||||
ret = -EINVAL;
|
||||
goto out_fput;
|
||||
}
|
||||
kiocb->ki_complete = io_complete_rw;
|
||||
}
|
||||
return 0;
|
||||
out_fput:
|
||||
fput(kiocb->ki_filp);
|
||||
|
|
@ -543,6 +755,9 @@ static int io_nop(struct io_kiocb *req, u64 user_data)
|
|||
struct io_ring_ctx *ctx = req->ctx;
|
||||
long err = 0;
|
||||
|
||||
if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
|
||||
return -EINVAL;
|
||||
|
||||
/*
|
||||
* Twilight zone - it's possible that someone issued an opcode that
|
||||
* has a file attached, then got -EAGAIN on submission, and changed
|
||||
|
|
@ -566,6 +781,8 @@ static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe)
|
|||
if (req->rw.ki_filp)
|
||||
return 0;
|
||||
|
||||
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
|
||||
return -EINVAL;
|
||||
if (unlikely(sqe->addr || sqe->ioprio))
|
||||
return -EINVAL;
|
||||
|
||||
|
|
@ -637,7 +854,22 @@ static int __io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
|
|||
break;
|
||||
}
|
||||
|
||||
return ret;
|
||||
if (ret)
|
||||
return ret;
|
||||
|
||||
if (ctx->flags & IORING_SETUP_IOPOLL) {
|
||||
if (req->error == -EAGAIN)
|
||||
return -EAGAIN;
|
||||
|
||||
/* workqueue context doesn't hold uring_lock, grab it now */
|
||||
if (s->needs_lock)
|
||||
mutex_lock(&ctx->uring_lock);
|
||||
io_iopoll_req_issued(req);
|
||||
if (s->needs_lock)
|
||||
mutex_unlock(&ctx->uring_lock);
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void io_sq_wq_submit_work(struct work_struct *work)
|
||||
|
|
@ -661,8 +893,19 @@ static void io_sq_wq_submit_work(struct work_struct *work)
|
|||
use_mm(ctx->sqo_mm);
|
||||
set_fs(USER_DS);
|
||||
s->has_user = true;
|
||||
s->needs_lock = true;
|
||||
|
||||
ret = __io_submit_sqe(ctx, req, s, false);
|
||||
do {
|
||||
ret = __io_submit_sqe(ctx, req, s, false);
|
||||
/*
|
||||
* We can get EAGAIN for polled IO even though we're forcing
|
||||
* a sync submission from here, since we can't wait for
|
||||
* request slots on the block side.
|
||||
*/
|
||||
if (ret != -EAGAIN)
|
||||
break;
|
||||
cond_resched();
|
||||
} while (1);
|
||||
|
||||
set_fs(old_fs);
|
||||
unuse_mm(ctx->sqo_mm);
|
||||
|
|
@ -799,6 +1042,8 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit)
|
|||
break;
|
||||
|
||||
s.has_user = true;
|
||||
s.needs_lock = false;
|
||||
|
||||
ret = io_submit_sqe(ctx, &s);
|
||||
if (ret) {
|
||||
io_drop_sqring(ctx);
|
||||
|
|
@ -947,6 +1192,9 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
|
|||
destroy_workqueue(ctx->sqo_wq);
|
||||
if (ctx->sqo_mm)
|
||||
mmdrop(ctx->sqo_mm);
|
||||
|
||||
io_iopoll_reap_events(ctx);
|
||||
|
||||
#if defined(CONFIG_UNIX)
|
||||
if (ctx->ring_sock)
|
||||
sock_release(ctx->ring_sock);
|
||||
|
|
@ -993,6 +1241,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
|
|||
percpu_ref_kill(&ctx->refs);
|
||||
mutex_unlock(&ctx->uring_lock);
|
||||
|
||||
io_iopoll_reap_events(ctx);
|
||||
wait_for_completion(&ctx->ctx_done);
|
||||
io_ring_ctx_free(ctx);
|
||||
}
|
||||
|
|
@ -1074,6 +1323,8 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
|
|||
goto out_ctx;
|
||||
}
|
||||
if (flags & IORING_ENTER_GETEVENTS) {
|
||||
unsigned nr_events = 0;
|
||||
|
||||
min_complete = min(min_complete, ctx->cq_entries);
|
||||
|
||||
/*
|
||||
|
|
@ -1085,7 +1336,13 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
|
|||
if (submitted < to_submit)
|
||||
min_complete = min_t(unsigned, submitted, min_complete);
|
||||
|
||||
ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
|
||||
if (ctx->flags & IORING_SETUP_IOPOLL) {
|
||||
mutex_lock(&ctx->uring_lock);
|
||||
ret = io_iopoll_check(ctx, &nr_events, min_complete);
|
||||
mutex_unlock(&ctx->uring_lock);
|
||||
} else {
|
||||
ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
|
||||
}
|
||||
}
|
||||
|
||||
out_ctx:
|
||||
|
|
@ -1282,7 +1539,7 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
|
|||
return -EINVAL;
|
||||
}
|
||||
|
||||
if (p.flags)
|
||||
if (p.flags & ~IORING_SETUP_IOPOLL)
|
||||
return -EINVAL;
|
||||
|
||||
ret = io_uring_create(entries, &p);
|
||||
|
|
|
|||
|
|
@ -30,6 +30,11 @@ struct io_uring_sqe {
|
|||
__u64 __pad2[3];
|
||||
};
|
||||
|
||||
/*
|
||||
* io_uring_setup() flags
|
||||
*/
|
||||
#define IORING_SETUP_IOPOLL (1U << 0) /* io_context is polled */
|
||||
|
||||
#define IORING_OP_NOP 0
|
||||
#define IORING_OP_READV 1
|
||||
#define IORING_OP_WRITEV 2
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче