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Subject[PATCH] io_uring: hook all linked requests via link_list
Date
Links are created by chaining requests through req->list with an
exception that head uses req->link_list. (e.g. link_list->list->list)
Because of that, io_req_link_next() needs complex splicing to advance.

Link them all through list_list. Also, it seems to be simpler and more
consistent IMHO.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 42 ++++++++++++++++++++----------------------
1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6c2b2afe985e..806d9c72d0c9 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -899,7 +899,6 @@ static bool io_link_cancel_timeout(struct io_kiocb *req)
static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
{
struct io_ring_ctx *ctx = req->ctx;
- struct io_kiocb *nxt;
bool wake_ev = false;

/* Already got next link */
@@ -911,24 +910,21 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
* potentially happen if the chain is messed up, check to be on the
* safe side.
*/
- nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb, list);
- while (nxt) {
- list_del_init(&nxt->list);
+ while (!list_empty(&req->link_list)) {
+ struct io_kiocb *nxt = list_first_entry(&req->link_list,
+ struct io_kiocb, link_list);

- if ((req->flags & REQ_F_LINK_TIMEOUT) &&
- (nxt->flags & REQ_F_TIMEOUT)) {
+ if (unlikely((req->flags & REQ_F_LINK_TIMEOUT) &&
+ (nxt->flags & REQ_F_TIMEOUT))) {
+ list_del_init(&nxt->link_list);
wake_ev |= io_link_cancel_timeout(nxt);
- nxt = list_first_entry_or_null(&req->link_list,
- struct io_kiocb, list);
req->flags &= ~REQ_F_LINK_TIMEOUT;
continue;
}
- if (!list_empty(&req->link_list)) {
- INIT_LIST_HEAD(&nxt->link_list);
- list_splice(&req->link_list, &nxt->link_list);
- nxt->flags |= REQ_F_LINK;
- }

+ list_del_init(&req->link_list);
+ if (!list_empty(&nxt->link_list))
+ nxt->flags |= REQ_F_LINK;
*nxtptr = nxt;
break;
}
@@ -944,15 +940,15 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
static void io_fail_links(struct io_kiocb *req)
{
struct io_ring_ctx *ctx = req->ctx;
- struct io_kiocb *link;
unsigned long flags;

spin_lock_irqsave(&ctx->completion_lock, flags);

while (!list_empty(&req->link_list)) {
- link = list_first_entry(&req->link_list, struct io_kiocb, list);
- list_del_init(&link->list);
+ struct io_kiocb *link = list_first_entry(&req->link_list,
+ struct io_kiocb, link_list);

+ list_del_init(&link->link_list);
trace_io_uring_fail_link(req, link);

if ((req->flags & REQ_F_LINK_TIMEOUT) &&
@@ -3173,10 +3169,11 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
* We don't expect the list to be empty, that will only happen if we
* race with the completion of the linked work.
*/
- if (!list_empty(&req->list)) {
- prev = list_entry(req->list.prev, struct io_kiocb, link_list);
+ if (!list_empty(&req->link_list)) {
+ prev = list_entry(req->link_list.prev, struct io_kiocb,
+ link_list);
if (refcount_inc_not_zero(&prev->refs)) {
- list_del_init(&req->list);
+ list_del_init(&req->link_list);
prev->flags &= ~REQ_F_LINK_TIMEOUT;
} else
prev = NULL;
@@ -3206,7 +3203,7 @@ static void io_queue_linked_timeout(struct io_kiocb *req)
* we got a chance to setup the timer
*/
spin_lock_irq(&ctx->completion_lock);
- if (!list_empty(&req->list)) {
+ if (!list_empty(&req->link_list)) {
struct io_timeout_data *data = &req->io->timeout;

data->timer.function = io_link_timeout_fn;
@@ -3226,7 +3223,8 @@ static struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req)
if (!(req->flags & REQ_F_LINK))
return NULL;

- nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb, list);
+ nxt = list_first_entry_or_null(&req->link_list, struct io_kiocb,
+ link_list);
if (!nxt || nxt->sqe->opcode != IORING_OP_LINK_TIMEOUT)
return NULL;

@@ -3367,7 +3365,7 @@ static bool io_submit_sqe(struct io_kiocb *req, struct io_submit_state *state,
goto err_req;
}
trace_io_uring_link(ctx, req, prev);
- list_add_tail(&req->list, &prev->link_list);
+ list_add_tail(&req->link_list, &prev->link_list);
} else if (req->sqe->flags & IOSQE_IO_LINK) {
req->flags |= REQ_F_LINK;

--
2.24.0
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