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io_uring: replace list with array for compl batch

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Reincarnation of an old patch that replaces a list in struct
io_compl_batch with an array. It's needed to avoid hooking requests via
their compl.list, because it won't be always available in the future.

It's also nice to split io_submit_flush_completions() to avoid free
under locks and remove unlock/lock with a long comment describing when
it can be done.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-02-10 00:03:13 +00:00 committed by Jens Axboe
parent 5087275dba
commit 6dd0be1e24
1 changed files with 11 additions and 24 deletions
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35
fs/io_uring.c
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@ -265,10 +265,11 @@ struct io_sq_data {
};
#define IO_IOPOLL_BATCH 8
#define IO_COMPL_BATCH 32
struct io_comp_state {
unsigned int nr;
struct list_head list;
struct io_kiocb *reqs[IO_COMPL_BATCH];
};
struct io_submit_state {
@ -1345,7 +1346,6 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_LIST_HEAD(&ctx->rsrc_ref_list);
INIT_DELAYED_WORK(&ctx->rsrc_put_work, io_rsrc_put_work);
init_llist_head(&ctx->rsrc_put_llist);
INIT_LIST_HEAD(&submit_state->comp.list);
return ctx;
err:
if (ctx->fallback_req)
@ -1927,33 +1927,20 @@ static inline void io_req_complete_nostate(struct io_kiocb *req, long res,
static void io_submit_flush_completions(struct io_comp_state *cs,
struct io_ring_ctx *ctx)
{
int i, nr = cs->nr;
spin_lock_irq(&ctx->completion_lock);
while (!list_empty(&cs->list)) {
struct io_kiocb *req;
for (i = 0; i < nr; i++) {
struct io_kiocb *req = cs->reqs[i];
req = list_first_entry(&cs->list, struct io_kiocb, compl.list);
list_del(&req->compl.list);
__io_cqring_fill_event(req, req->result, req->compl.cflags);
/*
* io_free_req() doesn't care about completion_lock unless one
* of these flags is set. REQ_F_WORK_INITIALIZED is in the list
* because of a potential deadlock with req->work.fs->lock
* We defer both, completion and submission refs.
*/
if (req->flags & (REQ_F_FAIL_LINK|REQ_F_LINK_TIMEOUT
|REQ_F_WORK_INITIALIZED)) {
spin_unlock_irq(&ctx->completion_lock);
io_double_put_req(req);
spin_lock_irq(&ctx->completion_lock);
} else {
io_double_put_req(req);
}
}
io_commit_cqring(ctx);
spin_unlock_irq(&ctx->completion_lock);
io_cqring_ev_posted(ctx);
for (i = 0; i < nr; i++)
io_double_put_req(cs->reqs[i]);
cs->nr = 0;
}
@ -6517,8 +6504,8 @@ again:
} else if (likely(!ret)) {
/* drop submission reference */
if (req->flags & REQ_F_COMPLETE_INLINE) {
list_add_tail(&req->compl.list, &cs->list);
if (++cs->nr >= 32)
cs->reqs[cs->nr++] = req;
if (cs->nr == IO_COMPL_BATCH)
io_submit_flush_completions(cs, req->ctx);
req = NULL;
} else {
@ -6657,7 +6644,7 @@ static int io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
static void io_submit_state_end(struct io_submit_state *state,
struct io_ring_ctx *ctx)
{
if (!list_empty(&state->comp.list))
if (state->comp.nr)
io_submit_flush_completions(&state->comp, ctx);
if (state->plug_started)
blk_finish_plug(&state->plug);