[PATCH 05/12] io_uring: don't cache number of dropped SQEs

Pavel Begunkov
2021-06-14T22:38:13Z

Kill ->cached_sq_dropped and wire DRAIN sequence number correction via
->cq_extra, which is there exactly for that purpose. User visible
dropped counter will be populated by incrementing it instead of keeping
a copy, similarly as it was done not so long ago with cq_overflow.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3baacfe2c9b7..6dd14f4aa5f1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -370,7 +370,6 @@ struct io_ring_ctx {
struct io_uring_sqe *sq_sqes;
unsigned cached_sq_head;
unsigned sq_entries;
- unsigned cached_sq_dropped;
unsigned long sq_check_overflow;
struct list_head defer_list;

@@ -5994,13 +5993,11 @@ static u32 io_get_sequence(struct io_kiocb *req)
{
struct io_kiocb *pos;
struct io_ring_ctx *ctx = req->ctx;
- u32 total_submitted, nr_reqs = 0;
+ u32 nr_reqs = 0;

io_for_each_link(pos, req)
nr_reqs++;
-
- total_submitted = ctx->cached_sq_head - ctx->cached_sq_dropped;
- return total_submitted - nr_reqs;
+ return ctx->cached_sq_head - nr_reqs;
}

static int io_req_defer(struct io_kiocb *req)
@@ -6701,8 +6698,9 @@ static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)
return &ctx->sq_sqes[head];

/* drop invalid entries */
- ctx->cached_sq_dropped++;
- WRITE_ONCE(ctx->rings->sq_dropped, ctx->cached_sq_dropped);
+ ctx->cq_extra--;
+ WRITE_ONCE(ctx->rings->sq_dropped,
+ READ_ONCE(ctx->rings->sq_dropped) + 1);
return NULL;
}

--
2.31.1