[PATCH for-next 6/6] io_uring: change ->cqe_cached invariant for CQE32

[Pavel Begunkov <asml.silence@gmail.com>]

With IORING_SETUP_CQE32 ->cqe_cached doesn't store a real address but
rather an implicit offset into cqes. Store the real cqe pointer and
increment it accordingly if CQE32.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.c | 15 ++++++++++-----
 io_uring/io_uring.h |  8 ++------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 263d7e4f1b41..11b4b5040020 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -698,11 +698,8 @@ struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx)
 {
 	struct io_rings *rings = ctx->rings;
 	unsigned int off = ctx->cached_cq_tail & (ctx->cq_entries - 1);
-	unsigned int shift = 0;
 	unsigned int free, queued, len;
 
-	if (ctx->flags & IORING_SETUP_CQE32)
-		shift = 1;
 
 	/* userspace may cheat modifying the tail, be safe and do min */
 	queued = min(__io_cqring_events(ctx), ctx->cq_entries);
@@ -712,11 +709,19 @@ struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx)
 	if (!len)
 		return NULL;
 
-	ctx->cached_cq_tail++;
+	if (ctx->flags & IORING_SETUP_CQE32) {
+		off <<= 1;
+		len <<= 1;
+	}
+
 	ctx->cqe_cached = &rings->cqes[off];
 	ctx->cqe_sentinel = ctx->cqe_cached + len;
+
+	ctx->cached_cq_tail++;
 	ctx->cqe_cached++;
-	return &rings->cqes[off << shift];
+	if (ctx->flags & IORING_SETUP_CQE32)
+		ctx->cqe_cached++;
+	return &rings->cqes[off];
 }
 
 static bool io_fill_cqe_aux(struct io_ring_ctx *ctx,
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index cd29d91c2175..f1b3e765495b 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -24,14 +24,10 @@ static inline struct io_uring_cqe *io_get_cqe(struct io_ring_ctx *ctx)
 	if (likely(ctx->cqe_cached < ctx->cqe_sentinel)) {
 		struct io_uring_cqe *cqe = ctx->cqe_cached;
 
-		if (ctx->flags & IORING_SETUP_CQE32) {
-			unsigned int off = ctx->cqe_cached - ctx->rings->cqes;
-
-			cqe += off;
-		}
-
 		ctx->cached_cq_tail++;
 		ctx->cqe_cached++;
+		if (ctx->flags & IORING_SETUP_CQE32)
+			ctx->cqe_cached++;
 		return cqe;
 	}
 
-- 
2.36.1